Method for extracting product from titanium-containing material

Abstract

The present invention relates to a method for extracting a product from a titanium-containing material or a composition produced in a method for producing titanium dioxide, and more particularly, but not exclusively, the present invention relates to a method for extracting titanium dioxide and / or one or more other products from ironmaking slag.

Description

[0001] This application is a divisional application of an application with an application date of December 16, 2019, international application number PCT / NZ2019 / 050159, national application number 201980082871.3, and invention name “Method for extracting products from titanium-containing materials”. Technical Field

[0002] The present invention relates to a process for extracting products from titanium-containing materials or compositions produced in a process for producing titanium dioxide, and more particularly, but not exclusively, the present invention relates to a process for extracting titanium dioxide and / or one or more other products from iron making slag. Background Art

[0003] It is currently not possible to recover valuable components from large mineral reserves by economically viable and / or environmentally friendly means. One reason is that the grade of such components in the mineral reserves is too low, resulting in high waste or by-product generation rates. Another problem may be the refractory nature of such components in the mineral structure, making them difficult to recover. In addition, traditional methods for recovering valuable components from mineral reserves usually require large amounts of energy and the use of large amounts of hazardous chemicals, resulting in the need to dispose of large amounts of waste and potentially toxic products.

[0004] Smelter slag is a byproduct of the iron and steel manufacturing process and is a mineral containing low levels of commercially valuable components, including titanium, aluminum and magnesium. When producing molten pig iron, impurities are removed as smelter slag. For some deposits, the slag is primarily perovskite (calcium titanate) and may contain 20% to 40% titanium dioxide.

[0005] Known smelter slag extraction processes focus on the extraction of titanium because it has the highest concentration and highest value in slag. Titanium is a valuable pigment used in many commercial applications, such as the production of paint, paper, cement and polymers. In smelter slag, titanium exists in the form of perovskite, a titanium-calcium oxide crystal structure that is difficult to recover. Titanium also exists in the form of perovskite in many naturally occurring ores.

[0006] An example of a known method for extracting titanium from perovskite includes reacting perovskite with carbon at high temperature in an electric furnace to produce titanium carbide. The titanium carbide is then chlorinated to produce titanium tetrachloride. Unfortunately, this process is energy intensive and the carbide produced has an extremely high melting point, which poses a disposal problem in the furnace.

[0007] Another method of extracting titanium from perovskite is the method disclosed in CA 1,052,581. In this method, the perovskite is treated by roasting at 1200°C in hydrogen sulfide gas. It is then leached to remove the calcium and iron sulfides, leaving the titanium in the form of titanium oxide. The disadvantages of this process are the high temperatures and the use of highly toxic gases.

[0008] Other methods of recovering titanium from minerals include processes known as the "sulfation process" and the "chlorination process." In the sulfation process, the mineral raw material is treated with concentrated sulfuric acid (H2SO4), and then titanyl sulfate (TiOSO4) is selectively extracted and converted into titanium dioxide. In the chlorination process, the titanium dioxide in the raw material is reduced by carbon and then oxidized again by chlorine. Liquid TiCl4 is distilled off and then converted back to TiO2 in a pure oxygen flame or in a plasma at a temperature of 1200-1700°C. The chlorination process requires a relatively pure ore or rutile as a raw material, which is much less than other raw materials. The raw material must contain at least 70% rutile.

[0009] The sulphate process and the chlorination process are usually carried out on ilmenite, which is an idealized titanium iron oxide mineral with the molecular formula FeTiO3, from which titanium can be more easily recovered. The sulphate process has been proposed for extracting titanium from perovskite.

[0010] Even small improvements in the process of extracting a saleable product from a mineral can have a significant impact on the efficiency and, especially, the commercial viability of that process.

[0011] Purpose

[0012] It is an object of the present invention to provide an improved process for recovering one or more products from titanium-containing materials including perovskites or compositions produced in processes for producing titanium dioxide, or at least to provide the public with a useful choice. Summary of the invention

[0013] In a first aspect, the present invention provides a method for recovering one or more products from a titanium-containing material comprising perovskite, the method comprising:

[0014] a) contacting the titanium-containing material with sulfuric acid to form a filter cake comprising at least titanyl sulfate

[0015] b) contacting the filter cake with water and / or dilute sulfuric acid to form a sulfated suspension comprising at least titanyl sulfate

[0016] c) separating solids from the liquid of the sulfated suspension to produce a first permeate (LL) comprising at least titanyl sulfate and a first retentate comprising at least calcium sulfate and silica

[0017] d) hydrolyzing titanyl sulfate in the first permeate to produce a first liquid comprising titanium dioxide hydrate

[0018] e) separating titanium dioxide hydrate from said first liquid to produce titanium dioxide hydrate and a second liquid (PHL) comprising at least aluminum sulfate

[0019] f) separating aluminium sulphate from said second liquid (PHL) to produce aluminium sulphate and a third liquid (PAL) comprising mixed metal sulphates.

[0020] In one embodiment of the first aspect, the method further comprises the following steps:

[0021] g) combining calcium carbonate and said third liquid (PAL) to produce a first composition (PAL') comprising mixed metal sulphates including calcium sulphate.

[0022] In another embodiment of the first aspect, the method further comprises the following steps:

[0023] h) separating calcium sulphate from said first composition (PAL') to produce calcium sulphate and a fourth liquid (PNL) comprising mixed metal sulphates.

[0024] In another embodiment of the first aspect, the method further comprises the following steps:

[0025] i) separating magnesium sulfate from said fourth liquid (PNL) to produce magnesium sulfate and a fifth liquid (PML) comprising mixed metal sulfates.

[0026] In another embodiment of the first aspect, the method further comprises the following steps:

[0027] j) combining calcium hydroxide and the fifth liquid (PML) to produce a second composition (PML') comprising mixed metal hydroxides and / or oxides and calcium sulfate, or combining magnesium hydroxide and the fifth liquid (PML) to produce a second composition (PML') comprising mixed metal hydroxides and / or oxides.

[0028] In another embodiment of the first aspect, the method further comprises the following steps:

[0029] k) recovering the mixed metal oxide and / or hydroxide from the second composition (PML'), or recovering the mixed metal oxide and / or hydroxide and calcium sulfate to produce a mixed metal solid.

[0030] In another embodiment of the first aspect, the method comprises the following alternative step i):

[0031] i) combining calcium hydroxide and the fourth liquid (PNL) to produce a second composition (PNL') comprising mixed metal oxides and / or hydroxides, calcium sulfate and magnesium sulfate, or combining magnesium hydroxide and the fourth liquid (PNL) to produce a second composition (PNL') comprising mixed metal oxides and / or hydroxides and magnesium sulfate.

[0032] In another embodiment of the first aspect described in the immediately preceding paragraph, the method further comprises the following alternative step j):

[0033] j) separating the mixed metal oxide and / or hydroxide or separating the mixed metal oxide and / or hydroxide and calcium sulfate from the second composition (PNL') to produce a mixed metal solid or a mixed metal solid comprising calcium sulfate and a fifth liquid (MRL) comprising magnesium sulfate.

[0034] In another embodiment of the first aspect described in the immediately preceding paragraph, the method further comprises the following alternative step k):

[0035] k) recovering magnesium sulfate from the fifth liquid (MRL) to produce magnesium sulfate.

[0036] In a second aspect, the present invention provides a method for recovering one or more products from a titanium-containing material comprising perovskite, the method comprising:

[0037] a) contacting the titanium-containing material with sulfuric acid to form a filter cake comprising at least titanyl sulfate

[0038] b) contacting the filter cake with water and / or dilute sulfuric acid to form a sulfated suspension comprising at least titanyl sulfate

[0039] c) separating solids from liquid in the sulfated suspension to produce a first permeate (LL) comprising at least titanyl sulfate and a first retentate comprising at least calcium sulfate and silicon dioxide

[0040] d) separating aluminum sulfate from said first permeate (LL) to produce aluminum sulfate and a first liquid comprising at least titanyl sulfate

[0041] e) hydrolyzing titanyl sulfate in the first liquid to produce a second liquid (PHL) comprising titanium dioxide hydrate

[0042] f) separating titanium dioxide hydrate from said second liquid (PHL) to produce titanium dioxide hydrate and a third liquid (PAL) comprising mixed metal sulfates.

[0043] In one embodiment of the second aspect, the method further comprises the following steps:

[0044] g) combining calcium carbonate and said third liquid (PAL) to produce a first composition (PAL') comprising mixed metal sulfates including calcium sulfate.

[0045] In another embodiment of the second aspect, the method further comprises the following steps:

[0046] h) separating calcium sulphate from said first composition (PAL') to produce calcium sulphate and a fourth liquid (PNL) comprising mixed metal sulphates.

[0047] In another embodiment of the second aspect, the method further comprises the following steps:

[0048] i) separating magnesium sulfate from said fourth liquid (PNL) to produce magnesium sulfate and a fifth liquid (PML) comprising mixed metal sulfates.

[0049] In another embodiment of the second aspect, the method further comprises the following steps:

[0050] j) combining calcium hydroxide and the fifth liquid (PML) to produce a second composition (PML') comprising mixed metal oxides and / or hydroxides and calcium sulfate, or combining magnesium hydroxide and the fifth liquid (PML) to produce a second composition (PML') comprising mixed metal oxides and / or hydroxides.

[0051] In another embodiment of the second aspect, the method further comprises the following steps:

[0052] k) recovering the mixed metal oxide and / or hydroxide and calcium sulfate from the second composition (PML'), or recovering the mixed metal oxide and / or hydroxide to produce a mixed metal solid or a mixed metal solid comprising calcium sulfate.

[0053] In another embodiment of the second aspect, the method further comprises the following alternative step i):

[0054] i) combining calcium hydroxide with the fourth liquid (PNL) to produce a second composition (PNL') comprising mixed metal oxides and / or hydroxides, calcium sulfate and magnesium sulfate, or combining magnesium hydroxide with the fourth liquid (PNL) to produce a second composition (PNL') comprising mixed metal oxides and / or hydroxides and magnesium sulfate.

[0055] In another embodiment of the second aspect described in the immediately preceding paragraph, the method further comprises the following alternative step j):

[0056] j) separating the mixed metal oxides and / or hydroxides, or separating the mixed metal oxides and / or hydroxides and calcium sulfate from the second composition (PNL') to produce a mixed metal solid, or a mixed metal solid comprising calcium sulfate and a fifth liquid (MRL) comprising magnesium sulfate.

[0057] In another embodiment of the second aspect described in the immediately preceding paragraph, the method further comprises the following alternative step k):

[0058] k) recovering magnesium sulfate from the fifth liquid (MRL) to produce magnesium sulfate.

[0059] In one embodiment of the first or second aspect, the step of combining calcium carbonate and the third liquid (PAL) to produce the first composition (PAL') is carried out under the following conditions: the titanium is in the Ti 4+ The iron is in the Fe 2+ To produce a first composition comprising calcium sulfate, one or more titanium oxides and / or hydroxides and mixed metal sulfates. In one embodiment, the first composition also comprises one or more aluminum oxides and / or hydroxides. In this embodiment, the method may further include the steps of separating calcium sulfate, one or more aluminum and / or titanium oxides and / or hydroxides from the composition to produce calcium sulfate, and one or more aluminum and / or titanium oxides and / or hydroxides and a fourth liquid (PNL) comprising mixed metal sulfates. In one embodiment, this step is performed at an ORP of about 270 mV.

[0060] In one embodiment of the first or second aspect, one or more products are selected from the group consisting of titanium dioxide, a first retentate, calcium sulfate, silicon dioxide, aluminum sulfate, magnesium sulfate, and mixed metal solids. In another embodiment, one or more products are further selected from one or more liquids or compositions produced in the method of the first or second aspect of the invention or produced in the method further described herein.

[0061] In one embodiment of the first aspect or the second aspect, a combination of two, three, four, five, six or seven products are recovered in the process. In one embodiment, a combination of titanium dioxide and aluminum sulfate is recovered. In another embodiment, a combination of titanium dioxide and magnesium sulfate is recovered. In another embodiment, a combination of titanium dioxide, magnesium sulfate and aluminum sulfate is recovered. In one embodiment, a combination of titanium dioxide, magnesium sulfate, aluminum sulfate and calcium sulfate is recovered. In a preferred embodiment, a combination of titanium dioxide, calcium sulfate, silicon dioxide, aluminum sulfate, magnesium sulfate and mixed metal solids is recovered in the method of the present invention. In a preferred embodiment, a combination of titanium dioxide, a first retentate, calcium sulfate, aluminum sulfate, magnesium sulfate and mixed metal solids is recovered in the method of the present invention.

[0062] In one embodiment, titanium dioxide is recovered as hydrated titanium dioxide. In certain embodiments, CaSO4 is recovered in one or more steps of the process as CaSO4.2H2O (e.g., from the first or second composition). In certain embodiments, aluminum sulfate is recovered as Al2(SO4)3.XH2O (e.g., from the second liquid (PHL) or the first permeate (LL)), where x is 14 to 18. In certain embodiments, magnesium sulfate is recovered as MgSO4.7H2O or MgSO4.6H2O or MgSO4.1H2O (e.g., from the fourth liquid (PNL) or the fifth liquid (MRL)).

[0063] In one embodiment of the first or second aspect, the titanium dioxide hydrate, calcium sulfate, silicon dioxide, aluminum sulfate, magnesium sulfate or mixed metal oxide and / or hydroxide separated from the composition or liquid is in a precipitated form. In certain embodiments, the step of separating one or more of the titanium dioxide hydrate, calcium sulfate, silicon dioxide, the first retentate, aluminum sulfate, magnesium sulfate or mixed metal oxide and / or hydroxide comprises one or more of filtration, centrifugation, evaporation, sedimentation and / or hydrocyclone separation. In certain embodiments, a continuous separation method is used.

[0064] In one embodiment of the first or second aspect, the step of separating the solids from the liquid of the sulfated suspension comprises filtering the sulfated suspension.

[0065] In one embodiment of the first or second aspect, the step of separating the titanium dioxide hydrate from the liquid comprises the step of filtering the titanium dioxide hydrate from the liquid.

[0066] In one embodiment of the first or second aspect, the step of separating CaSO 4 from the first composition comprises filtering the first composition.

[0067] In one embodiment of the first or second aspect, the step of separating the mixed metal hydroxides and / or oxides or mixed metal hydroxides and / or oxides and calcium sulfate from the second composition (PNL' or PML') comprises evaporating and / or filtering the second composition.

[0068] In one embodiment of the first or second aspect, the titanium-containing material and sulfuric acid are contacted at a ratio of sulfuric acid to titanium-containing material of about 0.75: 1 to about 2: 1. In a preferred embodiment, the ratio of sulfuric acid to titanium-containing material is about 1.3: 1 to about 1.7: 1.

[0069] In one embodiment of the first or second aspect, the concentration of sulfuric acid employed is preferably at least about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or at least about 98%. In a preferred embodiment, the concentration of sulfuric acid employed is about 75% to about 98%, more preferably about 80% to about 95% or about 80% to about 90%.

[0070] In another embodiment of the first or second aspect, step a) is performed so that the combined titanium-containing material and sulfuric acid reaches a temperature of about 130° C. to about 250° C. In a preferred embodiment, the temperature is about 130° C. to about 220° C. In another preferred embodiment, the temperature is about 170° C. or about 180 to about 210° C.

[0071] In one embodiment of the first or second aspect, step a) is performed (i.e., the mixture is maintained at temperature), or the sulfated mixture is contained in a reactor for a period of about 30 minutes to about 4 hours. In a preferred embodiment, the reaction is carried out for a period of up to about 3 hours. In another preferred embodiment, the reaction is carried out for a period of up to about 2 hours.

[0072] In one embodiment of the first aspect or the second aspect, the titanium-containing material includes a level of titanium dioxide, as described in the detailed description herein. In another embodiment, the material includes a level of calcium oxide, as described in the detailed description herein. In another embodiment, the material includes at least one or more of aluminum oxide, magnesium oxide, and silicon dioxide, in an amount as described in the detailed description herein.

[0073] In one embodiment of the first or second aspect, the titanium-containing material has a ratio of titanium dioxide to calcium oxide, titanium dioxide to aluminum oxide and / or titanium dioxide to magnesium oxide as described in the detailed description herein.

[0074] In one embodiment of the first or second aspect, the method further comprises the step of calcining the recovered titanium dioxide hydrate to form calcined titanium dioxide. In a preferred embodiment, the calcined titanium dioxide is ground, coated, washed, dried and / or micronized. In one embodiment, the titanium dioxide is pigment grade.

[0075] In one embodiment of the first or second aspect, the titanium dioxide (hydrated or otherwise) recovered from the process of the present invention is suitable for use as a feedstock in a titanium dioxide pigment manufacturing process.

[0076] In one embodiment of the first or second aspect, the titanium-containing material comprising perovskite is selected from the group consisting of slag, ore, upgraded slag and concentrate. In a specific embodiment, the titanium-containing material comprising perovskite is ironmaking slag. In one embodiment, the ironmaking slag is ironmaking slag or blast furnace slag. In another embodiment, the ore is vanadium titano-magnetite ore. In another embodiment, the slag is vanadium titano-magnetite slag. In other embodiments, the titanium-containing material comprising perovskite includes a combination of titanium-containing materials from two or more different sources.

