Process for leaching organic compounds from a phosphate composition

Abstract

The present invention relates to a process for leaching at least one organic compound from a phosphate composition comprising at least on phosphate source, said process comprising the following steps: providing a phosphate composition comprising at least one phosphate source, said phosphate composition comprising, based on the total weight of said phosphate composition, at least 10,0 wt.% and at most 40,0 wt.% of phosphorous, expressed in wt.% equivalent P2O5, and Y1 wt.%, which is equal to or more than 100.0 ppm, of at least one organic compound, expressed in total organic carbon [hereinafter, TOC] equivalent; contacting said phosphate composition with at least one first mineral acid, at a molar ratio H+ / P2O5 comprised between 0.5 and 5.0, thereby forming at least one first slurry comprising a first liquid phase and a first solid phase adding at least one alkaline additive to said first slurry, thereby forming a second slurry and separating said second solid phase from said second liquid phase.

Description

[0001] PROCESS FOR LEACHING ORGANIC COMPOUNDS FROM A PHOSPHATE COMPOSITION

[0002] The present invention relates to a process for leaching at least one organic compound from a phosphate composition. The invention, further relates to the use of the solid product obtained at the end of the process to supply various products, as well as the use of the solid product obtained as a raw material in a dihydrate, hemihydrate, or di-hemi process.

[0003] STATE OF THE ART

[0004] Phosphate ores are used in a variety of processes, notably wet-phosphoric acid production processes. In this process, a phosphate ore is etched with a mineral acid. The P2O5 content of the compositions obtained as well as the quality thereof depends on the type of phosphate ore.

[0005] The phosphate ores usually do not contain only phosphorus but various other elements, which can vary depending on the nature of those ores. Usually, those elements are considered undesirable and can end up as impurities in the phosphoric acid obtained from said resources.

[0006] For examples, phosphate ores usually contain impurities such as organic compounds in various amounts, depending on the origin of the phosphate ores.

[0007] To avoid the presence of these impurities in the final phosphoric acid, they often need to be removed during or after the wet-phosphoric acid production process, especially if the phosphoric acid is to be used in food or agricultural applications or to produce other phosphate derivatives used in food and agricultural applications, such as fertilizers.

[0008] The elimination or management of organic compounds in current processes may require additional purification steps, thereby increasing operational and production costs.

[0009] Some examples of costly & technically demanding downstream impurity removal processes to further treat phosphoric acid are solvent extraction, nanofiltration, ion exchange resins, electrodialysis [Phosphoric Acid, Purification, Uses, Technology, and Economics, R. Gilmour, CRC Press 2014, chap 2, Purification of phosphoric acid, pages 71 - 76], Most of the time, these techniques are applicable on a liquid phase which is previously processed (dearsenificated, desulfated, free of any solids, ...) after acid digestion from the rock. Most of the time, these technics should be combined, and they generate different impurity flows, which should be eliminated. In addition to complexify the process, these techniques are expensive to put in place and bring some complex operations regarding safety and used chemicals.

[0010] There is also a process for treating rock at temperatures equal to or greater than 800°C in expensive and complex (rotary) furnaces, which involves high energy consumption. This involves burning fuels that generate carbon dioxide, which is undesirable, particularly for environmental reasons.

[0011] Nowadays, the recovery of phosphoric acid from phosphate rock contaminated with organic compounds is complicated, costly, and difficult to apply on an industrial scale.

[0012] For all these reasons, there is a real need to provide a process suitable for reducing the organic compounds content in phosphate ore in order to be able to use these raw materials in a process that is easy to implement, efficient, and sustainable. The resulting phosphoric acid can be used in many different applications. This would make it possible to use phosphate ore of various origins.

[0013] SUMMARY OF THE INVENTION

[0014] The inventors have surprisingly found that the above technical problems can be solved by the present invention. The present invention relates to a process for leaching at least one organic compound from a phosphate composition comprising at least on phosphate source, said process comprising the following steps: a) providing a phosphate composition comprising at least one phosphate source, said phosphate composition comprising, based on the total weight of said phosphate composition: o at least 10,0 wt.% and at most 40,0 wt.% of phosphorous, expressed in wt.% equivalent P2O5, and o Y1 wt.%, which is equal to or more than 100.0 ppm, of at least one organic compound, expressed in total organic carbon [hereinafter, TOC] equivalent ; b) contacting said phosphate composition with at least one first mineral acid, at a molar ratio HVP2O5 comprised between 0.5 and 5.0, thereby forming at least one first slurry comprising a first liquid phase and a first solid phase, wherein H+represents the total number of moles of acidic protons from said acid and P2O5 represents the total number of moles of P2O5 comprised in said phosphate composition, wherein: o said first slurry has a predetermined pH [hereinafter, pH 1] , and; o said first liquid phase comprises at least part of said organic compound, and; o said solid phase comprises at least part of said phosphorus and has an amount of organic compound, expressed in TOC equivalent, of Y2wt.%, which is less than Y1, based on the total weight of said solid phase; c) adding at least one alkaline additive to said first slurry, thereby forming a second slurry comprising a second liquid phase and a second solid phase, wherein o said slurry has a pH [hereinafter, PH2] which is higher than pHi but equal to or more than 2, and; o said second solid phase has a phosphorous content which is increased compared to the phosphorous content of the first solid phase; d) separating said second solid phase from said second liquid phase.

[0015] The invention also concerns a continuous process for leaching at least one organic compound from a phosphate composition according to the present invention.

[0016] The invention also concerns a continuous process for leching at least one organic compound from a phosphate composition comprising at least one phosphate source, said process comprising the following steps: a) providing a phosphate composition comprising at least one phosphate source, said phosphate composition comprising, based on the total weight of said phosphate composition: o at least 10,0 wt.% and at most 40,0 wt.% of phosphorous, expressed in wt.% equivalent P2O5, and o Y1 wt.%, which is equal to or more than 100.0 ppm, of at least one organic compound, expressed in total organic carbon [hereinafter, TOC] equivalent ; b) contacting said phosphate composition with at least one first mineral acid at a molar ratio HVP2O5 comprised between 0.5 and 5.0, thereby forming at least one first slurry comprising a first liquid phase and a first solid phase, wherein H+represents the total number of moles of acidic protons from said acid and P2O5 represents the total number of moles of P2O5 comprised in said phosphate composition, wherein: o said first slurry has a predetermined pH [hereinafter, pH 1] , and; o said first liquid phase comprises at least part of said organic compound, and; o said solid phase comprises at least part of said phosphorus and has an amount of organic compound, expressed in TOC equivalent, of Y2wt.%, which is less than Y1, based on the total weight of said solid phase; c) adding at least one alkaline additive to said first slurry, thereby forming a second slurry comprising a second liquid phase and a second solid phase, wherein o said slurry has a pH [hereinafter, PH2] which is higher than pHi but equal to or more than 2, and; o said second solid phase has a phosphorous content which is increased compared to the phosphorous content of the first solid phase; d) separating said second solid phase from said second liquid phase.

[0017] The process according to the present invention enables efficient leaching of organic compounds from the phosphate composition. DETAILED DESCRIPTION

[0018] Withing the context of the present invention, the term “comprising”, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but it does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a process comprising the steps A and B” should not be limited to the process consisting only of steps A and B. It means that with respect to the present invention, the only relevant steps of the process are A and B. Thus, the process or method according to the present invention may encompass processes comprising steps A and B and additional steps after steps A and B or between steps A and B. Accordingly, the terms “comprising” and “including” encompass the more restrictive terms “consisting essentially of’ and “consisting of”. It is to be noted that any of the steps comprised in the process according to the present invention can be repeated at any number of times.

[0019] As used herein, the terms "optional" or "optionally" means that a subsequently described step, event or circumstance can or cannot occur, and that the description includes instances where said step, event or circumstance occurs and instances where it does not.

[0020] Within the context of the present invention, all the percentages % are percentages by weight except when specified otherwise. Within the context of the present invention, all the ppm are ppm by weight except when specified otherwise.

[0021] According to the present invention, the terms “slurry” and “suspension” can be use interchangeably.

[0022] Phosphate composition

[0023] The present invention concerns a process for leaching at least one organic compound from a phosphate composition.

[0024] The process according to the present invention can be carried out in batches or continuously.

[0025] The process according to the present invention comprises a step a) of providing a phosphate composition comprising at least on phosphate source, wherein said phosphate composition comprises, at least 10,0 wt.% and at most 40,0 wt.% of phosphorous, expressed in wt.% equivalent P2O5, based on the total weight of said phosphate composition.

[0026] Within the context of the present invention, the term “phosphate composition” is intended to denote any material comprising phosphates and / or phosphate ions and / or able to release phosphate ions in solution. The expression “phosphate composition” is intended to refer to a compound comprising at least one phosphate source or a composition comprising at least one phosphate source or a mixture thereof. Within the context of the present invention, the expression “at least one phosphate source” is intended to denote one or more than one phosphate source.

[0027] In the rest of the text, the expression “at least one phosphate source” is understood, for the purposes of the present invention, both in the plural and the singular.

[0028] Non-limiting examples of suitable phosphate source may be of natural origin, or be synthetically prepared by a variety of methods known in the art. Non-limiting examples of phosphate sources of natural origin may be phosphate ores, also called phosphate rocks.

[0029] Non-limiting examples of phosphate ores, also called phosphate rocks, may be sedimentary phosphate rocks and igneous phosphate rocks. Non-limiting example of sedimentary phosphate rocks is phosphorite. Non-limiting example of igneous phosphate rocks is carbonatite. The main phosphate mineral presents in both sedimentary and igneous rocks is apatite, non-limiting examples of apatites notably include hydroxyapatite, fluorapatite, and chlorapatite.

[0030] Preferably, when the phosphate source is a phosphate ore, also called phosphate rock, this phosphate composition may be an ore or rock containing in particular calcium phosphate in the form of apatite (and its derivatives, including fluoro-, chloro-, hydroxy-apatite, phosphorite) or tricalcium phosphate, dicalcium phosphate or whitlockite.

[0031] Non-limiting examples of phosphate source synthetically prepared may be phosphate salts such as tricalcium phosphate salts, dicalcium phosphate salts, ammonium phosphate salts, sodium phosphate salts, aluminum phosphate salts, iron phosphate salts, aluminum-iron phosphate salts, magnesium-ammonium phosphate salts (struvite) and mixture thereof. Another non-limiting example is hydroxyapatite, although it is a naturally occurring mineral, it is known by the skilled in the art that it can be synthetically prepared as well.

