Method for treating a phosphoric acid solution containing rare earths and vanadium

Abstract

The present invention relates to a method for the selective separation of rare earths (TR) and vanadium (V) contained in a phosphoric acid (ACP) solution, typically obtained by a wet process. The method may further be used to recover a purified ACP solution.

Description

[0001] DESCRIPTION

[0002] TITLE: Process for treating a phosphoric acid solution containing rare earths and vanadium

[0003] TECHNICAL FIELD OF THE INVENTION

[0004] The present invention relates to a process for the selective separation of rare earths (REs) and vanadium (V) contained in a phosphoric acid (ACP) solution, typically obtained by wet method. The process can further allow recovery of a purified ACP solution.

[0005] STATE OF THE ART

[0006] Phosphoric acid (H3PO4) can be produced wet by attacking natural phosphate rocks with a strong acid such as hydrochloric acid, nitric acid, and / or sulfuric acid. Many of the elements such as TRs and V originally present in the phosphate rock are found in the phosphoric acid solution from the wet process.

[0007] In recent years, the demand for TRs has increased significantly worldwide. These elements have become essential for high-tech applications. A strict purity level for these elements must therefore be met.

[0008] TRs consist of a group of fifteen lanthanides, plus scandium (Sc) and yttrium (Y) due to their lanthanide-like properties. TRs are commonly divided into two subgroups based on their molar mass and ionic radius, namely light TRs (LREE) (ranging from lanthanum (La) to europium (Eu)) and heavy TRs (HREE) (ranging from gadolinium (Gd) to lutetium (Lu)).

[0009] Geologically, TRs are found in nature mainly associated with carbonates, fluorides and phosphates. The main primary source minerals of TRs are bastnaesite ([(Ce,La)(CO3)F]), monazite [(Ce,La)PO4)] and xenotime [YPO4]. However, limited primary mineral resources make the extraction of TRs from secondary sources a real challenge to ensure the supply of TRs.

[0010] The V contained in phosphoric acid poses problems related to the large quantities of foreign cations and anions introduced into the phosphoric solution, their use leading in some cases to the release of troublesome gases, for example hydrogen, H2S or SO2.

[0011] Thus, there is a need for new methods to purify wet-produced phosphoric acid. There is also a need for a process to selectively separate and recover TRs and V from phosphoric acid. Advantageously, the proposed process will allow the separately removed elements such as TRs and V to be recovered to produce products that can be used for commercial applications.

[0012] SUMMARY OF THE INVENTION

[0013] The present invention relates to a method for treating a phosphoric acid solution containing rare earths and vanadium, the method comprising the following steps:

[0014] 1a) fixation of rare earths and vanadium by passing the phosphoric acid solution over an ion exchange resin functionalized by phosphonic groups;

[0015] 1 b) optionally washing by passing water over the resin obtained at the end of step 1a);

[0016] 1c) elution by passing a hydrochloric acid solution over the resin from step 1a) or 1b) to obtain a hydrochloric acid solution containing rare earths and vanadium;

[0017] 2a) fixing of rare earths by passing the hydrochloric acid solution from step 1c) over an ion exchange resin functionalized by phosphoric groups;

[0018] 2b) optionally washing by passing water over the resin from step 2a);

[0019] 2c) elution of the rare earths by passing a sulfuric acid solution over the resin functionalized by phosphoric groups from step 2a) or 2b).

[0020] Other aspects of the invention are as described below and in the claims.

[0021] FIGURES

[0022] Figure 1 illustrates the retention rate of TRs and V in the presence of metallic and non-metallic impurities by S950 resin in batch, with ACP 29% by weight of P2O5. Figure 2 illustrates the retention rate of TRs and V in the presence of metallic and non-metallic impurities by two columns in series of S950 resin with ACP 29% by weight of P2O5.

[0023] Figure 3 is an overall diagram of a particular embodiment of the ACP treatment method according to the invention.

[0024] DETAILED DESCRIPTION OF THE INVENTION

[0025] For the purposes of the present invention, unless otherwise indicated, the term "solution", for example "phosphoric acid solution", "hydrochloric acid solution", "sulfuric acid solution", denotes an aqueous solution.

