Method for recovering metal cations from metal cation supported extractant

Abstract

The invention relates to a method for recovering metal cations from an extraction agent loaded with the metal cations, and belongs to the technical field of wet-process phosphoric acid. The technical problem to be solved by the invention is to provide a method for recovering metal cations from an extraction agent loaded with metal cations. The method comprises the process steps of reverse extraction, circulating enrichment, metal ion recovery, washing and the like, and metal cations are recovered from an extraction agent loaded with the metal cations. According to the method, a single mixed stripping agent is adopted, circulating enrichment is combined, ammonia gas is introduced to adjust pH to precipitate the metal ions, the process is relatively simple, the metal ions can be effectively recycled, an external precipitator does not need to be introduced, efficient separation and recycling of the metal ions can be achieved, the stripping rate and the recycling rate are increased, meanwhile, energy consumption is reduced, and the product purity breaks through the battery grade standard; the limitation of a one-time reverse extraction process is thoroughly solved, and wet-process phosphoric acid metal recovery is promoted to be upgraded to the efficient and green direction.

Description

Technical Field

[0001] The invention relates to a method for recovering metal cations from an extractant loaded with metal cations, and belongs to the technical field of wet-process phosphoric acid. Background Art

[0002] The wet-process phosphoric acid process, due to its low energy consumption and significant cost advantages, has become the mainstream technology for industrial phosphoric acid production, particularly in the comprehensive utilization of phosphate rock resources. This process decomposes phosphate rock with inorganic acids to produce crude phosphoric acid, which is then purified through extraction and stripping steps. Compared to traditional thermal phosphoric acid, this process significantly reduces energy consumption and carbon emissions. However, during the wet-process phosphoric acid purification process, metal ions are selectively extracted using organic extractants (such as P204, P507, Cynex 272, DNNSA, cyclohexane acid, or versatile carbonic acid) to produce an extractant loaded with metal cations. Efficiently recovering these metal ions and regenerating the extractant remains a key challenge facing the wet-process phosphoric acid industry.

[0003] In the prior art, acid stripping (such as sulfuric acid, hydrochloric acid, nitric acid, etc.) is mainly used to separate metal ions from the organic phase, but there are generally defects such as poor metal separation selectivity, low stripping rate, waste of resources, and environmentally unfriendly process. At present, for the recovery of metals in wet-process phosphoric acid systems, there have been studies trying to use methods such as graded stripping, complexation enhanced separation or electrochemical reduction, but there are still problems such as complex process, high cost or difficulty in industrial application. For example, CN119265410A proposes a method for stepwise recovery of metal cations from wet-process phosphoric acid, which uses different stripping agents for stripping to recover metal ions. This method uses multiple levels of different stripping agents, which is complicated, costly, and has poor metal separation selectivity. Fe 3+ Iso-strip extraction is incomplete, with a stripping rate of only around 92%. It also lacks cyclic enrichment, resulting in significant resource waste and high energy consumption for ammonia distillation. Patent CN119503888A discloses a method for recovering metal cations from wet-process phosphoric acid, employing a single stripping step followed by distributed crystallization to produce various byproducts. The core drawbacks of this method are insufficient stripping stages, poor crystallization selectivity, and a lack of closed-loop enrichment, resulting in high energy consumption and low purity.

[0004] Therefore, there is an urgent need to develop a simple, efficient and energy-saving metal ion recovery method to achieve high stripping rate, high recovery rate and preparation of high value-added products, and further optimize resource recycling, reduce energy consumption and waste emissions, and meet the development needs of green chemistry. Summary of the Invention

[0005] In view of the above problems, the technical problem solved by the present invention is to provide a method for recovering metal cations from an extractant loaded with metal cations, and further improve the stripping rate and metal ion recovery rate.