[0077] In a particular embodiment, the titanium-containing material is in the form of a granular material having an average particle size of less than 180 μm. In a preferred embodiment, the average particle size of the granular material is from 10 μm to 180 μm, or from 40 μm to 110 μm. In a particular embodiment, the average particle size of the granular material is about 30 μm, 45 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0078] In certain embodiments, the methods of the present invention further comprise the step of grinding the titanium-containing material prior to step a) of the processes of the first to fourth aspects.

[0079] In one embodiment of the first or second aspect, the titanium-containing material is contacted with sulfuric acid in a continuous reactor.In one embodiment, the sulfation step a) is carried out in a continuous reactor suitable for continuously mixing sulfuric acid, the titanium-containing material and a filter cake comprising titanyl sulfate.

[0080] In a preferred embodiment, one or more further steps of the method of the first or second aspect of the invention are performed in a continuous manner.In a preferred embodiment of the first to fourth aspects, the entire method is performed in a continuous manner.

[0081] In a third aspect, the present invention provides one or more products produced by the method of the first or second aspect of the present invention, wherein the one or more products are selected from the group consisting of titanium dioxide, magnesium sulfate, a first retentate, calcium sulfate, silicon dioxide, aluminum sulfate, and mixed metal solids.

[0082] In certain embodiments, magnesium sulfate is in the form of MgSO4.7H2O, MgSO4.6H2O, or MgSO4.1H2O. In certain embodiments, aluminum sulfate is in the form of Al2(SO4)3.XH2O, wherein x is 14 to 18. In certain embodiments, calcium sulfate is in the form of CaSO4.2H2O.

[0083] In a fourth aspect, the invention provides one or more liquids or compositions produced by the method of the first or second aspect. In one embodiment, the liquid or composition is a first permeate, a first liquid, a second liquid, a third liquid, a fourth liquid, a fifth liquid, a first composition or a second composition.

[0084] In a fifth aspect, the present invention provides the use of a first permeate produced by the method of the first or second aspect of the invention in the production or recovery of titanium dioxide, aluminium sulphate, calcium sulphate, magnesium sulphate and / or mixed metal solids.

[0085] In a related aspect, the present invention provides a method for recovering titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from a first permeate produced by the method of the first or second aspect, the method comprising separating titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from the permeate or derived composition in any order.

[0086] In a sixth aspect, the present invention provides use of a first liquid produced by the method of the first or second aspect of the present invention in the production or recovery of titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0087] In a related aspect, the present invention provides a method for recovering titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from a first liquid produced by the method of the first or second aspect, the method comprising separating titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from the liquid or derived composition in any order.

[0088] In a seventh aspect, the present invention provides use of a second liquid produced by the method of the first or second aspect of the invention in the production or recovery of titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0089] In a related aspect, the present invention provides a method for recovering titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from a second liquid produced by the method of the first or second aspect, the method comprising separating titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from the liquid or derived composition in any order.

[0090] In an eighth aspect, the present invention provides use of a third liquid produced by the method of the first or second aspect of the present invention in the production or recovery of calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0091] In a related aspect, the invention provides a method for recovering calcium sulfate, magnesium sulfate and / or mixed metal solids from a third liquid produced by the method of the first or second aspect, the method comprising separating calcium sulfate, magnesium sulfate and / or mixed metal solids from the liquid or derived composition in any order.

[0092] In a ninth aspect, the present invention provides use of a fourth liquid produced by the method of the first or second aspect of the invention in the production or recovery of calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0093] In a related aspect, the present invention provides a method for recovering calcium sulfate, magnesium sulfate and / or mixed metal solids from a fourth liquid produced by the method of the first or second aspect, the method comprising separating calcium sulfate, magnesium sulfate and / or mixed metal solids from the liquid or derived composition in any order.

[0094] In a tenth aspect, the present invention provides use of a fifth liquid produced by the method of the first or second aspect of the present invention in the production or recovery of calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0095] In a related aspect, the present invention provides a method for recovering calcium sulfate, magnesium sulfate and / or mixed metal solids from a fifth liquid produced by the method of the first or second aspect, the method comprising separating calcium sulfate, magnesium sulfate and / or mixed metal solids from the liquid or derived composition in any order.

[0096] In an eleventh aspect, the present invention provides use of the first composition produced by the method of the first or second aspect of the present invention in the production or recovery of calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0097] In a related aspect, the present invention provides a method for recovering calcium sulfate, magnesium sulfate and / or mixed metal solids from a first composition produced by the method of the first or second aspect, the method comprising separating calcium sulfate, magnesium sulfate and / or mixed metal solids from the composition or derived composition in any order.

[0098] In a twelfth aspect, the present invention provides the use of a second composition produced by the method of the first or second aspect of the present invention in the production or recovery of titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids.

[0099] In a related aspect, the present invention provides a method for recovering titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from a second composition produced by the method of the first or second aspect, the method comprising continuously separating titanium dioxide, aluminum sulfate, calcium sulfate, magnesium sulfate and / or mixed metal solids from a liquid or derived composition in any order.

[0100] In a thirteenth aspect, the present invention provides the use of a filter cake or sulfated suspension produced by the method of the first or second aspect of the invention in the production or recovery of titanium dioxide, aluminum sulfate, calcium sulfate, silicon dioxide, a first retentate, magnesium sulfate and / or mixed metal solids.

[0101] In a related aspect, the present invention provides a method for recovering titanium dioxide, aluminum sulfate, calcium sulfate, silica, a first retentate, magnesium sulfate and / or mixed metal solids from a first permeate produced by the method of the first or second aspect, the method comprising separating titanium dioxide, aluminum sulfate, calcium sulfate, silica, a first retentate, magnesium sulfate and / or mixed metal solids from the filter cake or the sulfated suspension or derived composition in any order.

[0102] In a fourteenth aspect, the present invention provides a method for recovering one or more products from a composition produced in a process for producing titanium dioxide, the method comprising at least the following steps:

[0103] a) combining calcium carbonate and a composition to produce a composition (A) comprising calcium sulfate; and

[0104] b) separating calcium sulfate from composition (A) to produce calcium sulfate and a composition (B) comprising mixed metal sulfates.

[0105] In one embodiment, the method further comprises the following steps:

[0106] c) separating magnesium sulfate from composition (B) to produce magnesium sulfate and a composition (C) comprising mixed metal sulfates.

[0107] In another embodiment, the method further comprises the following steps:

[0108] d) combining calcium hydroxide and composition (C) to produce a composition (D) comprising mixed metal oxides and / or hydroxides and calcium sulfate; or

[0109] d1) combining magnesium hydroxide and composition (C) to produce a composition (D) comprising mixed metal oxides and / or hydroxides.

[0110] In another embodiment, the method further comprises the following steps:

[0111] e) recovering the mixed metal oxide and / or hydroxide and calcium sulfate, or the mixed metal oxide and / or hydroxide, from composition (D) to produce a mixed metal solid or a mixed metal solid comprising calcium sulfate.

[0112] In a fifteenth aspect, the present invention provides a method for recovering one or more product forms from a composition produced in a process for producing titanium dioxide, the method comprising at least the steps of:

[0113] a) combining calcium carbonate and a composition to produce a composition (A) comprising calcium sulfate; and

[0114] b) separating calcium sulfate from composition (A) to produce calcium sulfate and a composition (B) comprising mixed metal sulfates.

[0115] In one embodiment, the method further comprises the following steps:

[0116] c) combining calcium hydroxide and composition (B) to produce a composition (C') comprising magnesium sulfate, mixed metal oxides and / or hydroxides and calcium sulfate; or

[0117] c1) combining magnesium hydroxide and composition (B) to produce a composition (C') comprising magnesium sulfate and mixed metal oxides and / or hydroxides.

[0118] In one embodiment, the method further comprises the following steps:

[0119] d) separating the mixed metal oxides and / or hydroxides and calcium sulfate, or the mixed metal oxides and / or hydroxides, from composition (C') to produce a mixed metal solid comprising calcium sulfate or a mixed metal solid and a composition comprising magnesium sulfate (D').

[0120] In one embodiment, the method further comprises the following steps:

[0121] e) recovering magnesium sulfate from composition (D') to produce magnesium sulfate.

[0122] In one embodiment of the fourteenth or fifteenth aspect, step a) wherein titanium is in the form of Ti 4+ state and iron is in Fe 2 + In one embodiment, the first composition further comprises one or more oxides and / or hydroxides of aluminum. In this embodiment, step b) may comprise separating calcium sulfate and one or more oxides and / or hydroxides of aluminum and / or titanium from composition (A) to produce calcium sulfate, and one or more oxides and / or hydroxides of aluminum and / or titanium and a composition (B) comprising mixed metal sulfates. In one embodiment, step a) is performed at an ORP of about 270 mV.

[0123] In one embodiment, the composition produced in a process for producing titanium dioxide is an acidic waste composition. In one embodiment, the composition is an acidic composition produced after recovering titanium dioxide in a process for producing titanium dioxide. In one embodiment, the composition is an acidic composition produced after recovering titanium dioxide and aluminum in a process for producing titanium dioxide.

[0124] In a sixteenth aspect, the present invention provides a method for producing a titanium dioxide raw material for a titanium dioxide pigment manufacturing process, the method comprising one of the following:

[0125] - Steps a) to e) of the first aspect;

[0126] - Steps a) to f) of the second aspect.

[0127] In one embodiment, the process further comprises calcining the hydrous titanium dioxide recovered in the process.

[0128] In another aspect, the present invention provides the use of titanium dioxide recovered by the process of the invention as described herein as a titanium dioxide feedstock in a titanium dioxide pigment manufacturing process.

[0129] In one embodiment, the manufacturing process for the titanium dioxide pigment is a chlorination process.

[0130] The present invention also includes parts, elements and features that are referred to or indicated in the specification of the application individually, or parts, elements and features that are referred to or indicated together in any or all combinations of two or more of the parts, elements or features, and if specific integers mentioned herein have known equivalents in the field related to the present invention, these known equivalents are deemed to be incorporated herein as if they were set forth individually.

[0131] Other aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art after reading the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0132] Embodiments of the invention will be described in the specification by way of example only and with reference to the accompanying drawings, in which:

[0133] Figure 1 A process flow diagram depicting one embodiment of the present invention is shown.

[0134] Figure 2 A process flow diagram describing a preferred embodiment of the present invention is shown.

[0135] Figure 3 Process flow diagrams depicting two alternative embodiments of a process according to an aspect of the present invention are shown. DETAILED DESCRIPTION

[0136] The inventors have previously demonstrated novel methods and apparatus for commercially extracting a variety of products from smelter slag. These products may include at least titanium dioxide, aluminum sulfate and magnesium sulfate. In ongoing research, the inventors have discovered many improvements that provide significant advantages for the efficiency and economy of this process and for reducing its impact on the environment. Although the inventors' research has focused on processes for recovering valuable products from smelter slag, they believe that these processes will be equally useful for recovering such products from other titanium-containing materials (including, such as naturally occurring ores, concentrates, other slags, enriched slags, red mud) and compositions produced in the process of producing titanium dioxide.

[0137] definition

[0138] Unless otherwise defined, the following terms used in this specification are defined as follows:

[0139] Throughout the specification and any claims that follow, unless the context requires otherwise, the word "comprise" and variations such as "comprises" and "comprising" and similar words are to be interpreted in an inclusive sense rather than an exclusive sense, that is, in the sense of "including but not limited to."

[0140] As used herein, unless the context requires otherwise, "titanium-containing material" is any suitable material containing titanium dioxide in the form of perovskite. In preferred embodiments, the titanium-containing material also includes one or more of magnesium oxide, aluminum oxide, calcium oxide, silicon dioxide, iron oxide, and vanadium oxide. In certain embodiments, the material also includes manganese oxide and chromium oxide. In one embodiment, the material includes titanium dioxide, magnesium oxide, and aluminum oxide. In another embodiment, the material includes titanium dioxide, magnesium oxide, aluminum oxide, and calcium oxide. In certain embodiments, the titanium-containing material includes slag, enriched slag, ore, and concentrate. In certain embodiments, the slag is ironmaking slag or vanadium-titanium magnetite (VTM) slag. In one embodiment, the ironmaking slag is a melting furnace slag or a blast furnace slag. In another embodiment, the titanium-containing material is red mud. In certain embodiments, the titanium-containing material includes a combination of two or more different forms of titanium-containing materials.

[0141] "Slag" refers to any waste separated from metals in the smelting or refining of an ore. In certain embodiments, the slag is ironmaking slag or vanadium-titanium magnetite slag.

[0142] "Iron making slag" is slag produced from a steel or iron manufacturing process. In certain embodiments, the iron making slag is a melting furnace (or smelting furnace) slag or a blast furnace slag.

[0143] "Upgraded slag" is a material that has had its concentration of target metal oxides increased by separation and removal of one or more other metal species using, for example, pyrometallurgical techniques.

[0144] "VTM slag" is slag obtained during the processing or manufacture of products (such as steel and iron) from VTM-containing materials (such as VTM-containing ores).

[0145] A "concentrate" is a material that has had its concentration of target metal oxide increased by separation and removal of one or more other metal species using a form of enrichment such as gravity separation, flotation or magnetic separation.

[0146] "Ore" is a naturally occurring solid material from which a metal or mineral can be extracted. In one embodiment, the ore is vanadium titanomagnetite.

[0147] The term "cake" is used herein to refer to the solid material comprising titanyl sulfate resulting from the sulfation of the titanium-containing material, and includes reference to the cake in particulate or powder form that may be formed in the process.

[0148] The term "CalSi" may be used in the specification. This term refers to the first retentate of the process of the present invention. CalSi comprises calcium sulfate and silicon dioxide. In certain embodiments, the residue may further comprise unreacted metal oxides.

[0149] The terms "free acid" or "free acidity" refer to the sulfuric acid content of a composition or liquid.

[0150] The term "reactor" includes any device consisting of one or more vessels and / or towers or piping arrangements in which the materials of the present invention can be processed, mixed and / or heated. Examples of reactors of the present invention include continuous or intermittent injection reactors. In a preferred embodiment, one or more reactors are suitable for running a continuous process. In a preferred embodiment, the reactor used in the sulfation step of the various aspects of the present invention is suitable for comminuting the filter cake formed in this step into a powder or granular form.

[0151] "Perovskite" refers to a titanium-calcium oxide mineral composed of calcium titanate, CaTiO3. Perovskites generally have a cubic crystal structure, although the term is intended to refer to any form of calcium titanate as used herein. The terms perovskite and calcium titanate may be used interchangeably.

[0152] The term "water" herein refers to, for example, a solute or a reactant to effectuate the process. A person skilled in the art will appreciate that the term water does not imply the use of pure water; the water may be an aqueous solution containing one or more other components.

[0153] Where reference is made to the concentration or percentage of an element (e.g., iron), one skilled in the art will appreciate that the element is likely bound to other species, such as in an ionic salt such as ferric sulfate. However, analytical techniques may express the total amount of the element in the sample. In these cases, it is the total amount of the element in the sample that is being quoted, bound or unbound.

[0154] "Calcination" refers to the process of heating a substance to a high temperature but below its melting or fusion point, resulting in loss of water, reduction or oxidation, and decomposition of carbonates and other compounds.

[0155] A "product" is any compound or mixture of compounds that can be recovered in the process of the invention; as non-limiting examples, titanium dioxide, magnesium sulfate, aluminum sulfate, calcium sulfate, a first retentate, mixed metal solids. In certain embodiments, a "product" may be one or more liquids or compositions produced in the process of the invention.

[0156] In the case of referring to "recovering" one or more chemical compounds (e.g., in one embodiment, one or more products of the present invention), it should not be considered to mean that the product has been recovered with 100% purity. Similarly, when referring to "purifying" (or similar terms, such as purifying) a particular compound, it should not be considered to mean that the compound has been recovered with 100% purity. It should be understood that compounds may be contaminated to some extent by other compounds and tolerated. Similarly, when referring to "separating" chemical compounds (in one embodiment, such as, one or more products of the present invention) from a composition or liquid or from each other, it should not be considered to mean that one or more compounds are completely separated from each other, liquid or composition. It will be understood that some degree of contamination of each other may exist and be tolerated.

[0157] When referring to the separation of solids from liquids, any suitable means may be used, including, for example, filtration, centrifugation, sedimentation, settling, flotation separation, etc. In certain embodiments, continuous separation methods are preferred. Such methods may utilize, for example, a basket centrifuge or a conical plate centrifuge.

[0158] As used herein, reference to any chemical compound, such as oxides, hydroxides and sulfates of a particular chemical element (e.g., titanium, magnesium, aluminum, calcium, silicon and mixed metals) should be considered to include reference to the compound in any hydrated or anhydrous state, unless the context requires otherwise.

[0159] Reference may be made herein to the recovery, separation and / or production of a "titanium dioxide feedstock for a titanium dioxide pigment manufacturing process". This is intended to cover any suitable composition recovered from the process of the present invention, which contains titanium dioxide and can be fed into a titanium dioxide pigment manufacturing process. Those skilled in the art to which the present invention relates will readily appreciate from the method of the present invention suitable titanium dioxide feedstocks that can be used in a titanium dioxide pigment manufacturing process. However, by way of example, the feedstock may include titanium dioxide hydrate or calcined titanium dioxide recovered from the process of the present invention. In addition, the skilled person will readily appreciate the associated titanium dioxide pigment manufacturing process. However, by way of example, the titanium dioxide feedstock produced by the method of the present invention can be used in a process known as a "chlorination process".

