Phosphogypsum treatment process

Abstract

A reagent for phosphogypsum flotation, and a collector composition comprising it are provided. A related method for treating phosphogypsum using the reagent and / or the collector composition is also provided. The treatment of phosphogypsum upgrades properties, particularly in terms of whiteness and grade.

Description

[0001] Phosphogypsum Treatment Process

[0002] TECHNICAL FIELD

[0003] The present invention relates to a reagent for phosphogypsum flotation, a collector composition comprising it, a related method for treating phosphogypsum and corresponding uses.

[0004] TECHNICAL BACKGROUND

[0005] Phosphates [PO43-] have many applications, both in industry and in agriculture. Phosphates are particularly used for producing fertilizers, as phosphorus is one of the three main macronutrients for plants, enhancing the development of roots, flowers, seeds and / or fruits. Phosphates are also used in animal feed supplements, food preservatives, anti-corrosion agents, cosmetics, fungicides, ceramics, water treatment, metallurgy, and more.

[0006] Phosphate rocks are found all over the earth. They may comprise different groups of phosphate minerals. Phosphate minerals may, for example, belong to the group consisting of amblygonite, apatite, autunite, hinsdalite, lazulite, mitridadite, monazite, phosphophyllite, pyromorphite, struvite, triphylite, turquoise, wavellite, and xenotime. Apatite [Cas(PO4)3(F,CI,OH)] is the most common group of phosphate minerals, which is classified in subgroups particularly including hydroxylapatite, fluorapatite, chlorapatite and bromapatite.

[0007] The phosphate mineral resources are mainly found in China, Morocco, the United States and Middle East. Depending on their chemical composition, particularly their proportion in phosphates, mineral resources may be highgrade, medium-grade or low-grade resources, the resource grade impacting the degree of difficulty for extracting phosphates therein. Phosphates are extracted from phosphate ore to produce phosphoric acid. Phosphoric acid is produced by treating phosphate ore, particularly apatite ore, with sulfuric acid (known as the wet phosphoric acid process) according to the following equation:

[0008]

[0009] wherein H may be OG, F, Cl or Br.

[0010] Besides producing phosphoric acid, the treatment of phosphates also produces phosphogypsum (PG) as a by-product, which mainly comprises gypsum [CaSO4*2 H2O]. Phosphogypsum is usually radioactive, in that it comprises naturally occurring radioactive elements e.g., uranium [U], thorium [Th], radium [Ra], radon [Rn] and / or polonium [Po], Phosphogypsum alsocomprises additional non-radioactive elements including heavy metals, or components comprising them, e.g., aluminum [Al], arsenic [As], barium [Ba], cadmium [Cd], chromium [Cr], fluoride [F], iron [Fe], lead [Pb], magnesium [Mg], mercury [Hg], phosphorus [P], selenium [Se] and silicium [Si]. Phosphogypsum may also comprise other compounds, including organic matters. The composition of phosphogypsum greatly varies depending on the starting phosphate and the implemented method for producing phosphoric acid.

[0011] Part of phosphogypsum produced is used e.g., for manufacturing building materials or as a soil amendment. However, most of phosphogypsum remains as a solid waste, and is usually stacked on open-air landfills (also known as phosphogypsum stacks or gyp stacks). Over time, the phosphogypsum may leach into the environment, such that phosphorus, radioactive elements, heavy metals and / or other undesirable compounds may pollute the stack surroundings by contaminating the soil, the surface water (e.g., the rivers or the oceans), and the groundwater.

[0012] Due to the presence of impurities - phosphorus, radioactive elements, heavy metals and other undesirable compounds - phosphogypsum perse can hardly be used on a large scale. Phosphogypsum first needs to be treated e.g., using froth flotation.

[0013] Froth flotation is a known method for extracting a mineral from low-content ores by a stage of concentration. Froth flotation thus allows separating the valuable components (selected minerals) of an ore from the undesirable components (also known as the gangue) to produce a mineral concentrate. Froth flotation works by separating minerals from the gangue by exploiting differences in hydrophobicity. Froth flotation starts by crushing / grinding ore into fine particles to liberate ore particles of desirable minerals and undesirable gangue components. The ore particles are then mixed with water to obtain a slurry (also known as the pulp). The slurry is then mixed with a flotation composition (also known as flotation agent or collector composition) in a flotation cell. The flotation composition selectively renders the surfaces of the different types of particles hydrophobic or hydrophilic, depending on the chemistry, properties, etc. of the compounds comprised therein. The flotation steps are then carried out by passing a stream of air or inert gas bubbles through the slurry, such that the gas bubbles attach to and levitate the hydrophobic ore particles. The levitated, hydrophobic ore particles, which are attached to the air bubbles, are then collected in a floating portion (also known as a froth layer), which floats over the sink portion of the treated slurry. Theremaining part of the slurry may be either unaffected by the collector composition or rendered hydrophilic and settling at the bottom of the flotation cell. The flotation portion (direct flotation) or the sink portion (reverse flotation) has a content of the desired compounds, which is considerably higher than that in the starting ore. This content depends on the initial mineral content in the ore and / or the selectivity of the collector composition. Froth flotation is used for treating (and beneficiating) phosphate-containing resources or wastes including phosphogypsum. See for example the patent US 4,2344,14 published on 18 November 1980, and the Chinese patent application CN 117696265 A filed on 15 March 2024.

[0014] Even though known froth flotation techniques allow beneficiating phosphogypsum to a certain extent, there is the need for an improved method. There is particularly the need for a method allowing the removal of at least 90 % of impurities from phosphogypsum. There is also the need for a method that provides a treated phosphogypsum having an increased whiteness. There is also the need for a method that provides a treated phosphogypsum of sufficient grade for use in gypsum board building materials. There is also the need for treating phosphogypsum at a reduced cost. There is also the need for providing a method that provides a green and environmentally friendly way to treat phosphogypsum.

[0015] SUMMARY OF THE INVENTION

[0016] It is a first object of the invention to provide a reagent comprising a salt of an acid and a condensate of at least one polyalkylene polyamine and a mixture of at least two fatty acid compounds;

[0017] wherein the mixture of fatty acid compounds comprises about 15 wt.% or more, preferably from about 15 wt% to about 50 wt%, more preferably from about 20 to 40 wt.%, of at least one saturated fatty acid, by total weight of the mixture of fatty acid compounds; and

[0018] wherein the mixture of fatty acid compounds comprises about 85 wt.% or less, preferably from about 50 wt% to about 85 wt%, preferably from about 60 to about 80 wt.%, of at least one unsaturated fatty acid, by total weight of the mixture of fatty acid compounds.

[0019] In some embodiments, the at least one polyalkylene polyamine comprises alkylene groups in the polyalkylene polyamine selected from the group consisting of ethylene and / or propylene; preferably, the at least one polyalkylene polyamine has the following formula I:

[0020] H2N-(C2H4NH)X-C2H4-NH2 (I),wherein x is an integer from 2 to 11 ; and / or

[0021] the at least one saturated fatty acid is selected from the group consisting of C 12-30 saturated fatty acids; preferably C14-22 saturated fatty acids; more preferably C14-18 saturated fatty acids; most preferably C16-18 saturated fatty acids; and / or

[0022] the at least one unsaturated fatty acid is selected from the group consisting of C12-30 unsaturated fatty acids; preferably C14-22 unsaturated fatty acids; more preferably C14-18 unsaturated fatty acids; and / or

[0023] the acid is selected from the group consisting of acetic acid, citric acid, oxalic acid, sulfuric acid, hydrochloric acid, and mixtures thereof; preferably the acid is acetic acid.

[0024] In some embodiments, the content of formula I is higher than 80 wt%, preferably 90 wt% based on the total weight of polyalkylene polyamine.

[0025] In some embodiments, the mixture of fatty acid compounds comprises palmitic acid, stearic acid, oleic acid and linoleic acid.

[0026] In some embodiments, the content of the C16-18 fatty acid compounds is about 90 wt.% or more of the fatty acid compounds present in the mixture; and / or the content of the C16-18 saturated fatty acid compounds is about 90 wt.% or more of the saturated fatty acid compounds present in the mixture.

