Clean energy efficient hydrometallurgy process for producing critical minerals

Abstract

The subject disclosure is directed to improved methods for processing rare earth element bearing ores that is cleaner and more energy efficient than previous processes. The improved methods enables the recovery of most of the nitric acid required by the process, to reduce acid waste generated by previous processes.

Description

CLEAN ENERGY EFFICIENT HYDROMETALLURGY PROCESS FOR PRODUCING CRITICAL MINERALSTECHNICAL FIELD

[0001] The subject disclosure is directed to improved methods for processing rare earth element bearing ores that is cleaner and more energy efficient than previous processes. Suitable starting materials include any ores that contain rare earth elements, and preferably also contain titanium. More specifically, these improved methods are more energy efficient, and enable the recovery of most of the nitric acid required by the process, resulting in less acid waste than is generated by previous processes.BACKGROUND ART

[0002] Rare earth element (REE) bearing ore, such as phosphate minerals with REEs including crandallite, monazite, florencite, ion adsorption clays with REEs, alumino-silicate clays such as kaolinite, smectites and titanium bearing minerals such as anatase and ilemenite, represent a rich source of valuable metal compounds. Traditionally, only ores that have sufficient metal content and meet other detailed criteria have been useful for extracting the metals therein. The compositions of ores vary tremendously, even taken from the same mining site. Accordingly, processes that can extract valuable metal compounds from a full range of ores are desirable.

[0003] Traditional methods of ore processing generate significant waste products, and especially acidic waste products, that can be harmful to the environment. Accordingly, there is a need for more efficient and environmentally friendly techniques to extract valuable metal compounds from starting materials while reducing the generation of acidic wastes.

[0004] Traditional methods of ore processing are also energy intensive. Accordingly, there is a need for more energy efficient and environmentally friendly techniques in this regard as well.DISCLOSURE OF INVENTION

[0005] In various implementations, a method for obtaining recovered metal compounds from starting materials is provided. The disclosed methods are useful for obtaining recovered metal compounds from low grade starting materials that have previously been overlooked and / or discarded as waste. The term “starting materials” as used herein refers to phosphate minerals withDocket No. 15082-007REEs including crandallite, monazite, florencite, ion adsorption clays with REEs, alumino-silicate clays such as kaolinite, smectites and titanium bearing minerals such as anatase and ilemenite. The starting materials are leached using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue. The residue is preferably washed with a neutralizing solution. The leached solution is subjected to iron hydrolysis at about 150-200°C and up to 21 bar pressure, which results in iron in the form of hematite, a post iron hydrolysis (PIH) solution that has had much of the iron removed, and nitric acid in the vapor stream. The PIH solution is subjected to aluminum hydrolysis at 170-200°C and atmospheric pressure. Aluminum hydrolysis removes almost all the remaining iron and much of the aluminum in the form of an Al-Fe oxide product, and also yields a post aluminum hydrolysis (PAH) solution and nitric acid in the vapor stream.

[0006] The PAH solution is preferably treated to remove scandium either by ion exchange or solvent extraction, yielding scandium hydroxide and a raffinate solution. This raffinate solution is subjected to another ion exchange process to remove gallium therefrom. Once the gallium is removed, a second raffinate solution is created. The second raffinate solution is again subjected to another ion exchange process to remove rare earth elements therefrom. These removed rare earth elements are precipitated to create a mixed rare earth element carbonate, and a third raffinate solution. This third raffinate solution has excess water removed by evaporation and is heated to thermally decompose the nitrates therein, converting them to NOx gases which are recovered in the vapor phase. This thermal decomposition will also produce a mixed oxide product containing magnesium and calcium. This mixed oxide product can be used to neutralize acid in other steps of the overall process.

[0007] While in a preferred embodiment, the PAH solution is treated to remove and collect scandium, followed by collection of gallium, and then collection of rare earth elements, some starting materials will not contain enough of one or more of these elements to make such a process worthwhile. In some embodiments, one or more of these three steps is omitted entirely. Any one, two, or all three of these steps may be performed, or omitted.