[0160] As used herein, "titanium dioxide hydrate" or similar phrases are intended to encompass compositions containing both titanium dioxide and titanium dioxide hydrate. One skilled in the art will appreciate that the hydrolysis product of titanyl sulfate will be a mixture of titanium dioxide and titanium dioxide hydrate. Unless the context otherwise requires, when the term hydrated titanium dioxide is used herein, it is understood that titanium dioxide may also be present. The same shall be understood for other compounds referred to herein.

[0161] When referring to the proportion, ratio or percentage of titanium dioxide in the raw material, it will be understood by those skilled in the art that the actual form of titanium dioxide may not be a form suitable for purification. For example, in perovskites, titanium dioxide is primarily in the form of calcium titanate (CaTiO3). Where analytical results or text referring to titanium dioxide are provided, these analytical results or text are intended to be understood as the amount of titanium dioxide that may be combined with other elements (e.g., calcium titanate). The same shall be understood for other metal oxides referred to herein.

[0162] The phrase "producing rutile titanium dioxide" or similar language should not be construed to mean that pure 100% rutile titanium dioxide is formed. One skilled in the art will recognize that while the predominant species present will be rutile titanium dioxide, there will be some degree of contamination with contaminants or other forms of titanium dioxide.

[0163] A "dopant" is an impurity added to a substance, usually in relatively small amounts, to alter its crystal growth and morphology change characteristics.

[0164] As referred to herein, "sulphuric acid" can have any concentration and is referred to as the weight to weight percentage (% w / w) concentration in aqueous solution. Other nomenclatures may include m% or just %. These are intended to be used interchangeably and will be understood by those skilled in the art to be so.

[0165] As used herein, "mixed metal solids" refers to the balance of metal species present after the target metal species are removed in the method of the present invention. The mixed metal solids may include, for example, one or more (in one embodiment, a mixture of two or more) metal oxides and / or metal hydroxides. In one embodiment, the mixed metal solids also include calcium sulfate. In certain embodiments, the mixed metal solids may include oxides and / or hydroxides of one or more of titanium, aluminum, magnesium, iron, manganese, vanadium, chromium, niobium and zirconium.

[0166] As used herein, "precipitation", "precipitate" and similar terms refer to a process in which a compound is deposited from solution in solid form. These terms should be considered to include references to crystallising or crystallisation of the compound as well as insoluble products from hydrolysis reactions. Reference to a "precipitate" of a compound refers to the solid resulting from such a precipitation process and should be understood to include reference to the crystalline form of the compound.

[0167] "Composition" shall broadly include mixtures of two or more compounds. The composition may be aqueous, a suspension, or any other form of a mixture of one or more solids and / or liquids. For example, in certain embodiments of the present invention, composition X (e.g., a liquid) may be in aqueous form, and a neutralizing agent is added to form another composition Y. Composition Y may contain one or more solids and liquids, because the presence of the neutralizing agent may precipitate some of the compounds contained in the original composition X. Before the precipitate is separated from the liquid present, it is considered to form part of composition Y.

[0168] It can be mentioned herein to separate or recover a product from a composition or liquid or derivative composition. A "derivative composition" is a composition (including a reference to a liquid) downstream of a particular composition (including a reference to a liquid). For example, in certain embodiments of the present invention, a third liquid is subjected to a step of forming a first composition comprising calcium sulfate. Calcium sulfate is separated from the first composition to produce a fourth liquid comprising a mixed metal sulfate. Magnesium sulfate is then recovered from the fourth liquid to produce magnesium sulfate and a fifth liquid comprising a mixed metal sulfate. In this example, the first composition, the fourth liquid, and the fifth liquid are derivative compositions of the third liquid, the fourth and fifth liquids are derivative compositions of the first composition, and the fifth liquid is a derivative of the fourth liquid.

[0169] References to acid to feedstock ratios are on a weight-to-weight basis; that is, the weight of acid used to react with a given weight of feedstock (eg, ore or slag).

[0170] LL refers to leachate. PHL refers to post-hydrolysis liquid. PAL refers to post-aluminum liquid. PNL refers to post-neutralization liquid. PML refers to post-magnesium liquid. MRL refers to magnesium-rich liquid. This description of the various compositions of the process of the present invention is used herein to aid the reader in understanding the invention and should not be construed as limiting the scope of the invention in any way unless the context clearly requires otherwise.

[0171] This specification may include alternate spellings of the words "sulfur," "sulfation," "sulfate," etc.; for example, such as "sulphur," "sulphation," and "sulphate."

[0172] method

[0173] After extensive analysis, the inventors have devised an improved method for recovering one or more products from titanium-containing materials including perovskites, or a method for recovering products from a composition produced in a titanium dioxide production process. These products include one or more, two or more, three or more, four or more, five or more, six or all of the following: titanium dioxide, aluminum sulfate, magnesium sulfate, calcium sulfate, silicon dioxide, a composition comprising a combination of calcium sulfate and silicon dioxide (e.g., a first retentate), and mixed metal solids. In one embodiment, the product is a feedstock for a titanium dioxide pigment manufacturing process.

[0174] In designing the process of the present invention, the inventors had to overcome many problems and often competing requirements, including, for example: the refractory properties of the perovskite, environmental impact, product recovery efficiency, cost, energy requirements, relative recovery rates of different products, recovery time of different products. For example, if the process is optimized for the recovery of one product, the recovery rate of other products and process efficiency may be compromised, for example. In addition, the amount of waste generated may be undesirable. The inventors believe that the novel combination of steps and / or reagents used in the process of the present invention provides efficient recovery of products at desired yields in a commercially viable manner.

[0175] The inventors have found that the order of steps and / or the combination of reagents used in the process of the present invention is an important factor in optimizing the yield of the most valuable materials. For example, although it is feasible to recover aluminum sulfate from the process before titanyl sulfate hydrolysis in the context of the present invention, the inventors have found that if aluminum sulfate is recovered after titanyl sulfate hydrolysis, the efficiency is higher and the titanium dioxide yield is higher. Therefore, in one embodiment, the latter is preferred.

[0176] Additionally, while it is feasible to recover magnesium sulfate from a process prior to recovering mixed metal solids in the context of the present invention, the inventors have found that magnesium sulfate is more efficient, has a higher yield, and is of higher purity if the mixed metal solids are recovered first. In certain embodiments, this allows for the reduction or elimination of manganese and / or iron content from the magnesium sulfate product. Additionally, the inventors have found that if the mixed metal sulfates are recovered first, the magnesium sulfate crystals are in a more desirable form; for example, the crystals are more easily filtered, and liquid removal is improved.

[0177] In addition, the steps of magnesium sulfate precipitation and recovery are performed after the aluminum sulfate recovery and titanium dioxide recovery. If magnesium sulfate precipitation is performed before the aluminum sulfate or titanium dioxide recovery, the co-precipitation of these components with magnesium sulfate will reduce the economic feasibility of the process and reduce the purity of the product obtainable.

[0178] The inventors have also found that it is advantageous to use a two-step neutralization process in the relevant steps of the process of the present invention, which uses CaCO3 and Ca(OH)2 or Mg(OH)2 as neutralizing agents. The use of CaCO3 and Ca(OH)2 or Mg(OH)2 can gradually increase the pH, which provides optimal conditions for recovering calcium sulfate, mixed metal solids and magnesium sulfate, while minimizing the acidity of any wastewater. This can also improve product quality while minimizing the waste generated. The inventors envision that these steps form a stand-alone method that can effectively recover such products from compositions derived from the process for producing titanium dioxide. This may have the benefit of increasing the utilization of such compositions, which have traditionally been considered waste to be disposed of, thereby allowing more value to be extracted from this process and reducing its impact on the environment.

[0179] Prior to this, the process of the present invention was described in the "Summary of the Invention" section. Further description of various aspects, embodiments and steps of the method are provided below.

[0180] The process of the present invention or one or more individual steps of the process of the present invention can be carried out in a batch mode or in a continuous mode. In a preferred embodiment, one or more steps are carried out in a continuous mode. The skilled person will readily understand methods and equipment that can be used to run continuous steps or processes. In one embodiment, all steps are carried out in a continuous mode. In another embodiment, the leaching step and / or the hydrolysis step are carried out in batches.

[0181] Raw materials (Feedstock)

[0182] On the one hand, the raw material used in the process of the present invention can be any titanium-containing material containing perovskite. However, in certain embodiments, the titanium-containing material is selected from slag, enriched slag, ore, concentrate. In a preferred embodiment, the slag is ironmaking slag. In a specific embodiment, the ironmaking slag is a smelting furnace slag obtained from New Zealand Steel. In other embodiments, the ironmaking slag is a smelting furnace slag obtained from South Africa or a blast furnace slag obtained from China or Russia. In another embodiment, the material is an ore. In certain embodiments, the ore is a natural reserve found in North or South America.

[0183] In certain embodiments, the titanium-containing material comprising perovskite may comprise a combination of two or more different materials. For example, it may include a combination of natural ore and slag.

[0184] In certain embodiments, in addition to perovskite, the titanium-containing material used in the method of the present invention will preferably also include one or more of aluminum oxide and magnesium oxide. In certain embodiments, the material also includes one or more of iron oxide and vanadium oxide. In other embodiments, the material may also include chromium oxide and / or manganese oxide.

[0185] In one embodiment, the titanium-containing material comprises at least about 5% to at least about 65% w / w titanium dioxide. In certain embodiments, the titanium-containing material includes at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65% w / w titanium dioxide. In certain embodiments, the titanium-containing material comprises about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65% w / w titanium dioxide. In certain embodiments, the titanium-containing material comprises about 15% to about 60% titanium dioxide or to about 65% titanium dioxide. In certain embodiments, the titanium-containing material comprises about 30% to about 40% titanium dioxide. In one embodiment, the titanium-containing material comprises about 30% to about 35% w / w titanium dioxide. In another embodiment, the titanium-containing material comprises from about 25% to about 45% titanium dioxide. In one embodiment, the titanium-containing material comprises from about 5% to about 25% titanium dioxide.

[0186] In one embodiment, the titanium-containing material is ironmaking slag, and comprises at least about 5% to at least about 40% w / w titanium dioxide. In certain embodiments, the titanium-containing material comprises at least about 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40% w / w titanium dioxide. In certain embodiments, the ironmaking slag comprises about 5% to about 65%, about 5% to about 60%, about 5% to about 55%, about 5% to about 50%, about 5% to about 45%, about 5% to about 40%, about 5% to about 35%, about 5% to about 30% w / w titanium dioxide. In certain embodiments, the material comprises about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65% w / w titanium carbon dioxide. In certain embodiments, the ironmaking slag comprises about 15% to about 40% w / w titanium dioxide, about 15% to about 35%, or about 15% to about 30% w / w titanium dioxide. In certain embodiments, the ironmaking slag comprises about 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35% titanium dioxide. In other embodiments, the ironmaking slag comprises about 36%, 37%, 38%, 39% or 40% titanium dioxide.

[0187] In another embodiment, the titanium-containing material is an ore and comprises at least about 15% to at least about 60% w / w titanium dioxide. In certain embodiments, the ore comprises at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% w / w titanium dioxide. In certain embodiments, the ore comprises about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% w / w titanium dioxide.

[0188] In another embodiment, the titanium-containing material is an ore concentrate and comprises at least about 15% to at least about 45% or at least about 25% to at least about 45% w / w titanium dioxide. In certain embodiments, the ore concentrate comprises at least about 15%, 20%, 25%, 30%, 35%, 40% or 45% w / w titanium dioxide. In certain embodiments, the ore concentrate comprises about 15%, 20%, 25%, 30%, 35%, 40% or 45% w / w titanium dioxide.

[0189] In another embodiment, the titanium-containing material is red mud and comprises at least about 5% to at least about 25% w / w titanium dioxide. In one embodiment, the red mud comprises about 5% to about 35% titanium dioxide. In certain embodiments, the red mud comprises about 5%, 10%, 15%, 20% or 25% titanium dioxide.

[0190] In one embodiment, the titanium-containing material comprises at least about 2% to at least about 60% w / w calcium oxide. In one embodiment, it comprises about 2% to about 60% calcium oxide. In one embodiment, the titanium-containing material comprises about 5% to about 60% calcium oxide. In one embodiment, the material comprises about 5% to about 25% w / w calcium oxide. In a specific embodiment, the titanium-containing material comprises about 10% to about 20% w / w calcium oxide. In another embodiment, the titanium-containing material comprises about 25% to about 40% w / w calcium oxide. In another embodiment, the titanium-containing material comprises about 10% to about 60% calcium oxide. In another embodiment, the material comprises about 2% to about 10% calcium oxide. In certain embodiments, the titanium-containing material comprises about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% w / w calcium oxide.

[0191] In one embodiment, the titanium-containing material is an ironmaking slag and comprises at least about 5% to at least about 40% w / w calcium oxide. In one embodiment, the slag comprises about 5% to about 40%, about 5% to about 35%, about 5% to about 30%, or about 5% to about 25% w / w calcium oxide. In certain embodiments, the slag comprises about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45% w / w calcium oxide. In a specific embodiment, the slag comprises about 10% to about 30% w / w calcium oxide. In one embodiment, the slag comprises about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35% calcium oxide.

[0192] In another embodiment, the titanium-containing material is an ore and comprises at least about 10% to at least about 60% w / w calcium oxide. In one embodiment, the ore comprises about 10% to about 60% w / w calcium oxide. In certain embodiments, the ore comprises about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% w / w calcium oxide.

[0193] In another embodiment, the titanium-containing material is an ore concentrate and comprises at least about 15% to at least about 40% w / w calcium oxide. In other embodiments, it comprises about 15% to about 40%, about 20% to about 40%, or about 25% to about 40% w / w calcium oxide. In certain embodiments, the ore concentrate comprises about 15%, 20%, 25%, 30%, 35% or 40% w / w calcium oxide.

[0194] In another embodiment, the titanium-containing material is red mud and comprises at least about 2% to at least about 10% w / w calcium oxide. In one embodiment, the red mud comprises about 2% to about 10% w / w calcium oxide. In certain embodiments, the red mud comprises about 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% calcium oxide.

[0195] In one embodiment, the titanium-containing material comprises at least about 1% to at least about 50% w / w silicon dioxide. In one embodiment, the titanium-containing material comprises about 1% to about 50% w / w silicon dioxide. In one embodiment, the material comprises about 1% to about 40% silicon dioxide. In another embodiment, the material comprises about 3% to about 50% silicon dioxide. In certain embodiments, the titanium-containing material comprises about 5% to about 25% w / w silicon dioxide. In a specific embodiment, the titanium-containing material comprises about 10% to about 20% w / w silicon dioxide. In another embodiment, the titanium-containing material comprises about 1% to about 40% silicon dioxide. In another embodiment, the titanium-containing material comprises about 10% to about 35% silicon dioxide. In certain embodiments, the titanium-containing material comprises about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40% w / w silicon dioxide.

[0196] In one embodiment, the titanium-containing material is an ironmaking slag and comprises at least about 5% to at least about 30% w / w silicon dioxide. In one embodiment, the slag comprises about 5% to about 30% w / w silicon dioxide. In certain embodiments, the slag comprises about 5%, 10%, 15%, 20%, 25%, 30% w / w silicon dioxide. In a specific embodiment, the slag comprises about 10% to about 20% w / w silicon dioxide. In one embodiment, the slag comprises about 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30% silicon dioxide.

[0197] In another embodiment, the titanium-containing material is an ore and comprises at least about 1% to at least about 40% w / w silicon dioxide. In one embodiment, the titanium-containing material is an ore and comprises about 1% to about 40% w / w silicon dioxide. In certain embodiments, the titanium-containing material is an ore and comprises about 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40% w / w silicon dioxide.

[0198] In another embodiment, the titanium-containing material is an ore concentrate and comprises at least about 10% to at least about 35% w / w silicon dioxide. In one embodiment, the titanium-containing material is an ore concentrate and comprises about 10% to about 35% w / w silicon dioxide. In certain embodiments, the titanium-containing material is an ore concentrate and comprises about 10%, 15%, 20%, 25%, 30% or 35% w / w silicon dioxide.

[0199] In another embodiment, the titanium-containing material is red mud and comprises at least about 3% to at least about 50% w / w silicon dioxide. In one embodiment, the red mud comprises about 3% to about 50% w / w silicon dioxide. In certain embodiments, the red mud comprises about 3%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 45% or 50% w / w silicon dioxide.

[0200] In one embodiment, the titanium-containing material comprises at least about 0% to at least about 20% w / w magnesium oxide. In one embodiment, the titanium-containing material comprises about 0% to about 20% w / w magnesium oxide. In one embodiment, the titanium-containing material comprises about 1% to about 20% or 5% to about 20% magnesium oxide. In another embodiment, the material comprises about 10% to about 15% magnesium oxide. In another embodiment, the material comprises about 1% to about 5% magnesium oxide. In certain embodiments, the titanium-containing material comprises about 1%, 2%, 3%, 4%, 5%, 10%, 15% or 20% w / w magnesium oxide.