[0032] Non-limiting examples of phosphate source which are by-products of industrial processes may be ashes, beneficiation residues, residual acids from metallurgical treatments, industry side streams, black masses, and combinations thereof. Non-limiting examples of ashes may be bone ashes, manure ashes or may result from the incineration of sludges of wastewater treatment. Beneficiation residues may include one or more of phosphate tailing and phosphate slimes. In particular, industry side streams may be washing solutions from the chemical, phosphate, pharmaceutical, food-processing industries and mixture thereof.

[0033] Preferably, when the phosphate source is a by-product of industrial processes, the phosphate composition is a beneficiation residue.

[0034] Advantageously, said phosphate source is selected from the group consisting of phosphate ores, phosphate salts, beneficiation residues, bone ashes and sewage sludges ashes. Preferably, said phosphate source is selected from the group consisting of phosphate ores and beneficiation residues. Preferably, the phosphate salts are chosen in the group consisting of calcium phosphate, more preferably dicalcium phosphate and tricalcium phosphate. Said phosphate source may further comprise iron phosphate, aluminium phosphate or mixture thereof, especially when the phosphate source is bone ashes and / or sewage sludges ashes.

[0035] Preferably, when the phosphate source is a phosphate ore, the phosphate ore is a sedimentary phosphate rock.

[0036] In a certain embodiment of the invention, the phosphate source is a “beneficiation residue” comprising one or more phosphate residues and phosphate slimes. Beneficiation is a step in the mining process performed after the ore has been extracted from the ground. It preferably consists of mechanically separating the minerals present in the phosphate ore (or “matrix”) from each other. For example, phosphates can be mechanically separated from clay and quartz (or sand). This can be achieved, for example, by separating the minerals according to their grain size or density.

[0037] In a particular embodiment of the invention, the phosphate source is selected from:

[0038] - Phosphate ores, possibly in suspension (in water, in an aqueous solution or in a solvent),

[0039] - Beneficiation residues, including one or more phosphate residues and phosphate sludge, possibly in suspension,

[0040] In a certain embodiment of the invention, the phosphate composition may comprise at least one phosphate ore, as detailed above, and at least one other phosphate sources, as detailed above. In other words, the phosphate composition may comprise at least one phosphate ore, as detailed above, and at least one phosphate source selected from the group consisting of synthetic phosphates and phosphate sources that are by-products of industrial processes. Non-limiting examples of phosphate sources that are by-products of industrial processes are ashes, beneficiation residues, residual acids from metallurgical treatments, industry side streams, black masses, and combinations thereof, as detailed above. Preferably, the phosphate composition comprises at least one phosphate ore, as detailed above, and at least one beneficiation residue, as detailed above.

[0041] Preferably, said phosphate composition comprises based on the total weight of said phosphate composition at least 12,0 wt.%, preferably at least 15,0 wt.%, preferably at least 17,0 wt.%, preferably at least 20.0 wt.%, more preferably at least 25.0 wt.% of phosphorous, expressed in wt.% equivalent P2O5.

[0042] Preferably, said phosphate composition comprises based on the total weight of phosphate composition at most 35,0 wt.%, preferably at most 30.0 wt.%, more preferably at most 25.0 wt.% of phosphorous, expressed in wt.% equivalent P2O5.

[0043] In a preferred embodiment, said phosphate composition comprises based on the total weight of said phosphate composition at least 12,0 wt.% and at most 35.0 wt.%, preferably at least 15.0 wt.% and at most 35.0 wt.%, more preferably at least 17.0 wt.% and at most 35.0 wt.%, more preferably at least 20.0 wt.% and at most 35.0 wt.% more preferably at least 25.0 wt.% and at most 30.0 wt.% of phosphorous, expressed in wt.% equivalent P2O5.

[0044] In the context of the present invention, the weight percentage of P2O5 can be measured by any appropriate method known to those skilled in the art. Preferably, the weight percentage of P2O5 can be measured by colorimetry of phospho-vanadium-molybdate at 436 nm (yellow) (light absorption spectrophotometry). In other words, the phosphorus content expressed as wt.% of P2O5 can be measured by absorption spectrometry via reaction with a molybdovanadate reagent to form a yellow complex, the intensity of which is proportional to the concentration of reactive phosphorus and thus be measured by an absorption spectrometer at 436 nm (for example a HACH DR3900 spectrometer). It goes without saying that, the phosphorus content expressed as wt.% of P2O5 can also be measured by titration preferably with a standardized NaOH solution.

[0045] Advantageously, the phosphate composition comprises at least 50 wt.%, preferably at least 60 wt.%, more preferably at least 70 wt.%, even more preferably at least 80 wt.% of phosphate ore, based on the total weight of said phosphate composition. Said phosphate composition may essentially consist of phosphate ore or not.

[0046] In a particular embodiment of the invention, said phosphate composition is a phosphate ore or a beneficiation residue comprising a total amount of phosphorus, expressed as P2O5 equivalent, between 10 and 40 % by weight, preferably between 15 and 40 % by weight, preferably between 18 and 40% by weight of P2O5, preferably between 20 and 40% by weight of P2O5, more preferably between 20 and 40% by weight of P2O5, more preferably between 20 and 38% by weight of P2O5, most preferably between 20 and 35% by weight of P2O5, most preferably between 20 and 33% by weight of P2O5, most preferably between 20 and 30% by weight of P2O5, based on the total weight of said phosphate composition.

[0047] Said phosphate composition may be in solid form or in the form of a slurry. Preferably, said phosphate composition is in solid form. Preferably, when said phosphate composition is in the form of a slurry, said phosphate composition is at least partially dispersed and / or suspended into an aqueous solvent.

[0048] According to a specific embodiment, when the phosphate composition is a phosphate ore, this phosphate composition is supplied in suspension (in an aqueous solvent or in water). In this case, the solids concentration is greater than 30% by weight, preferably greater than 40% by weight, more preferably greater than 50% by weight, and even more preferably greater than 60% by weight.

[0049] The aqueous solvent referred to in the preceding paragraph may be provided by recirculating the recovery wash filtrate of said second solid phase (step d) (in whole or in part) and / or the purified filtrate, i.e. third liquid phase, (in whole or in part) and / or the second liquid phase (at least a portion) separated in step (d). The recirculated portion of the wash filtrate is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0050] The recirculated portion of the second liquid phase is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0051] The recirculated portion of the purified filtrate, i.e. third liquid phase, is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0052] The recirculated portion of the residual acid solution is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0053] According to the present invention, said phosphate composition comprises Yi wt.%, which is equal to or more than 100.0 ppm, of at least one organic compound, expressed in total organic carbon [hereinafter, TOC] equivalent.

[0054] Within the context of the present invention, the expression “at least one organic compound” is intended to denote one or more than one organic compound.

[0055] In the rest of the text, the expression “at least one organic compound” is understood, for the purposes of the present invention, both in the plural and the singular.

[0056] Preferably, said phosphate composition comprises, based on the total weight of said phosphate composition, Yi wt.%, which is at least 200.0 ppm, preferably at least 250.0 ppm, more preferably at least 300.0 ppm, even more preferably at least 350.0 ppm, even more preferably at least 400.0 ppm, even more preferably at least 450.0 ppm, even more preferably at least 500.0 ppm of said at least one organic compound, expressed in TOC equivalent.

[0057] Preferably, said phosphate composition comprises, based on the total weight of said phosphate composition, Yi wt.%, which is at most 15000.0 ppm, preferably at most 10000.0 ppm, more preferably at most 8000.0 ppm, even more preferably at most 6000.0 ppm, even more preferably at most 5700.0 ppm of said at least one organic compound, expressed in TOC equivalent.

[0058] Preferably, said phosphate composition comprises, based on the total weight of said phosphate composition, Yi wt.%, which is at least 200.0 ppm and at most 15000.0 ppm, preferably at least 250.0 ppm and at most 10000.0 ppm, more preferably at least 300.0 ppm and at most 8000.0 ppm, even more preferably at least 350.0 ppm and at most 6000.0 ppm, even more preferably at least 400.0 ppm and at most 6000.0 ppm, even more preferably at least 450.0 ppm and at most 5700.0 ppm, even more preferably at least 500.0 ppm and at most 5700.0 ppm of said at least one organic compound, expressed in TOC equivalent.

[0059] Preferably, when the phosphate composition is a phosphate ore or a beneficiation residue, the amount of organic compound, expressed in TOC equivalent of said phosphate composition is greater than 500 ppm, preferably greater than 800 ppm, more preferably greater than 1000 ppm.

[0060] Preferably, when the phosphate composition is a phosphate ore or a beneficiation residue, the amount of organic compound, expressed in TOC equivalent, of the phosphate composition is between 500 and 15,000 ppm, preferably between 500 and 10,000 ppm, more preferably between 500 and 8,000 ppm, and most preferably between 500 and 5700 ppm, based on the total weight of said phosphate composition.

[0061] In general, the content of organic compounds in a sample is determined by the quantification of organic carbon in this sample. Typically, the total organic carbon (TOC) indicates the total amount of carbon from organic material in a sample. Therefore, the expressions total organic carbon (TOC), total carbon from organic material and total carbon from organic compounds can be used interchangeably.

[0062] The TOC content can be estimated by determining the difference between the measurement of the total carbon and the inorganic carbon in said phosphate ore. It is understood that the total carbon content is estimated by the content of CO2 emitted during calcination under oxygen of said phosphate ore in question and that the inorganic carbon is estimated by the content of CO2 emitted during an acid attack or leaching of the phosphate ore. The measurement of CO2 is carried out using an infrared detector.

[0063] According to the present invention, the TOC content is calculated by making the difference between the total carbon content and the total inorganic carbon (TIC) content in the sample. It is understood that the total carbon content is estimated by the measurement of the content of CO2 emitted during calcination under oxygen of said sample. In general, the measurement is performed until the end of CO2 emissions, which corresponds to the end of calcination reaction, with a maximum of 900s. The total inorganic carbon (TIC) is estimated by measuring the content of CO2 emitted during a step of reacting the sample with phosphoric acid, preferably purified phosphoric acid, having a concentration of 40 wt.%. In general, the measurement is performed until the end of CO2 emissions, which corresponds to the end of the reaction, with a maximum of 900s. The measurement of CO2 is carried out using an infrared detector.

[0064] The first slurry

[0065] The process according to the present invention, further comprises a step b) of contacting said phosphate composition with at least one first mineral acid, at a molar ratio HVP2O5 comprised between 0.5 and 5.0, thereby forming at least one first slurry comprising a first liquid phase and a first solid phase.