[0008] Throughout the process steps of the present invention, it is readily possible to recover nitric acid, nitrates, and NOx gases created therein, and convert these nitrates and NOx gases to nitric acid, which can then be recovered and used again for the leaching of starting materials. AtDocket No. 15082-007least 80%, and up to 98% of nitric acid can be recovered from within the process. In a preferred embodiment, 95-98% range of the nitric acid can be recovered from the process, and recycled to the initial leaching step.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIGS. 1-2 are flow diagrams of an embodiment of a hydrometallurgy process in accordance with the disclosed subject matter.MODES FOR CARRYING OUT THE INVENTION

[0010] The subject disclosure is directed to improved methods for processing starting materials that are titanium-bearing and REE bearing ores. These starting materials include phosphate minerals with REEs including crandallite, monazite, florencite, ion adsorption clays with REEs, alumino-silicate clays such as kaolinite, smectites and titanium bearing minerals such as anatase and ilemenite. The process is able to recycle the majority of the acid used therein.

[0011] The detailed description provided below in connection with the appended drawings is intended as a description of examples and is not intended to represent the only forms in which the present examples can be constructed or utilized. The description sets forth functions of the examples and sequences of steps for constructing and operating the examples. However, the same or equivalent functions and sequences can be accomplished by different examples.

[0012] References to “one embodiment,” “an embodiment,” “an example embodiment,” “one implementation,” “an implementation,” “one example,” “an example” and the like, indicate that the described embodiment, implementation or example can include a particular feature, structure or characteristic, but every embodiment, implementation or example can not necessarily include the particular feature, structure or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment, implementation or example. Further, when a particular feature, structure or characteristic is described in connection with an embodiment, implementation or example, it is to be appreciated that such feature, structure or characteristic can be implemented in connection with other embodiments, implementations or examples whether or not explicitly described.Docket No. 15082-007

[0013] Numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments of the described subject matter. It is to be appreciated, however, that such embodiments can be practiced without these specific details.

[0014] Various features of the subject disclosure are now described in more detail with reference to the drawings, wherein like numerals generally refer to like or corresponding elements throughout. The drawings and detailed description are not intended to limit the claimed subject matter to the particular form described. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed subject matter. Unless otherwise indicated, percentages are expressed by weight.

[0015] In some cases, the starting materials for the disclosed process are sources of valuable metals that have previously been considered economically unviable for the extraction of the metals therein. Previously, such materials were not cost-effective for metal extraction, as they were relatively poor in metal content, or difficult to process. Using the present process, it is now possible to extract the valuable metals from these starting materials. This results in less waste material in total than that from previous processes.

[0016] The disclosed process includes leaching starting materials using nitric acid within a concentration range of about 10% to about 100% at a temperature range of about 100°C to about 115°C and at atmospheric pressure to leach valuables such as iron, nickel, cobalt, scandium, and others into the solution. In preferred embodiments, the concentration of the nitic acid is about 60- 90%. In more preferred embodiments, the concentration of the nitric acid is about 68-78%.

[0017] The lower and upper limit of temperature range is about 80-110°C. In a preferred embodiment, the temperature range is between about 100-110°C. However, the lower limit of the acceptable temperature range will change with the concentration of the nitric acid. As the nitricacid concentration increases, the boiling point of the nitric acid solution decreases, so that the lower limit of the temperature range can decrease.

[0018] The residue is preferably washed and neutralized to produce a product that is rich in silicates. For many of the starting material ores, this residue will also contain significant amounts of titanium that can be recovered. The rest of the solids are useful as engineered landfill, as well as other purposes known to those of skill in the art.

[0019] The leached solution is sent to an iron hydrolysis reactor to recover iron as hematite at about 150°C to about 200°C and at a pressure in the range of about 0.1-21 bar. In a preferredDocket No. 15082-007embodiment, the temperature range is about 165°C to about 195°C. In another preferred embodiment, the pressure is about 6 bar. Other products of this iron hydrolysis step include NOx gases in the vapor stream, and a PIH solution that is largely free from iron. In a preferred embodiment, about 90% to 95% of the iron is removed from the solution, and even more preferably up to 99% of the iron is removed. Preferably, the NOx gases are recovered and reused in this process to leach starting materials.