[0201] In one embodiment, the titanium-containing material is an ironmaking slag and comprises at least about 5% to about 20% w / w magnesium oxide. In certain embodiments, the titanium-containing material comprises about 5%, 10%, 15% or 20% w / w magnesium oxide. In a specific embodiment, the titanium-containing material comprises about 10% to about 15% w / w magnesium oxide. In one embodiment, the titanium-containing material comprises about 10%, 11%, 12%, 13%, 14% or 15% magnesium oxide.

[0202] In another embodiment, the titanium-containing material is an ore and comprises at least about 0% to at least about 5% magnesium oxide. In one embodiment, the ore comprises about 0% to about 5% magnesium oxide. In one embodiment, the ore comprises at least about 1% to at least about 5% magnesium oxide. In one embodiment, the ore comprises about 1% to about 5% magnesium oxide. In certain embodiments, the ore comprises about 1%, 2%, 3%, 4% or 5% w / w magnesium oxide.

[0203] In another embodiment, the titanium-containing material is an ore concentrate and contains at least about 1% to at least about 5% magnesium oxide. In one embodiment, the ore concentrate contains about 1% to about 5% magnesium oxide. In certain embodiments, the ore contains about 1%, 2%, 3%, 4% or 5% w / w magnesium oxide. In one embodiment, the ore concentrate comprises about 2% to about 3%, for example 2.5%.

[0204] In one embodiment, the titanium-containing material comprises at least about 0% to at least about at least about 25% w / w aluminum oxide. In one embodiment, the material comprises about 0% to about 25% aluminum oxide. In one embodiment, the material comprises about 10% to about 25% w / w aluminum oxide. In a specific embodiment, the material comprises about 15% to about 20% w / w aluminum oxide. In another embodiment, the material comprises about 10% to about 20% w / w aluminum oxide. In another embodiment, the material comprises about 0% to about 15% aluminum oxide. In one embodiment, the material comprises about 1% to about 15% aluminum oxide. In another embodiment, the material comprises about 1% to about 10% aluminum oxide. In certain embodiments, the material comprises about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or 25% alumina.

[0205] In one embodiment, the titanium-containing material is an ironmaking slag and contains at least about 10% to at least about 25% w / w alumina. In one embodiment, the slag contains about 10% to about 25% w / w alumina. In certain embodiments, the slag contains about 10%, 15%, 20%, 25% w / w alumina. In a specific embodiment, the slag contains about 10% to about 20% w / w alumina. In one embodiment, the slag contains about 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% alumina.

[0206] In another embodiment, the titanium-containing material is an ore and comprises at least about 0% (or at least about 1%) to at least about 15% alumina. In one embodiment, the ore comprises about 0% (or about 1%) to about 15% alumina. In one embodiment, the ore comprises at least about 1% to at least about 10% alumina. In one embodiment, the ore comprises about 1% to about 10% alumina. In certain embodiments, the ore comprises about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% w / w alumina.

[0207] In another embodiment, the titanium-containing material is an ore concentrate and contains at least about 1% to at least about 10% alumina. In one embodiment, the concentrate contains about 1% to about 10% alumina. In certain embodiments, the ore contains about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% w / w alumina. In one embodiment, the concentrate contains about 5% to about 8% alumina.

[0208] In one embodiment, the titanium-containing material is red mud and comprises at least about 10% to at least about 20% alumina. In one embodiment, the red mud comprises about 10% to about 20% alumina. In certain embodiments, the red mud comprises about 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% alumina.

[0209] In one embodiment, the titanium-containing material comprises at least about 0% to at least about 60% w / w of iron oxide. In one embodiment, the titanium-containing material comprises about 0% to about 60% w / w of iron oxide. In one embodiment, the material comprises about 30% to about 60% w / w of iron oxide. In one embodiment, the titanium-containing material comprises about 0% to about 10% w / w of iron oxide. In one embodiment, the titanium-containing material comprises about 1% to about 5% w / w of iron oxide. In certain embodiments, the titanium-containing material comprises about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% w / w of iron oxide. In other embodiments, the material comprises about 30%, 35%, 40%, 45%, 50%, 55% or 60% of iron oxide.

[0210] In one embodiment, the titanium-containing material is an ironmaking slag and comprises at least about 0% to at least about 10% w / w iron oxide. In one embodiment, the slag comprises about 0% to about 10% iron oxide. In one embodiment, the slag comprises at least about 1% to at least about 5% iron oxide. In one embodiment, the slag comprises about 1% to about 5% iron oxide. In certain embodiments, the slag comprises about 1%, 2%, 3%, 4%, 5% or 6% iron oxide.

[0211] In another embodiment, the titanium-containing material is an ore or ore concentrate and contains at least about 0% to at least about 10% w / w iron oxide. In one embodiment, the ore or ore concentrate contains about 0% to about 10%, or about 0% to about 5% iron oxide. In certain embodiments, the ore or ore concentrate contains about 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% iron oxide.

[0212] In one embodiment, the titanium-containing material is red mud and comprises at least about 30% to at least about 60% iron oxide. In one embodiment, the red mud comprises about 30% to about 60% iron oxide. In certain embodiments, the red mud comprises about 30%, 35%, 40%, 45%, 50%, 55% or 60% w / w iron oxide.

[0213] In other embodiments, the titanium-containing material also includes vanadium oxide. In certain embodiments, the material includes at least about 0% to at least about 2% vanadium oxide. In one embodiment, the material includes about 0% to about 2% vanadium oxide. In certain embodiments, the material is ironmaking slag, ore or ore concentrate, and includes about 0% to about 1%, or about 0% to about 0.5%, or about 0.25% to 0.5% vanadium oxide. In certain embodiments, slag, ore or ore concentrate includes about 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1% vanadium oxide.

[0214] In one embodiment, the titanium-containing material feedstock is ironmaking slag produced during the manufacture of iron or steel. An example of ironmaking slag composition is provided in Table 1 below, which details the composition of furnace slag produced by the steel production process of New Zealand Steel (NZSteel) in New Zealand. Each value was determined using X-ray fluorescence analysis technology.

[0215] Table 1: NZ Steel Melter Slag

[0216] Element m％ <![CDATA[TiO2]]> 32.1-33.3 <![CDATA[Al2O3]]> 17.8-19 MgO 13.2-13.3 CaO 15.5-15.9 <![CDATA[SiO2]]> 12.8-15.2 <![CDATA[Fe2O3]]> 2.34-3.9 <![CDATA[V2O5]]> 0.2

[0217] Further examples of ironmaking slag compositions are provided in Table 14 of the "Examples" section herein.

[0218] In a preferred embodiment, the titanium-containing material is slag and comprises about 15% to about 65% titanium dioxide, about 5% to about 40% calcium oxide, about 5% to about 20% magnesium oxide, and about 10% to about 25% aluminum oxide. In one embodiment, the slag also comprises about 5% to about 30% silicon dioxide.

[0219] In one embodiment, the ratio of titanium dioxide to calcium oxide (TiO2:CaO) in the titanium-containing material is from about 0.2 to about 3. In certain embodiments, the ratio is from about 0.2 to about 2.5 or from about 0.2 to about 2.

[0220] In one embodiment, the ratio of titanium dioxide to magnesium oxide (TiO2:MgO) in the titanium-containing material is from about 0.5 to about 25. In another embodiment, the ratio is from about 0.5 to about 18. In one embodiment, the ratio is from about 0.5 to about 10. In certain embodiments, the ratio is from about 0.7 or about 0.8 to about 3 or about 4, or from about 4 to about 10.

[0221] In one embodiment, the ratio of titanium dioxide to aluminum oxide (TiO2:Al2O3) in the titanium-containing material is from about 0.2 to about 21. In another embodiment, the ratio is from about 0.2 to about 6. In another embodiment, the ratio is from about 0.2 to about 2.6. In one embodiment, the ratio is from about 0.5 to about 2.5. In another embodiment, the ratio is from about 1 to about 5.

[0222] In a preferred embodiment, the titanium-containing material is slag and comprises a ratio of titanium dioxide to aluminum oxide of about 0.5 to about 2.5, a ratio of titanium dioxide to calcium oxide of about 0.2 to about 2.5, and a ratio of titanium dioxide to magnesium oxide of about 0.7 to about 4. In a preferred embodiment, the titanium-containing material is slag (e.g., ironmaking slag or VTM slag).

[0223] The titanium-containing material feedstock for the process of the present invention may be used in any suitable form and / or may be processed from its original state in one or more ways prior to being fed into the process of the present invention, as will be appreciated by those skilled in the art. Those of ordinary skill in the art. By way of example only, the titanium-containing material may be subjected to a beneficiation process to remove or reduce dirt or clay or one or more unwanted compounds, for example, to be concentrated or processed into a granular form prior to being fed into the process of the present invention. In a preferred embodiment, the titanium-containing material is in granular form. Granular material may be prepared according to known methods, such as grinding.

[0224] In a particular embodiment, the material is in the form of a granular material having a particle size sufficient to allow sulfuric acid to contact each metal oxide within the titanium-containing material that is to be recovered as a product by the process of the present invention. In one embodiment, the average particle size of the particular material is less than 180 μm. In a preferred embodiment, the average particle size of the granular material is 10 to 180 μm, or 40 to 110 μm. In a particular embodiment, the average particle size of the granular material is about 30 μm, 45 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm. In one embodiment, the titanium-containing material is processed to a target size having a D 90 of about <250 microns.

[0225] In certain embodiments, the method of the present invention further comprises the step of grinding the titanium-containing material before step a) of the method of the first or second aspect. One of ordinary skill in the art will readily appreciate the method of grinding the titanium-containing material and measuring the particle size. However, for example, a ball mill may be used for grinding and / or laser diffraction may be used to measure the particle size.

[0226] Metal sulphation

[0227] In one embodiment, the titanium-containing material and the desired amount of sulfuric acid are combined to form a sulfated mixture in a sulfation reaction. For example, the material is introduced into a suitable reactor where it is mixed with sulfuric acid. These conditions can convert the oxide present in the feedstock into sulfates in the following reaction, for example:

[0228] Al2O3+3H2SO4→Al2(SO4)3+3H2O

[0229] MgO+H2SO4→MgSO4+H2O

[0230] TiO2+H2SO4→TiOSO4+H2O

[0231] Fe2O3+3H2SO4→Fe2(SO4)3+3H2O

[0232] CaO+H2SO4→CaSO4+H2O

[0233] Any Si present does not react

[0234] In one embodiment, water is added to initiate an exothermic reaction, and upon addition of water, the temperature in the reactor increases to about 100°C or more. In one embodiment, external heating may also be applied. External heating may be applied using any known means. However, for example, by adding heated air or steam, using a jacketed reactor with heated hot fluid or a jacketed reactor with steam, indirect infrared heating, or contact electric tracing.

[0235] In another embodiment, for example where the sulfation step is performed continuously, the titanium-containing material is premixed with the desired amount of sulfuric acid and the mixture is fed into the reactor. In one embodiment, the material is premixed with the desired amount of sulfuric acid, water is added, and the mixture is then fed into the reactor. In one embodiment, the reactor is preheated. The reactor may be heated using any known means, including those illustrated in the immediately preceding paragraph. In one embodiment, the reactor is preheated to about 100° C. In another embodiment, for example where the process is continuous or semi-continuous, the reactor is operated at the desired sulfation temperature.

[0236] Although a variety of sulfation conditions may be used in this step of the process of the present invention to convert oxides present in the titanium-containing material to sulfates, the inventors have found that the use of the specific conditions outlined herein, and in particular a combination of these conditions, allows for efficient recovery of titanium dioxide, in particular pigmentary grade titanium dioxide, from titanium-containing feedstocks. In particular, the inventors believe that these conditions have the advantage of improving the quality of the leachate produced in the leaching step, and therefore improving the efficiency of the subsequent titanium dioxide hydrolysis step. The inventors believe that these conditions are particularly suitable for feedstocks that may be low in titanium dioxide, such as slag.

[0237] The reaction is preferably carried out at atmospheric pressure and external heat is applied to bring the sulfated mixture to a temperature of about 130° C. to about 250° C. In one embodiment, the temperature is about 130° C. to about 220° C. In a preferred embodiment, the temperature is about 170 or about 180 to about 210° C. In a preferred embodiment, the temperature is about 210° C. or less.

[0238] The reaction is continued for a time sufficient to convert the desired amount of oxides present in the feedstock into sulfates. In one embodiment, the reaction is carried out for a time sufficient to convert at least about 70%, 75%, 80% or at least about 85% or about 90% of the oxides in the slag into sulfates.

[0239] In one embodiment, react (i.e. keep the mixture of temperature), or the mixture of sulfation is included in the reactor, and lasts about 30 minutes to about 4 hours.In a specific embodiment, the reaction is carried out for about 30 minutes to about 4 hours.In a preferred embodiment, the reaction is carried out for about 3 hours, for example, about 30 minutes to about 3 hours.In another preferred embodiment, the reaction is carried out for about 2 hours, for example, about 30 minutes to about 2 hours, about 30 minutes to about 90 minutes, or about 30 minutes to about 1 hour.In another preferred embodiment, the reaction is carried out less than about 2 hours.In some preferred embodiments, the reaction times is about 30 minutes, about 45 minutes, about 60 minutes, about 75 minutes, about 90 minutes, about 105 minutes or about 2 hours.In another embodiment, the reaction times is about 3 hours or about 4 hours.

[0240] In a particularly preferred embodiment of the present invention, the reactor is a continuous reactor. Any suitable continuous reactor can be used in the present invention. However, when the reaction is complete, the sulfate solidifies in the reactor, so the continuous reactor is preferably suitable for converting the solid reaction product into a granular or powdered sulfate filter cake that can move in the reactor. In a preferred embodiment, a pug mill or reactor suitable for continuous mixing can be used. In a preferred embodiment, the feed is continuously added to the reactor, and the filter cake of the reaction is also continuously removed at a rate that allows appropriate reaction time. In one embodiment, the reaction time is as described in the previous paragraph, preferably up to three hours, more preferably up to about 2 hours or less than two hours.

[0241] The concentration of sulfuric acid used in the sulfation reaction is preferably at least about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or at least about 98%. In a preferred embodiment, the concentration of sulfuric acid used is about 75% to about 98%, more preferably about 80% to about 95% or about 80% to about 90%.

[0242] The ratio of sulfuric acid to titanium-containing material used in the sulfation reaction is preferably from about 0.75: 1 to about 2: 1. In one embodiment, the ratio is greater than about 1.3: 1. In a preferred embodiment, the ratio of sulfuric acid to titanium-containing material is from about 1.3: 1 to about 1.7: 1, such as about 1.3: 1, about 1.4: 1, about 1.5: 1, about 1.6: 1 to about 1.7: 1.

[0243] In a preferred embodiment, the reaction is carried out at a temperature of about 170 to about 210 degrees Celsius, using about 75% to about 98% (preferably about 80% to about 95% or about 80% to about 90%, such as 75%, 80%, 85%, 90% or 95%) sulfuric acid. The reaction is preferably carried out for a time of up to about 3 hours (or up to or less than about 2 hours, such as about 30, about 45, about 60, about 75, about 90, about 105). The ratio of sulfuric acid used to titanium-containing material is preferably about 0.75:1 to 2:1 (more preferably higher than about 1.3:1, or about 1.3:1 to 1.7:1, such as 1.4:1, 1.5:1, 1.6:1 or 1.7:1). In these preferred embodiments, the reactor used is preferably a reactor suitable for converting the solid reaction product into a granular or powdered sulfate filter cake. In a preferred embodiment, the titanium-containing material is a slag, more preferably an ironmaking slag or a VTM slag.

[0244] In certain embodiments, at least a portion of the sulfuric acid used in the method of the present invention is produced by a sulfur burner, which is co-located at the position where the process of the present invention is performed. For example, any sulfur waste gas produced from the sulfation step of the process of the present invention can be captured and fed into the sulfur burner to produce sulfuric acid, which can be fed back into the sulfation step. The sulfur burner will also produce heat and energy, which can also be used in one or more steps of the process of the present invention to reduce external energy requirements. In addition, the steam produced can be used for the heating requirements in the process of the present invention or for the jet milling of titanium dioxide recovered in the process of the present invention. One or more integrated sulfur burners in these ways can help reduce the carbon footprint of the entire process.

[0245] Leaching

[0246] The powdered sulfate filter cake from the sulfation reaction is subjected to a leaching step to extract at least sulfate species from the filter cake.

[0247] In one embodiment, the leaching step comprises mixing the filter cake with water to form a sulfated suspension. In a preferred embodiment, this step may also involve adding some sulfuric acid to the water: filter cake mixture to avoid premature hydrolysis of the TiO2. Therefore, in an alternative embodiment, this step comprises mixing the filter cake with dilute sulfuric acid to form a sulfated suspension.

[0248] In one embodiment, a reagent such as iron or aluminum is added to the mixture to reduce the oxidation-reduction potential (ORP) in the liquid. In one embodiment, the ORP is reduced to about -50 mV to about -250 mV, for example about -100 mV. In another embodiment, the ORP is reduced from a positive value to zero or below. In another embodiment, where the process of the present invention is performed at a location co-located with a facility having a coke oven (e.g., an ironmaking or steel manufacturing plant), a reducing gas from the coke oven may be fed into the leachate and bubbled through the leachate mixture, instead of or in addition to using a reducing agent such as an iron or aluminum reagent. Integrating the coke oven in this manner can help reduce the carbon footprint of the overall process.