[0066] Within the context of the present invention, the term “contacting” encompasses any form of contacting. Examples of contacting include (but are not limited to): mixing, adding, blending, combining, stirring together.

[0067] It is understood that the skilled person in the art will carry out said contacting or mixing according to general practice such as notably using optimal times, speeds, weights, volumes and batch quantities.

[0068] Generally said mixing, as detailed above, may be carried out by using a variety of mixing means known in the art. Non-limiting examples of such mixing means are: mechanical mixing such as traditional mixers and blenders, high intensity mixers and electric stirrers, said mixers, blenders and stirrers which can be equipped with at least one dispersion disk. A high sheer force can be applied during the mixing to improve the homogeneity of the mixture.

[0069] Advantageously, said contacting step is a leaching step.

[0070] In the context of this invention, a distinction will be made between the term “leaching” and the term “attack.” Leaching refers to an acid reaction that dissolves certain compounds. In other words, the leaching refers to extraction of at least part of certain compounds from a phosphate composition into a liquid phase, under acidic conditions. The term attack refers to a total reaction with possible recrystallization. In other words, the term “attack” refers to the reaction, also called digestion, of a phosphate composition with an acid to form a slurry.

[0071] In the context of the present invention and preferably, the term “leaching” according to the invention should be understood as referring to the solubilization of organic compounds, expressed in TOC equivalent, from the phosphate composition into a liquid phase. According to the present invention, after the leaching of a phosphate composition, the organic compounds, expressed in TOC equivalent, are in a liquid phase while the phosphorus, expressed in P2O5 equivalent is in the a solid phase. The term “attack” used in the context of the invention should be understood as referring to the recovery of P2O5 in soluble form, while promoting the retention of impurities in the solid phase. In other words, according to the present invention, after the attack of a phosphate composition, the organic compounds, expressed in TOC equivalent, are in a solid phase while the phosphorus, expressed in P2O5 equivalent is in the a liquid phase.

[0072] Within the context of the present invention, the expression “at least one first mineral acid” is intended to denote one or more than one first mineral acid.

[0073] In the rest of the text, the expression “at least one first mineral acid” is understood, for the purposes of the present invention, both in the plural and the singular. It goes without saying that the expression “mineral acid” according to the present invention, intends to refer to an acid derived from inorganic compound and can thus be also called inorganic acid.

[0074] Any mineral acid may be used. Suitable mineral acids include for example: production acids, recycled production acid (RPA), purified acids, acids from recycling processes of byproducts of industrial processes including, in particular, residual acids from metallurgical treatments, industrial side streams and combinations thereof. For example, said mineral acid may comprise acids obtained from gas scrubbing, for example gas scrubbing from PVC (polyvinyl chloride) production or incinerators processing PVC waste.

[0075] Preferably, said at least one first mineral acid is selected from the group consisting of HCI, HNO3, H2SO4, HBr, HI, HCIO3, HCIO4, H2SiF6, HF, H3PO4and mixtures thereof.

[0076] Advantageously, said at least one first mineral acid is selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, and mixtures thereof, preferably sulfuric acid.

[0077] Preferably, said at least one first mineral acid comprises at least sulfuric acid (H2SO4).

[0078] According to a particularly advantageous embodiment, the at least one first mineral acid is sulfuric acid.

[0079] The at least one first mineral acid according to the invention may have a concentration of between 1% by weight and 99% by weight, preferably between 45% and 98.5% by weight, more preferably between 50% and 98% by weight.

[0080] Preferably, the contacting step (step b)) is carried out with said at least one first mineral acid which has a concentration of between 5 and 25% by weight, preferably between 5 and 20% by weight, more preferably between 6 and 17% by weight, and most preferably between 10 and 15% by weight. Preferably, the concentration of said at least one first mineral acid in situ is between 5 and 25% by weight, preferably between 5 and 20% by weight, more preferably between 6 and 17% by weight, and most preferably between 10 and 15% by weight.

[0081] Within the context of the present invention, the expression “concentration of said at least one first mineral acid in situ” intend to refer to the concentration of the acid during the contacting step b). This means that the acid may be provided in step b) as a concentrated acid, without dilution, and that an aqueous solvent is provided in step b) thereby forming the acid having a concentration in situ, during step b), which is as defined above.

[0082] Alternatively or additionally, the at least one first mineral acid may be diluted before being provided in step b).

[0083] Advantageously, the at least one first mineral acid of the contacting step is diluted in situ, during step b) of the process according to the invention.

[0084] Preferably, said at least one first mineral acid is diluted with an aqueous solvent such as water and / or a residual acid solution and / or a diluted acid and / or a recycled acid and / or a purified filtrate and / or the wash filtrate and / or the raw phosphoric acid (RPA) and / or the liquid phase.

[0085] Preferably, said at least one first mineral acid is diluted until the concentration preferably reaches at least 5% by weight, preferably at least 10% by weight, and / or preferably at most 15% by weight, preferably at most 13% by weight, of the total solution.

[0086] According to a preferred mode, the at least one first mineral acid according to the invention is sulfuric acid. The at least one first mineral acid may be an acid mixture that comprises sulfuric acid as the major component. When an acid mixture is proposed, it comprises predominantly sulfuric acid with (in smaller quantities) an acid selected from phosphoric acid, hexafluorosilicic acid, hydrochloric acid, or mixtures thereof.

[0087] In a preferred embodiment, said at least one first mineral acid, preferably diluted, is sulfuric acid or a mixture of acids comprising predominantly sulfuric acid. Advantageously, the at least one first mineral acid is a mixture of acids comprising predominantly sulfuric acid, and optionally an acid selected from phosphoric acid, hydrochloric acid, hexafluorosilicic acid, and mixtures thereof. In a particularly advantageous mode, said at least one first mineral acid is a mixture of acids comprising mainly sulfuric acid and hydrochloric acid. In an even more advantageous mode, said at least one first mineral acid is a mixture of acids comprising mainly sulfuric acid and, in smaller quantities, an aqueous solution of residual acid recycled during phosphate production, such as a residual acid solution and / or during the washing of a plant or during the washing of gases from a plant, and any combination thereof.

[0088] According to a particularly preferred mode, said at least one first mineral acid, preferably sulfuric acid or hydrochloric acid, has a concentration of between 1 and 20% by weight, preferably between 1 and 15% by weight, more preferably between 10 and 14% by weight.

[0089] According to a particular embodiment, the phosphoric acid mixed with the sulfuric acid has a concentration of between 2 and 60% by weight, preferably between 10 and 65% by weight, preferably between 15 and 60% by weight, preferably between 20 and 57% by weight, preferably between 25 and 45% by weight.

[0090] According to a preferred embodiment, the hydrochloric acid mixed with the sulfuric acid has a concentration of between 1% by weight and 40% by weight, preferably between 5% by weight and 37% by weight, more preferably between 10% by weight and 30% by weight.

[0091] In a particularly advantageous mode, the at least one first mineral acid, which may be sulfuric acid or a mixture of acids as indicated above, may have one of the concentrations mentioned, taking into account all possible combinations between the information provided above.

[0092] The expression “RPA” refers to recycled phosphoric acid produced during a process for manufacturing phosphoric acid, preferably according to the present invention, i.e., the phosphoric acid produced and the solid residue, for example calcium sulfate, which are separated from each other, and when this solid residue is washed with water to provide an RPA solution. In addition, RPA may also be any phosphoric acid produced during the process of the invention.

[0093] According to the present invention, said contacting step (step b)) is performed at a molar ratio molar ratio I / P2O5 comprised between 0.5 and 5.0.

[0094] Advantageously, molar ratio I / P2O5 in the contacting step (step b)) is more than or equal to 0.6, preferably more than or equal to 0.7, more preferably more than or equal to 0.8, even more preferably more than or equal to 0.9, advantageously more than or equal to 1.0.

[0095] Advantageously, said molar ratio I / P2O5 in the contacting step (step b)) is between 0.6 and 5.0, preferably between 0.7 and 4.5, more preferably between 0.8 and 4.0, even more preferably between 0.8 and 3.5, advantageously between 0.9 and 3.3, more advantageously between 1.0 and 3.3.

[0096] In a preferred embodiment of the invention, the molar ratio HVP2O5 in the contacting step (step b)) is between 0.5 and 4.5, preferably between 0.5 and 4.0, preferably between 0.5 and 3.5, preferably between 0.5 and 3.3.

[0097] In an embodiment of the invention, said molar ratio I / P2O5 in the contacting step (step b)) is between 1 and 5, preferably between 1.5 and 4.5, more preferably between 2 and 4, even more preferably between 2.5 and 3.5, advantageously between 2.8 and 3.3, more advantageously between 2.9 and 3.1.

[0098] Preferably, the molar ratio I / P2O5 in the contacting step (b) is less than or equal to 5, more preferably less than 4.5, even more preferably less than 4, preferably less than 3.5, even more preferably less than 3.

[0099] In the molar ratio I / P2O5, H+represents the total number of moles of acidic protons from said first mineral acid, and P2O5 represents the total number of moles of P2O5 comprised in said phosphate composition in step a).

[0100] Preferably, said acidic proton can be defined as the proton(s) of said first mineral acid that can potentially react in an acid-base reaction (be exchanged) in water.

[0101] In the context of the present invention, only the acidic protons with a pKa lower than 3 are considered as contributing to the amount of H+. For example, sulfuric acid (H2SO4) has two acidic protons, both with pKa values below 3 (pKai » -3, pKa2» 1.99), and thus both are considered fully dissociated under typical conditions: H2SO4H++ HS04- 2H++ S042’

[0102] In contrast, phosphoric acid (H3PO4) has three acidic protons, but only the first one (pKa4» 2.15) is considered fully dissociated in this context. The second and third protons (pKa2» 7.2, pKa3» 12.3) are not included in the H+count due to their higher pKa values: H3PO4— > H++ H2PO4“ (only this step is considered) The selection of a particular molar ratio I / P2O5 allows the leaching to be controlled by improving the removal of the targeted impurities. This allows for the effective solubilization of organic compounds, expressed in TOC equivalent.

[0103] According to the present invention, said first slurry has a predetermined pH [hereinafter, pHi],

[0104] Advantageously, pHi is between 1.0 and 6.0, preferably between 1.2 and 5.5, more preferably between 1.5 and 5.0, and most preferably between 1.7 and 4.5.

[0105] The contacting step (step b)) is advantageously carried out until a pH of between 1.0 and 6.0, preferably between 1.2 and 5.5, more preferably between 1.5 and 5.0, and most preferably between 1.7 and 4.5 is reached in the first slurry.