[0006] The method for recovering metal cations from an extractant loaded with metal cations of the present invention comprises the following steps:

[0007] a. Stripping: Stripping the metal cation-loaded extractant with a stripping agent to obtain an aqueous phase 1 and an organic phase 1; the acid is oxalic acid or sulfuric acid; the aqueous phase 1 sequentially undergoes steps b and c, and the organic phase 1 undergoes step d; the stripping agent is an ammonium oxalate solution, or a mixed solution of ammonium oxalate and an oxoacid / salt, the oxoacid / salt is oxalic acid, sulfuric acid, or a sulfate, and the sulfate is lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, or ammonium sulfate;

[0008] b. Cyclic enrichment: specifically includes the following operations:

[0009] 1) returning the aqueous phase 1 to prepare a stripping agent for stripping in step a;

[0010] 2) Repeat step 1) until the iron ion concentration in the aqueous phase 1 is ≥50 g / L or the total metal ion concentration is ≥80 g / L, thereby obtaining an aqueous phase 1 rich in metal ions;

[0011] c. Recovering metal ions: recovering metal ions from the aqueous phase 1 rich in metal ions;

[0012] d. Washing: Using a stripping agent diluted 10 times or more as a washing agent, washing the organic phase 1, recovering the ammonium oxalate and / or ammonium sulfate entrained in the organic phase 1, and obtaining a wet-process phosphoric acid regeneration extractant.

[0013] In one embodiment of the present invention, in step a, the stripping agent is 1 wt.% to 14 wt.% ammonium oxalate solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 1 wt.% to 20 wt.% sulfuric acid solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 1 wt.% to 10 wt.% oxalic acid solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 8 wt.% to 35 wt.% sulfuric acid. A mixed solution of a salt solution; preferably, the stripping agent is a 3wt.% to 8wt.% ammonium oxalate solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and a 3.5wt.% to 10wt.% sulfuric acid solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and a 3.5wt.% to 5wt.% oxalic acid solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and an 8wt.% to 20wt.% sulfate solution.

[0014] In one embodiment of the present invention, in step a, the stripping is a two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 25 to 80°C, and the volume ratio O / A is 1:1 to 5; preferably, the stripping temperature of each stage is 60°C, and the volume ratio O / A is 1:2 to 3.

[0015] In one embodiment of the present invention, in step c, metal ions are recovered from the metal ion-rich aqueous phase 1 using method A, method B or method C.

[0016] The method A is:

[0017] A1. Precipitation: Ammonia gas is passed through the metal ion-rich aqueous phase 1 to adjust the pH to 8-11, preferably to 11, to cause precipitation, and solid-liquid separation to obtain a hydroxide precipitate of iron, aluminum and magnesium and an aqueous phase 2;

[0018] A2, ammonia evaporation: Heat aqueous phase 2 to evaporate the ammonia gas therein to obtain aqueous phase 3. The collected ammonia gas is returned to step A1 for use as gaseous ammonia; aqueous phase 3 is returned to step a for preparation of a stripping agent or aqueous phase 3 is subjected to step A3;

[0019] A3, treatment of aqueous phase 3: aqueous phase 3 is concentrated, crystallized and filtered to obtain ammonium oxalate solid and aqueous phase 4;

[0020] The aqueous phase 4 is concentrated, crystallized and filtered to obtain ammonium sulfate solid, and the mother liquor is returned to the aqueous phase 3; or the aqueous phase 4 is returned to step a for preparing a stripping agent;

[0021] The method B is:

[0022] B1. Precipitation: Crystallize and filter the metal ion-rich aqueous phase 1, dissolve the resulting oxalate, pass ammonia gas, adjust the pH to 8-11, preferably to 11, precipitate, separate the solid and liquid, and obtain the iron, aluminum and magnesium hydroxide precipitate and aqueous phase 2;

[0023] B2, cooling crystallization: Aqueous phase 2 is concentrated, crystallized, and filtered to obtain ammonium oxalate solid. The crystallization mother liquor is returned to be combined with aqueous phase 1 from the recycling enrichment step; or aqueous phase 2 is collected and returned to step B1 for dissolving oxalate;

[0024] The method C is:

[0025] After C1 and aqueous phase 1 are enriched, calcium oxalate and aqueous phase 2 are obtained by filtration; aqueous phase 2 is returned to step a to prepare a stripping agent; or aqueous phase 2 is subjected to step C2; or part of aqueous phase 2 is returned to step a to prepare a stripping agent, and part of aqueous phase 2 is subjected to step C2;

[0026] C2, aqueous phase 2 is cooled, crystallized and filtered to obtain aqueous phase 3 and oxalic acid complex, aqueous phase 3 is returned to step C1 and filtered together with the enriched aqueous phase 1;