[0026] The inventors have developed a method for treating an ACP solution containing TRs and V.

[0027] Advantageously, the method according to the present invention can be implemented to purify the ACP solution, and / or separate and recover the TRs and / or the vanadium. Typically, the method of the invention makes it possible to recover a purified ACP solution, a solution containing TRs and a solution containing V. These solutions can then be used in downstream steps to recover the ACP, the TRs and the V.

[0028] Thus, the present invention relates to a method for treating a phosphoric acid solution containing rare earths and / or vanadium, the method comprising the following steps:

[0029] 1a) fixing of rare earths and / or vanadium by passing the phosphoric acid solution over an ion exchange resin functionalized by phosphonic groups;

[0030] 1 b) optionally washing by passing water over the resin obtained at the end of step 1a);

[0031] 1c) elution by passing a hydrochloric acid solution over the resin from step 1a) or 1b) to obtain a hydrochloric acid solution containing rare earths and / or vanadium;

[0032] 2a) fixing of rare earths by passing the hydrochloric acid solution from step 1c) over an ion exchange resin functionalized by phosphoric groups;

[0033] 2b) optionally washing by passing water over the resin from step 2a); 2c) elution of the rare earths by passing a sulfuric acid solution over the resin functionalized by phosphoric groups from step 2a) or 2b).

[0034] Preferably, the method according to the invention relates to a method for treating a phosphoric acid solution containing rare earths and vanadium. In such a case, step 1a) consists of fixing the rare earths and vanadium as described above and step 1c) consists of elution which makes it possible to obtain a hydrochloric acid solution containing rare earths and / or vanadium, advantageously rare earths and vanadium, preferably as described above.

[0035] Ion exchange resins advantageously allow working with very dilute solutions of TRs and vanadium and obtaining a concentrate after elution.

[0036] The method according to the invention can be used for any ACP solution containing TRs and / or V, regardless of its origin. The ACP solution is typically a wet-process ACP solution, i.e. an aqueous ACP solution obtained by a process comprising an attack on the natural phosphate (contained in a sedimentary phosphate rock) by a strong acid such as hydrochloric acid, nitric acid and / or sulfuric acid. The majority of the impurities contained in the natural phosphate (the phosphate rock) are found in the ACP solution obtained and can be extracted from it for recovery.

[0037] The ACP solution may comprise from 10 to 60% by weight of P2O5, typically from 20 to 30% or from 50 to 58% by weight of P2O5, for example 29% or even 54% by weight of P2O5. The phosphoric acid solution generally comprises TRs. It generally comprises V.

[0038] The phosphoric acid solution typically comprises at least 45 ppm of TRs, typically 45 to 150 ppm of TRs, or 50 to 140 ppm of TRs or 55 to 130 ppm of TRs and / or the phosphoric acid solution typically comprises at least 70 ppm of V, typically 70 to 600 ppm of V, or 80 to 560 ppm of V or 95 to 510 ppm of V.

[0039] Rare earths, TRs, refer to a group of metals including scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and / or lutetium (Lu).

[0040] For example, a 29 wt% P2O5 ACP solution typically comprises 55 to 70 ppm TRs and / or 95 to 250 ppm V or a 54 wt% P2O5 phosphoric acid solution typically comprises 100 to 120 ppm TRs and / or 490 to 510 ppm V.

[0041] The ACP solution may further contain iron (Fe) and / or aluminum (Al) in the form of oxides. Preferably, the ACP solution further contains iron.

[0042] Preferably, the ACP solution treated in the process according to the invention has a solids content of less than 1% by weight, preferably less than 0.7% by weight, and / or an organic carbon content of less than 1000 ppm, preferably less than or equal to 100 ppm. Thus, before being subjected to the process according to the invention, the hydrochloric acid solution may, if necessary, be pretreated to reduce the solids content and / or the organic carbon content. The pretreatment may be as described below.

[0043] Solid content refers to the amount of solid in the ACP solution relative to the total weight of the ACP solution.

[0044] Typically, the ACP solution is pre-treated in a pre-treatment step to remove any organic matter and suspended matter that may be present. In particular, organic matter and suspended matter can significantly impede the binding of metal ions when the phosphoric acid solution passes over the resins. This step improves the performance and lifespan of the resins used in the proposed process.