[0249] The leaching step can be carried out at any suitable temperature. However, in a preferred embodiment, it is carried out at about 30°C to about 95°C. In one embodiment, it is carried out at about 30°C to about 80°C. In certain embodiments, it is carried out at about 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C.

[0250] The water is preferably mixed with the filter cake in a ratio of about 0.75:1 to about 2:1, such as about 1:1. If dilute sulfuric acid is used, its concentration is about 0.05% or about 0.1% to about 15% of the liquid from which the filter cake is leached. In one embodiment, sulfuric acid is used at a concentration of about 0.1% to about 15% of the liquid from which the filter cake is leached. In other embodiments, a concentration of about 0.5% to about 15%, about 5% to about 15%, or about 5% to about 10% is used. In one embodiment, where dilute sulfuric acid is used, the pH of the liquid from which the filter cake is leached is about 2 or less.

[0251] The leaching step is performed for a sufficient time to allow the desired level of sulfate species to be extracted from the filter cake. In one embodiment, leaching is performed for a sufficient time to allow at least about 70%, 75%, 80%, 85%, 90%, or 95% of the sulfate species to be extracted from the filter cake. In a preferred embodiment, at least about 90% of the sulfate species are extracted. In certain embodiments, leaching is performed for a time of about 30 minutes to about 4 hours. In one embodiment, leaching is performed for about 30 minutes, 1 hour, 2 hours, 3 hours, or 4 hours.

[0252] As will be readily appreciated by those skilled in the art, leaching may be performed in any suitable vessel.

[0253] Sulfate species present in the titanium-containing material (including, for example, titanyl sulfate, magnesium sulfate, aluminum sulfate) will dissolve during the leaching process, in addition to CaSO4, SiO2 and any other unreacted oxides.

[0254] In one embodiment, the permeate (e.g., liquid) produced by the leaching step of the method of the present invention comprises about 120 g or less of titanium dioxide / L of permeate in terms of titanium equivalent, such as about 30 to about 120 g of titanium dioxide / L of permeate, about 40 to about 110 g of titanium dioxide / L of permeate, or about 50 to about 100 g of titanium dioxide / L of permeate. In other embodiments, the composition comprises about 100 g or less of titanium dioxide / L of permeate, such as about 95, 90, 85, 80, 75, 70, 65, or 60 g / L or less of titanium dioxide / L of permeate. In one embodiment, the raw material used in these embodiments is slag, preferably ironmaking slag or VTM slag.

[0255] Separation of the first permeate and the first retentate

[0256] The sulfated suspension is subjected to a separation step to separate the dissolved sulfate species (e.g., titanyl sulfate, magnesium sulfate, aluminum sulfate) from the insoluble compounds (i.e., to separate the solid from the liquid). Filtration is preferred, but other methods may be used. The separation produces a first permeate comprising at least titanyl sulfate (and preferably magnesium sulfate and aluminum sulfate) and a first retentate comprising at least CaSO4 and SiO2. The first retentate may contain other unreacted oxides (e.g., silicates) due to encapsulation by refractory materials or due to incomplete reaction of the feed.

[0257] As known to those skilled in the art, any suitable filtering means can be used to filter the sulfated mixture. However, for example, the filtering device may include a filter and a filter press. In one embodiment, the filtering unit is assisted by a pressure gradient on the filter. Preferably, the pressure difference is at least 1 bar. In a specific embodiment, the mixture is circulated through a filtering unit that allows liquid to pass through, while solids are collected on the surface of the filter. In a specific embodiment, the pressure difference on the filter is 2 to 10 bars. Preferably, the pressure difference is about 6 bars. In other examples, the filtration may include: thickening, followed by drum filtration; centrifugation and vacuum belt filtration. Filter aids, such as perlite, can be used to facilitate filtration.

[0258] The separation step is performed for a sufficient time to allow the first permeate and the first retentate to be fully separated. However, in certain embodiments, the separation step is performed for a time of about 15 minutes to about 3 hours, such as about 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours or 3 hours.

[0259] The separation step is carried out at a temperature above the freezing point of the metal salt in the liquid.

[0260] Calcium Sulfate / Silica Recovery

[0261] The titanium-containing material as a raw material for the process of the present invention contains perovskite. Such raw materials include a certain amount of silicon dioxide and calcium oxide. These components are relatively low in value and are generally regarded as problematic wastes, contaminating compositions containing high-value materials (such as titanium dioxide). However, through extensive experiments, the inventors have found that these components can be extracted in the form of silicon dioxide and calcium sulfate, respectively. Both products have uses in industry. The inventors have found that the sulfation of calcium oxide and its removal as an insoluble residue before the hydrolysis of titanium sulfate provide a particularly effective and cost-effective method for recovering these components. In addition, in any subsequent method steps, the removal of the insoluble residue containing silicon dioxide and calcium sulfate can increase the purity of the recovered titanium dioxide and any aluminum sulfate and magnesium sulfate present. Overall, these steps and their sequence help to provide a creative, cost-effective and industrially effective method for recovering the product with minimal waste.

[0262] In the process of the present invention, the first retentate can be recovered in this form (i.e., a combination of silica and calcium sulfate and any other compounds that may be present) for future use. For example, in one embodiment, the first retentate comprising calcium sulfate and silica is preferably washed with a mixture of water and a compound that is capable of at least partially and preferably substantially neutralizing any acid present. In one embodiment, the compound is CaO or Ca(OH)2. A second filtration step is then performed to form a solid rich in CaSO4:SiO.

[0263] In another embodiment, one or more additional processing steps may be used to recover calcium sulfate and / or silica, respectively, from the first retentate or the CaSO4:SiO-rich solid.

[0264] After recovery, the first retentate, calcium sulfate and / or silica may be further processed using standard methods, taking into account its intended use. However, for example, the product may be washed or re-pulped (or re-pulped) and re-filtered. As a further example, it may be dried.

[0265] Titanyl sulfate hydrolysis

[0266] The hydrolysis of titanyl sulfate present in the first permeate (or first liquid) occurs by the following reaction: TiOSO4 + H2O → → → TiO2 + H2SO4. The oxide form of titanium can then be separated from other materials present in the composition in which it resides, such as the first permeate (first aspect of the invention) or liquid (second aspect of the invention).

[0267] As known to the skilled person, the hydrolysis may take place by the Mecklenburg process or the Blumenfeld process. However, by way of example, such processes are described in US 1758528 and US 1795467, respectively.

[0268] In one embodiment, a composition comprising titanyl sulfate (e.g., a first permeate (first aspect of the invention) or a liquid (second aspect of the invention)) is contacted with water to form another composition comprising titanium dioxide hydrate (e.g., a first liquid (first aspect of the invention) or a second liquid (second aspect of the invention)) using the Blumenfeld process. In this embodiment, water may be used in any suitable volume to allow a desired or sufficient amount of hydrolysis to occur.

[0269] In a preferred embodiment, the Mecklenburg process is used, and the hydrolysis reaction occurs by contacting the first permeate or the first liquid with the TiO2 core. The titanium dioxide particles act as nucleation sites for crystallization, thereby achieving uniform particle formation. Those skilled in the art will readily understand the core used in the present invention and the method for producing them, particularly in view of the Mecklenburg process referred to herein. However, in one embodiment, the TiO2 core can be anatase or rutile. In another embodiment, there is a mixture of anatase and rutile seed crystals. Preferably, the particle size of the TiO2 core is 2nm to 10nm, more preferably 3 to 6nm or about 5nm.

[0270] In a preferred embodiment, the TiO2 cores are suspended in water and the mixture of cores and water is contacted with a composition comprising titanyl sulfate (e.g., a first permeate (first aspect of the invention) or a first liquid (second aspect of the invention). As will be appreciated by those skilled in the art, the TiO2 core:water mixture may comprise any suitable concentration of TiO2 cores.

[0271] The volume of TiO2 cores and / or water added to the composition comprising titanyl sulfate (e.g., the first permeate (first aspect of the invention) or the first liquid (second aspect of the invention)) can vary, but, in one embodiment, the volume used is calculated based on the predicted amount of TiO2 produced by the hydrolysis reaction.

[0272] The hydrolysis reaction is preferably carried out at elevated temperature and atmospheric pressure. In certain embodiments, the first liquid is heated to a hydrolysis reaction temperature of about 75 to about 120°C, about 80 to about 120°C, about 85 to about 110°C, about 90 to about 110°C, about 90 degrees Celsius to about 105°C.

[0273] The reaction temperature is maintained for a sufficiently long time to allow the desired TiO2 yield to be formed. In a specific embodiment, the reaction is maintained at a temperature for a period of time to allow at least about 70%, at least about 80%, at least about 85%, at least about 90% or at least about 95% TiO2 yield to be produced from TiOSO4. In one embodiment, the temperature is maintained for a period of time to allow TiOSO4 to be substantially completely hydrolyzed into TiO2. In other embodiments, the temperature is maintained for a time sufficient to allow about 70%, 75%, 80%, 85%, 90% or 95% hydrolysis. Those skilled in the art will be able to determine the TiO2 yield using standard procedures. In certain embodiments, the reaction temperature is preferably maintained for a period of time of about 60 minutes to about 3 hours, about 90 minutes to about 3 hours, about 90 minutes to about 2 hours, about 60 minutes, about 100 minutes, about 2 hours or about 3 hours.

[0274] The hydrolysis reaction can be carried out in any suitable container known to those skilled in the art. However, for example, it is a tank. For example, the first permeate (first aspect of the invention) or the first liquid (second aspect of the invention) is fed into the hydrolysis tank from the leaching step. The temperature of the first permeate or the first liquid is then raised to the desired temperature, TiO2 cores, water and / or a TiO2 core: water mixture is added to the first permeate (first aspect of the invention) or the first liquid (second aspect of the invention) to form the first liquid or the second liquid (respectively), and then the temperature is raised to the hydrolysis temperature and the temperature is maintained at this temperature for a sufficient time to convert the desired amount of titanyl sulfate into hydrated TiO2.

[0275] In one embodiment, the composition used in this step of the method of the present invention (leaching solution, such as the first permeate or the first liquor) contains a titanium equivalent of about 120 g or less of titanium dioxide / L of composition, for example, about 30 to about 120 g of titanium dioxide / L of composition, about 40 to about 110 g of titanium dioxide / L of composition, or about 50 to about 100 g of titanium dioxide / L of composition. In other embodiments, the composition contains about 100 g or less of titanium dioxide / L of composition, such as about 95, 90, 85, 80, 75, 70, 65 or 60 g / L or less of titanium dioxide / L of composition. In one embodiment, the raw material used in these embodiments is slag, preferably ironmaking slag or VTM slag.

[0276] Separation of hydrated titanium dioxide from liquids

[0277] Separation of the hydrated titanium dioxide from the composition (e.g., the first liquid) in which it resides can be accomplished by any of a variety of methods known to those skilled in the art. In particular embodiments, separation is performed in a separation unit adapted to receive the composition (e.g., the first liquid, or in other embodiments, the second liquid) and the titanium dioxide hydrate is isolated.

[0278] In a particular embodiment, the separation unit comprises a filtration unit adapted to receive a liquid and produce a retentate comprising titanium dioxide hydrate and a permeate comprising one or more of aluminum sulfate, magnesium sulfate and other metal sulfates. In an alternative embodiment, the separation unit comprises a centrifugation unit adapted to separate titanium dioxide hydrate.

[0279] In certain embodiments, the separated hydrated titanium dioxide may then be washed prior to further processing. The inventors contemplate that the washing step removes any soluble material and excess unbound acid from the TiO2.H2O.H2SO4 material.

[0280] In one embodiment of the present invention, the separated hydrated titanium dioxide may be optionally bleached. As known to those skilled in the art, this may occur in any suitable container. After bleaching, the TiO2 hydrate may be filtered and washed with water.

[0281] The TiO2 hydrate produced in the process of the present invention can be used as a raw material for the titanium dioxide pigment manufacturing process.

[0282] TiO2 calcination

[0283] The titanium dioxide recovered from the hydrolysis reaction may be calcined (heated) in an oxidizing environment which removes any remaining sulfuric acid and water.

[0284] As known to those skilled in the art, calcination may be carried out in any suitable equipment. Typically, calcination will involve passing heated air through the product in the relevant equipment.

[0285] The temperature and heating time can be any amount and time sufficient to remove the desired level of sulfuric acid and water from the hydrated TiO2. In a preferred embodiment, in a suitable reactor, the titanium dioxide is heated to a temperature of about 800 to about 1100°C, about 800 to about 1050°C, about 850 to about 1050°C, about 900 to about 1000°C, or about 800 to about 900°C. In certain embodiments, the temperature is about 800, 810, 820, 830, 840, 850, 860, 870, 880, or 900°C. In certain embodiments, the heating time is about 30 minutes to about 4 hours. In a preferred embodiment, the heating time is about 30 minutes to about 2 hours, about 45 minutes to about 1 hour and 45 minutes, about 1 hour to about 1 hour and 30 minutes.

[0286] In certain embodiments, the TiO2 hydrate is calcined in the presence of one or more dopants. In one embodiment, the doping is performed while the TiO2 passes through a calcining bed. Any one or more suitable dopants may be used. However, in certain embodiments, magnesium, phosphorus, zinc, aluminum, and / or potassium may be used.

[0287] After calcination, the titanium dioxide product can be further processed or finished to the desired specifications to achieve its intended end use. Those skilled in the art will readily understand such finishing steps. However, for example, the calcined titanium dioxide can be ground, coated and washed. In certain embodiments, finishing the product using standard equipment known in the art will include dry grinding, wet grinding, coating, filtering, drying and micronization.

[0288] The calcined titanium dioxide produced in the process of the present invention can be used as a raw material for a titanium dioxide pigment manufacturing process.

[0289] Aluminum sulfate recovery

[0290] Aluminium sulphate is recovered from the process of the invention at an appropriate stage. In one embodiment, aluminium sulphate is precipitated and separated from the second liquid (or post-titanium hydrolysis liquid (PHL)) after the hydrolysis of titanyl sulphate to TiO2 hydrate. In another embodiment, aluminium sulphate is precipitated and separated from the first permeate before the hydrolysis of titanyl sulphate to TiO2 hydrate.

[0291] The inventors have found that a higher yield of titanium dioxide can be achieved by performing aluminum sulfate precipitation after hydrolysis and removal of titanium dioxide. It is believed that if aluminum sulfate precipitation is performed before hydrolysis, the aluminum sulfate will lose some titanyl sulfate, thereby reducing the yield of TiO2, although this is still a viable option in the context of the present invention. In addition, the inventors have found that the increased acidity in the post-hydrolyzate liquid (PHL) after titanium hydrolysis helps the recovery of aluminum sulfate. If aluminum sulfate is recovered first, there may be process advantages, such as not having to keep the leachate heated to prevent the liquid from freezing due to the higher metal salt content.

[0292] Aluminum sulfate may be recovered from the process of the present invention using any suitable method as will be understood in the art. However, for example, it may be precipitated and then separated from the liquid in which it resides (e.g., in one embodiment, the post-aluminum liquid (PAL), or in another embodiment, the first liquid). In certain embodiments, precipitation may occur by cooling to a temperature at which aluminum sulfate precipitates. In one embodiment, a composition comprising aluminum sulfate is heated to a temperature at which aluminum sulfate is soluble and then cooled to precipitate and recover the aluminum sulfate in the composition. For example, it may be precipitated by cooling to about 4°C to about 10°C, preferably about 5°C. In another embodiment, precipitation occurs at ambient temperature (e.g., about 15°C to about 30°C, such as about 25°C). In one embodiment, the temperature is gradually reduced over time to a selected temperature (e.g., 25°C) to precipitate aluminum sulfate. In another embodiment, evaporative crystallization may be employed; for example, using vacuum concentration. In one embodiment, a combination of concentration of the liquid and precipitation by cooling may be employed; for example, as described in the "Examples" section of this document.

[0293] In certain embodiments, this step may be seeded with aluminum sulfate seeds. This may aid in the filterability of the resulting slurry and, therefore, in the separation of the precipitated aluminum sulfate. A skilled artisan will readily appreciate the use of aluminum sulfate seeds in the present invention. However, by way of example, the seeds may be aluminum sulfate initially crystallized from a solution of pure aluminum sulfate and sulfuric acid, or aluminum sulfate obtained in the process of the present invention and recycled back to this step. In a preferred embodiment, the reaction is seeded with about 2% to about 20% of the expected aluminum sulfate yield.

[0294] Separation of the precipitated aluminum sulfate can be carried out by any of a number of known methods. However, for example, it can include filtration, centrifugation, sedimentation and / or deposition. In a preferred embodiment, filtration is used. For example, belt filtration.

[0295] In certain embodiments, at least about 70%, 75%, 80%, 85%, 90%, or 95% of the aluminum sulfate is recovered from the composition (e.g., the second liquor (or post-titanium hydrolysis liquor (PHL)) after the hydrolysis of titanyl sulfate to TiO2 hydrate, or the first permeate before the hydrolysis of titanyl sulfate to TiO2 hydrate) in the methods of the present invention.