[0027] C3. After the oxalic acid complex is dissolved, ammonia gas is passed through to adjust the pH to 8-11, preferably to 11, and precipitation occurs. Solid-liquid separation is performed to obtain iron, aluminum and magnesium hydroxide precipitates and aqueous phase 4;

[0028] C4, heating aqueous phase 4 to evaporate the ammonia therein to obtain aqueous phase 5, and the collected ammonia is returned to step C3 to be used as gaseous ammonia;

[0029] C5, collecting aqueous phase 5, concentrating, crystallizing, and filtering to obtain ammonium oxalate solid and aqueous phase 6; adding ammonium oxalate to aqueous phase 6 and returning to step a for preparing a stripping agent, or returning aqueous phase 6 to step C3 for dissolving the oxalic acid complex;

[0030] Alternatively, the aqueous phase 5 is collected, cooled, crystallized, and filtered to obtain crude ammonium oxalate and aqueous phase 6. The crude ammonium oxalate is acidified and crystallized to obtain oxalic acid, which is returned to step (1) to prepare a stripping agent. The aqueous phase 6 is returned to step C3 to dissolve the oxalic acid complex.

[0031] Alternatively, the aqueous phase 5 is returned to step C3 to dissolve the oxalic acid complex.

[0032] In one embodiment of the present invention, the detergent in step d is the stripping agent in step a diluted 10 times.

[0033] In one embodiment of the present invention, step d is replaced by:

[0034] d1. Washing: Washing the organic phase 1 with an oxalic acid solution to obtain an organic phase 2 and an acid phase, and returning the acid phase to the oxalic acid solution;

[0035] e. Reverse extraction of ammonium phase separation: Use a mixed solution of ammonium oxalate, oxalic acid or sulfuric acid as a reverse extraction agent to reverse extract the organic phase 2 to obtain a wet-process phosphoric acid regeneration extractant.

[0036] In one embodiment of the present invention, in step d1, the concentration of the oxalic acid solution is 0.9 wt.% to 4.5 wt.%.

[0037] In one embodiment of the present invention, in step e, two-stage three-stage countercurrent stripping of the organic phase 2 is adopted, the stripping temperature of each stage is 30-80°C, and the volume ratio O / A is 1:2-4; preferably, the stripping temperature of each stage is 60°C, and the volume ratio O / A is 1:3.

[0038] In one embodiment of the present invention, the metal cation-loaded extractant is the extractant obtained after extraction, washing and phase separation by dilute phosphoric acid in the wet-process phosphoric acid production process.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The method of the present invention for recovering metal cations from an extractant loaded with metal cations adopts a single mixed stripping agent, combined with cyclic enrichment and pH adjustment by passing ammonia gas to precipitate metal ions. The process is relatively simple and can effectively recover metal ions without introducing an external precipitating agent. The method can achieve efficient separation and recovery of metal ions, with high stripping rate and metal ion recovery rate and lower energy consumption.

[0041] The method of the present invention can accurately control the amount of ammonia used, optimize crystallization conditions, enhance washing recovery, and adjust the stripping agent composition. It can achieve efficient recovery of metal cations with a small amount of ammonia evaporation or even without ammonia evaporation, thereby reducing energy consumption.

[0042] The method of the present invention has obvious recycling advantages: the back extraction mother liquor is recycled and the organic phase is regenerated and recycled, which reduces the waste of raw materials, reduces waste emissions, improves resource utilization, reduces production costs, and complies with the concept of green chemistry.

[0043] The present invention uses an innovative process of multi-stage countercurrent stripping + cyclic enrichment + graded precipitation to improve the stripping rate and recovery rate, while reducing energy consumption by 15-40%. The product purity exceeds the battery-grade standard, completely solving the limitations of the single-stage stripping process and promoting the upgrading of wet-process phosphoric acid metal recovery towards high efficiency and greenness. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 1 of the present invention.

[0045] Figure 2 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 2 of the present invention.

[0046] Figure 3 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 3 of the present invention.

[0047] Figure 4 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 4 of the present invention.

[0048] Figure 5 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 5 of the present invention.