[0045] Generally, the ACP solution is subjected to a pretreatment step so as to have a solids content of less than 1% by weight, preferably less than 0.7% by weight, and an organic carbon content of less than 1000 ppm, preferably less than or equal to 100 ppm.

[0046] Pretreatment can be by precipitation, adsorption, coagulation / flocculation, filtration and / or ultrafiltration. Pretreatment is generally carried out in the presence of activated carbon. Activated carbon treatment typically removes more than 98% by weight of organic matter and suspended solids from the ACP solution.

[0047] Extraction of TRs and / or Vs

[0048] The method comprises steps 1a), 1c) and optionally 1b) to carry out the extraction of the TRs and / or V contained in the ACP solution, optionally in the pretreated ACP solution.

[0049] Fixation 1a) of TRs and / or V is carried out by passing the ACP solution over an ion exchange resin functionalized by phosphonic groups.

[0050] Typically, the phosphonic groups of the resin are aminophosphonic groups, generally aminoethylphosphonic groups.

[0051] The resin is generally in the form of grains of which more than 95% by volume of the grains have an average particle size of approximately 300 to 1250 pm.

[0052] The resin functionalized by phosphonic groups is typically in H form + and can be prepared during a conditioning step allowing for example to pass from a Na form + to an H shape + . Typically, this step includes passing an acid solution over the resin. For example, the conditioning step may include passing 5BV (BV, for "bed volume" in English, designates the volume of the resin bed) of a 10% by weight aqueous solution of H2SO4 for one hour, followed by washing with water to remove traces of H2SO4.

[0053] The term “bed volume” refers to the total volume occupied by the bed of resin or material, in this case resin, in a chromatography column or other type of separation column. This term is well known to those skilled in the art. It includes both the volume of solid particles and the volume of void spaces between the particles. It is used here to express the amount of solution that passes through the resin column at each stage of the process.

[0054] The resin functionalized by phosphonic groups may comprise a polymer support based on styrene divinylbenzene on which phosphonic functional groups, typically aminophosphonic, are adsorbed. A resin functionalized by aminophosphonic groups useful in the context of step 1) of the process of the present invention is the Purolite S-950 resin supplied by the company Purolite.

[0055] Purolite S-950 resin is stable at very acidic pH and has a lifespan of over 10 years. This resin also offers several other advantages:

[0056] It does not retain P2O5: retention is zero for treated acid BVs;

[0057] It allows the implementation of the TRs and V extraction process at low temperature, i.e. in a range from 20 to 70°C.

[0058] It does not generate any discharge, except for equipment cleaning solutions.

[0059] Step 1a) may be carried out in at least one column containing the resin functionalized with phosphonic groups. Typically, step 1a) is carried out with at least two columns in series, and / or in parallel, containing the same resin. Step 1a) may also be carried out with 1 to 10 columns, or even 2 to 5 columns in series and / or in parallel containing the same resin. Typically, when step 1a) is carried out with at least three columns containing the same resin, the columns may be arranged by combining columns in series and in parallel.

[0060] The use of at least two columns in series and / or in parallel makes it possible to improve the retention rate of TRs and V, i.e. the quantity of TRs and V fixed on the resin.

[0061] A volume ranging from 1 to 10 BV, typically 5 to 10 BV; of the ACP solution is passed through the ion exchange resin bearing phosphonic groups in step 1a).

[0062] "BV" stands for "bed volume" in English, and refers to the volume of the resin bed. Thus, 1 BV of a phosphoric acid solution corresponds to a volume equivalent to the resin bed.

[0063] Each bed of phosphoric acid (BV acid) typically circulates through the bed of resin carrying phosphonic groups (BV resin) for a period of time ranging from 12 min to 15 min or at an extraction rate ranging from 4 BV to 5 BV (acid) / h (equivalent to 6.66 to 8.33 mL of acid / min), preferably at room temperature (20°C to 25°C).