[0020] The PIH solution is subjected to another hydrolysis step, this time aluminum hydrolysis at about 150°C to about 200°C, at or close to atmospheric pressure, thereby producing an Al-Fe oxide product, NOx gases in the vapor stream, and a post aluminum hydrolysis (PAH) solution that is largely free of both iron and aluminum. In a preferred embodiment, this hydrolysis step occurs at a temperature range of about 175°C to about 200°C. In a preferred embodiment, about 95% to about 99% of the remaining iron is removed from the solution, and even more preferably about 98% to about 99% of the iron is removed. In a preferred embodiment, about 80% to about 95% of the aluminum is removed from the solution, and even more preferably about 90% to about 95% of the aluminum is removed. Preferably, the NOx gases are recovered, converted back to nitric acid, and reused in this process to leach starting materials.

[0021] In a preferred embodiment, the PAH solution is treated to remove and collect the scandium therein by ion exchange and / or solvent extraction. After one or both of these treatments, the scandium can be precipitated as a hydroxide, and a raffinate solution will also be produced.

[0022] The raffinate solution that remains after scandium is removed is preferably sent through another ion exchange process to remove and recover gallium therefrom. Gallium is recovered in the form of gallium hydroxide or other relevant compound, and a second raffinate solution is also produced. If the starting materials do not contain sufficient gallium for this step to be cost effective, it is preferably omitted.

[0023] The second raffinate solution that remains after gallium is removed is sent through another ion exchange process to remove and recover rare earth elements therefrom. The rare earth elements are precipitated and recovered in the form of mixed rare earth element carbonates, and a third raffinate solution is also produced.

[0024] The third raffinate solution is subjected to an evaporation step to remove excess water, and then subjected to thermal decomposition at a temperate of about 500°C to about 900°C. This thermal decomposition will convert the nitrates in the solution to NOx gases that can be recovered,Docket No. 15082-007converted to nitric acid, and recycled back into the leaching step. This thermal decomposition will also produce a mixed oxide solid product that is rich in magnesium and calcium. This mixed oxide solid product can be used to neutralize acid in other steps of the process, such as when treating the residue of the leaching step.

[0025] For certain starting material, such as kaolinite, it is useful and sometimes even necessary to first subject the starting materials to a heat treatment step prior to leaching. In these cases, the starting materials are heated to about 600°C for about 4 hours. This step will transform the kaolinite mineral to metakaolin by removing chemically bound water at those conditions. The metakaolin produced is leachable with nitric acid.

[0026] The disclosed systems and methods represent improvements over the systems and methods disclosed within U.S. Patent Nos. 8,016,913 and 8,038,767 to Drinkard, Jr., the entire disclosures of which, except for any definitions, disclaimers, disavowals, and inconsistencies, are incorporated herein by reference.

[0027] Referring now to the drawings and, in particular, to FIGS. 1-2, there is shown an improved hydrometallurgy process, generally designated with the numeral 100, for recovering valuable metal compounds through leaching, hydrolysis, and other processing steps. The process 100 can be used to process starting materials in the form of titanium-bearing and REE bearing ores. Exemplary raw ores include phosphate minerals with REEs including crandallite, monazite, florencite, ion adsorption clays with REEs, alumino-silicate clays such as kaolinite, smectites and titanium bearing minerals such as anatase and ilemenite.

[0028] The process 100 can be used to recover metals and metal compounds. Exemplary metals include REEs, titanium, iron, aluminum, scandium, and other metals.

[0029] The process 100 begins by combining a nitric acid solution 110 with starting materials 112 for leaching at 114. The nitric acid solution 110 contains a predetermined concentration of nitric acid, which can range from about 10% to about 100%. In one exemplary embodiment, the predetermined concentration is about 68% to about 78%. The starting materials 112 are any of a variety of titanium bearing and REE bearing ores.