[0049] Figure 6 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 6 of the present invention.

[0050] Figure 7 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 7 of the present invention.

[0051] Figure 8 This is a process flow chart for recovering metal cations from an extractant loaded with metal cations in Example 8 of the present invention. DETAILED DESCRIPTION

[0052] The method for recovering metal cations from an extractant loaded with metal cations of the present invention comprises the following steps:

[0053] a. Stripping: Stripping the metal cation-loaded extractant with a stripping agent to obtain an aqueous phase 1 and an organic phase 1; the acid is oxalic acid or sulfuric acid; the aqueous phase 1 sequentially undergoes steps b and c, and the organic phase 1 undergoes step d; the stripping agent is an ammonium oxalate solution, or a mixed solution of ammonium oxalate and an oxoacid / salt, the oxoacid / salt is oxalic acid, sulfuric acid, or a sulfate, and the sulfate is lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, or ammonium sulfate;

[0054] b. Cyclic enrichment: specifically includes the following operations:

[0055] 1) returning the aqueous phase 1 to prepare a stripping agent for stripping in step a;

[0056] 2) Repeat step 1) until the total metal ion concentration in the aqueous phase 1 is ≥80 g / L or the iron ion concentration is ≥50 g / L, thereby obtaining an aqueous phase 1 rich in metal ions;

[0057] c. Recovering metal ions: recovering metal ions from the aqueous phase 1 rich in metal ions;

[0058] d. Washing: Using a stripping agent diluted 10 times or more as a washing agent, washing the organic phase 1, recovering the ammonium oxalate and / or ammonium sulfate entrained in the organic phase 1, and obtaining a wet-process phosphoric acid regeneration extractant.

[0059] Step a is stripping, using a mixed solution of ammonium oxalate + sulfuric acid, or a mixed solution of ammonium oxalate + oxalic acid as a stripping agent to strip the extractant loaded with metal cations to obtain an aqueous phase 1 and an organic phase 1.

[0060] In one embodiment of the present invention, in step a, the stripping agent is 1 wt.% to 14 wt.% ammonium oxalate solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 1 wt.% to 20 wt.% sulfuric acid solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 1 wt.% to 10 wt.% oxalic acid solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 8 wt.% to 35 wt.% sulfuric acid. A mixed solution of a salt solution; preferably, the stripping agent is a 3wt.% to 8wt.% ammonium oxalate solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and a 3.5wt.% to 10wt.% sulfuric acid solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and a 3.5wt.% to 5wt.% oxalic acid solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and an 8wt.% to 20wt.% sulfate solution.

[0061] In one embodiment of the present invention, in step a, the stripping is a two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 25-80°C, and the O / A ratio is 1:1-5 (volume ratio); preferably, the stripping temperature of each stage is 60°C, and the O / A ratio is 1:2-3 (volume ratio).

[0062] Step b is a cyclic enrichment step, in which aqueous phase 1 is returned to prepare a stripping agent for stripping in step a, and this step is repeated until the total metal ion concentration in aqueous phase 1 is ≥80 g / L or the iron ion concentration is ≥50 g / L, thereby obtaining an aqueous phase 1 rich in metal ions. In one embodiment of the present invention, controlling the iron ion concentration to ≥50 g / L enables more precise control of key ions and improves the purity of the hydroxide precipitate.

[0063] Step c is to recover metal ions.

[0064] In one embodiment of the present invention, in step c, metal ions are recovered from the metal ion-rich aqueous phase 1 using method A, method B or method C.

[0065] The method A is:

[0066] A1. Precipitation: Ammonia gas is passed through the metal ion-rich aqueous phase 1 to adjust the pH to 8-11, preferably to 11, to cause precipitation, and solid-liquid separation to obtain a hydroxide precipitate of iron, aluminum and magnesium and an aqueous phase 2;

[0067] A2, ammonia evaporation: Heat aqueous phase 2 to evaporate the ammonia gas therein to obtain aqueous phase 3. The collected ammonia gas is returned to step A1 for use as gaseous ammonia; aqueous phase 3 is returned to step a for preparation of a stripping agent or aqueous phase 3 is subjected to step A3;