[0064] The passage through the ion exchange resin functionalized by phosphonic groups is typically carried out at room temperature (from 20 to 25°C) but also varying from 20°C to 70°C. Thus, this step can be carried out at temperatures preferably ranging from 20°C to 25°C.

[0065] Alternatively, the fixing step can be carried out in batch by mixing the phosphoric acid solution with the resin under agitation. Typically, the mixing can be carried out under agitation ranging from 400 to 600 rpm for at least 2 hours in a ratio m / V (mass of resin / volume of phosphoric acid solution) ranging from 0.20 to 0.30.

[0066] Preferably, step 1a) allows the fixation on the resin of at least 50% of the TRs and V initially contained in the phosphoric acid solution. Preferably, at least 55%, preferably at least 60% and very preferably at least 65% of the TRs and V initially contained in the phosphoric acid solution are fixed on the resin. Typically, the fixation is 68% of the TRs and 65% of the V initially contained in the phosphoric acid solution.

[0067] Optional washing 1b) is carried out by passing water over the resin obtained at the end of step 1a), usually distilled or demineralized water. This step usually makes it possible to eliminate traces of phosphoric acid from the resin at the end of sub-step 1a).

[0068] Elution 1c) is carried out by passing a hydrochloric acid solution over the resin functionalized by phosphonic groups from step 1a) or 1b). The HCl solution has a concentration less than or equal to 15% by weight, typically ranging from 5 to 15% by weight. Generally, the HCl solution is at a concentration of 10% by weight. At the end of elution step 1c), the HCl solution contains TRs and V.

[0069] A volume ranging from 1 to 9 BV, typically 5 to 9 BV of the hydrochloric acid solution passes through the ion exchange resin bearing phosphonic groups in step 1c). For example, the volume may be 9 BV for a 10% by weight HCl elution solution.

[0070] Elution 1c) allows the recovery of at least 85% of the TRs bound to the resin in the HCl solution. At least 95% of the TRs can be recovered, typically at least 97%.

[0071] Elution 1c) allows the recovery of at least 84% of the V bound to the resin in the HCl solution. At least 90% of the V can be recovered, typically at least 99%.

[0072] When the phosphoric acid solution treated in the process according to the invention also contains iron (Fe) and / or aluminum (Al), the Fe remains bound to the resin at the end of elution 1c). The AI ​​is recovered in the HCl solution with the TRs and the V. The Fe and / or Al are generally in the form of oxides. The Fe can be recovered from the resin during an optional elution step 1d) by passing an ethylenediaminetetraacetic acid (EDTA) elution solution (step 1d) over the resin resulting from elution 1c). The EDTA solution can have a concentration ranging from 0.1 to 2.5M (M corresponding to mol / L) and typically from 0.2 to 1M and for example 0.4M. Elution with the EDTA solution makes it possible to completely recover the Fe bound to the resin.

[0073] The EDTA solution passes through the ion exchange resin obtained at the end of elution 1c) in a volume which can typically vary from 1 to 9 BV, preferably from 5 to 9 BV. For example, the volume can be 9 BV for a 0.4M EDTA solution.

[0074] A volume varying from 1 to 9 BV, typically from 5 to 9 BV of EDTA solution passes through the ion exchange resin carrying phosphonic groups obtained at the end of the elution. For example, the volume can be 9 BV for a 0.4M EDTA solution.

[0075] Step 1d) therefore leads to the production of a solution comprising iron and EDTA. The iron can then be recovered from this solution, for example by precipitation in the form of ferric iron hydroxide. The EDTA can then be recycled for use again in the process according to the invention.

[0076] When the phosphoric acid solution treated in the process according to the invention also contains iron, it is particularly advantageous to carry out elution step 1d) since it allows the resin used in step 1a to be regenerated, this resin then being able to be used again in the process according to the invention. Step 1d) makes it possible to limit the fouling phenomenon, i.e. scaling of the resin.

[0077] The eluting HCl solution containing the TRs, V and possibly AI is then sent to a separation step.

[0078] The method comprises the separation of the TRs and / or V contained in the HCl solution resulting from elution 1c). Preferably, this step allows the separation of the TRs and V, i.e. the HCl solution resulting from elution 1c) contains TRs and V. The fixation 2a) of the TRs is carried out by passing the HCl solution resulting from elution 1c) over an ion exchange resin functionalized by phosphoric groups.