[0027] In some embodiments, the reagent comprises from about 45 to about 80 wt.%, preferably from about 50 to about 75 wt.%, more preferably from about 55 to about 70 wt.%, of the salt of the acid and the condensate, by total weight of the reagent.

[0028] It is a second object of the invention to provide a composition, wherein the composition comprises the reagent as described herein, and at least one additive; preferably the at least one additive is selected from the group consisting of at least one mineral oil, at least one alcohol, at least one flotation auxiliary, and mixtures thereof.

[0029] In some embodiments, the composition comprises from about 80 to about 95 wt.%, preferably from about 82 to about 92 wt.%, more preferably from about 83 to about 90 wt.%, of the reagent, by total weight of the composition.

[0030] In some embodiments, the composition comprises, by total weight of the composition:

[0031] - from about 1 to about 18 wt.%, preferably from about 3 to about 15 wt.%, more preferably from about 5 to about 13 wt.%, of the at least one mineral oil;- from about 1 to about 18 wt.%, preferably from about 2 to about 15 wt.%, more preferably from about 3 to about 10 wt.%, of the at least one alcohol; and / or

[0032] - from about 1 to about 18 wt.%, preferably from about 1.5 to about 15 wt.%, more preferably from about 1.8 to about 10 wt.%, of the at least one flotation auxiliary.

[0033] In some embodiments, the composition comprises, by total weight of the composition:

[0034] - from about 25 to about 95 wt% of the reagent;

[0035] - from about 1 to about 25 wt% of the at least one mineral oil;

[0036] - from about 1 to about 18 wt% of the at least one alcohol;

[0037] - from about 0 to about 15 wt% of the acid;

[0038] - from about 0 to 40 wt% of water;

[0039] - from about 0 to 10 wt% of the at least one flotation auxiliary.

[0040] The acid could be the same or different from the one in the reagent. In some embodiments, the composition comprises the mixture / reaction product of, by total weight of the composition:

[0041] - from about 12 to about 60 wt% of the condensate;

[0042] - from about 1 to about 25 wt% of the at least one mineral oil;

[0043] - from about 1 to about 35 wt% of the at least one alcohol;

[0044] - from about 1 to about 15 wt% of the acid;

[0045] - from about 4 to 50 wt% of water;

[0046] - from about 0 to 10 wt% of the at least one flotation auxiliary.

[0047] In some embodiments, in the composition, the ratio of the condensate to the at least one alcohol is 1 :2 to 2:1 ; and / or

[0048] the ratio of the condensate to the at least one mineral oil is higher than 0.8.

[0049] It is a third object of the invention to provide a method for treating phosphogypsum, wherein the method comprises the following steps:

[0050] (1) providing phosphogypsum ore;

[0051] (2) grinding phosphogypsum ore for obtaining ground phosphogypsum ore;

[0052] (3) preparing a raw slurry by adding an aqueous carrier, preferably water, to the ground phosphogypsum ore; and

[0053] (4) carrying out at least one reverse flotation using the reagent as described herein or the composition as described herein.

[0054] In some embodiments, the ground phosphogypsum ore comprises:- from about 10 to about 40 wt.%, preferably from about 15 to about 35 wt.%, more preferably from about 20 to about 35 wt.%, of ore particles with a particle size of about 0.037 mm or less;

[0055] - from about 30 to about 60 wt.%, preferably from about 35 to about 55 wt.%, more preferably from about 35 to about 50 wt.%, of ore particles with a particle size from about 0.037 to about 0.048 mm;

[0056] - from about 20 to about 60 wt.%, preferably from about 25 about to 50 wt.%, more preferably from about 28 to about 43 wt.%, of ore particles with a particle size of about 0.048 mm to about 0.15 mm; and

[0057] - about 5 wt.% or less, preferably about 1 wt.% or less, more preferably about 0.1 wt.% or less, most preferably 0 wt.% (free), of ore particles with a particle size of about 0.15 mm or more.

[0058] In some embodiments, the raw slurry comprises from about 30 to about 40 wt.%, preferably from about 32 to about 40 wt.%, more preferably from about 35 to about 40 wt.%, of ground phosphogypsum ore, by total weight of the raw slurry.

[0059] In some embodiments, step (4) comprises the following sub-steps: - (4.1 ) a rougher reverse flotation;

[0060] - (4.2) a first cleaner reverse flotation;

[0061] - (4.3) a second cleaner reverse flotation;

[0062] - (4.4) a third cleaner reverse flotation; and

[0063] - optionally (4.5) a fourth cleaner reverse flotation.

[0064] The rougher reverse flotation directly processes raw phosphogypsum to separate 1st concentrate (to be further treated, the sink portion) and 1st tailings (discarded, the floating portion). The cleaner reverse flotation treats the sink portion to further remove the impurities (floats) and get higher grade gypsum (sink).

[0065] In some embodiment, step 4.4, or even 4.3 are optional.

[0066] In some embodiments, the sub-steps (4.1) to (4.5) are carried out as follows:

[0067] - (4.1) preparing a rougher reverse flotation slurry by adding the composition as described herein to the raw slurry, and subjecting it to flotation for obtaining a treated rougher slurry; and / or

[0068] - (4.2) preparing a first cleaner reverse flotation slurry by adding the composition as described herein to the sink portion of the treated rougher reverse flotation slurry, and subjecting it to flotation for obtaining a treated first cleaner reverse flotation slurry; and / or- (4.3) preparing a second cleaner reverse flotation slurry by adding the composition as described herein to the sink portion of the treated first reverse flotation slurry, and subjecting it to flotation for obtaining a treated second cleaner reverse flotation slurry; and / or

[0069] - (4.4) preparing a third cleaner reverse flotation slurry by adding the composition as described herein and at least one frothing agent to the sink portion of the treated second reverse flotation slurry, and subjecting it to flotation for obtaining a treated third cleaner reverse flotation slurry; and / or - optionally (4.5) preparing a fourth cleaner reverse flotation slurry by adding the composition as described herein to the sink portion of the treated third reverse flotation slurry, and subjecting it to flotation for obtaining a treated fourth cleaner reverse flotation slurry.

[0070] In some embodiments, the sub-steps (4.1), (4.3) and (4.4) further comprise the following steps:

[0071] - (4.1 ) the pH of the rougher reverse flotation slurry is adjusted to a pH from 3 to 4, preferably using sulfuric acid; and / or

[0072] - (4.3) the pH of the second cleaner reverse flotation slurry is adjusted to a pH from 2 to 3, preferably using phosphoric acid; and / or

[0073] - (4.4) the frothing agent comprises from 20 to 40 wt.% of at least one mineral oil, from 20 to 40 wt.% of at least one alcohol, and from 30 to 60 wt.% of at least one flotation auxiliary, by total weight of the frothing agent.

[0074] It is a fourth object of the invention to provide the use of the reagent as described herein, or the composition comprising the reagent, wherein the reagent, or the composition comprising it, is used in phosphogypsum flotation.

[0075] The present invention makes it possible to overcome the drawbacks of the prior art, and to enhance the grade and whiteness of gypsum. The invention provides a reagent for phosphogypsum flotation, a collector composition comprising the reagent, a related method for treating phosphogypsum and corresponding uses. The inventors have shown the reagent, and the collector composition comprising it, according to the invention, is particularly suitable for treating phosphogypsum by froth flotation. The reagent, and the collector composition comprising it, together with the method steps satisfactorily allow removing at least 90 % of impurities from phosphogypsum. The reagent, and the collector composition comprising it, together with the method steps also satisfactorily allow providing a treated phosphogypsum having an increased whiteness. The formulation of the reagent, and the collector composition comprising it, and / or the design of the method steps, for example the grinding step, allows providing a treatedphosphogypsum of sufficient grade for being used in gypsum board building materials at a reduced cost.

[0076] DESCRIPTION OF EMBODIMENTS

[0077] The invention will now be described in more detail without limitation in the following description.