[0106] According to a particular embodiment of the invention, the contacting step (step b)) is carried out until the pH (measured before step c and / or in the digested suspension) is greater than 1.5 and / or less than 4.

[0107] Within the context of the present invention, the pH can be measured directly in the slurry at the temperature at which leaching takes place using a Metier Toledo pH meter (PtIOOO) (calibration is performed before each measurement using calibrated solutions).

[0108] In a preferred embodiment, the pH is measured in the digested suspension, the first slurry, before the step (c), under leaching conditions, for example at 75°C.

[0109] According to the present invention, said first liquid phase comprises at least part of said organic compound and said first solid phase comprising at least part of said phosphorus and has an amount of organic compound, expressed in TOC equivalent, of Y2 wt.%, which is less than Y1, based on the total weight of said solid phase.

[0110] Advantageously, said first liquid phase comprises at least 30.0 %, preferably at least 35.0 %, preferably at least 40.0 %, preferably at least 45.0 %, preferably at least 50.0 %, preferably at least 55.0 %, preferably at least 60.0 %, preferably at least 65.0 %, preferably at least 70.0 %, preferably at least 75.0 %, more preferably at least 80.0 %, even more preferably at least 85.0 %, even more preferably at least 90.0 %, even more preferably at least 95.0 %, even more preferably at least 99.0 % of the at least one organic compound, expressed in TOC equivalent, comprised in said phosphate composition in step a).

[0111] In a preferred embodiment of the invention, at least 50% by weight, preferably at least 60% by weight, more preferably at least 65% by weight, more preferably at least 70% by weight, advantageously at least 85% by weight, more advantageously at least 90% by weight, preferably up to 100% by weight of said organic compound, expressed as TOC equivalent, present in said phosphate composition is solubilized in said first liquid phase.

[0112] Advantageously, said first solid phase comprises at least 60.0 wt.%, preferably at least 65.0 wt.%, more preferably at least 70.0 %, preferably at least 75.0 %, more preferably at least 80.0 %, even more preferably at least 85.0 %, even more preferably at least 90.0 %, even more preferably at least 95.0 %, even more preferably at least 99.0 % of the phosphorus comprised in said phosphate composition in step a).

[0113] Advantageously, the P2O5 yield at the end of step b) is greater than 65%, preferably greater than 75%, more preferably greater than 85%, even more preferably greater than 90%, advantageously greater than 95%, and more advantageously greater than 98%.

[0114] The P2O5 yield of step b) is a mass ratio and is calculated from the total phosphorus content by weight, expressed as P2O5 equivalent, in the first solid phase, comprising mainly phosphorus-containing compounds, divided by the total phosphorus content by weight, expressed as P2O5 equivalent, in said phosphate composition, preferably phosphorus- containing rock.

[0115] Advantageously, said first solid phase comprises an amount of organic compound, expressed in TOC equivalent, of Y2 wt.%, which is less than Y1, but at most 1000 ppm, preferably at most 750 ppm, preferably at most 500 ppm, preferably at most 200 ppm, preferably at most 120 ppm, based on the total weight of said solid phase.

[0116] Preferably, the first slurry has a solid content of between 30 and 50% by weight, preferably between 20 and 40% by weight relative to the total weight of the first slurry.

[0117] The process according to the present invention advantageously enables to leach and solubilize significant amount or most of the organic compounds comprised in the phosphate composition while avoiding leaching large amounts of phosphorus from the phosphate composition. In other words, the liquid phase advantageously comprises significant amount or most of the organic compounds while the solid phase advantageously comprises significant amount or most of the phosphorus. This is especially important if the first solid phase is intended to be used as a phosphate source in a wet-phosphoric acid process.

[0118] In an advantageous embodiment, said contacting step is carried out at a temperature below 100 °C, preferably below 95°C, preferably below 85°C, more preferably between 25°C and 80°C, advantageously between 30°C and 78°C, more advantageously between 60°C and 75°C, and even more advantageously equal to or close to 75°C.

[0119] In an additional preferred embodiment, said contacting step is carried out for a period of time of less than 300 minutes, preferably less than 280 minutes, more preferably less than 250 minutes and preferably at least 30 minutes.

[0120] Advantageously said contacting step is carried out for a period of time comprised between 5 and 300 minutes, preferably between 60 and 270 minutes.

[0121] In a preferred embodiment of the invention, said step b) is a leaching of a phosphate composition, preferably a phosphate ore or a benefaction residue, with at least one mineral acid, preferably sulfuric acid, at a molar ratio of I / P2O5 of between 1 and 5 and at a temperature below 100°C for a period of between 5 and 300 minutes, leading to the formation of a slurry comprising a liquid phase containing a majority of organic compound, expressed in TOC equivalent, relative to its content in said phosphate composition prior to leaching, and a solid phase comprising mainly phosphorus-containing compounds and being depleted in organic compound, expressed in TOC equivalent, relative to said phosphate composition supplied.

[0122] Preferably, said step b) of contacting is carried out in a vessel.

[0123] The vessel may be any reaction vessel, such as any reactor, container or tank. Said vessel may includes homogenization means, such as stirrer, or agitators.

[0124] Preferably, said step b) of contacting is carried out in reactor, preferably equipped with an agitator.

[0125] Preferably, the leaching step (b) is carried out with agitation.

[0126] In certain preferred embodiments, the pressure applied during the contacting step (step b)) may be atmospheric pressure or a slight vacuum of approximately 0.02 ± 0.01 bar.

[0127] According to a particularly preferred embodiment, the contacting step (step b)) is carried out in one or more reactors where the acid is added at the same time as the phosphate composition, before or after it.

[0128] According to a particularly preferred embodiment, the contacting step (step b)) is carried out in a reactor divided into different successive compartments (preferably in fluid communication by overflow) where the acid is added in the same compartment as the phosphate composition, or prior, in the previous compartment, or after, in the next compartment.

[0129] In a certain embodiment of the invention, the process may comprise a step of removing at least part of organic compounds from the first liquid phase thereby reducing the amount of organic compound in said first liquid phase. This can be performed by any method known by the person skilled in the art to effectively removing at least part of organic compounds from a liquid phase.

[0130] Non-limiting examples of method for removing organic compounds from a liquid phase are: nanofiltration, high temperature pulverisation, biological digestion, precipitation by adding an alkaline additive or combinations thereof.

[0131] Alkaline additive

[0132] The process according to the present invention comprises a step c) of adding at least one alkaline additive to said first slurry, thereby forming a second slurry comprising a second liquid phase and a second solid phase, wherein: o said second slurry has a pH [hereinafter, PH2] which is higher than pHi but equal to or more than 2, and; o said second solid phase has a phosphorous content which is increased compared to the phosphorous content of the first solid phase; In other word, this step of adding at least one alkaline additive to said first slurry, allows an increase of the pH with the formation of a second solid phase having a phosphorous content which is increased compared to the phosphorous content of the first solid phase, prior to step c).

[0133] The inventors have surprisingly found that the step of adding an alkaline additive is complementary with the preceding step b) because it helps at recovering phosphorus in the solid phase while maintain the organic compounds in the liquid phase.

[0134] This is really challenging because the solubility limit of the organic compounds and of the phosphorus are very close in acidic conditions. Therefore, selectively leaching the organic compounds from the phosphate composition while maintaining the phosphorus in the solid phase is clearly not obvious.

[0135] The inventors have found that by controlling the molar ratio HVP2O5 of the contacting step and then by adding at least one alkaline additive to the slurry, it is possible to selectively leach the organic compounds from the phosphate composition while maintaining the phosphorus in the solid phase.

[0136] Advantageously, said second slurry has a pH2 which is higher than pHi but equal to or more than 3, more preferably equal to or more than 4, preferably equal to or more than 4.5, preferably equal to or more than 5, or equal to or more than 5.5, or equal to or more than 6. It is understood that the higher limit of the pH2 of said second slurry can be at most 8, preferably at most 7, more preferably at most 6.

[0137] Within the context of the present invention, the expression “at least one alkaline additive” is intended to denote one or more than one alkaline additive.

[0138] It is to be understood that the at least one alkaline additive can be any substance capable of neutralizing an acid. The term “neutralizing” is to be understood as the general meaning given to it by the person skilled in the art. Non-limiting examples of alkaline additives are sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, calcium carbonate, magnesium carbonate, sodium bicarbonate, calcium oxide, magnesium oxide, ammonia.

[0139] Advantageously, the alkaline additive has a general formula XY, wherein X is a cation selected from the group consisting of alkali metal, alkaline earth metal, and mixtures thereof, and wherein Y is a counter-anion. Preferably, Y is selected from the group consisting of carbonates, oxalates, oxides and hydroxides. Preferably, Y is selected from the group consisting of hydroxide and carbonates. More preferably, Y is a carbonate. Preferably, X is an alkaline earth metal. More preferably, X is selected from the group consisting of Ca and Mg. According to the present invention, the alkaline additive may be in different forms such as solid form or liquid form such as at least partially dissolved in an aqueous solution or at least partially suspended or dispersed an aqueous slurry.

[0140] In a preferred embodiment of the invention, the alkaline additive is a base selected from the group comprising ammonia, alkaline compounds and their corresponding oxides or hydroxides, alkaline earth compounds and their corresponding oxides or hydroxides, quicklime, slaked lime, powdered lime, lime milk, calcium hydroxide, lithium hydroxide, limestone (finely ground), sodium oxide, aluminum hydroxide, sodium hydroxide, potassium hydroxide, aluminum oxide, sodium hydroxide, potassium hydroxide compounds based on carbonate such as calcium carbonate, basic phosphate salt (KH2PO4, potassium phosphate (mono-, di-), ammonium phosphate (mono-, di-), calcium phosphate (mono-, di-, tri-), calcium sulfate), NaOH, ammonium-based compounds, Cas(PO4)2 derivatives, calcium phosphate, mixtures and combinations thereof.

[0141] For the purpose of the present invention, the term “solid” is intended to refer to a composition in the form of powders, pebbles dusts, tablets, pellets, aggregates, compacts or briquettes or a granular form. Preferably, the form of alkaline additive is selected from the group consisting of powder, pebbles, aggregates, granules and mixture thereof. More preferably, the form of the alkaline additive is a powder.

[0142] The alkaline additive may be solid. Alternatively, or additionally, the alkaline additive is a solid suspended in an aqueous solvent to form an aqueous alkaline suspension. Alternatively, or additionally, the alkaline additive is solubilized in an aqueous solvent to form an aqueous alkaline solution.

[0143] Preferably, said aqueous solvent is water or process water (recycled water) or sea water.