[0030] At 114, the precursor materials 112 are leached with the nitric acid solution 110 at a predetermined temperature and predetermined atmospheric pressure. In this exemplary embodiment, the predetermined temperature is within the range of about 100°C to about 115°C. The predetermined atmospheric pressure is within the range of about 0.95 atmospheres to aboutDocket No. 15082-0071.05 atmospheres. In this exemplary embodiment, the predetermined atmospheric pressure is about 1.0 atmosphere.

[0031] The leaching step at 114 produces a leached solution 115 and a residue 113. The leached solution is transported to iron hydrolysis apparatus 116. This iron hydrolysis step produces hematite 117 and a post-iron hydrolysis (PIH) solution 118 that has had much of the iron removed therefrom. This step also produces a vapor stream containing nitric acid, which is then purified and recycled back to the leaching step 114.

[0032] Iron hydrolysis within iron hydrolysis apparatus 116 can be accomplished through any suitable means. In a preferred embodiment, the leached solution 115 is heated to about 150°C to about 200°C and subjected to a pressure of about 1-21 bar. In a more preferred embodiment, the pressure is about 6 bar.

[0033] The PIH solution 118 is moved into an aluminum hydrolysis apparatus 120. This aluminum hydrolysis step produces an Al-Fe oxide product 122, and a post-aluminum hydrolysis (PAH) solution 124 that is almost entirely free of iron, and largely free of aluminum.

[0034] Aluminum hydrolysis within aluminum hydrolysis apparatus 120 can be accomplished through any suitable means. In a preferred embodiment, the PIH solution 118 is heated to about 170°C to about 200°C at approximately atmospheric pressure. This step also produces a vapor stream containing nitric acid, which is then purified and recycled back to the leaching step 114.

[0035] The PAH solution 124 is preferably treated to remove and collect scandium therefrom. PAH solution 124 can be treated by ion exchange or solvent extraction in apparatus 127 to remove a scandium hydroxide product 128 therefrom. A raffinate solution 130 is also produced by this step. It is quite similar in composition to the PAH solution 124, except for the removal of the scandium. This step is not mandatory, however.

[0036] The raffinate solution 130, or the PAH solution 124 if scandium removal is not performed, is next sent to ion exchange apparatus 132 where gallium is removed therefrom. The gallium product 134 is produced in the form of gallium hydroxide or a relevant gallium product, and a second raffinate solution 136 is created. Some starting materials will not contain sufficient amounts of gallium for this step to be cost effective, and it may be omitted.

[0037] Next the rare earth elements are collected at ion exchange apparatus 140. The source of rare earth elements can be the PAH solution 124 (if removal of scandium and gallium are both omitted), the raffinate solution 130 (if removal of gallium is omitted), or the raffinate solution 136Docket No. 15082-007(which could include the scandium removal step, or omit it). Scandium and gallium removal are both optional steps, and will be omitted when the starting materials do not contain sufficient amounts of either element. The output of ion exchange apparatus 140 is a mixed rare earth element carbonate 142 and a third raffinate solution 144.

[0038] The third raffinate solution 144 is sent to apparatus 150 for evaporation of excess water, followed by thermal decomposition at about 600°C for about 4 hours. This will produce NOx gases that can converted to nitric acid and recycled back to the leaching step at 114. It will also produce a mixed oxide product 152 that contains magnesium and calcium. This mixed oxide product 152 is useful for neutralizing acid such as when the residue 113 is washed and neutralized prior to the collection of titanium therefrom.Supported Features and Embodiments

[0039] The detailed description provided above in connection with the appended drawings explicitly describes and supports various features of systems, apparatus, and methods for processing starting materials such as rear earths phosphates such as monazite, crandalite and ion adsorption clays containing rear earths such as kaolinite, alumino silicates clays containing rare earths and titanium minerals such as anatase, rutile, illemenite to recover metal compounds therein through hydrometallurgy. By way of illustration and not limitation, supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue; subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution; subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution; treating said PAH solution to remove scandium, gallium, and REEs sequentially either by ion exchange or solvent extraction, producing scandium hydroxide and / or gallium hydroxide or similar and / or REE carbonate or hydroxide and a raffinate solution; the raffinate solution is subjected to an evaporation step to remove excess water, and then subjected to thermal decomposition at a temperate of about 500°C to about 900°C. This thermal decomposition will convert the nitric acid and nitrates in the solution to NOx gases that can be recovered, converted to nitric acid, and recycled back into the leaching step. This thermalDocket No. 15082-007decomposition will also produce mixed oxide solid products that is rich in magnesium and calcium. This mixed oxide solid product can be used to neutralize acid in other steps of the process, such as when treating the residue of the leaching step.