[0078] Definition

[0079] The following definitions are provided to determine how terms used in this application, and in particular how the claims, are to be construed. The organization of the definition is for convenience only and is not intended to limit any of the definitions to any particular category.

[0080] The term “collector means a compound or a composition of matter containing a selection of compounds that selectively adhere to a particular constituent of the ore and facilitate the adhesion of the particular constituent to the micro-bubbles that result from the sparging of the ore slurry.

[0081] The term “ground (to grind)" means powdered, pulverized, or otherwise rendered in fine solid particles. The terms “ground’ and “grinded’ are used interchangeably.

[0082] The term “floating portion" means the portion of the ore that is separated from the slurry by flotation and collected within the froth layer.

[0083] The term “ore" means a composition of matter containing a mixture of a more wanted material (the beneficiary), and a less wanted material (the gangue).

[0084] The term “frotheh (which can be interchangeably used with the expression “frothing agent’) means a composition of matter that enhances the formation of micro-bubbles and / or preserves the formed micro-bubbles bearing the hydrophobic fraction that result from the sparging of slurry.

[0085] The term “slurry” means a mixture comprising a liquid medium within which ore particles (finely divided solids) are dispersed or suspended, and when the slurry is sparged, some compounds remain in the slurry and at least some of the other compounds adhere to the sparge bubbles and rise up out of the slurry into a froth layer above the slurry. The liquid medium may be entirely water or a partially aqueous system.

[0086] Throughout the description, all the percentages of the various constituents of the composition are given by weight (%w / w), except if mentioned otherwise. The concentration ranges have to be considered as including the limits.Reagent for phosphoqypsum flotation

[0087] In an aspect, the invention relates to a reagent. The reagent is used in phosphogypsum flotation.

[0088] The reagent comprises a salt of an acid and a condensate of at least one polyalkylene polyamine, and a mixture of at least two fatty acid compounds.

[0089] The condensate of at least one polyalkylene polyamine and a mixture of at least two fatty acid compounds corresponds to the reaction product of the at least two fatty acids with the at least one polyalkylene polyamine. The expressions “condensate" and “reaction product” can be used interchangeably.

[0090] The alkylene groups may be selected from the group consisting of ethylene and / or propylene.

[0091] The at least one polyalkylene polyamine preferably has the following formula I:

[0092] H2N-(C2H4NH)X-C2H4-NH2 (I),

[0093] wherein x is an integer from 2 to 11 , e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11.

[0094] The at least one polyalkylene polyamine may be one polyalkylene polyamine or a mixture of polyalkylene polyamines with different x number.

[0095] Preferably, the polyalkylene polyamine is polyethylene polyamine. For example, in one embodiment, the at least one polyalkylene polyamine comprises 40-60 wt% triethylenetetramine, 15-25 wt% tetraethylenepentamine, and 20-40 wt% pentaethylenehexamine.

[0096] Preferably, the content of formula I is higher than 80 wt%, preferably 90 wt% based on the total weight of the at least one polyalkylene polyamine. The fatty acid compounds may be selected from the group consisting of fatty acids, fatty acid esters, and mixtures thereof; preferably the fatty acid compounds are fatty acids.

[0097] A fatty acid, and a fatty acid ester derived from it, may be a saturated fatty acid or an unsaturated fatty acid.

[0098] Saturated fatty acids may be selected from the group consisting of caprylic acid (Cs), capric acid (C10), lauric acid (C12), myristic acid (C14), palmitic acid (Cie), stearic acid (Cis), arachidic acid (C20), behenic acid (C22), lignoceric acid (C24), cerotic acid (C26), and mixtures thereof.

[0099] Unsaturated fatty acids may be selected from the group consisting of myristoleic acid (C14), palmitoleic acid (Cie), sapienic acid (Cie), elaidic acid (Cis), linoelaidic acid (Cis), linoleic acid (Cis), oleic acid (Cis), vaccenic acid(Cis), arachidonic acid (C20), eicosapentaenoic acid (C20), docosahexaenoic acid (C22), erucic acid (C22), and mixtures thereof.

[0100] Amongst the at least two fatty acid compounds, at least one of them is a saturated fatty acid. The at least one saturated fatty acid may be selected from the group consisting of C12-30 saturated fatty acids, preferably C14-22 saturated fatty acids; more preferably C14-18 saturated fatty acids; most preferably C16-18 saturated fatty acids. The at least one saturated fatty acids may be selected from the group consisting of myristic acid (C14), palmitic acid (Cis), stearic acid (Cis), arachidic acid (C20), behenicacid (C22), lignoceric acid (C24), cerotic acid (C26), and mixtures thereof; preferably from the group consisting of myristic acid (C14), palmitic acid (Cie), stearic acid (Cis), arachidic acid (C20), behenic acid (C22), and mixtures thereof; more preferably from the group consisting of myristic acid (C14), palmitic acid (Cie), stearic acid (Cis), and mixtures thereof; most preferably from the group consisting of palmitic acid (Cie), stearic acid (Cis), and mixtures thereof.

[0101] Amongst the at least two fatty acid compounds, the remaining at least one fatty acid is at least one unsaturated fatty acid. The at least one unsaturated fatty acid may be selected from the group consisting of C12-30 unsaturated fatty acids; preferably C14-22 unsaturated fatty acids; more preferably C14-18 unsaturated fatty acids; most preferably C16-18 unsaturated fatty acids. The at least one unsaturated fatty acids may be selected from the group consisting of myristoleic acid (C14), palmitoleic acid (Cie), sapienic acid (Cie), elaidic acid (Cis), linoelaidicacid (Cis), linoleic acid (Cis), oleic acid (Cis), vaccenic acid (Cis), arachidonic acid (C20), eicosapentaenoic acid (C20), docosahexaenoic acid (C22), erucic acid (C22), and mixtures thereof; preferably from the group consisting of myristoleic acid (C14), palmitoleic acid (Cie), sapienic acid (Cie), elaidic acid (Cis), linoelaidic acid (Cis), linoleic acid (Cis), oleic acid (Cis), vaccenic acid (Cis), and mixtures thereof; more preferably from the group consisting of palmitoleic acid (Cie), sapienic acid (Cie), elaidic acid (Cis), linoelaidic acid (Cis), linoleic acid (Cis), oleic acid (Cis), vaccenic acid (Cis), and mixtures thereof; most preferably from the group consisting of linoleic acid (Cis), oleic acid (Cis), and mixtures thereof.

[0102] The mixture of fatty acid compounds comprises about 15 wt.% or more, preferably from about 15 wt% to 50 wt%, more preferably from about 20 to about 40 wt.%, of at least one saturated fatty acid, by total weight of the mixture of fatty acid compounds. The mixture of fatty acid compounds thus comprises about 85 wt.% or less, preferably from about 60 to about 80 wt.%, of at leastone unsaturated fatty acids, by total weight of the mixture of fatty acid compounds.

[0103] The content of the C16-18 fatty acid compounds is about 90 wt.% or more of the fatty acid compounds present in the mixture.

[0104] The content of the C16-18 saturated fatty acid compounds is about 90 wt.% or more of the saturated fatty acid compounds present in the mixture.

[0105] In an embodiment, the mixture of fatty acids comprises palmitic acid, stearic acid, oleic acid and linoleic acid.

[0106] The acid may be selected from the group consisting of acetic acid, citric acid, oxalic acid, sulfuric acid, hydrochloric acid, and mixtures thereof; preferably the acid is acetic acid.

[0107] The reagent may comprise from about 45 to about 80 wt.%, preferably from about 50 to about 75 wt.%, more preferably from about 55 to about 70 wt.%, of the salt of the acid and the condensate of the at least one polyalkylene polyamine and the mixture of the at least two fatty acid compounds, by total weight of the reagent.

[0108] The acid and the condensate may be mixed at a ratio from about 10:90 to about 15:85 by weight.

[0109] The salt may comprise from about 10 wt% to about 15 wt% of the acid, by total weight of the salt.

[0110] The salt may comprise from about 85 wt% to about 90 wt% of the condensate of the at least one polyalkylene polyamine and the mixture of the at least two fatty acid compounds, by total weight of the salt.