[0144] Advantageously, the aqueous alkaline suspension or the aqueous alkaline solution comprises at least one alkaline additive in an amount equal to or more than 20.0 wt.%, preferably equal to or more than 22.0 wt.%, more preferably equal to or more than 24.0 wt.%, more preferably equal to or more than 26.0 wt.%, more preferably equal to or more than 28.0 wt.%, even more preferably equal to or more than 30.0 wt.%, relative to the total weight of the aqueous alkaline suspension or the aqueous alkaline solution. It is further understood that the upper limit of the amount of the at least one alkaline additive comprised in the aqueous alkaline suspension or in the aqueous alkaline solution, as detailed above, is equal to or less than 45.0 wt.%, more preferably equal to or less than 43.0 wt.%, more preferably equal to or less than 41.0 wt.%, more preferably equal to or less than 39.0 wt.%, more preferably equal to or less than 37.0 wt.%, even more preferably equal to or less than 35.0 wt.%, relative to the total weight of the aqueous alkaline suspension or the aqueous alkaline solution. In an embodiment of the method of the present invention, the aqueous alkaline suspension or the aqueous alkaline solution comprises the at least one alkaline additive in an amount ranging from 20.0 to 45.0 wt.%, preferably from 22.0 to 43.0 wt.%, more preferably from 24.0 to 41.0 wt.%, more preferably from 26.0 to 39.0 wt.%, more preferably from 28.0 to 37.0 wt.%, even more preferably between 30.0 and 35.0 wt.%, relative to the total weight of the aqueous alkaline suspension or the aqueous alkaline solution.

[0145] Preferably, during this step c) of adding at least one alkaline additive to said first slurry the measured pH is adjusted by adding at least one base to the first slurry (digested suspension) in order to precipitate the phosphate ions in the solid phase and thus increase the P2O5 yield.

[0146] The pH is slightly increased, leading to the formation of phosphate salt in the slurry (digested suspension) with the re-precipitation of phosphorus. This is an advantageous embodiment of the present invention. In a preferred embodiment, the alkaline additive is a basic compound or a base which is preferably in liquid form (slurry, suspension, or solution of a basic compound or base, preferably a calcium-containing compound) or in solid form. More preferably, the alkaline additive is a basic compound or a base which is a calcium source selected from the group consisting of quicklime, slaked lime, powdered lime, milk of lime, calcium hydroxide, calcium carbonate, and combinations thereof.

[0147] Advantageously, the P2O5 yield at the end of step c) is greater than 65.0 %, preferably greater than 75.0 %, more preferably greater than 85.0 %, even more preferably greater than 90.0 %, preferably greater than 95.0 %, more preferably greater than 98.0 %, more preferably greater than 99.0 %, even more preferably greater than 99.5 %, most preferably 99.9 %.

[0148] The P2O5 yield of step c) is a mass ratio and is calculated from the total phosphorus content by weight, expressed as P2O5 equivalent, in the second solid phase, comprising mainly phosphorus-containing compounds, divided by the total phosphorus content by weight, expressed as P2O5 equivalent, in said phosphate composition, preferably phosphorus- containing rock.

[0149] Preferably, the alkaline additive is added in said first slurry in an amount from 5.0 wt.% to 25.0 wt.%, relative to the total weight of the phosphate composition.

[0150] Advantageously, the alkaline additive is added in the first slurry in an amount equal to or more than 5.0 wt.%, preferably equal to or more than 6.0 wt.%, more preferably equal to or more than 7.0 wt.%, more preferably equal to or more than 8.0 wt.%, more preferably equal to or more than 9.0 wt.%, even more preferably equal to or more than 10.0 wt.%, relative to the total weight of the phosphate composition. It is further understood that the upper limit at which the alkaline additive is added in the first slurry is equal to or less than 25.0 wt.%, preferably equal to or less than 23.0 wt.%, more preferably equal to or less than 21.0 wt.%, more preferably equal to or less than 19.0 wt.%, more preferably equal to or less than 17.0 wt.%, even more preferably equal to or less than 15.0 wt.%, relative to the total weight of the phosphate composition.

[0151] In an embodiment of the method of the present invention, alkaline additive is added in the first slurry in an amount ranging from 5.0 to 25.0 wt.%, preferably from 6.0 to 23.0 wt.%, more preferably from 7.0 to 21.0 wt.%, more preferably from 8.0 to 19.0 wt.%, more preferably from 9.0 to 17.0 wt.%, even more preferably between 10.0 and 15.0 wt.%, relative to the total weight of the phosphate composition.

[0152] Preferably, the contacting step (step b)) is carried out in a first reactor and the addition of the alkaline additive (for phosphorus precipitation) (step c)) is carried out in a second or third reactor prior to step (d).

[0153] In a particularly preferred embodiment, the contacting step ( step b)) is carried out in a reactor divided into different successive compartments (preferably in fluid communication by overflow). In this case, the addition of the alkaline additive (for phosphorus precipitation) (step c)) is carried out in one or more successive compartments prior to step (d).

[0154] Separating step d)

[0155] The process according to the present invention comprises a step d) of separating said second solid phase from said second liquid phase.

[0156] Said separation step d) according to the present invention can be performed by any method known by the person skilled in the art to effectively separate a solid phase from a liquid phase.

[0157] Advantageously, the phosphorus content, expressed in wt.% equivalent P2O5, of said second solid phase is increased relative to the phosphorous content, expressed in wt.% equivalent P2O5, of said first solid phase.

[0158] Advantageously, the phosphorus concentration, expressed in wt.% equivalent P2O5, of said second solid phase is increased relative to the phosphorous content, expressed in wt.% equivalent P2O5V of said phosphate composition.

[0159] According to a preferred mode, said second solid phase comprises between 15 and 40% by weight of phosphorus expressed as P2O5 equivalent, based on the total weight of said second solid phase.

[0160] Advantageously, the content of organic compounds, expressed in TOC equivalent, of said second solid phase is reduced compared to the content of organic compound, expressed in TOC equivalent, in said phosphate composition.

[0161] This is especially important if the second solid phase is intended to be used as a phosphate source in a wet-phosphoric acid process.

[0162] In other words, this second solid phase can then be attacked to provide phosphoric acid of a quality depending on the intended application. This constitutes a surprising step in view of the prior art. The second solid phase contains sufficient phosphorus (expressed as P2O5 equivalent) to enable the production of high-quality phosphoric acid.

[0163] Thus, the second liquid phase comprises the solubilized organic compounds, expressed as TOCs, and the second solid phase constitutes the phase of interest in the context of the present invention.

[0164] The recovery of the phase of interest, the second solid phase, allows the phosphoric acid produced to be used in many areas of application.

[0165] The process according to the invention is thus easy to implement, efficient, and profitable on an industrial scale, while being sustainable and more environmentally friendly than known processes.

[0166] The present invention allows rocks containing phosphorus to be treated in order to reduce their organic compounds, expressed in TOC equivalent, content. The leaching carried out in step b) of the process provides a slurry (suspension) comprising a liquid phase and a solid phase. The liquid phase contains most of the organic compound, expressed in TOC equivalent, that have been solubilized by leaching, and the solid phase mainly comprises phosphorus-containing compounds while being depleted in TOC compared to the rock supplied. The content of phosphorus is then further improved by step c) of the process according to the present invention.

[0167] It is clear that the balance between maintaining the phosphorus content in the solid phase (expressed as P2O5 equivalent) and solubilizing the organic compounds, expressed in TOC equivalent, in the liquid phase is important in order to extract the maximum amount of organic compounds, expressed in TOC equivalent, into the liquid phase while maintaining a high phosphorus yield in the solid phase. However, this is really challenging because the solubility limit of the organic compounds and of the phosphorus are very close in acidic conditions. Therefore, selectively leaching the organic compounds from the phosphate composition while maintaining the phosphorus in the solid phase is clearly not obvious.

[0168] As explained above, the phosphorus content in the solid phase will make it possible to condition the remaining process steps during the production of phosphoric acid of sufficient quality for final application in various fields.

[0169] Thus, when a phosphorus-containing rock also contains organic compounds, expressed in TOC equivalent, the present invention allows the use of these raw materials for the production of phosphoric acid of sufficient quality.

[0170] Non-limiting examples of method for separating the first solid phase from the first liquid phase are: sedimentation, settling, filtration, centrifugation or combinations thereof.

[0171] Preferably, the separation step d) is a filtration step.

[0172] The separation step d) can be performed by any method known by the person skilled in the art. Preferably, the separation step d) is performed by means of a filter. Non-limiting examples of filters to perform a separation step are band filter, drum filter, press filter, belt filter, centrifugal filter or tilting pan filter. Preferably, the separation step is performed using a press filter or a band filter.

[0173] The separation step may be carried out under pressure or reduced pressure or vacuum.

[0174] In general, when the separation step is carried out under pressure, the pressure at which a separation step is performed is equal to or less than 10 bar, preferably equal to or less than 9 bar, more preferably equal to or less than 8 bar, more preferably equal to or less than 7 bar, even more preferably equal to or less than 6 bar. It is further understood that the lower pressure limit at which a separation step is performed is equal to or more than 1 bar, preferably equal to or more than 2 bar, preferably equal to or more than 3 bar, more preferably equal to or more than 4 bar, even more preferably equal to or more than 5 bar.

[0175] In an embodiment of the method of the present invention, the pressure at which the separation step is performed is ranging from 1 to 10 bar, preferably from 2 to 9 bar, more preferably from 3 to 8 bar, more preferably from 4 to 7 bar, even more preferably from 5 to 6 bar.

[0176] Preferably, when said separation step is carried out under reduced pressure (such as in a band filter) or under vacuum, the pressure at which the separation step is performed is at most 900 mbar, preferably at most 800 mbar, even more preferably at most 700 mbar, even more preferably at most 600 mbar, even more preferably at most 500 mbar.

[0177] Preferably, when said separation step is carried out under reduced pressure or under vacuum, the pressure at which the separation step is performed is at least 100 mbar and 900 mbar, preferably at least 200 mbar and at most 800 mbar, even more preferably at least 300 mbar and at most 700 mbar, even more preferably at least 400 mbar and at most 700 mbar.

[0178] It goes without saying that the temperature at which the separation step (Step d)) is carried depends on the temperature of the first slurry obtained in step c). Preferably, the separation step (Step d)) is carried at a temperature at least 0°C lower, or at least 0.1 °C lower, or at least 0.5 °C lower, or at least 1°C lower, or at least 2°C lower, or at least 3°C lower, or at least 4°C lower, or at least 5°C lower or at least 6°C lower, or at least 7°C lower or at least 8°C lower, or at least 9°C lower, or at least 10°C lower than the temperature of the first slurry obtained in step c). Preferably, the separation step (Step d)) is carried at a temperature at most 15°C lower, or at most 12°C lower, or at most 10 °C lower, or at most 9°C lower, or at most 8°C lower, or at most 7°C lower than the temperature of the first slurry obtained in step c).