[0079] The resin is generally in the form of grains, of which more than 90% of the grains have an average particle size ranging from 300 to 1400 pm.

[0080] The resin functionalized by phosphoric groups used in fixing step 2a) may comprise a polymer support based on macroporous polystyrene crosslinked with divinylbenzene functionalized by phosphoric groups. The resin used in step 2a) may for example be functionalized by di-(2-ethylhexyl) phosphoric acid (D2EHPA) groups. These types of resin are particularly advantageous because they allow working at high concentrations, and they also have good chemical resistance to strongly acidic environments.

[0081] A resin functionalized by phosphoric groups suitable for carrying out step 2a) is the Puromet MTX7010 resin supplied by the company Purolite.

[0082] Puromet MTX7010 resin is stable at very acidic pH and has a lifespan of over 10 years. This resin also offers several other advantages:

[0083] It hardly retains V: retention is very low for treated acid BVs;

[0084] It allows the separation of TRs and V at low temperature, i.e. in a range from 20 to 40°C;

[0085] It does not generate any discharge, except for equipment cleaning solutions.

[0086] A volume varying from 1 to 12 BV, typically from 5 to 12 BV of the HCl solution passes through the ion exchange resin carrying phosphoric groups in step 2a).

[0087] Each bed of HCl (BV acid) typically circulates through the bed of resin carrying phosphoric groups (BV resin) for a period of time ranging from 20 min to 45 min or at an extraction rate ranging from 1.33 BV to 3 BV acid per hour (equivalent to 6.66 to 8.33 mL of acid / min), preferably at room temperature (20°C to 25°C).

[0088] When passing the HCl solution over the resin, the TRs are fixed on the resin.

[0089] Optional washing 2b) is carried out by passing water over the resin obtained at the end of step 2a), commonly distilled or demineralized water and typically water having a pH lower than 4, for example at a pH of 2. This step commonly makes it possible to eliminate traces of HCI from the resin at the end of fixation 2a).

[0090] Elution 2c) of the TRs is carried out by passing a sulfuric acid solution (H2SO4) over the resin functionalized by phosphoric groups from step 2a) or 2b). The H2SO4 solution may have an H2SO4 concentration greater than or equal to 5% by weight, typically ranging from 10 to 20% by weight. Advantageously, the sulfuric acid solution has a pH less than or equal to 2.

[0091] Typically 1 to 10 BV, usually 5 to 9 BV, of the sulfuric acid solution passes through the ion exchange resin bearing phosphoric groups in step 2c).

[0092] The HCl solution at the end of fixation 2a) comprises at least 70% by weight relative to the weight of V initially in the HCl solution. The HCl solution obtained at the end of fixation 2a) may comprise at least 75% by weight of the V initially present in the HCl solution, typically at least 80% by weight or even at least 90%. By initially, we mean the quantity of V in the HCl solution after step 1c) and before carrying out fixation 2a).

[0093] The HCl solution after fixation 2a) may include traces of TRs, typically less than 13 ppm of TRs.

[0094] The H2SO4 solution at the end of elution 2c) comprises at least 70% by weight relative to the weight of TRs initially loaded onto the resin resulting from fixation 2a). The H2SC>4 solution at the end of elution 2c) may comprise at least 70% by weight of the TRs initially loaded into the resin, typically at least 75% by weight or even at least 80% by weight. By initially, we mean the quantity of TRs in the HCl solution after step 1c) and before carrying out fixation 2a).

[0095] The H2SO4 solution after elution 2c) does not contain Vanadium, typically less than 1 ppm of V.

[0096] The TRs contained in the H2SO4 solution can be precipitated by different routes, typically by adding oxalate-type derivatives [1]. Commonly, the H2SO4 solution containing the TRs can be used in a step 3) of precipitation of the TRs. The precipitated TRs can be recovered after filtration. Conventionally, the TR precipitation step can be carried out by mixing the H2SO4 solution by adding oxalate-type derivatives.

[0097] Advantageously, the process according to the invention does not comprise any extraction step other than those described previously. In particular, the process according to the invention advantageously does not involve an ion exchange resin functionalized by sulfonic groups.