[0111] The reagent may also comprise at least one non-ionic surfactant. The at least one non-ionic surfactant may be selected from the group consisting of short carbon-chain alcohols (for example C1-10 mono-alcohols such as methanol, ethanol, propanol, butanol, pentanol; C1-10 di-alcohols, which are also called diols, such as etohexadiols), glycols, and mixtures thereof. The reagent may comprise from about 20 to about 35 wt.% of the at least one non-ionic surfactant, by total weight of the reagent.

[0112] The reagent may also comprise water q.s..

[0113] Collector composition for phosphoqypsum flotation

[0114] In a further aspect, the present invention relates to a composition comprising the reagent as described herein. The composition is used in phosphogypsum flotation. The composition thus is a collector composition.

[0115] The composition comprises the reagent as described herein and at least one additive.The composition may comprise from about 25 to about 95 wt% of the reagent. In an embodiment, the composition comprises about 80 to about 95 wt.%, preferably from about 82 to about 92 wt.%, more preferably from about 83 to about 90 wt.%, of the reagent, by total weight of the composition. In another embodiment, the composition comprises about 25 to about 80 wt%, e.g., about 25 to about 50 wt%, about 25 to about 40 wt% of the reagent, by total weight of the composition.

[0116] The additive may be selected from the group consisting of at least one mineral oil, at least one alcohol, at least one flotation auxiliary, and mixtures thereof.

[0117] The at least one mineral oil may be selected from the group consisting of kerosene, gasoline, diesel fuel, and mixtures thereof. The composition may comprise from about 1 to about 18 wt.%, preferably from about 3 to about 15 wt.%, more preferably from about 5 to about 13 wt.%, of the at least one mineral oil, by total weight of the composition. The addition of at least one mineral oil is advantageous in that it may help achieving a favorable whiteness and recovery rate.

[0118] The at least one alcohol may be selected from the group consisting of C4-12 alcohols, C4-12 alcohol ethoxylates, and mixtures thereof; preferably from the group consisting of C4-12 alcohols; more preferably from the group consisting of terpineols. For example, a suitable source of terpineols may be pine oil. The composition may comprise from about 1 to about 18 wt.%, preferably from about 2 to about 15 wt.%, more preferably from about 3 to about 10 wt.%, of the at least one alcohol, by total weight of the composition. For the avoidance of doubt, such ranges does not include any alcohol that is already present in the reagent, if any. The addition of at least one alcohol is advantageous in that it may help achieving a favorable whiteness and recovery rate.

[0119] The at least one flotation auxiliary may be selected from the group consisting of sodium alcohol ether sulphates, alcohol sulphates, alkoxylated alcohol sulphates, tributyl citrate, tributyl phosphate, and mixtures thereof. Sodium alcohol ether sulphates normally has the structure of RO(CH2CH2O)n-SO3Na, wherein n is 1-4, R is C10-16 alkyl. The composition may comprise from about 1 to about 18 wt.%, preferably from about 1.5 to about 15 wt.%, more preferably from about 1.8 to about 10 wt.%, of the at least one flotation auxiliary, by total weight of the composition. For the avoidance of doubt, such ranges does not include any flotation auxiliaries that were already present in the reagent, if any. The addition of at least one flotation auxiliary isadvantageous in that it may help achieving a favorable whiteness and recovery rate.

[0120] As an option, acid could also be added. Preferably, the acid may be selected from the group consisting of acetic acid, citric acid, oxalic acid, sulfuric acid, hydrochloric acid, and mixtures thereof; preferably the acid is acetic acid. It can be the same or different than the acid that is used to form the salt in the reagent. Such acid may be further neutralized with the condensate in the reagent.

[0121] The composition may also comprise water q.s..

[0122] In an embodiment, the composition comprises, by total weight of the composition:

[0123] - from about 25 to about 95 wt% of the reagent;

[0124] - from about 1 to about 25 wt% of the at least one mineral oil;

[0125] - from about 1 to about 18 wt% of the at least one alcohol;

[0126] - from about 0 to about 15 wt% of the acid;

[0127] - from about 0 to 40 wt% of water;

[0128] - from about 0 to 10 wt% of the at least one flotation auxiliary.

[0129] For example, the composition comprises from about 80 to about 95 wt % of the reagent;

[0130] - from about 1 to about 18 wt% of the at least one mineral oil;

[0131] - from about 1 to about 18 wt% of the at least one alcohol;

[0132] - from about 1 to about 18 wt% of the at least one flotation auxiliary. For example, the composition comprises from about 20 to 40 wt% of the reagent, from about 10 to about 25 wt% of the at least one mineral oil; - from about 1 to about 10 wt% of the at least one alcohol;

[0133] - from about 1 to about 15 wt% of the acid,

[0134] with water as a balance of 100% composition.

[0135] In an embodiment, the composition comprises, the mixture / reaction product of, by total weight of the composition:

[0136] - from about 12 to about 60 wt% of the condensate;

[0137] - from about 1 to about 25 wt% of the at least one mineral oil;

[0138] - from about 1 to about 35 wt% of the at least one alcohol;

[0139] - from about 1 to about 15 wt% of the acid;

[0140] - from about 4 to 50 wt% of water;

[0141] - from about 0-10 wt% of the at least one flotation auxiliary.

[0142] For example, the composition comprises by total weight of the composition, about 35 wt% to 55 wt% of the condensate, about 4 wt% to 10wt% of the at least one mineral oil, about 20 wt% to 35 wt% of the at least one alcohol, about 1 wt% to 8 wt% of the acid, 2 wt% to 8 wt% of the at least one flotation auxiliary, and about 4 wt% to 20 wt% of water.

[0143] For example, the composition comprises by total weight of the composition, about 12 wt% to 25 wt% of the condensate, about 10 wt% to 25 wt% of the at least one mineral oil, about 10 wt% to 25 wt% of the at least one alcohol, about 5 wt% to 15 wt% of the acid, and about 30 wt% to 50 wt% of water.

[0144] To avoid confusion, as the condensate would be neutralized with at least a part of the acid, the wording “reaction product of” refers to such neutralization.

[0145] Preferably, the ratio of the condensate to the at least one alcohol is 1 :2 to 2:1.

[0146] Preferably, the ratio of the condensate to the at least one mineral oil is higher than 0.8, e.g., 0.8 to 20.

[0147] Method for treating phosphogypsum

[0148] In a further aspect, the invention relates to a method for treating (also called a method for beneficiating) phosphogypsum, which is based on the froth flotation technique.

[0149] The method comprises the following steps:

[0150] - (1) providing phosphogypsum ore (extraction step);

[0151] - (2) grinding phosphogypsum ore (grinding step);

[0152] - (3) preparing a raw slurry (slurring step);

[0153] - (4) carrying out at least one reverse flotation using the reagent defined above or the composition defined above (flotation step); and - optionally (5) treating the sink portion(s).

[0154] In the context, “phosphogypsum ore” and “phosphogypsum” has the same meaning. A person skilled in the art would know that it is a by product for wet phosphoric acid process of phosphate ore).

[0155] Extraction step (1)

[0156] The extraction step includes providing phosphogypsum ore. Phosphogypsum ore may originate from any phosphogypsum stack. Phosphogypsum ore may also be called phosphogypsum waste or phosphogypsum feed.

[0157] Grinding step (2)

[0158] The grinding step includes grinding phosphogypsum ore for obtaining ground phosphogypsum ore. In an embodiment, when grinding is carried out,phosphogypsum ore may be ground using a rod mill. Using a rod mill is advantageous for avoiding over-grinding phosphogypsum ore, which may negatively impact the efficiency of the method.

[0159] Grinding is carried out to obtain ore particles having a specific particle size distribution. The particle size may be measured using suitable mesh sieves, for example 100, 300, and 400 mesh sieves.