[0179] Preferably, the separation step (Step d)) is carried at a temperature at least 0.1°C and at most 15°C lower, or at least 0.5°C and at most 12°C lower, or at least 1°C and at most 10 °C lower, or at least 1 °C and at most 9°C lower, or at least 1 °C and at most 8°C lower, than the temperature of the first slurry obtained in step c). Advantageously, the separation step (Step d)) is carried out at a temperature equal to or more than 15 °C, preferably equal to or more than 20°C, more preferably equal to or more than 25 °C, more preferably equal to or more than 30 °C, more preferably equal to or more than 40 °C, even more preferably equal to or more than 50 °C. It is further understood that the upper limit for the temperature at which the separation step (Step d)) is carried out is equal to or less than 110 °C, more preferably equal to or less than 100°C, more preferably equal to or less than 90°C, more preferably equal to or less than 80°C, more preferably equal to or less than 70°C, even more preferably equal to or less than 60°C.

[0180] In an embodiment of the method of the present invention, the temperature at which the separation step (Step d)) is carried out, as detailed above, is ranging from 15 °C to 110 °C, preferably from 20 °C to 100 °C, more preferably from 25 °C to 90 °C, more preferably from 25 °C to 80 °C, more preferably from 25 °C to 70 °C, more preferably from 25 °C to 60 °C, more preferably 25 °C to 50 °C, more preferably 30 °C to 50 °C, even more preferably 30 °C to 40 °C.

[0181] According to a preferred embodiment, the second solid phase (containing mainly phosphorus compounds) is stored or used as is, unless otherwise specified.

[0182] According to a preferred embodiment, the second solid phase (containing mainly phosphorus compounds) is dried.

[0183] Advantageously, at least part of said second liquid phase can be recycled and used in a subsequent process cycle step a) and / or step b) and / or step c).

[0184] Preferably, said process according to the present invention may comprise at least one washing step of the second solid phase obtained in step d). Preferably, the washing step can comprise washing the second solid with water, a composition comprising water or an aqueous solution. The water used in the washing step may include for example (but not limited to): distilled water, tap water, sea water, or process water.

[0185] Preferably, the second solid phase (containing mainly phosphorus compounds) is further washed during and / or after the separation step d), preferably with water or slightly acidic water, yielding a wash filtrate.

[0186] This wash filtrate can be advantageously used at any stage of the process. In other words, the wash filtrate can be used in at least one of the steps a), step b) and step c) of the process of the invention.

[0187] More preferably, the second solid phase, optionally collected after the step (d), is washed with water (recycled water or fresh water, in countercurrent or co-current washing), before being stored or used. All or part of the wash filtrate may be recirculated to the contacting step (b) as a component of the digested slurry or used as a diluent for the at least one first mineral acid or as a carrier for the phosphate composition, or any combination or mixture thereof, or part of the wash filtrate may be neutralized in a subsequent step. The portion of the wash filtrate that is recirculated is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and most preferably between 15 and 50% by weight.

[0188] According to a preferred embodiment, the process comprises a step of recycling the second liquid phase and / or the wash filtrate in the contacting step (b). The portion of the liquid phase that is recirculated is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight. The portion of the wash filtrate that is recirculated is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0189] If desired, part of said second liquid phase can be removed or purged out. Thus, if desired, part of said second liquid phase is not used in the subsequent steps of the process.

[0190] If desired, said second slurry can be subjected to a concentration step before step d).

[0191] Preferably, said process according to the present invention can comprise a series of step sequences, each sequence comprising at least the steps a), b), c) and d), defined above.

[0192] Preferably, the contacting step (step b) and / or step c) of adding an alkaline additive and / or the separation step (step d) is carried out continuously.

[0193] In a certain embodiment the present invention provides a method for reducing the total organic compound content (hereinafter referred to as “TOC”) in phosphorus-containing rock, comprising the following steps: a) Providing phosphorus-containing rock containing between 18 and 40% by weight of phosphorus expressed as P2O5 equivalent and having a predetermined total TOC content, b) Leaching said phosphorus-containing rock with at least one first mineral acid, preferably sulfuric acid, at a molar ratio I / P2O5 of between 1 and 5 and at a temperature below 100°C for a period of time of between 5 and 300 minutes, leading to the formation of a suspension comprising a liquid phase containing a majority portion of said TOC relative to its content in said rock prior to leaching, and a solid phase comprising mainly phosphorus- containing compounds and being depleted in TOC relative to said supplied rock, c) Recovering said solid phase from said suspension wherein the process comprises adding a base to said suspension with precipitation of phosphate ions.

[0194] Preferably, said at least one first mineral acid, preferably diluted, is sulfuric acid or a mixture of acids comprising predominantly sulfuric acid. Preferably, said at least one first mineral acid is a mixture of acids comprising predominantly sulfuric acid, and optionally an acid selected from phosphoric acid, hydrochloric acid, hexafluorosilicic acid and mixtures thereof.

[0195] Preferably, the leaching step (b) is carried out by adding said at least one first mineral acid which has a concentration of between 5 and 25% by weight, preferably between 5 and 20% by weight, more preferably between 6 and 17% by weight, and most preferably between 10 and 15% by weight.

[0196] Preferably, the predetermined total TOC content of said phosphorus-containing rock is between 500 and 15,000 ppm, preferably between 500 and 10,000 ppm, more preferably between 500 and 8,000 ppm, most preferably between 500 and 5,700 ppm.

[0197] Preferably, said suspension has a solid content of between 30 and 50% by weight, preferably between 20 and 40% by weight, relative to the total weight of the suspension.

[0198] Preferably, at least 50% by weight, preferably at least 60% by weight, more preferably at least 65% by weight, and even more preferably at least 70% by weight, advantageously at least 85% by weight, more advantageously at least 90% by weight, preferably up to 100% by weight of said TOC present in said rock are solubilized in said liquid phase.

[0199] Preferably, said leaching is carried out at a temperature below 95°C, preferably below 85°C, more preferably between 25°C and 80°C, advantageously between 30°C and 78°C, more advantageously between 60°C and 75°C, and most advantageously equal to or close to 75°C.

[0200] Preferably, said leaching is carried out for a period of time of less than 300 minutes, preferably less than 280 minutes, more preferably less than 250 minutes and preferably at least 30 minutes, advantageously between 60 and 270 minutes.

[0201] Preferably, said leaching is carried out until a pH of between 1.0 and 6.0, preferably between 1.2 and 5.5, more preferably between 1.5 and 5.0, more preferably between 1.7 and 4.5 is reached in the suspension.

[0202] Preferably, the recovered solid phase is reacted with sulfuric acid, optionally in the presence of phosphoric acid, to produce phosphoric acid in a dihydrate, hemihydrate or di- hemihydrate form.

[0203] Preferably, said solid phase contains between 15 and 40% by weight of phosphorus expressed as P2O5.

[0204] Step e)

[0205] The process according to the present invention may further comprise a Step e) of removing at least part of the organic compounds of the second liquid phase thereby forming a third slurry comprising a third solid phase and a third liquid phase, wherein said third liquid phase has an organic compound content, expressed in TOC equivalent, which is decreased compared to the organic compound content, expressed in TOC equivalent, of the second liquid phase, prior to step e).

[0206] Preferably, the organic compounds are removed from the second liquid phase of the second slurry after being separated (step d) to produce a purified filtrate (obtained after an additional separation step).

[0207] Said step e) can be performed by any method known by the person skilled in the art to effectively removing at least part of organic compounds from a liquid phase.

[0208] Non-limiting examples of method for removing organic compounds from a liquid phase are: nanofiltration, high temperature pulverisation, biological digestion, precipitation by adding an alkaline additive or combinations thereof.

[0209] Preferably, Step e) of the process according to the present invention is a step of adding at least one alkaline additive to said second liquid phase, thereby forming a third slurry; said third slurry comprising a third solid phase and a third liquid phase.

[0210] Preferably, said third slurry has to a pH of at least 6, preferably at least 7, preferably at least 8, preferably at least 8.5, preferably at least 9, or at least 9.5, or at least 10, or at least 10.5, or at least 11 , or at least 11.5, or at least 12, or at least 12.5, or at least 13. It is understood that the higher limit of the pH of said third slurry can be at most 13, preferably at most 12, more preferably at most 11.

[0211] Preferably, said third slurry has a pH of at least 7 and at most 13, more preferably at least 8 and at most 13, more preferably at least 9 and at most 12.

[0212] Within the context of the present invention, the expression “at least one alkaline additive” is intended to denote one or more than one alkaline additive.

[0213] It is to be understood that the at least one alkaline additive can be any substance capable of neutralizing any acid. The term “neutralizing” is to be understood as the general meaning given to it by the person skilled in the art. Non-limiting examples of alkaline additives are sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, calcium carbonate, magnesium carbonate, sodium bicarbonate, calcium oxide, magnesium oxide and ammonia.

[0214] Advantageously, the alkaline additive has a general formula XY, wherein X is a cation selected from the group consisting of alkali metal, alkaline earth metal, and mixtures thereof, and wherein Y is a counter-anion. Preferably, Y is selected from the group consisting of carbonates, oxalates, oxides and hydroxides. Preferably, Y is selected from the group consisting of hydroxide and carbonates. More preferably, Y is a carbonate. Preferably, X is an alkaline earth metal. More preferably, X is selected from the group consisting of calcium and magnesium. According to the present invention, the alkaline additive may be in different forms such as solid form and liquid form, or dissolved in an aqueous solution or dispersed or suspended into an aqueous solution.

[0215] For the purpose of the present invention, the term “solid” is intended to refer to a composition in the form of powders, pebbles dusts, tablets, pellets, aggregates, compacts or briquettes or a granular form. Preferably, the form of alkaline additive is selected from the group consisting of powder, pebbles, aggregates, granules and mixture thereof. More preferably, the form of the alkaline additive is a powder.

[0216] The alkaline additive may be solid. Alternatively, or additionally, the alkaline additive is a solid suspended in an aqueous solvent to form an aqueous alkaline suspension. Alternatively, or additionally, the alkaline additive is solubilized in an aqueous solvent to form an aqueous alkaline solution.

[0217] Preferably, said aqueous solvent is water or process water (recycled water).