[0068] A3, treatment of aqueous phase 3: aqueous phase 3 is concentrated, crystallized and filtered to obtain ammonium oxalate solid and aqueous phase 4;

[0069] The aqueous phase 4 is concentrated, crystallized and filtered to obtain ammonium sulfate solid, and the mother liquor is returned to the aqueous phase 3; or the aqueous phase 4 is returned to step a for preparing a stripping agent;

[0070] The method B is:

[0071] B1. Precipitation: Crystallize and filter the metal ion-rich aqueous phase 1 to obtain metal oxalates, mainly iron oxalate, magnesium oxalate, and aluminum oxalate. Dissolve the oxalates, pass ammonia gas, and adjust the pH to 8-11, preferably to 11, to produce precipitation. Solid-liquid separation is performed to obtain iron, aluminum, and magnesium hydroxide precipitates and aqueous phase 2.

[0072] B2, cooling crystallization: Aqueous phase 2 is concentrated, crystallized, and filtered to obtain ammonium oxalate solid. The crystallization mother liquor is returned to be combined with aqueous phase 1 from the recycling enrichment step; or aqueous phase 2 is collected and returned to step B1 for dissolving oxalate;

[0073] The method C is:

[0074] After C1 and aqueous phase 1 are enriched, calcium oxalate and aqueous phase 2 are obtained by filtration; aqueous phase 2 is returned to step a to prepare a stripping agent; or aqueous phase 2 is subjected to step C2; or part of aqueous phase 2 is returned to step a to prepare a stripping agent, and part of aqueous phase 2 is subjected to step C2;

[0075] C2, aqueous phase 2 is cooled, crystallized and filtered to obtain aqueous phase 3, which is returned to step C1 and filtered together with the enriched aqueous phase 1;

[0076] C3. After the oxalic acid complex is dissolved, ammonia gas is passed through to adjust the pH to 8-11, preferably to 11, and precipitation occurs. Solid-liquid separation is performed to obtain iron, aluminum and magnesium hydroxide precipitates and aqueous phase 4;

[0077] C4, heating aqueous phase 4 to evaporate the ammonia therein to obtain aqueous phase 5, and the collected ammonia is returned to step C3 to be used as gaseous ammonia;

[0078] C5, aqueous phase 5 returns to step C3 to dissolve the oxalic acid complex;

[0079] Alternatively, aqueous phase 5 is collected, concentrated, crystallized, and filtered to obtain ammonium oxalate solid and aqueous phase 6; ammonium oxalate is added to aqueous phase 6 and returned to step a for preparing a stripping agent, or aqueous phase 6 is returned to step C3 for dissolving the oxalic acid complex. Here, the crystallized ammonium oxalate is at a temperature of 40-60°C and a pH of 7-9;

[0080] Alternatively, aqueous phase 5 is collected, cooled, crystallized, and filtered to obtain crude ammonium oxalate and aqueous phase 6. The crude ammonium oxalate is acidified and crystallized to obtain oxalic acid, which is returned to step (1) for preparing a stripping agent. Aqueous phase 6 is returned to step C3 for dissolving the oxalic acid complex. Here, the crystallized crude oxalic acid is crystallized by cooling at ≤20°C and pH 1-3, and subsequently purified by acidification.

[0081] The crystallization of oxalic acid in the present invention utilizes low-temperature acid precipitation to remove impurities, while the crystallization of ammonium oxalate is achieved by stabilizing ammonium with alkali at medium temperature. The difference in conditions between the two precisely matches the core of the invention of "oxalic acid recycling acidification and ammonium salt recycling complexation", achieving dual optimization of metal recovery and reagent circulation.

[0082] In one embodiment of the present invention, the detergent in step d is the stripping agent in step a diluted 10 times.

[0083] In one embodiment of the present invention, step d is replaced by:

[0084] d1. Washing: Washing the organic phase 1 with an oxalic acid solution to obtain an organic phase 2 and an acid phase, and returning the acid phase to the oxalic acid solution;

[0085] e. Reverse extraction of ammonium phase separation: Use a mixed solution of ammonium oxalate, oxalic acid or sulfuric acid as a reverse extraction agent to reverse extract the organic phase 2 to obtain a wet-process phosphoric acid regeneration extractant.