[0160] The ground phosphogypsum ore may comprise:

[0161] - from about 10 to about 40 wt.%, preferably from about 15 to about 35 wt.%, more preferably from about 20 to about 35 wt.%, of ore particles with a particle size of about 0.037 mm or less;

[0162] - from about 30 to about 60 wt.%, preferably from about 35 to about 55 wt.%, more preferably from about 35 to about 50 wt.%, of ore particles with a particle size from about 0.037 to about 0.048 mm; and

[0163] - from about 20 to about 60 wt.%, preferably from about 25 about to 50 wt.%, more preferably from about 28 to about 43 wt.%, of ore particles with a particle size of about 0.048 mm to about 0.15 mm. The ore particles may have about 5 wt.% or less, preferably about 1 wt.% or less, more preferably about 0.1 wt.% or less, most preferably 0 wt.% (free of), of ore particles with a particle size of about 0.15 mm or more.

[0164] Slurring step (3)

[0165] The method comprises at least one slurring step.

[0166] The slurring step is carried out by adding an aqueous carrier, preferably water, to the ground phosphogypsum ore to obtain a raw slurry.

[0167] The raw slurry may comprise from about 30 to about 40 wt.%, preferably from about 32 to about 40 wt.%, more preferably from about 35 to about 40 wt.%, of the ground phosphogypsum ore (particle ores), by total weight of the raw slurry. The raw slurry may thus comprise from about 60 to about 70 wt.%, preferably from about 60 to about 68 wt.%, more preferably from about 60 to about 65 wt.%, of water, by total weight of the raw slurry.

[0168] Reverse flotation steps (4)

[0169] The method comprises at least one reverse flotation step, preferably at least two reverse flotation steps, more preferably at least three reverse flotation steps, most preferably at least four reverse flotation steps. The first reverse flotation step is called rougher. The subsequent reverse flotation steps are called cleaner.

[0170] The method may comprise:

[0171] - (4.1 ) a rougher reverse flotation step;- (4.2) a first cleaner reverse flotation step;

[0172] - (4.3) a second cleaner reverse flotation step;

[0173] - (4.4) a third cleaner reverse flotation step; and

[0174] - optionally (4.5) a fourth reverse cleaner flotation step.

[0175] - In some embodiment, step 4.4 or even step 4.3 is optional.

[0176] After carrying out a reverse flotation step, different portions are obtained i.e., a sink portion and floating portion (also called froth floats).

[0177] A reverse flotation step may be carried out using a flotation cell.

[0178] Rougher reverse flotation step

[0179] The method may comprise the step of carrying out a rougher reverse flotation using a rougher reverse flotation slurry.

[0180] The rougher reverse flotation slurry (also called “rougher”) may be prepared by adding the composition as defined above to the raw slurry. The rougher slurry may be prepared by adding from about 100 to about 300 g, preferably from about 100 to about 280 g, more preferably from about 100 to about 250 g, of the composition per ton of the ground phosphogypsum ore.

[0181] The pH of the rougher slurry may be adjusted to a pH from 3 to 4. The pH of the rougher slurry may be adjusted using sulfuric acid. The use of sulfuric acid for adjusting the pH of the rougher slurry is advantageous in that it enhances the performance of the composition and / or improves the whiteness of the treated material.

[0182] The rougher slurry may be subjected to froth flotation for obtaining a treated rougher slurry.

[0183] The froth flotation may be carried out from 3 to 10 min, preferably from 3 to 8 min, more preferably from 3 to 5 min.

[0184] After carrying out the rougher reverse flotation step, the treated rougher slurry may comprise a floating portion and a sink portion. The floating portion may have a whiteness of 50 % or less. The flotation portion may thus be discarded (wastes). The sink portion may be kept for further treatment.

[0185] First cleaner reverse flotation step

[0186] The method may comprise the step of carrying out a first cleaner reverse flotation using a first cleaner reverse flotation slurry (also called “first cleaner slurry”).

[0187] The first cleaner slurry may be prepared by further adding the composition as defined above to the sink portion of the treated rougher slurry (if the floating portion is discarded).

[0188] The first cleaner slurry may be prepared by adding from about 50 to about 150 g, preferably from about 50 to about 120 g, more preferably fromabout 50 to about 100 g, of the composition per ton of the original ground phosphogypsum ore.

[0189] The first cleaner reverse flotation step may be carried out from 2 to 5 min, preferably from 2 to 4 min, more preferably from 2 to 3 min.

[0190] After carrying out the first cleaner reverse flotation step, the treated first cleaner slurry may comprise a floating portion and a sink portion. The floating portion may have a whiteness of 50 % or less. The flotation portion may thus be discarded (wastes). The sink portion may be kept for further treatment.

[0191] Second cleaner reverse flotation step

[0192] The method may comprise the step of carrying out a second cleaner reverse flotation using a second cleaner reverse flotation slurry (also called “second cleaner slurry”).

[0193] The second cleaner reverse flotation step may be carried out by further adding the composition as defined above to the sink portion of the treated first cleaner slurry (if the floating portion is discarded), for obtaining a second cleaner slurry.

[0194] The second cleaner slurry may be prepared by adding from about 25 to about 100 g, preferably from about 25 to about 80 g, more preferably from about 25 to about 60 g, of the composition per ton of the original ground phosphogypsum ore.

[0195] The pH of the second cleaner slurry may be adjusted to a pH from 2 to 3. The pH of the second cleaner slurry may be adjusted using phosphoric acid. The use of phosphoric acid for adjusting the pH of the second cleaner is advantageous in that it enhances the selectivity of the composition and / or improves the whiteness of the treated material.

[0196] The second cleaner flotation step may be carried out from 2 to 10 min, preferably from 2 to 5 min, more preferably from 2 to 4 min.

[0197] After carrying out the second cleaner flotation step, the floating portion may have a whiteness from 60 to 70 %. The floating portion may be beneficiated / re-used (middling). The remaining sink portion of the treated second cleaner slurry may be further treated.

[0198] Third cleaner reverse flotation step

[0199] The third cleaner reverse flotation step may be carried out by further adding the composition as defined above and at least one frothing agent to the remaining sink portion of the treated second cleaner flotation slurry, for obtaining a third cleaner reverse flotation slurry (also called “third cleaner slurry”).The third cleaner slurry may be prepared by adding from about 25 to about 100 g, preferably from about 25 to about 80 g, more preferably from about 25 to about 60 g, of the composition per ton of original ground phosphogypsum ore.

[0200] At least one frothing agent could also be added. The frothing agent may comprise from 20 to 40 wt.% of at least one mineral oil (preferably at least one mineral oil selected from the group consisting of kerosene, gasoline, diesel fuel, and mixtures thereof), from 20 to 40 wt.% of at least one alcohol (preferably at least one Cs-12 alcohol, e.g., at least one Cs-12 alcohol selected from the group consisting of pine oil and terpineol), and from 30 to 60 wt.% of at least one flotation auxiliary (preferably at least at least one flotation auxiliary selected from the group consisting of tributyl phosphate, ethoxylated fatty acid, tributyl citrate, sodium alcohol ether sulphates, alcohol sulphates, alkoxylated alcohol sulphates, and mixtures thereof), by total weight of the frothing agent. Sodium alcohol ether sulphates normally has the structure of RO(CH2CH2O)n-SO3Na, wherein n is 1-4, R is C10-16 alkyl.

[0201] The third cleaner slurry may be prepared by adding the at least one frothing agent, preferably about 1 to about 60 g, more preferably from about 5 to about 50 g, even more preferably from about 10 to about 40 g, of the at least one frothing agent per ton of original ground phosphogypsum ore.

[0202] The third cleaner reverse flotation step may be carried out from 2 to 10 min, preferably from 2 to 5 min, more preferably from 2 to 3 min.

[0203] Any of the portions obtained - i.e., the flotation portion and / or the sink portion - may be beneficiated, without carrying out any additional flotation step. Alternatively, the flotation portion may be beneficiated / re-used (middling), and the sink portion may be further used in the fourth cleaner reverse flotation step.

[0204] Optional fourth cleaner reverse flotation step

[0205] The fourth cleaner reverse flotation step may be carried out by further adding the composition as defined above to the sink portion of the treated third cleaner slurry for obtaining a fourth cleaner reverse flotation slurry (also called “fourth cleaner slurry").