[0218] Advantageously, the aqueous alkaline suspension or the aqueous alkaline solution comprises at least one alkaline additive in an amount equal to or more than 20.0 wt.%, preferably equal to or more than 22.0 wt.%, more preferably equal to or more than 24.0 wt.%, more preferably equal to or more than 26.0 wt.%, more preferably equal to or more than 28.0 wt.%, even more preferably equal to or more than 30.0 wt.%, relative to the total weight of the aqueous alkaline suspension or the aqueous alkaline solution. It is further understood that the upper limit of the amount of the at least one alkaline additive comprised in the aqueous alkaline suspension or in the aqueous alkaline solution, as detailed above, is equal to or less than 45.0 wt.%, more preferably equal to or less than 43.0 wt.%, more preferably equal to or less than 41.0 wt.%, more preferably equal to or less than 39.0 wt.%, more preferably equal to or less than 37.0 wt.%, even more preferably equal to or less than 35.0 wt.%, relative to the total weight of the aqueous alkaline suspension or the aqueous alkaline solution.

[0219] In an embodiment of the method of the present invention, the aqueous alkaline suspension or the aqueous alkaline solution comprises the at least one alkaline additive in an amount ranging from 20.0 to 45.0 wt.%, preferably from 22.0 to 43.0 wt.%, more preferably from 24.0 to 41.0 wt.%, more preferably from 26.0 to 39.0 wt.%, more preferably from 28.0 to 37.0 wt.%, even more preferably between 30.0 and 35.0 wt.%, relative to the total weight of the aqueous alkaline suspension or the aqueous alkaline solution.

[0220] Advantageously, the alkaline additive is added in said second liquid phase in an amount from 5.0 wt.% to 25.0 wt.%, relative to the total weight of the second liquid phase.

[0221] Advantageously, the alkaline additive is added in the second liquid phase in an amount equal to or more than 5.0 wt.%, preferably equal to or more than 6.0 wt.%, more preferably equal to or more than 7.0 wt.%, more preferably equal to or more than 8.0 wt.%, more preferably equal to or more than 9.0 wt.%, even more preferably equal to or more than 10.0 wt.%, relative to the total weight of the second liquid phase. It is further understood that the upper limit at which the alkaline additive is added in the second liquid phase is equal to or less than 25.0 wt.%, preferably equal to or less than 23.0 wt.%, more preferably equal to or less than 21.0 wt.%, more preferably equal to or less than 19.0 wt.%, more preferably equal to or less than 17.0 wt.%, even more preferably equal to or less than 15.0 wt.%, relative to the total weight of the second liquid phase.

[0222] In an embodiment of the method of the present invention, alkaline additive is added in the second liquid phase in an amount ranging from 5.0 to 25.0 wt.%, preferably from 6.0 to 23.0 wt.%, more preferably from 7.0 to 21 .0 wt.%, more preferably from 8.0 to 19.0 wt.%, more preferably from 9.0 to 17.0 wt.%, even more preferably between 10.0 and 15.0 wt.%, relative to the total weight of the second liquid phase.

[0223] Preferably, said second liquid phase comprises at least 70.0 %, preferably at least 75.0 %, more preferably at least 80.0 %, even more preferably at least 85.0 %, even more preferably at least 90.0 %, even more preferably at least 95.0 %, even more preferably at least 99.0 % of the anion comprised in said first liquid phase.

[0224] Preferably, said third solid phase comprises at least 60.0 wt.%, preferably at least 65.0 wt.%, more preferably at least 70.0 %, preferably at least 75.0 %, more preferably at least 80.0 %, even more preferably at least 85.0 %, even more preferably at least 90.0 %, even more preferably at least 95.0 %, even more preferably at least 99.0 % of the at least one organic compound, expressed in TOC equivalent, comprised in said second liquid phase.

[0225] If desired, part of said third liquid phase is removed or purged out. Thus, if desired, part of said third liquid phase is not used in the subsequent steps of the process.

[0226] Advantageously, the neutralization step of the second liquid phase enables to precipitate a significant amount of the at least one organic compound initially comprised in the second liquid phase, which can then be removed by a subsequent separating step. After separation, the third liquid phase can be used as in steps a) and / or b) and / or c) if desired.

[0227] Preferably, all or part of the purified filtrate, i.e. the third liquid phase, may be recirculated to the contacting step (b) as a component of the first slurry or used as a carrier for the phosphate composition or as a diluent for the acid, or any combination or mixture thereof. The portion of the purified filtrate, i.e. the third liquid phase, that is recirculated is preferably between 0 and 100% by weight, more preferably between 1 and 99% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and most preferably between 15 and 50% by weight.

[0228] The purified filtrate produced can be recirculated throughout the process, particularly in step b, preferably as a diluent for the mineral acid. All or part of the purified filtrate may be recirculated to the contacting step (b) as a component of the digested slurry or used as a carrier for the phosphate composition or used as a diluent for the mineral acid or any combination or mixture thereof.

[0229] The third solid phase may or may not be washed to produce a wash filtrate which may be recirculated into the process. Preferably, the third solid phase is washed with water (countercurrent or co-current washing) before being stored or used, the entire amount of wash filtrate or a portion of the wash filtrate may be recirculated to the contacting step or as a component of the digested slurry or as a carrier for the phosphate composition or any combinations or mixtures thereof. The portion of the wash filtrate that is recirculated is preferably between 1 and 100% by weight, preferably between 5 and 90% by weight, preferably between 10 and 80% by weight, preferably between 15 and 50% by weight.

[0230] Separating step f)

[0231] The process according to the present invention can comprise a step f) of separating said third solid phase from said third liquid phase.

[0232] Preferably, said third solid phase comprises at least part of said at organic compound, expressed in TOC equivalent.

[0233] Said separation step f) can be performed by any method known by the person skilled in the art to effectively separate a solid phase from a liquid phase.

[0234] Non-limiting examples of method for separating the first second phase from the second liquid phase are: sedimentation, settling, filtration, centrifugation or combinations thereof.

[0235] Preferably, the separation step f) is a filtration step.

[0236] It goes without saying that all definitions and preferences described above for the separating step d) equally apply for the separating step f).

[0237] Advantageously, at least part of said third liquid phase can be used as or comprised in the solvent used to provide the phosphate composition in step a). Alternatively or additionally, at least part of said third liquid phase can be used as or comprised in the mineral acid used in the contacting step b). Alternatively or additionally, at least part of said third liquid phase can be used as or comprised in the solvent used to add the alkaline additive in step d).

[0238] Using the third liquid phase in steps a) and / or b) and / or c) of the process of the invention is beneficial because that means that less or no additional solvent and / or acid must be added in order to continue the process in the subsequence step sequences.

[0239] If desired, part of said third liquid phase is removed or purged out. Thus, if desired, part of said third liquid phase is not used in the subsequent steps of the process.

[0240] If desired, said third liquid phase can be subjected to a concentration step.

[0241] Preferably, said process according to the present invention may comprise a washing step of the third solid phase obtained in step f) thereby forming a wash filtrate which can be used in step a) and / or b) and / or c). According to a preferred embodiment, at a temperature below 100°C for less than 300 minutes, at least one phosphate ore containing between 18% and 40% by weight of phosphorus (expressed as P2O5 equivalent) is reacted with sulfuric acid (optionally in the presence of HCI), leading to a digested suspension, first slurry, comprising a first liquid phase and a first solid phase. The first solid phase mainly contains phosphorus compounds and the first liquid phase comprises most of the organic compounds, expressed in TOC equivalent, from the ore. The I / P2O5 molar ratio is between 1 and 5. An alkaline additive is added to said first slurry, thereby forming a second slurry comprising a second liquid phase and a second solid phase, wherein the second solid phase has an increased phosphorus content compared to said first solid phase. The second slurry, is filtered. The second liquid phase is neutralized and filtered so that the purified filtrate can be reused in the leaching step (b). The portion of the purified filtrate that is recirculated to the leaching step (b) is preferably between 1 and 100% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0242] Process for producing a phosphoric acid

[0243] The present invention also aims to produce a purified solid phase comprising mainly phosphorus-containing compounds, i.e. said second solid phase, and which can be used in the production of phosphoric acid to produce commercial grade acid or food grade acid and salts or food grade acid and salts.

[0244] In other words, the second solid phase obtained by the process according to the present invention, described above, may be used as a phosphate source in a wet-phosphoric acid process.

[0245] In other words, this second solid phase can be attacked to provide phosphoric acid of a quality depending on the intended application. This constitutes a surprising step in view of the prior art.

[0246] The second solid phase contains sufficient phosphorus (expressed as P2O5 equivalent) to enable the production of high-quality phosphoric acid.

[0247] Therefore, the present invention, provides a process for manufacturing a phosphoric acid from the second solid phase, described above.

[0248] The step of solid phase recovery (step c)) provides a solid, i.e. the second solid phase, that can be attacked by a second mineral acid, preferably sulfuric acid or hydrochloric acid, to form high-quality phosphoric acid. The second mineral acid may be selected from the group comprising sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, hexafluorosilicic acid, and combinations thereof.

[0249] The recovery of the phase of interest, the second solid phase, allows the phosphoric acid produced to be used in many areas of application. Advantageously, the recovered solid phase, i.e. the second solid phase, is reacted with sulfuric acid (step g), possibly in the presence of phosphoric acid, to produce phosphoric acid in a dihydrate, hemihydrate, or dihemihydrate process. This provides a valuable phosphoric acid and calcium sulfate that can also be used, particularly in the construction industry.

[0250] According to a preferred embodiment, the second solid phase, containing mainly phosphorus compounds, is reacted (step g) with an acid solution comprising sulfuric acid to produce phosphoric acid and calcium sulfate, which can be separated and optionally washed in a subsequent step. Reaction step g is carried out under hemic hydrate (HH), dihydrate (DH), anhydrous, or double crystallization (HH-DH or DH-HH) conditions, as known by those skilled in the art. The molar ratio H+ / Ca of this reaction is preferably between 1 .8 and 2.2, where the H+ions come from the acid solution, preferably comprising sulfuric acid, and the Ca atoms come from said solid phase containing mainly phosphorus compounds. In a preferred embodiment, dihydrate conditions can be used to carry out step e.

[0251] DH conditions or dihydrate conditions are known to those skilled in the art. HH conditions are disclosed, for example, in document CA 915 883, which is incorporated by reference herein with respect to the conditions to be applied in the context of “HH conditions.” DH-HH conditions are disclosed, for example, in documents EP 2,507,168 and WO 2012 163,425, which are incorporated by reference herein with respect to the conditions to be applied in the context of “DH-HH conditions.”