[0086] In one embodiment of the present invention, in step d1, the concentration of the oxalic acid solution is 0.9 wt.% to 4.5 wt.%.

[0087] In one embodiment of the present invention, in step e, two-stage three-stage countercurrent stripping of the organic phase 2 is performed, with the stripping temperature of each stage being 30 to 80° C. and the O / A ratio being 1:2 to 4 (volume ratio). Preferably, the stripping temperature of each stage is 60° C. and the O / A ratio is 1:3 (volume ratio).

[0088] In one embodiment of the present invention, the metal cation-loaded extractant is the extractant after dilute phosphoric acid extraction, washing, and phase separation during the wet-process phosphoric acid production process. The extractant may be P204, P507, Cynex 272, DNNSA, cyclohexane acid, or versatic acid.

[0089] The specific embodiments of the present invention are further described below in conjunction with examples, but the present invention is not limited to the scope of the examples.

[0090] Example 1

[0091] like Figure 1 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0092] (1) Stripping: A mixed solution of ammonium oxalate and sulfuric acid was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of sulfuric acid was 3.5 wt.%. The metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping, the stripping temperature of each stage was 60°C, and the O / A ratio was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0093] (2) Enrichment: The aqueous phase 1 is returned to prepare a stripping agent for stripping; the resulting aqueous phase is then returned to the stripping agent for circulation until the iron ion concentration in the aqueous phase is greater than 50 g / L.

[0094] (3) Recovery of metal ions:

[0095] After A1 and aqueous phase 1 are enriched, gaseous ammonia is introduced to adjust the pH to 11, precipitation occurs, and solid-liquid separation is performed to obtain iron, aluminum, and magnesium hydroxide precipitates and aqueous phase 2;

[0096] A2. Heat aqueous phase 2 to evaporate the ammonia therein to obtain aqueous phase 3. The collected ammonia is returned to step A1 as gaseous ammonia.

[0097] A3, aqueous phase 3 is concentrated and crystallized (60-70°C) and filtered to obtain a product mainly composed of ammonium oxalate solid and aqueous phase 4. Aqueous phase 4 is concentrated and crystallized (80-90°C) and filtered to obtain a product mainly composed of ammonium sulfate solid. The liquid is collected and returned to aqueous phase 3.

[0098] (4) Washing: The organic phase 1 is washed in two-stage countercurrent with a dilute ammonium oxalate solution having a concentration of 0.1 wt.% and a dilute ammonium sulfate solution having a concentration of 0.1 wt.% at a temperature of 30°C and an O / A ratio of 3:1 (volume ratio). The ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are recovered to obtain a regenerated extractant that can be recycled.

[0099] This embodiment uses ammonia circulation + concentrated crystallization to achieve ammonium oxalate / ammonium sulfate recovery (recovery rate>90%), without the need to introduce an external precipitant, and the process is closed-loop.

[0100] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0101] Comparative Example 1

[0102] A method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0103] (1) Stripping: A mixed solution of ammonium oxalate and sulfuric acid was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of sulfuric acid was 3.5 wt.%. The metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping, the stripping temperature of each stage was 60°C, and the O / A ratio was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0104] (2) Recovery of metal ions:

[0105] A1, pass gaseous ammonia through aqueous phase 1 to adjust the pH to 11, causing precipitation, solid-liquid separation, and obtaining iron, aluminum, and magnesium hydroxide precipitates and aqueous phase 2;

[0106] A2. Heat aqueous phase 2 to evaporate the ammonia therein to obtain aqueous phase 3. The collected ammonia is returned to step A1 as gaseous ammonia.

[0107] A3, aqueous phase 3 is concentrated and crystallized (60-70°C) and filtered to obtain a product mainly composed of ammonium oxalate solid and aqueous phase 4. Aqueous phase 4 is concentrated and crystallized (80-90°C) and filtered to obtain a product mainly composed of ammonium sulfate solid. The liquid is collected and returned to aqueous phase 3.

[0108] (3) Washing: The organic phase 1 is washed in two-stage countercurrent with a dilute ammonium oxalate solution having a concentration of 0.1 wt.% and a dilute ammonium sulfate solution having a concentration of 0.1 wt.% at a temperature of 30°C and an O / A ratio of 3:1 (volume ratio). The ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are recovered to obtain a regenerated extractant that can be recycled.