[0206] The fourth cleaner flotation slurry may be prepared by adding from about 20 to about 80 g, preferably from about 20 to about 60 g, more preferably from about 20 to about 50 g, of the composition per ton of the original ground phosphogypsum ore.

[0207] The fourth cleaner flotation step may be carried out from 0.2 to 10 min, preferably from 0.5 to 5 min, more preferably from 0.5 to 3 min.After carrying out the fourth cleaner reverse flotation step, the floating portion may have a whiteness from 70 to 80 %. The floating portion may thus be re-used (middling). The remaining sink portion of the treated fourth cleaner slurry may have a whiteness of 78 % or above, thereby forming the final concentrate.

[0208] Uses and applications

[0209] In a further aspect, the invention relates to the use of the reagent, or the composition comprising it as described above, for treating phosphogypsum, preferably for treating phosphogypsum by flotation.

[0210] EXAMPLE 1

[0211] Materials

[0212] Phosphogypsum: Sample extracted from Hubei province, China (whiteness 30-40%)

[0213] Condensate 1: reaction product of a mixture of fatty acids (14 wt.% palmitic acid, 15 wt.% stearic acid, 30 wt.% oleic acid, 35 wt.% linoleic acid, 6 wt.% other fatty acids, based on the total weight of the mixture of fatty acids) with polyalkylene polyamine comprising 40 wt% triethylenetetramine (TETA), 20 wt% tetraethylenepentamine (TEPA), and 40 wt% pentaethylenehexamine (PEHA).

[0214] Reagent 1: 68 wt.% of a salt of acetic acid and the condensate 1 (61 wt% condensate, 7 wt% acetic acid), 26 wt% alcohols, q.s. water, based on the total weight of reagent 1.

[0215] Collector composition 1: 85 wt.% of reagent 1, 5 wt.% diesel fuel, 5 wt.% pine oil, 5 wt.% tributyl phosphate, based on the total weight of collector composition 1 (i.e. , 52 wt% of the condensate, 5 wt% of at least one mineral oil (diesel fuel), 27 wt% of at least one alcohol (pine oil and the alcohols in the reagent), 6 wt% of the acid, 5 wt.% tributyl phosphate, with water as rest) Slurries

[0216] Raw slurry: 30-40% of ground phosphogypsum, q.s. water, based on total weight of the raw slurry.

[0217] Rougher flotation slurry: about 200 g of the collector composition 1 per ton of the original ground phosphogypsum ore, pH adjusted to 3 using sulfuric acid.

[0218] First cleaner flotation slurry: about 100 g of the collector composition 1 per ton of the original ground phosphogypsum ore.Second cleaner flotation slurry: about 50 g of the collector composition 1 per ton of the original ground phosphogypsum ore, pH adjusted to 2-3 using phosphoric acid.

[0219] Third cleaner flotation slurry: about 50 g of the collector composition 1 and 30 g of the frothing agent (mixture of diesel fuel, pine oil, and tributyl phosphate in a weight ratio of 1:1:2) per ton of the original ground phosphogypsum ore.

[0220] Fourth cleaner flotation slurry: about 50 g of the collector composition 1 per ton of the original ground phosphogypsum ore.

[0221] Method

[0222] Grindinq / Comminution step: phosphogypsum is ground using a rod mill, before being screened, in order to obtain a ground phosphogypsum ore comprising about 25 wt.% of ore particles with a particle size of about 0.037 mm (400 mesh sieve) or less, about 45 wt.% of ore particles with a particle size from about 0.037 mm (400 mesh sieve) to about 0.048 mm (300 mesh sieve), about 30 wt.% of ore particles with a particle size of about 0.048 mm (300 mesh sieve) to about 0.15 mm, and about 0 wt% of ore particles with a particle size of 0.15 mm (100 mesh sieve) or more.

[0223] Slurring step: a raw slurry is prepared by adding water to the ground phosphogypsum ore, for obtaining a raw slurry.

[0224] Rougher reverse flotation step: the rougher flotation slurry is subjected to froth flotation for 5 min.

[0225] First cleaner reverse flotation step: the first cleaner slurry is subjected to froth flotation for 3 min.

[0226] Second cleaner reverse flotation step: the second cleaner slurry is subjected to froth flotation for 2 min.

[0227] Third cleaner reverse flotation step: the third cleaner slurry is subjected to froth flotation for 1 min.

[0228] Fourth cleaner reverse flotation step: the fourth cleaner slurry is subjected to froth flotation for 50 sec.

[0229] Measurement of the gypsum [CaSO4-2 H2O] content (Grade % of gypsum CaSO4'2H2O)

[0230] Prior to measuring the gypsum content of the sample, the sample is dried at 45°C for 2h. The measurement was done by GB / T23456-2018 (mandatory national standard in China).

[0231] Measurement of the whiteness of gypsumPrior to measuring the whiteness of the sample, the sample is dried at 200°C for 3h. The measurement was done by GB / T5950-2008 (mandatory national standard in China).

[0232] Calculation of Recovery of gypsum CaSO4-2H2O

[0233] (Proportions in (concentrate / middling / tailing) X Grade % of gypsum CaSO4'2H2O) / ((Proportions in Feed) X Grade % of gypsum CaSO4'2H2O in Feed)

[0234] Results

[0235] Table 1

[0236]

[0237] The concentrate corresponds to the sink portion of the treated fourth cleaner slurry.

[0238] The middling corresponds to the flotation portions of the treated second cleaner slurry and of the treated third cleaner slurry. For example, whiteness of the middling is calculated as follows: the sum of flotation portions of the treated second cleaner slurry (whiteness 69.65 %) by its proportions (12.45 wt.% / 34.23 wt.%) + flotation portions of the treated third cleaner slurry (whiteness 79.56 %) by its proportions (21.78 wt.% / 34.23 wt.%).

[0239] The tailing corresponds to the flotation portions of the treated rougher slurry and of the treated first cleaner slurry.

[0240] When it is considered that a material having a whiteness of 70 % is acceptable, the recovery rate would thus be of 73.26 % ( / .e., 38.76 % + 34.50 %).

[0241] EXAMPLE 2

[0242] Materials

[0243] Condensate 2: reaction product of a mixture of fatty acids (11 wt.% palmitic acid, 20 wt.% stearic acid, 35 wt.% oleic acid, 30 wt.% linoleic acid, 4 wt.% other fatty acids, based on the total weight of the mixture of fatty acids)with polyalkylene polyamine comprising 60% triethylenetetramine (TETA), 20% tetraethylenepentamine (TEPA), and 20% pentaethylenehexamine (PEHA).

[0244] Reagent 2: 61 wt.% of a salt of acetic acid and the condensate 2 (54 wt% condensate, 7 wt% acetic acid), 33wt% alcohols, q.s. water, based on the total weight of reagent 2.

[0245] Collector composition 2: 85 wt.% reagent 2, 7 wt.% diesel fuel, 3 wt.% sodium alcohol ether sulphates (with the structure of RO(CH2CH2O)n-SO3Na, wherein n is 1-4, R is C10-16 alkyl), 5 wt.% a-terpineol, based on the total weight of collector composition 2. . (i.e. , 46 wt% of the condensate, 7 wt% of at least one mineral oil (diesel fuel), 33 wt% of at least one alcohol (a-terpineol and the alcohols in the reagent, 6 wt% of the acid, 3 wt.% sodium alcohol ether sulphates, with water as rest)

[0246] Slurries (similar as the slurries of example 1 , but with the reagent 2 and the collector composition 2)

[0247] Method

[0248] Grinding / Comminution step: phosphogypsum is ground using a rod mill, before being screened, in order to obtain a ground phosphogypsum ore comprising about 22 wt.% of ore particles with a particle size of about 0.037 mm (400 mesh sieve) or less, about 35 wt.% of ore particles with a particle size from about 0.037 mm to about 0.048 mm (300 mesh sieve), about 43 wt.% of ore particles with a particle size of about 0.048 mm to about 0.15 mm(300 mesh sieve), and about 0 wt% of ore particles with a particle size of 0.15 mm (100 mesh sieve) or more.