[0040] In more preferred embodiments, at least 90% of the nitric acid is recoverable, and in the most preferred embodiments, at least 95% (and up to 100%) of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0041] Supported embodiments also include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution, separating gallium from said raffinate solution by ion exchange to produce purified gallium and a second raffinate solution, separating rare earth elements from said second raffinate solution by ion exchange to produce purified rare earth elements and a third raffinate solution, precipitating said rare earth elements to produce a mixed rare earth elements carbonate, and heating said third raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0042] Supported embodiments include any of the foregoing methods, wherein said starting materials are selected from the group consisting of phosphate minerals containing REEs, crandallite, monazite, florencite, ion adsorption clays containing REEs, alumino-silicate clays, kaolinite, smectites, titanium bearing minerals, anatase and ilemenite.

[0043] Supported embodiments include any of the foregoing methods, wherein the predetermined nitric acid concentration is within the range of about 10% to about 100%.

[0044] Supported embodiments include any of the foregoing methods, wherein the predetermined nitric acid concentration is within the range of about 60% to about 90%.

[0045] Supported embodiments include any of the foregoing methods, wherein the predetermined nitric acid concentration is within the range of about 68% to about 78%.Docket No. 15082-007

[0046] Supported embodiments include any of the foregoing methods, wherein the predetermined temperature is within the range of about 80°C to about 110°C.

[0047] Supported embodiments include any of the foregoing methods, wherein the predetermined temperature is within the range of about 100°C to about 110°C.

[0048] Supported embodiments include any of the foregoing methods, wherein the predetermined pressure is within the range of about 0.95 to about 1.05 atmospheres.

[0049] Supported embodiments include any of the foregoing methods, wherein at least 95% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0050] Supported embodiments include any of the foregoing methods, wherein said iron hydrolysis occurs at a temperature range of about 150°C to about 200°C.

[0051] Supported embodiments include any of the foregoing methods, wherein said iron hydrolysis occurs at a temperature range of about 165°C to about 195°C.

[0052] Supported embodiments include any of the foregoing methods, wherein said iron hydrolysis occurs at a pressure of about 0.1 bar to about 21 bar.

[0053] Supported embodiments include any of the foregoing methods, wherein said iron hydrolysis occurs at a pressure of about 6 bar.

[0054] Supported embodiments include any of the foregoing methods, wherein said iron hydrolysis removes between about 90% and about 95% of the iron from said leached solution.

[0055] Supported embodiments include any of the foregoing methods, wherein said iron hydrolysis removes between about 95% and about 99% of the iron from said leached solution.

[0056] Supported embodiments include any of the foregoing methods, wherein said aluminum hydrolysis occurs at a temperature range of about 150°C to about 200°C.

[0057] Supported embodiments include any of the foregoing methods, wherein said aluminum hydrolysis occurs at a temperature range of about 175 °C to about 200°C.

[0058] Supported embodiments include any of the foregoing methods, wherein said aluminum hydrolysis removes between about 95% and about 99% of the remaining iron from said PIH solution.

[0059] Supported embodiments include any of the foregoing methods, wherein said aluminum hydrolysis removes between about 98% and about 99% of the remaining iron from said PIH solution.Docket No. 15082-007

[0060] Supported embodiments include any of the foregoing methods, wherein said aluminum hydrolysis removes between about 80% and about 95% of the aluminum from said PIH solution.

[0061] Supported embodiments include any of the foregoing methods, wherein said aluminum hydrolysis removes between about 90% and about 95% of the aluminum from said PIH solution.