[0109] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0110] Example 2

[0111] like Figure 2 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0112] (1) Stripping: A mixed solution of ammonium oxalate and ammonium sulfate was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of ammonium sulfate was 10 wt.%, and the metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping. The temperature of each stripping stage was 60°C, and the ratio O / A was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0113] (2) Enrichment: The aqueous phase 1 is returned to prepare the stripping agent for stripping; the obtained aqueous phase is returned to the stripping agent for circulation until the total metal ion concentration in the aqueous phase is greater than 80 g / L, or the iron ion concentration is greater than 50 g / L, and the single stripping efficiency is less than 95%, and the circulation enrichment is stopped.

[0114] (3) Recovery of metal ions:

[0115] B1, after the aqueous phase 1 is circulated and enriched, crystallized and filtered, the oxalate is dissolved, ammonia is passed through, the pH is adjusted to 11, precipitation occurs, and solid-liquid separation is performed to obtain the hydroxide precipitate of iron, aluminum and magnesium and the aqueous phase 2;

[0116] B2. Aqueous phase 2 is collected and transferred to the dissolution step to dissolve the oxalate. The remaining portion is concentrated at 60-70°C to a density of 1.20-1.25 g / mL, then cooled to 20-30°C for crystallization for 24 hours. Filtering yields ammonium oxalate solid (purity ≥95%) and aqueous phase 4. The ammonium oxalate solid is returned to the stripping agent preparation step, and aqueous phase 4 is combined with aqueous phase 1 from the recycling enrichment step for further stripping and enrichment.

[0117] (4) Washing: The organic phase 1 is washed in two-stage countercurrent with a dilute ammonium oxalate solution having a concentration of 0.1 wt.% and a dilute ammonium sulfate solution having a concentration of 0.1 wt.% at a temperature of 30°C and an O / A ratio of 3:1 (volume ratio). The ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are recovered to obtain a regenerated extractant that can be recycled.

[0118] This embodiment eliminates the need for ammonia distillation and saves energy by using ammonia water directly to adjust pH, eliminating the ammonia distillation step and reducing energy consumption by 40%. Low-temperature precipitation: 25°C inhibits the decomposition of ammonium oxalate, resulting in a metal hydroxide purity greater than 99%. The entire process is closed-loop, with mother liquor fully recycled, and total reagent loss is less than 3%.

[0119] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0120] Example 3

[0121] like Figure 3 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0122] (1) Stripping: A mixed solution of ammonium oxalate and sulfuric acid was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of sulfuric acid was 3.5 wt.%. The metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping, the stripping temperature of each stage was 60°C, and the O / A ratio was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0123] (2) Enrichment: The aqueous phase 1 is returned to prepare the stripping agent for stripping; the obtained aqueous phase is returned to the stripping agent for circulation until the total metal ion concentration in the aqueous phase is greater than 80 g / L, or the iron ion concentration is greater than 50 g / L, and the single stripping efficiency is less than 95%, and the circulation enrichment is stopped.

[0124] (3) Recovery of metal ions:

[0125] After A1 and aqueous phase 1 are enriched, gaseous ammonia is introduced to adjust the pH to 11, precipitation occurs, and solid-liquid separation is performed to obtain iron, aluminum, and magnesium hydroxide precipitates and aqueous phase 2;

[0126] A2. Heat aqueous phase 2 to evaporate the ammonia therein to obtain aqueous phase 3. The collected ammonia is returned to step A1 as gaseous ammonia.

[0127] A3, aqueous phase 3 returns to step (1) for use in preparing a stripping agent.

[0128] (4) Washing: The organic phase 1 is washed in two-stage countercurrent with a dilute ammonium oxalate solution having a concentration of 0.1 wt.% and a dilute ammonium sulfate solution having a concentration of 0.1 wt.% at a temperature of 30°C and an O / A ratio of 3:1 (volume ratio). The ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are recovered to obtain a regenerated extractant that can be recycled.