[0098] The method according to the invention is particularly effective for separating TRs, V and iron from a phosphoric acid solution containing these elements, each of these elements (TRs, V and iron) being extracted separately.

[0099] According to one embodiment, the method according to the invention consists of the steps described previously.

[0100] The figures illustrate in a non-limiting manner devices capable of implementing the treatment method using resin according to the invention.

[0101] Figure 3 is an overall diagram illustrating an embodiment of the treatment method according to the invention successively comprising steps 1a), 1b), 1c), 1d), 2a), 2b), 2c) and 3). In this embodiment, an ACP solution at 29% by weight of P2O5, previously pretreated by passing over carbon, is used in a step 1a) of fixing the TRs and the V by passing over an S950 resin as described above.

[0102] The S950 resin is then washed, during a washing step 1 b), by passing distilled or demineralized water. The washed resin is eluted, during an elution step 1 c), by passing a 10% by weight HCl solution.

[0103] When the ACP solution used contains Fe, the Fe is fixed by the S950 resin and can be recovered during an elution step 1d) by a 0.4M EDTA solution.

[0104] In a preferred embodiment, steps 1a) to 1d) are repeated on a second S950 resin by passing the ACP solution recovered at the end of step 1a). The two S950 resins are denoted C1 and C2. In this case, the two HCl elution solutions are combined before being used in step 2a).

[0105] Thus, the HCl elution solution containing TRs and V is engaged in a step 2a) of fixing the TRs, by passing over the MTX7010 resin described above. The HCl solution after passing over the MTX7010 resin essentially contains Vanadium.

[0106] The MTX7010 resin is then washed, in step 2b), by passing a distilled water solution having a pH lower than 2. Then the washed resin is eluted, in step 2c), by passing a H2SO4 solution. After passing through the MTX7010 resin, the H2SO4 solution essentially contains TRs. The H2SO4 solution is used in a precipitation step 3) to recover the TRs.

[0107] The various embodiments presented throughout the description may be used alone or in combination with each other, without limitation of combination.

[0108] EXAMPLES

[0109] The following non-restrictive examples illustrate exemplary embodiments of the invention.

[0110] Materials and methods

[0111] Ion exchange resin functionalized by aminoethylphosphonic groups in H form + is the Purolite S950 resin supplied by the Purolite company

[0112] In the examples below, the S950 resin in H form + is prepared by carrying out a conditioning step of the S950 chelating resin by passing a quantity of 5BV of 10% by weight sulfuric acid for a period of 1 h.

[0113] The ion exchange resin functionalized by phosphoric groups is the Puromet MTX7010 resin supplied by the company Purolite.

[0114] The concentrated ACP solution used in the examples below was previously subjected to a pretreatment step using activated carbon to remove organic matter and suspended matter. At the end of this pretreatment, the ACP solution has a solids content of less than 0.7% by weight and an organic carbon content of less than or equal to 100 ppm.

[0115] Example 1: Study of the Fixation of TRs and Vs

[0116] The ACP solution is mixed with the S950 resin for 2 hours under agitation of 500 rpm (rotations per minute) in a ratio mass of resin / Volume of ACP solution equal to 0.24.

[0117] The S950 resin is then recovered by filtration, washed with demineralized water. The washed S950 resin is eluted by a 10% by weight HCl solution with a mass of resin / Volume of HCl solution ratio equal to 0.24. The fixation step is carried out at room temperature, at atmospheric pressure, with a contact time equal to 2 h, stirring: 500 rpm, mass of resin / Volume of ACP solution ratio equal to 0.24.

[0118] Table 1 shows the concentrations of impurities in the ACP solution before and after treatment with S950 resin in batch and the retention rate of the S950 resin of the impurities of interest.

[0119] Table 1: Concentration of metallic impurities as well as non-metallic impurities obtained after contact of ACP solution by S950 resin

[0120] Figure 1 illustrates that the retention rates of Fe, TRs, V and Al are significantly higher than those of other elements such as Cu, As, Mg, Ca...