[0062] Supported embodiments include any of the foregoing methods, wherein said residue is washed, the acid is neutralized, and then beneficiated to produce titanium.

[0063] Supported embodiments include any of the foregoing methods, wherein said starting materials are heat treated at about 600°C for about 4 hours to produce a treated starting material that is more effective for leaching minerals.

[0064] Supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, separating gallium from said PAH solution by ion exchange to produce purified gallium and a raffinate solution, separating rare earth elements from said raffinate solution by ion exchange to produce purified rare earth elements and a second raffinate solution, precipitating said rare earth elements to produce a mixed rare earth elements carbonate, and heating said second raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0065] Supported embodiments include any of the foregoing methods, wherein at least 90% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0066] Supported embodiments include any of the foregoing methods, wherein at least 95% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0067] Supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting saidDocket No. 15082-007leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution, separating rare earth elements from said raffinate solution by ion exchange to produce purified rare earth elements and a second raffinate solution, precipitating said rare earth elements to produce a mixed rare earth elements carbonate, and heating said second raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0068] Supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution, separating gallium from said raffinate solution by ion exchange to produce purified gallium and a second raffinate solution, and heating said second raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0069] Supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producingDocket No. 15082-007scandium hydroxide and a raffinate solution, and heating said raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0070] Supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, separating gallium from said PAH solution by ion exchange to produce purified gallium and a raffinate solution, and heating said raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0071] Supported embodiments include a method for obtaining recovered metal compounds from starting materials comprising leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue, subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution, subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution, separating rare earth elements from said PAH solution by ion exchange to produce purified rare earth elements and a raffinate solution, precipitating said rare earth elements to produce a mixed rare earth elements carbonate, and heating said raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium, wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

[0072] Supported embodiments include a hydrometallurgical process that uses nitric acid recycle and recovery technology. The technology can be used to recycle the majority of the acid used in the process.Docket No. 15082-007

[0073] Supported embodiments include a hydrometallurgical process that utilizes leaching, crystallization, hydrolysis, ion exchange, solvent extraction, precipitation, thermal decomposition, solid liquid separation, and gravity separation / magnetic separation.

[0074] The detailed description provided above in connection with the appended drawings is intended as a description of examples and is not intended to represent the only forms in which the present examples can be constructed or utilized. It is to be understood that the configurations and / or approaches described herein are exemplary in nature, and that the described embodiments, implementations and / or examples are not to be considered in a limiting sense, because numerous variations are possible.

[0075] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are presented as example forms of implementing the claims.

Claims

Docket No. 15082-007CLAIMSWhat is claimed is:

1. A method for obtaining recovered metal compounds from starting materials comprising:leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution;separating gallium from said raffinate solution by ion exchange to produce purified gallium and a second raffinate solution;separating rare earth elements from said second raffinate solution by ion exchange to produce purified rare earth elements and a third raffinate solution;precipitating said rare earth elements to produce a mixed rare earth elements carbonate; andheating said third raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

2. The method of claim 1, wherein said starting materials are selected from the group consisting of phosphate minerals containing REEs, crandallite, monazite, florencite, ion adsorption clays containing REEs, alumino-silicate clays, kaolinite, smectites, titanium bearing minerals, anatase and ilemenite.

3. The method of claim 1, wherein the predetermined nitric acid concentration is within the range of about 10% to about 100%.Docket No. 15082-0074. The method of claim 3, wherein the predetermined nitric acid concentration is within the range of about 60% to about 90%.

5. The method of claim 4, wherein the predetermined nitric acid concentration is within the range of about 68% to about 78%.

6. The method of claim 1 , wherein the predetermined temperature is within the range of about 80°C to about 110°C.

7. The method of claim 6, wherein the predetermined temperature is within the range of about 100°C to about 110°C.

8. The method of claim 1, wherein the predetermined pressure is within the range of about 0.95 to about 1.05 atmospheres.