[0249] Subsequent steps were carried out as in example 1.

[0250] Measurement of the gypsum [CaSO4-2H2O] content (see the protocol of example 1 )

[0251] Measurement of the whiteness of gypsum (see the protocol of example 1)

[0252] Results

[0253] Table 2

[0254]

[0255]

[0256] The concentrate corresponds to the sink portion of the treated fourth cleaner slurry.

[0257] The middling corresponds to the flotation portions of the treated second cleaner slurry and of the treated third cleaner slurry. For example, whiteness of the middling is calculated as follows: the sum of flotation portions of the treated second cleaner slurry (whiteness 73.25 %) by its proportions (14.88 wt.% / 38.67 wt.%) + flotation portions of the treated third cleaner slurry (whiteness 78.97 %) by its proportions (23.79 wt.% / 38.67 wt.%). The tailing corresponds to the flotation portions of the treated rougher slurry and of the treated first cleaner slurry.

[0258] When it is considered that a material having a whiteness of 70 % is acceptable, the recovery rate would thus be of 72.49 % ( / .e., 33.82 % + 38.67 %).

[0259] EXAMPLE 3

[0260] Materials (see the materials of example 2)

[0261] Slurries (similar as the slurries of example 1 , but with the reagent 2 and the collector composition 2)

[0262] Method

[0263] Grinding / Comminution step: phosphogypsum is ground using a rod mill, in order to obtain a ground phosphogypsum ore comprising about 15 wt.% of ore particles with a particle size of about 0.037 or less (400 mesh sieve), about 30 wt.% of ore particles with a particle size from about 0.037 to about 0.048 mm (300 mesh sieve), about 55 wt.% of ore particles with a particle size of about 0.048 mm (300 mesh sieve) to about 0.15 mm, and about 5 wt% of ore particles with a particle size of 0.15 mm (100 mesh sieve) or more.

[0264] Subsequent steps were carried out as in example 1.

[0265] Measurement of the gypsum [CaSO4-2H2O] content (see the protocol of example 1 )

[0266] Measurement of the whiteness of gypsum (see the protocol of example 1)

[0267] Results

[0268] Table 3

[0269]

[0270]

[0271] The concentrate corresponds to the sink portion of the treated fourth cleaner slurry.

[0272] The middling corresponds to the flotation portions of the treated second cleaner slurry and of the treated third cleaner slurry. For example, the whiteness of the middling is calculated as follows: the sum of flotation portions of the treated second cleaner slurry (whiteness 68.25 %) by its proportions (14.58 wt.% / 37.23 wt.%) + flotation portions of the treated third cleaner slurry (whiteness 76.14 %) by its proportions (22.65 wt.% / 37.23 wt.%). The tailing corresponds to the flotation portions of the treated rougher slurry and of the treated first cleaner slurry.

[0273] When it is considered that a material having a whiteness of 70 % is acceptable, the recovery rate would thus be of 69.60 % ( / .e., 31.60 % + 38.00 %).

[0274] Comparative EXAMPLE 1

[0275] Materials

[0276] Condensate 3: reaction product of oleic acid with polyalkylene polyamine comprising 40% triethylenetetramine (TETA), 20% tetraethylenepentamine (TEPA), and 40% pentaethylenehexamine (PEHA).

[0277] Reagent 3: 60 wt.% of a salt of acetic acid and the condensate 3 (54 wt% condensate, 6 wt% acetic acid), 33wt% alcohols, q.s. water, based on the total weight of reagent 3.

[0278] Collector composition 3: 85 wt.% reagent 3, 7 wt.% diesel fuel, 3 wt.% sodium alcohol ether sulphates (with the structure of RO(CH2CH2O)n-SO3Na, wherein n is 1-4, R is C10~16 alkyl), 5 wt.% a-terpineol, based on the total weight of collector composition 3. . (i.e. , 46 wt% of the condensate, 7 wt% of at least one mineral oil (diesel fuel), 33 wt% of at least one alcohol (a-terpineol and the alcohols in the reagent, 5 wt% of the acid, 3 wt.% sodium alcohol ether sulphates, with water as rest)

[0279] Slurries and method (similar as the slurries, method of example 1) ResultTable 4

[0280]

[0281] The concentrate corresponds to the sink portion of the treated fourth cleaner slurry.

[0282] The middling corresponds to the flotation portions of the treated second cleaner slurry and of the treated third cleaner slurry. For example, the whiteness of the middling is calculated as follows: the sum of flotation portions of the treated second cleaner slurry (57.67 %) by its proportions (12.94 wt.% / 28.23 wt.%) + flotation portions of the treated third cleaner slurry (59.32 %) by its proportions (15.29wt.% / 28.23 wt.%).

[0283] The tailing corresponds to the flotation portions of the treated rougher slurry and of the treated first cleaner slurry.

[0284] None of the samples tested has an acceptable grade i.e., a whiteness of 70 % or above.

[0285] EXAMPLE 4

[0286] Materials

[0287] Reagent 2: 61 wt.% of a salt of acetic acid and the condensate 2 (54 wt% condensate, 7 wt% acetic acid), 33wt% alcohols, q.s. water, based on the total weight of reagent 2.

[0288] Collector composition 4:

[0289] 30 wt.% reagent 2, 18 wt.% diesel fuel, 6 wt% alcohols, 8 wt.% acetic acid, based on the total weight of collector composition 4 (i.e., 16 wt.% condensate 2, 18 wt.% diesel fuel, 10 wt.% acetic acid, 16 wt.% alcohols (including the alcohols in the reagent), with water as a balance of 100% composition).

[0290] Phosphogypsum: Sample extracted from Guizhou Province, China(whiteness 60-70%).

[0291] Method: carried out as Example 1, but 1) without grinding ; 2) without third and fourth cleaner reverse flotation steps ; 3) conducted screen at 0.15mm after second cleaner reverse flotation step. The satisfactory result is listed in Table 5.

[0292] Measurement of the gypsum [CaSO4-2H2O] content (see the protocol of example 1)

[0293] Measurement of the whiteness of gypsum (see the protocol of example 1 ) Results

[0294] Table 5

[0295]

[0296] EXAMPLE 5

[0297] Materials

[0298] Collector composition 4 is used.

[0299] Phosphoqypsum: Sample extracted from Hubei Province, China.

[0300] Method: carried out as Example 1 for grinding.

[0301] Slurries

[0302] Raw slurry: 30-40% of ground phosphogypsum, q.s. water, based on total weight of the raw slurry.

[0303] Rougher flotation slurry: about 250 g of the collector composition 1 per ton of the original ground phosphogypsum ore, pH adjusted to 3 using sulfuric acid.

[0304] First cleaner flotation slurry: about 100 g of the collector composition 1 per ton of the original ground phosphogypsum ore.

[0305] Second cleaner flotation slurry: about 80 g of the collector composition 1 per ton of the original ground phosphogypsum ore, pH adjusted to 2-3 using phosphoric acid.

[0306] Third cleaner flotation slurry: about 80 g of the collector composition 1 and 100g of the frothing agent (mixture of diesel fuel, pine oil, and tributyl phosphate in a weight ratio of 1:1:2) per ton of the original ground phosphogypsum ore.Fourth cleaner flotation slurry: about 50 g of the collector composition 1 per ton of the original ground phosphogypsum ore.

[0307] .The satisfactory result is listed in Table 6.

[0308] Measurement of the gypsum [CaSO4-2H2O] content (see the protocol of example 1)

[0309] Measurement of the whiteness of gypsum (see the protocol of example 1 ) Results

[0310] Table 6

[0311]

Claims

CLAIMS1. A reagent comprising a salt of an acid and a condensate of at least one polyalkylene polyamine and a mixture of at least two fatty acid compounds;wherein the mixture of fatty acid compounds comprises about 15 wt.% or more, preferably from about 15 wt% to 50 wt%, more preferably from about 20 to 40 wt.%, of at least one saturated fatty acid, by total weight of the mixture of fatty acid compounds; andwherein the mixture of fatty acid compounds comprises about 85 wt.% or less, preferably from about 60 to about 80 wt.%, of at least one unsaturated fatty acid, by total weight of the mixture of fatty acid compounds.