[0296] After recovery, the aluminum sulfate may be further processed using standard methods, taking into account its intended use. However, for example, it may be washed and / or dried.

[0297] In certain embodiments, the aluminum sulfate formed in this step comprises Al2(SO4)3·XH2O (wherein x is about 14 to 18, preferably 18).

[0298] Free acid neutralization and calcium sulfate recovery

[0299] In one embodiment of the invention, calcium carbonate (CaCO 3 ) is combined with a third liquid (PAL) to produce a first composition (PAL′) comprising calcium sulfate and other metal sulfates including magnesium sulfate.

[0300] Calcium carbonate is preferably added to the liquid in any amount sufficient to raise the pH in the liquid to at least partially neutralize any sulfuric acid present. In a preferred embodiment, calcium carbonate is added to raise the pH to a pH of about 1 to about 4. In certain embodiments, calcium carbonate is added to raise the pH to about 1, about 2, about 3, or about 4. The calcium sulfate formed in this step is preferably CaSO4.2H2O.

[0301] As will be appreciated by those skilled in the art, the neutralization step may be performed for any suitable time or temperature to achieve the desired neutralization. However, in one embodiment, the temperature is maintained below the boiling point of the composition (e.g., the third liquid (PAL)). In certain embodiments, during neutralization, the temperature may be maintained at about 85°C or below, or at about 80°C or below, at about 60°C or below, or at about 40°C or below. In one embodiment, the neutralization step is performed at room temperature or ambient temperature (e.g., about 15 to about 30°C, such as about 25°C).

[0302] As will be appreciated in the art, any suitable method can be used to reclaim calcium sulfate from the first composition. Adding calcium carbonate to the liquid and the resulting pH will result in a calcium sulfate precipitate that can be separated from the composition in which it is retained subsequently. The separation of the precipitate can be carried out by any of many known methods. But, for example, it can include filtering, centrifuging, settling and / or deposition. In a preferred embodiment, use filtration, such as belt filtration or the filtration of a filter press.

[0303] After recovery, the calcium sulfate may be further processed using standard methods, taking into account its intended use. However, for example, it may be washed and / or dried.

[0304] In a preferred embodiment of the present invention, this step is carried out under conditions such that the titanium will be in the Ti 4+ The iron will be in the Fe 2+ state. In one embodiment, the ORP of this step is controlled or adjusted. In one embodiment, the ORP is from about 200mV to about 300mV, for example about 270mV. This embodiment will help to increase the recovery rate of any titanium present in the first composition produced with calcium sulfate in the free acid neutralization step, and help to ensure that any iron present is reported to the mixed metal solids recovered in the method of the present invention. It can also increase the recovery level of any aluminum present with calcium sulfate from the first composition and reduce the amount of aluminum reported to any subsequent recovery steps. The skilled person will readily understand the method of determining the ORP. In this embodiment, titanium and / or aluminum will be recovered with calcium sulfate in the form of one or more titanium and aluminum oxides and / or hydroxides. This embodiment is Figure 3 (Option 1) is shown in .

[0305] Although the method of the present invention may be performed without testing, adjusting and / or controlling the conditions to ensure that the titanium is in the Ti 4+ The iron is in the Fe 2+ Although the invention provides a method for reducing the amount of gypsum produced by the process (e.g., by adjusting or controlling the ORP), the inventors note that implementation of the method according to this embodiment is advantageous because it can reduce waste and improve the utilization of the products produced by the method and the overall economic efficiency of the process. For example, the total amount of mixed metal solids produced, which is considered to be a lower value product relative to other products produced by the process of the present invention, can be reduced in this way. Although calcium sulfate contains certain amounts of aluminum and titanium, the content is low enough that it can still be sold as a substitute for other gypsum sources (e.g., to the construction industry).

[0306] This embodiment of the free acid neutralization step (adjusting or controlling the conditions so that the titanium is in the Ti 4+ The iron is in the Fe 2+The Mg(OH)2 state is preferably used in conjunction with an embodiment of a subsequent metal neutralization step that uses Mg(OH)2 rather than Ca(OH)2, but may be used with either.

[0307] In one embodiment, the conditions of the free acid neutralization step are adjusted or controlled to achieve the desired ORP. Those skilled in the art will readily appreciate methods for achieving this purpose. However, for example, in one embodiment, this step is performed under oxidizing conditions. "Oxidizing conditions" may include using a calcium carbonate (CaCO3) composition that has been oxidized before combining with the third liquid (PAL), or using a third liquid that has been oxidized before combining with calcium carbonate or once calcium carbonate is combined with the third liquid. Oxidation can occur in any suitable manner, such as by bubbling air through the composition or liquid to reach the relevant oxidation potential. Oxidation can be performed at any suitable temperature, however, for example, it can be performed at ambient temperature (e.g., about 15 to about 30°C), or heated to about 45 or about 50°C.

[0308] Calcium sulfate (including titanium and aluminum) can be recovered from the first composition using any suitable method described previously herein. Similarly, calcium sulfate (including titanium and aluminum) can be further processed using standard methods described previously herein.

[0309] Magnesium sulfate recovery

[0310] The magnesium sulfate is recovered from the process of the invention at an appropriate stage. The inventors have found that it is preferred to recover the magnesium sulfate at least after the recovery of the titanium dioxide and the aluminum, because if this is done in this order, the purity of the resulting magnesium sulfate precipitate is improved. This is because under conditions suitable for precipitating magnesium sulfate, aluminum sulfate and titanyl sulfate will also co-precipitate, and it would be difficult and uneconomical to have to separate the substantially pure compounds afterwards. The yields of titanium dioxide and aluminum sulfate may be affected.

[0311] In one embodiment, magnesium sulfate is recovered in the process of the present invention (e.g., from the fourth liquid (or post neutralization liquor (PNL) of the first aspect) before mixed metal solids are recovered in the process of the present invention. The inventors have found that there are economic advantages to performing the steps in this order. In a particularly preferred embodiment, magnesium sulfate is recovered after mixed metal solids are recovered in the process (e.g., from the fifth liquid (or post-mixed metal liquid) of the second aspect). The inventors have found that by recovering magnesium sulfate after MMS, a higher purity of magnesium sulfate can be achieved, and its value is increased. For example, in certain embodiments, contaminants such as manganese that may otherwise be present in magnesium sulfate recovered from such a process are reduced or substantially eliminated, which may have the benefit of improving the potential utility of the recovered magnesium sulfate in the agricultural industry, especially where the manganese content of the raw materials used is high.

[0312] Magnesium sulfate may be recovered from the process of the present invention using any suitable method as will be understood in the art. However, for example, it may be precipitated and then separated from the liquid or composition in which it resides (e.g., in one embodiment, the fifth liquid (or MRL), in another embodiment, the fourth liquid (PML)). In one embodiment, precipitation may occur by cooling to a temperature at which magnesium sulfate precipitates. For example, it may be precipitated by cooling to about 4°C or less, or about 0°C to about 4°C, preferably about 3°C. In a preferred embodiment, evaporative crystallization is employed; for example, using vacuum concentration. In one embodiment, evaporative crystallization is performed at a temperature of less than about 50 degrees Celsius.

[0313] The separation or recovery of magnesium sulfate can be carried out by any of many known methods. However, for example, it can include filtering, centrifuging, sedimentation and / or settling. In a preferred embodiment, magnesium sulfate is separated using filtration, such as belt filtration.

[0314] In certain embodiments, at least about 75%, 80%, 85%, 90% or 95% of the magnesium sulfate is recovered from the composition or liquid fed to this step of the process of the invention.

[0315] After recovery, the magnesium sulfate may be further processed using standard methods, taking into account its intended use. However, for example, it may be washed and / or dried.

[0316] The magnesium sulfate recovered in this step is preferably MgSO4.7H2O, MgSO4.6H2O and / or MgSO4.1H2O (kieserite); and for example, MgSO4.7H2O or .6H2O can be recovered and then dried to recover MgSO4.1H2O.

[0317] In one embodiment of the invention wherein mixed metal solids are recovered prior to magnesium sulfate, the magnesium sulfate separated or recovered in the process has a purity of at least about 75% to about 90%, preferably at least about 90%.

[0318] Metal neutralization and recovery of mixed metal solids and calcium sulfate

[0319] In one embodiment, calcium hydroxide (Ca(OH)2) is added to the relevant composition to produce a composition comprising mixed metal oxides and / or hydroxides and calcium sulfate. In one embodiment, calcium hydroxide is added to the fifth liquid (PML) to produce a second composition (PML') comprising mixed metal oxides and / or hydroxides and calcium sulfate. In a preferred embodiment, this step is performed before the recovery step of magnesium sulfate in the process of the present invention; for example, calcium hydroxide is added to the fourth liquid (PNL) to produce a second composition (PNL') comprising magnesium sulfate, mixed metal oxides and / or hydroxides and calcium sulfate.

[0320] Calcium hydroxide is preferably added to the relevant composition in any amount sufficient to increase the pH in the composition to at least partially neutralize any H2SO4 present in the composition. In a preferred embodiment, calcium hydroxide is added to increase the pH to a pH of about 7 to about 10. In certain embodiments, calcium hydroxide is added to increase the pH to about 7, about 8, about 9, or about 10. The calcium sulfate formed in this step is preferably CaSO4.2H2O.

[0321] As will be appreciated by those skilled in the art, this step can be performed for any suitable time or temperature to achieve the desired neutralization. However, for example, the temperature is maintained below the boiling point of the composition. In certain embodiments, during neutralization, the temperature can be maintained at or below about 85°C, or the temperature can be maintained at or below about 80°C, at or below about 60°C, or at or below about 40°C. In one embodiment, the neutralization step is performed at room temperature or ambient temperature (e.g., from about 15 to about 30°C, such as about 25°C).

[0322] The mixed metal solid and / or calcium sulfate can be recovered from the composition (for example liquid PNL' and PML') using any suitable method that will be understood in the art. Calcium hydroxide is added to the liquid and the pH value obtained will cause mixed metal oxides and / or hydroxides and calcium sulfate precipitation, which can be separated from the composition in which they are retained as solids subsequently. The separation of the precipitate can be carried out by any of many known methods. But, for example, it can include filtering, centrifuging, depositing and / or settling. In a preferred embodiment, filtration is used. In a preferred embodiment, a filter press or a belt filter is used.

[0323] In a preferred embodiment, the mixed metal solid and calcium sulfate are recovered as a mixture. In other embodiments, the mixed metal solid and calcium sulfate can be recovered separately. In one embodiment, the method can include separating calcium sulfate from the mixed metal solid. The technician will understand the appropriate method for performing this operation.

[0324] After recovery, the mixed metal solids and / or calcium sulfate are further processed using standard methods, taking into account their intended use. However, for example, it may be washed and / or dried.

[0325] Metal neutralization and mixed metal solids recovery

[0326] In one embodiment, magnesium hydroxide (Mg(OH)2) is added to the relevant composition to produce a composition comprising mixed metal oxides and / or hydroxides. In one embodiment, magnesium hydroxide (Mg(OH)2) is added to the fifth liquid (PML) to produce a second composition (PML') comprising mixed metal oxides and / or hydroxides. In a preferred embodiment, this step is performed before the magnesium sulfate recovery step in the process of the present invention; for example, magnesium hydroxide is added to the fourth liquid (PNL) to produce a second composition (PNL') comprising magnesium sulfate, mixed metal oxides and / or hydroxides.

[0327] Magnesium hydroxide is preferably added to the relevant composition in any amount sufficient to increase the pH in the composition to at least partially neutralize any H2SO4 present in the composition. In a preferred embodiment, magnesium hydroxide is added to increase the pH to a pH of about 7 to about 10. In certain embodiments, magnesium hydroxide is added to increase the pH to about 7, about 8, about 9, or about 10.

[0328] As will be appreciated by those skilled in the art, this step can be performed for any suitable time or temperature to achieve the desired neutralization. However, for example, the temperature is maintained below the boiling point of the composition. In certain embodiments, during neutralization, the temperature can be maintained at or below about 85°C, or the temperature can be maintained at or below about 80°C, at or below about 60°C, or at or below about 40°C. In one embodiment, the neutralization step is performed at room temperature or ambient temperature (e.g., from about 15 to about 30°C, such as at about 25°C).

[0329] Mixed metal solids can be recovered from the composition (e.g., liquid PNL' and PML') using any suitable method that will be understood in the art. Adding magnesium hydroxide to the liquid and obtaining a pH value will result in mixed metal oxides and / or hydroxide precipitation, which can then be separated as solids from the composition in which they are retained. Separation of the precipitate can be carried out by any of many known methods. However, for example, it can include filtering, centrifuging, sedimentation and / or settling. In a preferred embodiment, filtration is used. In a preferred embodiment, a filter press or a belt filter is used.

[0330] After recovery, the mixed metal solids may be further processed using standard methods, taking into account their intended use. However, for example, the mixed metal solids product may be washed and / or dried.

[0331] Although the inventors have determined that including a metal neutralization step and using Ca(OH)2 in the process of the present invention (e.g., a method for recovering a product or a combination of products from a titanium-containing material or a composition produced in a process for producing titanium dioxide) and in that step provide significant advantages over existing methods for recovering such products from these materials, they have determined that using Mg(OH)2 as a reagent in the metal neutralization step provides previously unrecognized advantages. For example, using Mg(OH)2 has the advantage of avoiding or at least reducing the amount of red gypsum that may be produced and reported in the mixed metal solids product. In certain embodiments, iron hydroxide is a major component of the mixed metal solids. In one embodiment, the iron hydroxide can be separated from the other components in the mixed metal solids and sold as a separate product.

[0332] In the case where the titanium-containing material, the composition produced in the process for producing titanium dioxide, or any other composition described herein (e.g., the fourth liquid (PNL) or the fifth liquid (PML)) contains relatively high or undesirable iron levels, the inventors believe that this embodiment of the invention is more suitable than the embodiment using Ca(OH)2. . The inventors believe that the embodiment using Ca(OH)2 may be more suitable for the case where the titanium-containing material, the composition produced in the process for producing titanium dioxide, or any other composition described herein (e.g., the fourth liquid (PNL) or the fifth liquid (PML)) contains relatively low or acceptable levels of iron.

[0333] Wastewater treatment

[0334] The inventors expect that any wastewater leaving the inventive method has minimal environmental risk. However, it can be selected to be subjected to any number of known water treatment processes to minimize the risk of being considered an environmental hazard. In one embodiment, the wastewater produced in the method of the present invention, such as in one or more washing steps, can be fed into a zero liquid discharge (ZLD) process to recycle water back into the process. The wastewater can be treated to remove any solute that may be present. For example, the wastewater can be treated by evaporation to produce water vapor and solid residue. The water vapor can be captured and condensed, and then recycled back into the process. The solid residue can be recovered and combined with a retentate comprising calcium sulfate and silicon dioxide recovered from the leaching step of the method of the present invention to form a combined product.

[0335] Recovery of products from compositions produced in processes for the production of titanium dioxide

[0336] The present inventors have developed processes for recovering calcium sulfate, mixed metal solids and / or magnesium sulfate from compositions produced in a sulfation process for producing titanium dioxide from titanium-containing materials (such as those previously described herein or any other titanium-containing material, which contains titanium dioxide in any form, such as ilmenite). The processes are surprisingly effective in recovering relatively low concentrations of metal values ​​(calcium, mixed metals and / or magnesium) from such waste compositions in the form of products that are considered to be saleable. Therefore, the benefits of the processes developed by the inventors are that they improve the economics of traditional methods of recovering titanium dioxide from feedstocks or provide an alternative revenue stream. They also have the advantage of minimizing the waste that must be disposed of and thus reducing the impact of such processes on the environment.

[0337] In one aspect, the present invention provides a method for recovering one or more calcium sulfate, mixed metal solids, and / or magnesium sulfate from a composition produced in a sulfation process for producing titanium dioxide. In certain embodiments, a) calcium sulfate, b) calcium sulfate and mixed metal solids, c) calcium sulfate, mixed metal solids, and magnesium sulfate, or d) calcium sulfate and magnesium sulfate are recovered from the method. In certain embodiments, for example, the recovered calcium sulfate can be used as an alternative gypsum source, and the magnesium sulfate can be used, for example, in plant fertilizer applications.

[0338] The skilled person will readily appreciate methods of producing or recovering titanium dioxide using the sulfation process. However, for example, a feedstock comprising titanium dioxide (e.g., comprising ilmenite or perovskite) is sulfated using sulfuric acid, and in some methods the solid and liquid phases are separated after a leaching step. The phase comprising the sulfated titanium salt (e.g., titanyl sulfate) is then subjected to a hydrolysis reaction to produce hydrated titanium dioxide. The hydrated titanium dioxide is typically separated from the other components of the composition in which it resides, and then calcined to produce titanium dioxide. The methods described herein provide more detailed examples of methods for producing titanium dioxide.