9. The method of claim 1 , wherein at least 95% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

10. The method of claim 1 , wherein said iron hydrolysis occurs at a temperature range of about 150°C to about 200°C.

11. The method of claim 10, wherein said iron hydrolysis occurs at a temperature range of about 165°C to about 195°C.

12. The method of claim 1, wherein said iron hydrolysis occurs at a pressure of about 0.1 bar to about 21 bar.

13. The method of claim 12, wherein said iron hydrolysis occurs at a pressure of about 6 bar.

14. The method of claim 1, wherein said iron hydrolysis removes between about 90% and about 95% of the iron from said leached solution.Docket No. 15082-00715. The method of claim 14, wherein said iron hydrolysis removes between about 95% and about 99% of the iron from said leached solution.

16. The method of claim 1, wherein said aluminum hydrolysis occurs at a temperature range of about 150°C to about 200°C.

17. The method of claim 16, wherein said aluminum hydrolysis occurs at a temperature range of about 175°C to about 200°C.

18. The method of claim 1, wherein said aluminum hydrolysis removes between about 95% and about 99% of the remaining iron from said PIH solution.

19. The method of claim 18, wherein said aluminum hydrolysis removes between about 98% and about 99% of the remaining iron from said PIH solution.

20. The method of claim 1, wherein said aluminum hydrolysis removes between about 80% and about 95% of the aluminum from said PIH solution.

21. The method of claim 20, wherein said aluminum hydrolysis removes between about 90% and about 95% of the aluminum from said PIH solution.

22. The method of claim 1, wherein said residue is washed, the acid is neutralized, and then beneficiated to produce titanium.

23. The method of claim 1, wherein said starting materials are heat treated at about 600°C for about 4 hours to produce a treated starting material that is more effective for leaching minerals.

24. A method for obtaining recovered metal compounds from starting materials comprising:Docket No. 15082-007leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;separating gallium from said PAH solution by ion exchange to produce purified gallium and a raffinate solution;separating rare earth elements from said raffinate solution by ion exchange to produce purified rare earth elements and a second raffinate solution;precipitating said rare earth elements to produce a mixed rare earth elements carbonate; andheating said second raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

25. The method of claim 24, wherein at least 90% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

26. The method of claim 25, wherein at least 95% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

27. A method for obtaining recovered metal compounds from starting materials comprising:leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;Docket No. 15082-007subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution;separating rare earth elements from said raffinate solution by ion exchange to produce purified rare earth elements and a second raffinate solution;precipitating said rare earth elements to produce a mixed rare earth elements carbonate; andheating said second raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

28. A method for obtaining recovered metal compounds from starting materials comprising:leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution;separating gallium from said raffinate solution by ion exchange to produce purified gallium and a second raffinate solution; andheating said second raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.Docket No. 15082-00729. A method for obtaining recovered metal compounds from starting materials comprising:leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;treating said PAH solution to remove scandium either by ion exchange or solvent extraction, producing scandium hydroxide and a raffinate solution; andheating said raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

30. A method for obtaining recovered metal compounds from starting materials comprising:leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;separating gallium from said PAH solution by ion exchange to produce purified gallium and a raffinate solution; andheating said raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

31. A method for obtaining recovered metal compounds from starting materials comprising:Docket No. 15082-007leaching said starting materials using a nitric acid solution containing a predetermined nitric acid concentration, at a predetermined temperature, and at a predetermined atmospheric pressure to produce a leached solution and a residue;subjecting said leached solution to iron hydrolysis, thereby producing iron in the form of hematite and a post iron hydrolysis (PIH) solution;subjecting said PIH solution to aluminum hydrolysis, thereby producing an Al-Fe oxide product and a post aluminum hydrolysis (PAH) solution;separating rare earth elements from said PAH solution by ion exchange to produce purified rare earth elements and a raffinate solution;precipitating said rare earth elements to produce a mixed rare earth elements carbonate; andheating said raffinate solution to produce NOx gases and a mixed oxide product containing magnesium and calcium;wherein through this process, at least 80% of the nitric acid is recoverable and suitable for reuse in leaching starting materials.

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