2. The reagent, according to claim 1 , whereino the at least one polyalkylene polyamine comprises alkylene groups being selected from the group consisting of ethylene and / or propylene; preferably the at least one polyalkylene polyamine has the following formula I:H2N-(C2H4NH)X-C2H4-NH2,wherein x is an integer from 2 to 11 ; and / oro the at least one saturated fatty acid is selected from the group consisting of C12-30 saturated fatty acids; preferably C14-22 saturated fatty acids; more preferably C14-18 saturated fatty acids; most preferably C16-18 saturated fatty acids; and / or o the at least one unsaturated fatty acid is selected from the group consisting of C12-30 unsaturated fatty acids; preferably C14-22 unsaturated fatty acids; more preferably C14-18 unsaturated fatty acids; and / oro the acid is selected from the group consisting of acetic acid, citric acid, oxalic acid, sulfuric acid, hydrochloric acid, and mixtures thereof; preferably the acid is acetic acid; and / or o the content of formula I is higher than 80 wt%, preferably 90 wt% based on the total weight of polyalkylene polyamine.

3. The reagent, according to any preceding claims, wherein the mixture of fatty acid compounds comprises palmitic acid, stearic acid, oleic acid and linoleic acid.

4. The reagent, according to any preceding claims, wherein the content of the C16-18 fatty acid compounds is about 90 wt.% or more of the fatty acid compounds present in the mixture; and / or the content of the C16-18 saturated fatty acid compounds is about 90 wt.% or more of the saturated fatty acid compounds present in the mixture.

5. The reagent, according to any preceding claims, wherein the reagent comprises from about 45 to about 80 wt.%, preferably from about 50 to about 75 wt.%, more preferably from about 55 to about 70 wt.%, of the salt of the acid and the condensate, by total weight of the reagent.

6. A composition, wherein the composition comprises the reagent according to any claims 1 to 5, and at least one additive; preferably the at least one additive is selected from the group consisting of at least one mineral oil, at least one alcohol, at least one flotation auxiliary, and mixtures thereof.

7. The composition, according to claim 6, wherein the composition comprises from about 80 to about 95 wt.%, preferably from about 82 to about 92 wt.%, more preferably from about 83 to about 90 wt.%, of the reagent, by total weight of the composition.

8. The composition, according to claims 6 or 7, wherein the composition comprises, by total weight of the composition:- from about 1 to about 18 wt.%, preferably from about 3 to about 15 wt.%, more preferably from about 5 to about 13 wt.%, of the at least one mineral oil;- from about 1 to about 18 wt.%, preferably from about 2 to about 15 wt.%, more preferably from about 3 to about 10 wt.%, of the at least one alcohol; and / or- from about 1 to about 18 wt.%, preferably from about 1.5 to about 15 wt.%, more preferably from about 1.8 to about 10 wt.%, of the at least one flotation auxiliary.

9. The composition according to claims 6, wherein the composition comprises, by total weight of the composition:- from about 25 to about 95 wt% of the reagent;- from about 1 to about 25 wt% of the at least one mineral oil; - from about 1 to about 18 wt% of the at least one alcohol;- from about 0 to about 15 wt% of the acid;- from about 0 to 40 wt% of water;- from about 0-10 wt% of the at least one flotation auxiliary.

10. A composition comprises a mixture of, by total weight of the composition:- from about 12 to about 60 wt% of the condensate;- from about 1 to about 25 wt% of the at least one mineral oil; - from about 1 to about 35 wt% of the at least one alcohol;- from about 1 to about 15 wt% of the acid;- from about 4 to 50 wt% of water;- from about 0-10 wt% of the at least one flotation auxiliary.

11. The composition according to claim 10, wherein theratio of the condensate to the at least one alcohol is 1:2 to 2:1; and / orthe condensate to the at least one mineral oil is higher than 0.8.

12. A method for treating phosphogypsum, wherein the method comprises the following steps:(1) providing phosphogypsum ore;(2) grinding phosphogypsum ore for obtaining ground phosphogypsum ore;(3) preparing a raw slurry by adding an aqueous carrier, preferably water, to the ground phosphogypsum ore; and (4) carrying out at least one reverse flotation using the reagent according to any one of claims 1 to 5 or the composition according to any of claims 6 to 11.

13. The method for treating phosphogypsum, according to claim 12, wherein the ground phosphogypsum ore comprises:- from about 10 to about 40 wt.%, preferably from about 15 to about 35 wt.%, more preferably from about 20 to about 35 wt.%, of ore particles with a particle size of about 0.037 or less;- from about 30 to about 60 wt.%, preferably from about 35 to about 55 wt.%, more preferably from about 35 to about 50 wt.%, of ore particles with a particle size from about 0.037 mm to about 0.048 mm;- from about 20 to about 60 wt.%, preferably from about 25 about to 50 wt.%, more preferably from about 28 to about 43 wt.%, of ore particles with a particle size of about 0.048 mm to about 0.15 mm; and- about 5 wt.% or less, preferably about 1 wt.% or less, more preferably about 0.1 wt.% or less, most preferably 0 wt.% (free), of ore particles with a particle size of about 0.15 mm or more.

14. The method for treating phosphogypsum, according to any one of claim 12 or 13, wherein the raw slurry comprises from about 30 to about 40 wt.%, preferably from about 32 to about 40 wt.%, more preferably from about 35 to about 40 wt.%, of ground phosphogypsum ore, by total weight of the raw slurry.

15. The method for treating phosphogypsum, according to any one of claims 12 to 14, wherein step (4) comprises the following substeps:- (4.1 ) a rougher reverse flotation;- (4.2) a first cleaner reverse flotation;- (4.3) a second cleaner reverse flotation;- (4.4) a third cleaner reverse flotation; and- optionally (4.5) a fourth cleaner reverse flotation.

16. The method for treating phosphogypsum, according to claim 15, wherein the sub-steps (4.1) to (4.5) are carried out as follows: - (4.1) preparing a rougher reverse flotation slurry by adding the composition according to claims 6 to 11 to the raw slurry, and subjecting it to flotation for obtaining a treated rougher slurry; and / or- (4.2) preparing a first cleaner reverse flotation slurry by adding the composition according to claims 6 to 11 to the sink portion ofthe treated rougher reverse flotation slurry, and subjecting it to flotation for obtaining a treated first cleaner reverse flotation slurry; and / or- (4.3) preparing a second cleaner reverse flotation slurry by adding the composition according to claims 6 to 11 to the sink portion of the treated first reverse flotation slurry, and subjecting it to flotation for obtaining a treated second cleaner reverse flotation slurry; and / or- (4.4) preparing a third cleaner reverse flotation slurry by adding the composition according to claims 6 to 11 and at least one frothing agent to the sink portion of the treated second reverse flotation slurry, and subjecting it to flotation for obtaining a treated third cleaner reverse flotation slurry; and / or- optionally (4.5) preparing a fourth cleaner reverse flotation slurry by adding the composition according to claims 6 to 11 to the sink portion of the treated third reverse flotation slurry, and subjecting it to flotation for obtaining a treated fourth cleaner reverse flotation slurry.

17. The method for treating phosphogypsum, according to claim 16, wherein the sub-steps (4.1) to (4.5) are further carried out as follows:- (4.1) the pH of the rougher reverse flotation slurry is adjusted to a pH from 3 to 4, preferably using sulfuric acid; and / or- (4.3) the pH of the second cleaner reverse flotation slurry is adjusted to a pH from 2 to 3, preferably using phosphoric acid; and / or- (4.4) the frothing agent comprises from 20 to 40 wt.% of at least one mineral oil, from 20 to 40 wt.% of at least one alcohol, and from 30 to 60 wt.% of at least one flotation auxiliary, by total weight of the frothing agent.

18. Use of the reagent according to any of claims 1 to 5, or the composition comprising it according to any of claims 6 to 11, wherein the reagent, or the composition comprising it, is used in phosphogypsum flotation.

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