[0252] Preferably, the calcium sulfate is washed and a recycled phosphoric acid (RPA) solution is obtained. This RPA solution can be used as a mineral acid and / or as a diluted mineral acid and / or as a diluent for mineral acid and / or recycled in the contacting step (b) and / or recycled in step (g) and / or added to the produced phosphoric acid or as a carrier for the phosphate composition. The portion of the RPA solution that is recirculated is preferably between 1 and 100% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and most preferably between 15 and 50% by weight. In a particularly preferred embodiment, the RPA solution is entirely recycled in step (g).

[0253] Preferably, the RPA solution from the washing of calcium sulfate is entirely recycled in reaction step (g).

[0254] In a preferred embodiment, said second solid phase (comprising mainly phosphorus- containing compounds) is reacted (step g) with sulfuric acid, optionally in the presence of phosphoric acid, to provide phosphoric acid that can be used in various applications. This reaction step (step g) is carried out at a molar ratio of H+ / Ca of between 1 .8 and 2.2, where the H+ions come from the acid solution comprising sulfuric acid and the Ca atoms come from the second solid phase (comprising mainly phosphorus-containing compounds).

[0255] In a preferred embodiment, under ‘dihydrate’ process conditions, this reaction step g is carried out with a molar ratio of H7Ca between 1 .8 and 2.2, where the H+ions come from the acid solution comprising sulfuric acid and the Ca atoms come from the second solid phase (comprising mainly phosphorus-containing compounds).

[0256] The solid phase containing mainly phosphorus compounds can be reacted with H2SO4 (step g) to produce phosphoric acid and calcium sulfate, which are subsequently separated. This step g can preferably be carried out under dihydrate conditions, the H+ / Ca molar ratio in step e being between 1 .8 and 2.2. The calcium sulfate is washed after separation and the collected RPA solution is reused in step e. The portion of the RPA solution that is recirculated in step e is preferably between 1 and 100% by weight, more preferably between 5 and 90% by weight, more preferably between 10 and 80% by weight, and even more preferably between 15 and 50% by weight.

[0257] Alternatively or additionally, the recovered solid phase, i.e. the second solid phase, is reacted with hydrochloric acid to produce phosphoric acid (step g).

[0258] In a preferred embodiment of the invention, the second solid phase comprising (mainly phosphorus-containing compounds) is reacted (step g) with hydrochloric acid to provide phosphoric acid that can be used in various applications. This reaction step (step g) is carried out at a molar ratio of H+ / Ca between 1.6 and 2.2, where the H+ions come from the acid solution comprising hydrochloric acid and the Ca atoms come from the second solid phase (comprising mainly phosphorus-containing compounds).

[0259] All the preferred features, embodiments and definitions described above also applies when the process according to the present invention is continuous.

[0260] The invention also provides a use of the second solid phase obtained by the process according to any of the preceding claims as a raw material for a dihydrate, hemihydrate, or dihemihydrate process.

[0261] All the preferred features, embodiments and definitions described above also applies for the use of the second solid phase obtained by the process.

[0262] The present invention also relates to a use of the second solid phase obtained by the process according to the invention for producing:

[0263] - A fertilizer, preferably of the monoammonium phosphate or diammonium phosphate (MAP or DAP) type, monopotassium phosphate (MKP), NPK fertilizer (ammonium-potassium phosphate fertilizer), NPS fertilizer (ammonium phosphate-sulfate fertilizer), MCP (monocalcium phosphate), DCP (dicalcium phosphate), SSP (single superphosphate), TSP (triple superphosphate), and / or

[0264] Commercial grade (MGA) or purified phosphoric acid, and / or,

[0265] Purified phosphate salts.

[0266] Other embodiments of the use according to the invention are set forth below and in the claims. EXAMPLES

[0267] The invention will be now described in more details with reference to the following example and comparative-examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.

[0268] Test methods

[0269] Measurement of the percentage by weight of P2O5

[0270] Within the context of the present invention, the phosphorus content expressed as wt.% of P2O5 was measured following the method as detailed above.

[0271] Measurement of the percentage by weight and ppm of organic compound (TOC)

[0272] Within the context of the present invention, the organic compound content expressed in TOC equivalent was measured following the method as detailed above.

[0273] A phosphate ore was used as phosphate composition in the tests that are presented below. The chemical composition of this phosphate ore (rock) is reported in Table 1.

[0274] MATERIALS

[0275] A phosphate rock (as detailed in Table 1) was leached with sulfuric acid for (comparative) examples 1-12 and 17-18 and hydrochloric acid for (comparative) examples 13- 16 (first mineral acid) at a temperature of 75 °C.

[0276] Table 1

[0277] The experimental parameters for the examples (1-3-5-7-9-11-13-15) and comparative examples (2-4-6-8-10-12-14-16-17-18) are reported in Table 2. The different parameters were measured at four times during the leaching process. The alkaline additive was calcium oxide.

[0278] Table 2

[0279] After the addition of the alkaline additive, the second solid phase was separated from the second liquid phase.

[0280] It has been found that, with the process according to the present invention, the amount of organic compounds, TOC, decreases significantly while an advantageous P2O5 yield is maintained in the second solid phase.

[0281] It can be observed from the results presented in Table 3, that the TOC content reduction was similar with or without the addition of the alkaline additive. The addition of an alkaline additive had an effect on the yield of P2O5. Indeed, in the comparative examples (2-4-6-8-10-12-14-16) the yield range was between 52 % and 68 % whereas in the examples (1-3-5-7-9-11-13-15) where the alkaline additive was added, the yield of P20s was improved with values always superior to 85 %, which are industrially, and thus economically, more advantageous.

[0282] Comparative examples 17 and 18 also highlight that at a molar ratio H P2O5 below 0.5, the P2O5 yield is acceptable but the reduction in organic compounds, TOC, is clearly not optimal with a reduction of 26% and 27% for a ratio of respectively 0.3 and 0.4.

[0283] These examples highlight that the combination between the particular molar ratio H7P2O5 and the addition of an alkaline additive allowed to provide a process wherein the amount of organic compounds, TOC, decreases significantly while an advantageous P2O5 yield is maintained in the second solid phase. This second solid residue can therefore be used as raw material in a process for manufacturing a phosphoric acid.

[0284] Table 3 - Second solid phase

Claims

CLAIMS1 . Process for leaching at least one organic compound from a phosphate composition comprising at least on phosphate source, said process comprising the following steps: a) providing a phosphate composition comprising at least one phosphate source, said phosphate composition comprising, based on the total weight of said phosphate composition: o at least 10,0 wt.% and at most 40,0 wt.% of phosphorous, expressed in wt.% equivalent P2O5, and o Y1 wt.%, which is equal to or more than 100.0 ppm, of at least one organic compound, expressed in total organic carbon [hereinafter, TOC] equivalent ; b) contacting said phosphate composition with at least one first mineral acid, at a molar ratio I / P2O5 comprised between 0.5 and 5.0, thereby forming at least one first slurry comprising a first liquid phase and a first solid phase, wherein H+represents the total number of moles of acidic protons from said acid and P2O5 represents the total number of moles of P2O5 comprised in said phosphate composition, wherein: o said first slurry has a predetermined pH [hereinafter, pH 1], and; o said first liquid phase comprises at least part of said organic compound, and; o said solid phase comprises at least part of said phosphorus and has an amount of organic compound, expressed in TOC equivalent, of Y2wt.%, which is less than Y1, based on the total weight of said solid phase; c) adding at least one alkaline additive to said first slurry, thereby forming a second slurry comprising a second liquid phase and a second solid phase, wherein o said slurry has a pH [hereinafter, PH2] which is higher than pHi but equal to or more than 2, and; o said second solid phase has a phosphorous content which is increased compared to the phosphorous content of the first solid phase; d) separating said second solid phase from said second liquid phase.

2. Process according to claim 1 wherein said at least one first mineral acid is selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, and mixtures thereof, preferably sulfuric acid.

3. Process according to claim 1 or claim 2, wherein said at least one first mineral acid, preferably diluted, is sulfuric acid or a mixture of acids comprising predominantly sulfuric acid.

4. Process according to any one of claims 1 to 3, wherein said at least one first mineral acid is a mixture of acids comprising predominantly sulfuric acid, and optionally an acid selected from phosphoric acid, hydrochloric acid, hexafluorosilicic acid, and mixtures thereof.

5. Process according to any one of claims 1 to 4, wherein the contacting step (b) is carried out by adding said at least one first mineral acid which has a concentration of between 5 and 25% by weight.

6. Process according to any one of claims 1 to 5, wherein said first slurry obtained is step b) has a solid content of between 30 and 50% by weight, relative to the total weight of the first slurry.

7. Process according to any one of claims 1 to 6, wherein at least 50% by weight of said organic compound, expressed in TOC equivalent, present in said phosphate composition are solubilized in said first liquid phase.

8. Process according to any one of claims 1 to 7, wherein said contacting step b) is carried out at a temperature below 100 °C.

9. Process according to any one of claims 1 to 8, wherein said contacting step b) is carried out for a period of time between 5 and 300 minutes.

10. Process according to any one of claims 1 to 9, wherein said contacting step b) is carried out until a pH of between 1.0 and 6.0 is reached.

11. Process according to any one of claims 1 to 10, wherein the P2O5 yield at the end of step b) is greater than 65%, preferably greater than 75%, more preferably greater than 85%, even more preferably greater than 90%, advantageously greater than 95%, and more advantageously greater than 98%..

12. Process for manufacturing a phosphoric acid from at least one second solid phase obtained according any one of claims 1 to 11 , wherein the second solid phase is reacted with sulfuric acid, possibly in the presence of phosphoric acid, to produce phosphoric acid in a dihydrate, hemihydrate, or di-hemi process.

13. Use of the second solid phase obtained by the process according to any of claims 1 to 11 as a raw material for a dihydrate, hemihydrate, or di-hemihydrate process.

14. Use of the second solid phase obtained by the process according to any of claims 1 to 11 for producing:- A fertilizer, preferably of the monoammonium phosphate or diammonium phosphate (MAP or DAP) type, monopotassium phosphate (MKP), NPK fertilizer (ammoniumpotassium phosphate fertilizer), NPS fertilizer (ammonium phosphate-sulfate fertilizer), MCP (monocalcium phosphate), DCP (dicalcium phosphate), SSP (single superphosphate), TSP (triple superphosphate), and / or- A Commercial grade (MGA) or purified phosphoric acid, and / or Purified phosphate salts.

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