[0121] It emerges from these results that a resin functionalized by aminophosphonic groups in H form + such as S950 allows to selectively fix TRs, V, Fe and AI contained in an ACP solution.

[0122] Example 2: Study of the fixation of TRs and V by a cascade of columns of S950 resin

[0123] This example is carried out under similar conditions to Example 1, except that the fixation step is carried out on two columns in series containing the S950 resin. This example is implemented by the sequence of the following steps:

[0124] - Fixation of TRs and V by passing ACP at 29% by weight of P2O5 on two columns in series containing the S950 resin;

[0125] - Washing of each of the two columns with S950 resin by passing demineralized water;

[0126] - Elution of the two columns with S950 resin by passing a 10% by weight HCl solution;

[0127] - Washing of the two columns with S950 resin using demineralized water to remove traces of the 10% HCl solution by weight;

[0128] - Elution of Fe by passage of a 0.4 M EDTA solution;

[0129] - Washing of the two columns with S950 resin by passing demineralized water through it to eliminate traces of the EDTA solution;

[0130] The fixation step is carried out at room temperature, at atmospheric pressure, with a contact time equal to 1BV / 12min, and an acid percolation rate equal to 5BV / h (equivalent to 8.33ml / min).

[0131] Table 2, below, presents the concentrations of metallic and non-metallic impurities obtained by the S950 resin of the two columns (Column 1 + Column 2).

[0132] Table 2: Concentration of major, minor and non-metallic impurities obtained by S950 resin in two columns (column 1 + column 2) (BV from 2.5 to 12.5)

[0133] Figure 2 illustrates that the retentions of: Fe, TRs, V and Al are always significantly higher than those of other elements such as Cu, As, Mg, Ca, etc. These results are identical to those obtained in Example 1. The results in Table 2 show that 68% of TRs and 65% of V are fixed by the resin for a treatment ratio of 1 BV (resin) / 5 BV (acid). In Example 2, the loading capacity of S950 resin for TRs and V are 0.6 mg / g and 1.05 mg / g respectively.

[0134] Example 3: Study of selective fixation and separation of TRs and V by the combination of S950 Resin and MTX7010 Resin

[0135] This example illustrates the selective separation of TRs and V contained in a 29 wt% P2O5 ACP solution using a cascade of S950 Resin + MTX7010 Resin.

[0136] Example 3 is carried out according to the overall diagram of Figure 3 and under the conditions summarized below in Table 3.

[0137] Table 3: Protocol of filtration tests carried out with phosphoric acid 29% P2O5

[0138] In step 1), TRs, Fe, V and AI are selectively fixed by two columns of S950 Resin.

[0139] Step 2) corresponds to the selective separation of TRs and V by the MTX7010 resin.

[0140] The fixation / elution steps to recover the TRs and V in solution are carried out by the successive implementation of two columns (C1 and C2) containing the S950 resin.

[0141] A first 10% HCl elution solution is recovered, after passing through column C1, the HCl solution contains TRs, V and AI in the proportions presented in table 4.

[0142] A second 10% by weight HCl elution solution is recovered, after passing through column C2, the HCl solution contains TRs, V and AI in the proportions presented in table 5.

[0143] Table 5: Chemical analysis of HCl acid solution (10%), 9BV / column C2 of S950 resin

[0144] Resins C1 and C2 are eluted with 0.4 M EDTA solution to recover iron in the quantities shown in Table 6.

[0145] Table 6: Elution of Fe by passage of 0.4 M EDTA solution

[0146] The first and second HCl solutions are combined. The combined HCl solution is introduced in step 2) by passing it over the MTX7010 resin.

[0147] The MTX7010 resin strongly retains TRs (63% by weight at BV11) and partially V (20% by weight at BV11). The 10% by weight HCl solution after passing through the MTX7010 resin mainly contains V, which can be sent to a downstream recovery step.

[0148] The MTX7010 resin is then washed (2b) by passing distilled water at a pH < 4. The TRs retained on the MTX7010 resin are then selectively eluted (2c) by passing a 5% by weight sulfuric acid solution, preferably with a concentration > 5% by weight, for example at 20% by weight. Example 3 demonstrates that:

[0149] - Fe is moderately retained (> 72%) for a treatment ratio of 1 BV (S950 resin) / 5 BV (Acid). Iron was selectively eluted from the resin and precipitated in the form of Fe(OH)s of high purity (>99%).