[0339] In such a process for producing titanium dioxide, a composition may be produced - for example, a composition remaining after the titanium dioxide is recovered. The technician will readily understand other compositions produced in the titanium dioxide production process that can be used in the present invention. In one embodiment, the composition derived from the sulfation process for producing or recovering titanium dioxide can be any acidic composition produced or recovered in the sulfation process. In one embodiment, the composition contains at least magnesium. In one embodiment, the composition also contains iron and / or aluminum and / or titanium and / or calcium. Magnesium, iron, titanium and aluminum are generally present in the form of sulfates, such as magnesium sulfate, iron sulfate, titanyl sulfate and aluminum sulfate. In a preferred embodiment, the composition is considered to be a waste of the sulfation process for producing or recovering titanium dioxide. In one embodiment, the composition is an acidic composition produced or recovered after hydrolysis and recovery of hydrated titanium dioxide during the sulfation process for producing titanium dioxide. By way of example only, in the context of other methods described herein, it can be a post-hydrolyzed liquid (PHL). In another embodiment, the composition is an acidic composition produced or recovered after aluminum is recovered in the sulfation process for producing titanium dioxide. In one embodiment, the composition is an acidic composition produced or recovered after hydrolysis and recovery of hydrated titanium dioxide and recovery of aluminum in a sulfation process for producing titanium dioxide. As a further example, separation of titanium dioxide hydrate in step e) of the first aspect of the invention produces a second liquid (PHL), while separation of titanium dioxide hydrate in step f) of the second aspect of the invention produces a third liquid (PAL), and each of these liquids can be used as the starting composition for this aspect of the invention.

[0340] In one embodiment, the method of this aspect of the invention comprises at least the following steps: adding calcium carbonate and a composition produced in a process for producing titanium dioxide to produce a composition (A) comprising calcium sulfate and one or more other metal sulfates (including magnesium sulfate). The calcium sulfate can then be separated from the composition (A) to produce calcium sulfate and a second composition (B) comprising magnesium sulfate and one or more other metal sulfates. The magnesium sulfate can then be separated from the composition (B) if desired to produce magnesium sulfate and a third composition (C) comprising mixed metal sulfates. Calcium hydroxide or magnesium hydroxide can then be mixed with the third composition (C) to produce a fourth composition (D) comprising mixed metal oxides and / or hydroxides and calcium sulfate (in the case of using calcium hydroxide) or mixed metal oxides and / or hydroxides (in the case of using magnesium hydroxide). . The mixed metal oxides and / or hydroxides and calcium sulfate, or the mixed metal oxides and / or hydroxides, can then be separated from the fourth composition (D) if desired.

[0341] In a preferred alternative embodiment, the mixed metal solid is recovered before the magnesium sulfate is recovered. Using this sequence can improve the purity of the recovered magnesium sulfate. In this embodiment, the method includes the following steps: calcium carbonate is added to the composition produced in the sulfation process for producing titanium dioxide to produce a composition (A) comprising calcium sulfate and one or more other metal sulfates (including magnesium sulfate). Calcium sulfate is then separated from the composition (A) to produce calcium sulfate and a second composition (B) comprising magnesium sulfate and one or more other metal sulfates. Calcium hydroxide or magnesium hydroxide can then be mixed with the second composition (B) to produce a third composition (C') comprising mixed metal oxides and / or hydroxides and calcium sulfate (in the case of using calcium hydroxide), mixed metal oxides and / or hydroxides (in the case of using magnesium hydroxide). . Then, when necessary, the mixed metal oxides and / or hydroxides and calcium sulfate, or the mixed metal oxides and / or hydroxides are separated from the third composition (C') to produce a mixed metal solid comprising calcium sulfate, or a mixed metal solid, and a fourth composition (D') comprising magnesium sulfate. The magnesium sulfate can then be separated from the fourth composition (D') to produce magnesium sulfate. Figure 3 (Option 2).

[0342] In one embodiment of this aspect of the invention, in the first step of combining the calcium carbonate and the composition, the conditions are such that the titanium will be in the Ti 4+ state and iron will be in Fe 2+state, thereby producing a composition (A) comprising calcium sulfate and one or more titanium oxides and / or hydroxides. In a preferred embodiment, the conditions are controlled in such a way that composition (A) will contain one or more aluminum oxides and / or hydroxides. In this embodiment, the next step may include separating calcium sulfate and one or more aluminum and / or titanium oxides and / or hydroxides from composition (A) to produce calcium sulfate, and one or more aluminum and / or titanium oxides and / or hydroxides and a composition (B) comprising mixed metal sulfates (including magnesium sulfate). The preferred method according to this embodiment of the invention is Figure 3 (Option 1) is shown in .

[0343] The steps of the method of this aspect of the invention can be carried out using equivalent steps of the methods of other aspects of the invention as described herein before and illustrated in the following examples. Where methods are described herein with reference to specific liquids or compositions, it is to be understood that reference to the relevant compositions of this aspect of the invention may be substituted for those references.

[0344] In certain embodiments of this aspect of the invention, the composition produced in a process for producing titanium dioxide may be treated or processed prior to the first step of the process (ie, combining the composition with calcium carbonate).

[0345] Example

[0346] Example 1

[0347] like Figure 1As shown, this example describes an embodiment of the method of the present invention. Slag is prepared by grinding to a desired particle size. Slag and sulfuric acid are fed into a continuous reactor suitable for continuous mixing of slag, sulfuric acid and the formed sulfuric acid filter cake. Slag and sulfuric acid are mixed and fed into the reactor at a rate sufficient to achieve sulfation of titanium, magnesium, aluminum and calcium and other minority substances present in the slag raw material. The sulfated filter cake leaves the reactor and is fed to a leaching step, in which it is contacted with water or dilute acid to produce a solid phase and a liquid phase, and the solid phase and the liquid phase are separated, preferably by filtering. The solid phase is recovered as calcium sulfate and silicon dioxide, and the liquid leaching liquid phase is fed to the titanium hydrolysis step. In the hydrolysis step, the TiO2 core is contacted with a liquid leachate in a suitable container at a suitable temperature and a suitable time sufficient to hydrolyze titanyl sulfate into hydrated titanium dioxide. The hydrated titanium dioxide is then separated from the liquid phase contained therein, preferably by filtering. The hydrated titanium dioxide is then fed to a calcination step, and the liquid phase (PHL) is fed to an aluminum sulfate recovery step. Calcination occurs in a calcination device at an appropriate temperature and for an appropriate time sufficient to produce TiO2. The titanium dioxide can be further processed to meet the individual requirements of different industries; for example, to produce a pigment-grade TiO2 product. The liquid PHL phase is fed to an aluminum sulfate crystallization step, preferably evaporative crystallization, to recover Al2(SO4)3·XH2O (wherein X is about 14 to 18, preferably 18). The liquid phase (PAL) obtained from this step is then fed to a neutralization step, in which it is partially neutralized with CaCO3 to produce a solid phase and a liquid phase. The solid and liquid phases (PNL) are separated, preferably by filtration, and a solid white CaSO4·2H2O gypsum product is recovered. The liquid PNL phase is fed to another neutralization step, in which it is neutralized with Ca(OH)2 to precipitate and recover metal oxides and / or hydroxides and calcium sulfate (MMS). The MMS is separated from the liquid phase (MRL), preferably by filtration. The liquid MRL phase is fed to a crystallization step to produce MgSO4.7H2O. The MgSO4.7H2O is preferably crystallized by evaporative crystallization. The MgSO4.7H2O is then separated and recovered from the liquid phase in which it is present, preferably by filtration. The remaining liquid is then optionally treated using a water treatment process.

[0348] Example 2

[0349] This embodiment describes an embodiment of a preferred method of the present invention, such as Figure 2As shown. Slag is prepared by grinding to the desired particle size. Slag and sulfuric acid are fed into a continuous reactor suitable for continuous mixing of slag, sulfuric acid and the formed sulfation filter cake. Slag and sulfuric acid are mixed and fed through the reactor at a rate sufficient to achieve sulfation of titanium, magnesium, aluminum and calcium and other minor substances present in the slag raw material. The sulfation filter cake leaves the reactor and is fed to a leaching step, in which it is contacted with water or dilute acid to produce a solid phase and a liquid phase, and the solid phase and the liquid phase are separated, preferably by filtration. The solid phase is calcium sulfate and silicon dioxide to be recovered, and the liquid leaching liquid phase is fed to the titanium hydrolysis step. In the hydrolysis step, the TiO2 core is contacted with the liquid leachate in a suitable container at a suitable temperature and a suitable time sufficient to hydrolyze titanyl sulfate into hydrated titanium dioxide. The hydrated titanium dioxide is then separated from the liquid phase contained therein, preferably by filtration. The hydrated titanium dioxide is then sent to the calcination step, and the liquid phase (PHL) is sent to the aluminum sulfate recovery step. Calcination occurs in the calcination equipment at an appropriate temperature and for an appropriate time sufficient to produce TiO2. Titanium dioxide can be further processed to meet the individual requirements of different industries; for example, to produce pigment-grade TiO2 products. The liquid PHL phase is fed to an aluminum sulfate crystallization step, preferably evaporative crystallization, to recover Al2(SO4)3·XH2O (wherein X is about 14 to 18, preferably 18). The liquid phase (PAL) obtained from this step is then fed to a neutralization step, in which it is partially neutralized with CaCO3 to produce a solid phase and a liquid phase. The solid and liquid phases (PNL) are separated, preferably by filtration, and a solid white CaSO4·2H2O gypsum product is recovered. The liquid PNL phase is fed to another neutralization step, in which Mg(OH)2 is neutralized to precipitate and recover a mixture of metal oxides or hydroxides (MMS). MMS is separated from the liquid phase (MRL), preferably by filtration. The liquid MRL phase is fed to a crystallization step to produce MgSO4·7H2O. MgSO4.7H2O is preferably crystallized by evaporative crystallization. MgSO4.7H2O is then separated and recovered from the liquid phase in which it is present, preferably by filtration.

[0350] In the examples below, when referring to the % of any compound in any composition / liquid, this has been calculated from the measured % concentration of the element using the following formula:

[0351]

[0352] Example 3 - New Zealand Steel Slag

[0353] Example 3A- raw material

[0354] The raw material was perovskite VTM slag containing GAP 5 (<5 mm particle size) from New Zealand Steel. The slag was ground to a target size of D90 < 250 microns and dried to a free moisture level of < 2% wt. The slag was analyzed by XRF. Table 2 reports the results of the content of key elements.

[0355] Table 2 – XRF analysis of New Zealand steel slag

[0356] element symbol NZS magnesium Mg 7.51％ aluminum Al 8.10％ silicon Si 6.71％ sulfur S 0.269％ calcium Ca 12.7％ titanium Ti 19.7％ vanadium V 0.177％ chromium Cr 0.006％ manganese Mn 0.777％ iron Fe 3.22％

[0357] Example 3B - Sulfation

[0358] Sulfuric acid with a concentration of 89% and NZS slag were mixed in a pre-mixing vessel at ambient temperature with an acid-ore ratio of 1.4:1. The mixture was then added to a preheated reactor at 100°C and the temperature was raised until the peak of the reaction exotherm temperature was reached and maintained for 1 hour, during which the mixture was continuously mixed. Once sulfation was complete, the mixed mixture (sulfate cake) was discharged from the reactor and collected to be added to a leach tank.

[0359] Example 3C - Leaching and separation of leachate and residue

[0360] The sulfate filter cake prepared according to the method described in Example 3B was recovered from the continuous reactor and transferred to a heated leaching tank, where it was dissolved in dilute sulfuric acid at pH 2 at a mass ratio of 1:1 liquid to filter cake, and the oxidation-reduction potential (ORP) in the solution was then reduced to -78 mV by the addition of iron. The filter cake was leached at 65°C for 60 minutes, then filtered through a filter press for 30 minutes, and the residue was subsequently separated from the leachate by a polishing filter. The residue was subjected to a washing process, and the leachate was reported to a hydrolysis tank and sampled for analysis by XRF and titrated to obtain free acidity.

[0361] The residue (CalSi) was washed by slurrying for 30 minutes with water at a ratio of 10:1 water to residue. The mixture was then filtered and the solids were recovered and dried in an oven at 100°C for 2 hours. The residues from the separate sulfation reactions (performed as described in Example 3B) were pooled and analyzed using XRF. Tables 3 and 4 report the results for the key element levels.

[0362] Table 3: XRF analysis of leachate

[0363] TiO2* 61.523g / kg Fe 12.208g / kg Ca 0.152g / kg Ti 36.852g / kg Al 14.772g / kg Mg 15.212g / kg Mn 1.604g / kg Cr 0.088g / kg Free acidity 8.18％

[0364] *TiO2 is calculated from element Ti.

[0365] Table 4: CalSi XRF analysis (DS103)

[0366] Fe 0.916％ Ca 15.15％ Si 6.437％ Al 4.234％ Mg 3.947％ Mn 0.330％ Cr 0.017％ Ti 5.215％

[0367] Example 3D - Hydrolysis, separation and calcination of TiO2

[0368] The leachate obtained according to the method of Example 3C was transferred to a hydrolysis tank maintained at 40°C, and then 1.35wt% of TiO2 seeds / nuclei (6nm) were added. The mixture was then heated to a hydrolysis temperature of 92°C at atmospheric pressure at about 1°C / min and maintained at this temperature until the hydrolysis reaction was complete (i.e., the TiO2 yield was stable, as tested by sampling and XRF). The reacted mixture was then passed through a filter press to separate the TiO2 filter cake from the spent hydrolysis liquor (SHL), and the SHL was analyzed by XRF and titrated to determine the free acidity. The results of the key element contents are reported in Table 5. The TiO2 filter cake was first filtered with a warm 10% Ti-containing 3+ The TiO2 was washed with H2SO4 solution and then washed with warm water to remove excess acid. The hydrated TiO2 recovered from the hydrolysis was doped by adding MgO, K2O, P2O5 and heated in a rotary furnace at 900°C for 1 hour and then ground to produce TiO2. The calcined titanium dioxide was analyzed and found to be pigment grade. The TiO2 seeds / cores used were produced using the Mecklenburg process.

[0369] Table 5: XRF analysis of wastewater lysate

[0370] Mg 19.056g / kg Mn 1.576g / kg Al 13.820g / kg Ca 0.120g / kg Ti 3.736g / kg Cr 0.084g / kg Mn 1.576g / kg Fe 10.796g / kg Free acidity 14.4％ ORP -85mV density 1.316kg /

[0371] Table 5A: XRF analysis of NZS hydrated TiO2

[0372] Mg 0.032cps Al 0.027cps Si 0.001cps Ca 0.003cps Mn 0cps Ti 99.633cps Cr / V 0.002cps Fe 0cps

[0373] cps – counts per second

[0374] Chromium and vanadium are reported as a combined peak because the calibration method used cannot distinguish their emission peaks.

[0375] Example 3E - Recovery of aluminum sulfate

[0376] The post hydrolysis liquor (PHL) prepared according to the method of Example 3D was concentrated by evaporation until the aluminum sulfate in the solution was soluble between 60-65°C. The liquor was then cooled to 3°C below the dissolution temperature of aluminum sulfate and seeded with aluminum sulfate seeds initially crystallized from pure aluminum sulfate and 25% sulfuric acid solution. Seeding was performed by adding 10%wt of the expected aluminum sulfate yield. The seeded liquor was then cooled at 4°C / hr for more than 8 hours to 25°C while maintaining a well-stirred mixture. The slurry was then filtered by vacuum filtration to separate the aluminum sulfate crystals from the post-aluminium liquor. The aluminum sulfate crystals and post-aluminium liquor were analyzed by XRF. The results of the key element contents are reported in Tables 6 and 7. The purity of the aluminum sulfate was approximately 99%.

[0377] Table 6: XRF results of aluminum sulfate crystals

[0378] Al 72811mg / kg Ca 115mg / kg Cr 28mg / kg Fe 115mg / kg Mg 671mg / kg Mn 6mg / kg Ti 43mg / kg V 22mg / kg

[0379] Table 7: XRF analysis of post aluminum liquid

[0380] Al 6.29g / kg Ca 0.08g / kg Cr 0.12g / kg Fe 14.23g / kg Mg 19.52g / kg Mn 2.26g / kg Ti 4.04g / kg Free acidity 21.96％

[0381] Example 3F - Free acid neutralization and calcium sulfate recovery

[0382] An aqueous slurry of CaCO3 was gradually added to post aluminium liquor (PAL) prepared according to the method described in Example 3E at a water to solid ratio of 1:1 and mixed at 25°C for more than 12 hours to neutralize the free acid to pH 2. The residue and post neutralization liquor (PNL) were filtered and the residue was slurried with water for 30 minutes, filtered and then plug washed with fresh water. The solids were collected and dried in an oven at 70°C for 4 hours. The recovered solids were analyzed by XRF and XRD, and the PNL was analyzed by XRF. The XRF content results of key elements in the solids and PNL are reported in Tables 8 and 9. Using XRD, the solid showed ~99.99% calcium sulfate dihydrate.

[0383] Table 8: XRF and pH analysis of N108 post-neutralization solution

[0384] Mg 15.736g / Kg Al 7.528g / Kg S 134.392g / Kg Ca 0.528g / Kg Ti 1.552g / Kg Cr 0.084g / Kg Mn 2.032g / Kg Fe 11.18g / Kg pH 1.23

[0385] Table 9: XRF analysis of CaSO4.2H2O (solid)

[0386] Compound Mg 0.691％ Al 0.44％ Si 0.171％ S 19.13％ Fe Below detection limit Ca 22.464％ Ti 0.136％ Cr Below detection limit

[0387] Example 3G - Free acid neutralization and calcium sulfate recovery using Ti and Al

[0388] An alternative process to that described in Example 3F was performed in which calcium sulfate was used to recover any Ti and Al that might remain in the PAL.

[0389] Stage 1: Oxidation of titanium (III) to titanium (IV) (N122, N124). Air was bubbled through a stirred PAL liquid at 45°C until an ORP of 270 mV was reached. The liquid was then removed from the bubbler and heated to 85°C, and an aliquot of a CaCO slurry in water was added to reach a pH of 4. The mixture was then filtered by vacuum filtration to separate the solids from the liquid. The liquid was analyzed by XRF and found to contain no Ti or Al (Table 9A). These are expected to be reported in the solid phase.

[0390] Table 9A: XRF analysis of post-neutralization liquid of N124

[0391] Mg 16.684g / kg Al 0g / kg Mn 1.877g / kg Fe 10.567g / kg Ca 0.585g / kg Ti Below detection limit Cr Below detection limit pH 4.01

[0392] Example 3H - Metal neutralization using Ca(OH)2 and recovery of mixed metal solids

[0393] A slurry of Ca(OH)2 was gradually added to a PNL prepared according to the method described in Example 3F at a water to solid ratio of 1.75:1 and mixed at 25°C for more than 12 hours to neutralize the free acid to pH 7.5. The residue and liquid were separated by vacuum filtration, and the filtrate was slurried with water for 30 minutes, filtered, and then washed with fresh water. The solids were collected and dried in an oven at 70°C for 4 hours and then analyzed by XRF. The separated liquid was also analyzed by XRF. The XRF content results of key elements in the solids and PNL are reported in Tables 10 and 11.

[0394] Table 10: XRF analysis of separated liquids

[0395] Mg 13.028g / kg Al 0.016g / kg S 113.408g / kg Ca 0.46g / kg Ti Below detection limit Cr 0.004g / kg Mn 1.528g / kg Fe 0.608g / kg pH 6.14

[0396] Table 11: XRF analysis of mixed metal solids

[0397] Mg 1.092％ Al 4.452％ Si 0.693％ S 16.209％ Ca 16.701％ Ti 2.122％ V 0.18％ Cr 0.026％ Mn 0.384％ Fe 6.018％

[0398] Example 3I - Metal Neutralization and Mixed Metal Solids Recovery Using Mg(OH)2

[0399] Mg(OH)2 was added to the stirred post-neutralized solution obtained according to the method outlined in Example 3G until the pH rose to 7. At this stage, air was bubbled through the solution for more than 8 hours, and additional Mg(OH)2 was added thereto to maintain the pH at 7. Bubbling continued for more than 12 hours, and then the mixture was filtered by vacuum filtration to separate the neutralized liquid from the solid. The solid was washed with RO water and placed in an oven at 70°C for 12 hours. The filtrate was analyzed via XRF. The results are shown in Table 12.

[0400] Table 12: XRF analysis of N112 separated liquid

[0401] Mg 35.284g / kg Al Below detection limit S 176.872g / kg Ca 0.328g / kg Ti 0.168g / kg Cr Below detection limit Mn Below detection limit Fe Below detection limit

[0402] The separated solids were not analyzed. However, the inventors expect that about 90% or more of the trace elements in the liquid report to the solid material.

[0403] Example 3J - Recovery of magnesium sulfate

[0404] The liquid obtained according to the method of Example 3H was concentrated by evaporation at a constant rate in a container at 42° C. in a vacuum of −90 kPa until a suitable magnesium sulfate yield was obtained, and then the crystallized solid was separated from the liquid by filtration. The solid was washed with RO water before being analyzed by XRF. The solid was analyzed by XRF and the results are listed in Table 13.

[0405] Table 13 - XRF analysis of magnesium sulfate crystals

[0406] Mg 93.9335g / kg Al 0.0044g / kg Ca 0.1820g / kg Ti 0.0009g / kg Cr 0.0005g / kg Mn 1.6634g / kg Fe 0.1429g / kg V 0.0009g / kg

[0407] These results indicate that high purity magnesium sulfate crystals are recovered with acceptable concentrations of <1% Mn and <2% Fe. The purity of the recovered magnesium sulfate is at least about 95%.

[0408] Example 4

[0409] Table 14 provides examples of components contained in titanium-containing materials for use in the present invention. This provides detailed information on the composition of melter slag samples produced in New Zealand and South Africa, and blast furnace slag produced in China and Russia. The Chinese slags come from Chinese steel mills that process the Panzhihua ore body located in the Sichuan region. It also details the composition of a VTM ore concentrate sample containing perovskite obtained from Brazil. Values ​​were calculated using the equations before Example 3 above based on element mass % data obtained using X-ray fluorescence analysis techniques (performed by or on behalf of the inventor).

[0410] Table 14

[0411]

[0412]

[0413] *Assuming compounds are reported. Metals may exist as one or more other oxides.

[0414] Example 5 China VTM-Slag

[0415] Slag

[0416] The perovskite-containing VTM slag was sourced from a Chinese steel mill processing the Panzhihua ore body located in the Sichuan region of China and ground to obtain an overall desired grind size of D90 < 250 microns. The ground slag was dried to the desired level, e.g. free moisture content < 2%wt.

[0417] Sulfate

[0418] Sulfuric acid of about 80% to about 90% concentration and slag are mixed at ambient temperature at a ratio of about 1.3:1 to about 1.7:1 acid to ore. The mixture is then added to a preheated reactor at 100°C and the temperature is raised to a roasting temperature of about 170 to about 210°C and then held for 1 hour during which the mixture is continuously mixed. Once sulfation is complete, the mixed mixture (sulfate cake) is discharged from the reactor and collected for addition to a leaching tank.

[0419] Leaching and separation of leachate and residue

[0420] The sulfuric acid filter cake is recovered from the continuous reactor and transferred to a heated leaching vessel where it is dissolved in dilute sulfuric acid at pH 2 at a mass ratio of liquid to cake of about 0.75:1 to about 2:1. A reducing agent is then added, if necessary, to reduce the ORP to about -50 mV or less. Sulfuric acid is added to the mixture to reduce the pH to 2 (0.1% wt H2SO4) to avoid premature hydrolysis. For example, the filter cake is leached at about 30°C to 80°C for about 60 minutes and then filtered through a filter cloth using vacuum filtration until a clear liquid is obtained. The residue remaining after filtration can be subjected to a washing process. The obtained leachate can be filtered.

[0421] Most of the calcium and silica present in the sulfate filter cake will be reported in the residual as calcium sulfate and silica. Titanyl sulfate, as well as any other metal sulfates, including aluminum sulfate and magnesium sulfate, will be reported in the leachate.

[0422] Hydrolysis, separation and calcination of TiO2

[0423] The leachate is transferred to a hydrolysis tank maintained at, for example, 40°C, and TiO2 seeds / nuclei are then added. The mixture is then heated to the desired hydrolysis temperature, for example, from 85°C to 110°C, at atmospheric pressure, and maintained at that temperature until the hydrolysis reaction is complete. The reaction mixture is then passed through a filter press to separate the TiO2 filter cake from the post-hydrolysis liquid (PHL). The TiO2 filter cake is first filtered with a warm diluted (e.g., 10%) Ti-containing 3+ The TiO2 is washed with H2SO4 solution and then with warm water to remove excess acid. The hydrated TiO2 recovered from the hydrolysis is doped by adding MgO, K2O, P2O5 and then heated in a rotary furnace at 900°C for 1h. It can then be ground.

[0424] Aluminum sulfate recovery

[0425] The PHL is concentrated by evaporation until the aluminum sulfate in the solution is soluble between 60-65°C. The liquid is then cooled to 5°C below the solubility temperature of aluminum sulfate and seeded with aluminum sulfate crystals. Seeding is performed by adding 2% to 20% wt of the expected aluminum sulfate yield. The seeded liquid is cooled at about 4°C / hr to a temperature between 15°C and 30°C while maintaining a well-stirred mixture. The resulting slurry is filtered by vacuum filtration to separate the aluminum sulfate crystals from the liquid. The aluminum sulfate is expected to be at least about 95% pure.

[0426] Free acid neutralization and calcium sulfate recovery

[0427] A slurry of CaCO3 in water with a water to solid ratio of 1:1 was gradually added to the liquid obtained from the aluminum sulfate recovery process and mixed at 25°C for more than 12 hours to neutralize the free acid to a pH of 1-4. The residue and post-neutralization liquid (PNL) were filtered, and the filtrate was slurried with water at a ratio of 1:1 10% H2SO4 to the residue for 30 minutes and heated to 60°C before filtering. The solid was washed with water, collected and dried in an oven at 70°C for 4 hours. The solid was expected to contain calcium sulfate.

[0428] Metal neutralization and mixed metal solids recovery

[0429] Mg (OH) is added to the stirred liquid obtained by the free acid neutralization step, so that the pH is raised to pH 7 to 10, while bubbling air into the solution. The solution is stirred for more than 3 hours, during which time additional Mg (OH) is added so that the pH is maintained at a pH of 7 to 10. The final slurry is then filtered by vacuum filtration to separate the neutralized liquid from the solid. The solid can be washed and dried. It is estimated that the solid comprises mixed metal oxides and hydroxides.

[0430] Magnesium sulfate recovery

[0431] The liquid obtained from the metal neutralization step is concentrated by evaporation at a constant rate at a temperature below 50° C. in a vacuum of −90 kPa until a suitable magnesium sulfate yield is obtained. The crystallized solid is separated from the liquid by filtration. The solid may be washed. The magnesium sulfate crystals are expected to be at least about 95% pure and contain very low levels of Mn and Fe (e.g., Mn<1% and Fe<2%).

[0432] The present invention has been described herein with reference to preferred embodiments to enable the reader to practice the invention without excessive experimentation. It will be appreciated by those skilled in the art that the present invention may be practiced with a large number of variations and modifications other than those specifically described. It should be understood that the present invention includes all such variations and modifications. In addition, titles, headings, etc. are provided to help the reader understand the text and should not be construed as limiting the scope of the present invention.

[0433] The entire disclosures of all applications, patents and publications cited herein are incorporated herein by reference. However, the reference to any prior art in this specification is not, and should not be taken as, an admission or any form of suggestion that the prior art forms part of the common general knowledge in any national field of endeavor.

Claims

1. A method for recovering one or more products from a titanium-containing material comprising perovskite, the method comprising: a) contacting the titanium-containing material with sulfuric acid to form a filter cake comprising at least titanyl sulfate; b) contacting the filter cake with water and / or dilute sulfuric acid to form a sulfated suspension comprising at least titanyl sulfate; c) separating solids from liquid in the sulfated suspension to produce a first permeate (LL) comprising at least titanyl sulfate and a first retentate comprising at least calcium sulfate and silica; and d) hydrolyzing titanyl sulfate in the first permeate to produce a first liquid comprising titanium dioxide hydrate; e) separating titanium dioxide hydrate from said first liquid to produce titanium dioxide hydrate and a second liquid (PHL) comprising at least aluminum sulfate; f) separating aluminium sulphate from said second liquid (PHL) to produce aluminium sulphate and a third liquid (PAL) comprising mixed metal sulphates; or d') separating aluminum sulfate from said first permeate (LL) to produce aluminum sulfate and a first liquid comprising at least titanyl sulfate; e') hydrolyzing titanyl sulfate in the first liquid to produce a second liquid (PHL) comprising titanium dioxide hydrate; f') separating titanium dioxide hydrate from said second liquid (PHL) to produce titanium dioxide hydrate and a third liquid (PAL) comprising mixed metal sulfates, wherein steps d), e) and f) or steps d'), e') and f') are carried out, The titanium-containing material is contacted with sulfuric acid in a mass ratio of about 0.75:1 to about 2:

1.

2. The method according to claim 1, further comprising the steps of: g) combining calcium carbonate and the third liquid to produce a first composition comprising mixed metal sulfates including calcium sulfate.

3. The method according to claim 2, further comprising the steps of: h) separating calcium sulfate from the first composition to produce calcium sulfate and a fourth liquid comprising mixed metal sulfates.

4. The method according to claim 3, further comprising the steps of: i) separating magnesium sulfate from the fourth liquid to produce magnesium sulfate and a fifth liquid (PML) comprising mixed metal sulfates.

5. The method according to claim 4, further comprising the steps of: j) combining calcium hydroxide and the fifth liquid to produce a second composition comprising mixed metal hydroxides and / or oxides and calcium sulfate, or combining magnesium hydroxide and the fifth liquid to produce a second composition comprising mixed metal hydroxides and / or oxides.

6. The method according to claim 5, further comprising the steps of: k) recovering the mixed metal oxide and / or hydroxide or recovering the mixed metal oxide and / or hydroxide and calcium sulfate from the second composition to produce a mixed metal solid.

7. The method according to claim 3, further comprising the steps of: i) combining calcium hydroxide and the fourth liquid to produce a second composition comprising mixed metal oxides and / or hydroxides, calcium sulfate and magnesium sulfate, or combining magnesium hydroxide and the fourth liquid to produce a second composition comprising mixed metal oxides and / or hydroxides and magnesium sulfate.

8. The method according to claim 7, further comprising the steps of: j) separating the mixed metal oxide and / or hydroxide or separating the mixed metal oxide and / or hydroxide and calcium sulfate from the second composition to produce a mixed metal solid or a mixed metal solid and calcium sulfate and a fifth liquid comprising magnesium sulfate.

9. The method according to claim 8, further comprising the steps of: k) recovering magnesium sulfate from the fifth liquid to produce magnesium sulfate.

10. The method according to claim 2, wherein the conditions in step g) are such that titanium is Ti 4+ in the form of Fe 2+ to produce a first composition comprising calcium sulphate and one or more oxides and / or hydroxides of titanium, and then optionally separating the calcium sulphate and one or more oxides and / or hydroxides of titanium from the first composition to produce calcium sulphate and one or more oxides and / or hydroxides of titanium, and a fourth liquid comprising mixed metal sulphates.

11. The method according to claim 1, wherein: The method further comprises the step of calcining the hydrated titanium dioxide to produce titanium dioxide.

12. The method according to claim 1, wherein: The titanium-containing material is selected from the group consisting of ironmaking slag, melting furnace slag, blast furnace slag, vanadium-titanium magnetite, vanadium-titanium magnetite slag, or a combination of two or more thereof.

13. The method according to claim 1, wherein: Step a) is performed such that the combined titanium-containing material and sulfuric acid reaches a temperature of about 130°C to about 250°C.

14. The process of claim 1 wherein the concentration of sulfuric acid used is at least about 60%.

15. The method according to claim 1, wherein: Step a) is performed for a period of about 30 minutes to about 4 hours.

16. A method for recovering one or more products from a composition obtained from a sulfation process for producing titanium dioxide, the method comprising at least the following steps: a) combining calcium carbonate and said composition to produce a composition (A) comprising calcium sulfate; and b) separating calcium sulfate from said second composition (A) to produce calcium sulfate and a composition (B) comprising mixed metal sulfates, said metal sulfates comprising magnesium sulfate, wherein the calcium carbonate and the composition are combined such that the pH is from about 1 to about 4, and wherein the oxidation reduction potential (ORP) is from about 200 mV to about 300 mV.

17. The method according to claim 16, further comprising the steps of: c) separating magnesium sulfate from composition (B) to produce magnesium sulfate and a composition (C) comprising mixed metal sulfates.

18. The method according to claim 17, further comprising the steps of: d) combining calcium hydroxide and said composition (C) to produce a composition (D) comprising mixed metal oxides and / or hydroxides and calcium sulfate; or d1) combining magnesium hydroxide with said composition (C) to produce a composition (D) comprising mixed metal oxides and / or hydroxides.

19. The method according to claim 18, further comprising the steps of: e) recovering the mixed metal oxides and / or hydroxides and calcium sulfate, or recovering the mixed metal oxides and / or hydroxides from the composition (D) to produce a mixed metal solid or a mixed metal solid comprising calcium sulfate.

20. The method according to claim 16, further comprising the steps of: c) combining calcium hydroxide with said composition (B) to produce a composition (C') comprising magnesium sulfate, mixed metal oxides and / or hydroxides and calcium sulfate; or c1) combining magnesium hydroxide with said composition (B) to produce a composition (C') comprising magnesium sulfate and mixed metal oxides and / or hydroxides.

21. The method according to claim 20, further comprising the steps of: d) separating the mixed metal oxides and / or hydroxides and calcium sulfate from the composition (C'), or separating the mixed metal oxides and / or hydroxides to produce a mixed metal solid comprising calcium sulfate or a mixed metal solid and a composition comprising magnesium sulfate (D').

22. The method according to claim 21, further comprising the steps of: e) recovering magnesium sulfate from composition (D') to produce magnesium sulfate.

23. The method according to claim 16, wherein: The conditions are such that titanium is Ti 4+ In the form of Fe 2+ form to produce a composition (A) comprising calcium sulfate and one or more oxides and / or hydroxides of titanium.

24. The method according to claim 23, wherein: The method further comprises separating calcium sulfate and one or more titanium oxides and / or hydroxides from composition (A) to produce calcium sulfate and one or more titanium oxides and / or hydroxides and a mixed metal sulfate composition (B).

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