[0150] - TRs and V are retained by S950 resin with a retention rate of 68% and 65% respectively for the same treatment ratio 1BV (resin) / 5 BV (Acid).

[0151] - TRs can be selectively separated from V during extraction step 2 using MTX7010 resin.

[0152] - The adsorbed TRs are eluted by passing a 20% by weight sulfuric acid solution. - The elution solutions containing TRs, V and / or Fe can be sent to downstream recovery steps.

[0153] REFERENCES

[0154] [1] A. Nawab, X. Yang, R. Honaker, Parametric study and speciation analysis of rare earth precipitation using oxalic acid in a chloride solution system, Minerals Engineering. 176 (2022) 107352. https: / / doi.Org / 10.1016 / j.mineng.2021.107352.

Claims

CLAIMS 1. A method of treating a phosphoric acid solution containing rare earths and vanadium, the method comprising the following steps: 1a) fixation of rare earths and vanadium by passing the phosphoric acid solution over an ion exchange resin functionalized by phosphonic groups; 1 b) optionally washing by passing water over the resin obtained at the end of step 1a); 1c) elution by passing a hydrochloric acid solution over the resin from step 1a) or 1b) to obtain a hydrochloric acid solution containing rare earths and vanadium; 2a) fixing of rare earths by passing the hydrochloric acid solution from step 1c) over an ion exchange resin functionalized by phosphoric groups; 2b) optionally washing by passing water over the resin from step 2a); 2c) elution of rare earths by passing a sulfuric acid solution over the resin functionalized by phosphoric groups from step 2a) or 2b).

2. The method of claim 1 wherein the phosphoric acid solution comprises from 10 to 60% by weight of P2O5, or from 20 to 30% by weight, or from 50 to 58% by weight of P2O5.

3. The method of claim 1 or 2, wherein the phosphoric acid solution comprises at least 45 ppm of rare earths and at least 70 ppm of vanadium.

4. Method according to any one of claims 1 to 3, in which the phosphoric acid solution has a solids content of less than 1% by weight, preferably less than 0.7% by weight, and / or an organic carbon content of less than 1000 ppm, preferably less than or equal to 100 ppm.

5. Method according to any one of claims 1 to 4, in which the phosphonic groups functionalizing the resin are aminophosphonic groups.

6. Method according to any one of claims 1 to 5, in which step 1a) is carried out in at least two columns in series containing the same ion exchange resin functionalized by phosphonic groups.

7. A method according to any one of claims 1 to 6, wherein a volume varying from 1 to 10 BV of the phosphoric acid solution passes through the ion exchange resin carrying phosphonic groups in step 1a).

8. A method according to any one of claims 1 to 7, wherein a volume varying from 1 to 9 BV of the hydrochloric acid solution passes through the ion exchange resin carrying phosphonic groups in step 1c).

9. Method according to any one of claims 1 to 8, in which the phosphoric groups functionalizing the resin are di-(2-ethylhexyl) phosphoric acid (D2EHPA) groups.

10. A method according to any one of claims 1 to 9, wherein a volume varying from 1 to 12 BV of the hydrochloric acid solution passes through the ion exchange resin carrying phosphoric groups in step 2a).

11. Method according to any one of claims 1 to 10, in which a volume varying from 1 to 10 BV, typically from 5 to 9 BV of the sulfuric acid solution passes through the ion exchange resin carrying phosphoric groups in step 2c).

12. Method according to any one of claims 1 to 11, in which the phosphoric acid solution further contains iron, the method further comprising a step 1d) of elution by passing an ethylenediaminetetraacetic acid solution over the resin resulting from step 1c).

13. Method according to claim 12, wherein the method further comprises a step 1d) of recovering iron from the solution obtained at the end of step 1d).

14. Method according to any one of claims 1 to 13, in which the resin functionalized by phosphoric groups used in step 2a) comprises a polymer support based on macroporous polystyrene crosslinked with divinylbenzene functionalized by phosphoric groups.

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