[0129] This embodiment directly acidifies the stripping agent after ammonia distillation, eliminating the ammonium oxalate crystallization step and reducing energy consumption by 30%. Ammonia gas recycling: The ammonia gas evaporated from the heated aqueous phase is returned to the gaseous ammonia addition step, achieving ammonia recycling, reducing ammonia consumption and costs. Furthermore, the aqueous phase is collected and returned to the stripping agent addition step, allowing the stripping agent to be recycled and improving its efficiency.

[0130] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0131] Example 4

[0132] like Figure 4 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0133] (1) Stripping: A mixed solution of ammonium oxalate and sulfuric acid was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of sulfuric acid was 3.5 wt.%. The metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping, the stripping temperature of each stage was 60°C, and the O / A ratio was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0134] (2) Enrichment: The aqueous phase 1 is returned to prepare the stripping agent for stripping; the obtained aqueous phase is returned to the stripping agent for circulation until the total metal ion concentration in the aqueous phase is greater than 80 g / L, or the iron ion concentration is greater than 50 g / L, and the single stripping efficiency is less than 95%, and the circulation enrichment is stopped.

[0135] (3) Recovery of metal ions:

[0136] After A1 and aqueous phase 1 are enriched, gaseous ammonia is introduced to adjust the pH to 11, precipitation occurs, and solid-liquid separation is performed to obtain iron, aluminum, and magnesium hydroxide precipitates and aqueous phase 2;

[0137] A2. Heat aqueous phase 2 to evaporate the ammonia therein to obtain aqueous phase 3. The collected ammonia is returned to step A1 as gaseous ammonia.

[0138] A3, aqueous phase 3 is concentrated and crystallized (60-70°C) and filtered to obtain a product mainly composed of ammonium oxalate solid and aqueous phase 4. Aqueous phase 4 is returned to step (1) and used to prepare a stripping agent.

[0139] (4) Washing: The organic phase 1 is washed in two-stage countercurrent with a dilute ammonium oxalate solution having a concentration of 0.1 wt.% and a dilute ammonium sulfate solution having a concentration of 0.1 wt.% at a temperature of 30°C and an O / A ratio of 3:1 (volume ratio). The ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are recovered to obtain a regenerated extractant that can be recycled.

[0140] In this embodiment, the purity of ammonium oxalate is increased to 99.5% by fractional concentration of aqueous phase and low temperature crystallization. 2+ ) content is less than 0.1%. The aqueous phase is concentrated and crystallized to obtain ammonium oxalate solid, enabling the recycling of ammonium oxalate, increasing product variety and economic benefits. Throughout the entire process, from metal ion recovery and ammonia circulation to ammonium oxalate recovery, comprehensive resource utilization is highly achieved.

[0141] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0142] Example 5

[0143] like Figure 5 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0144] (1) Stripping: A mixed solution of ammonium oxalate and oxalic acid was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of oxalic acid was 3.5 wt.%, and the metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping. The stripping temperature of each stage was 60°C, and the O / A ratio was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0145] (2) Enrichment: The aqueous phase 1 is returned to prepare a stripping agent for stripping; the resulting aqueous phase is then returned to the stripping agent for circulation until the total metal ion concentration in the aqueous phase is greater than 80 g / L, or the iron ion concentration is greater than 50 g / L, thereby obtaining an aqueous phase 1 rich in metal ions;

[0146] (3) Recovery of metal ions:

[0147] After enrichment of C1 and aqueous phase 1, calcium oxalate and aqueous phase 2 are obtained by filtration, and part of aqueous phase 2 is returned to step (1) to prepare a stripping agent;

[0148] C2, aqueous phase 2 is cooled, crystallized and filtered to obtain aqueous phase 3 and oxalic acid complex solid. Aqueous phase 3 is returned to step C1 and filtered together with the enriched aqueous phase 1;

[0149] After the solid oxalic acid complex C3 dissolves and reacts, ammonia gas is introduced to adjust the pH to 11, precipitation occurs, and solid-liquid separation is performed to obtain a hydroxide precipitate of iron, aluminum, and magnesium and an aqueous phase 4;

[0150] C4, heating aqueous phase 4 to evaporate the ammonia therein to obtain aqueous phase 5, and the collected ammonia is returned to step C3 to be used as gaseous ammonia;

[0151] C5. Collect the aqueous phase 5, concentrate, crystallize and filter to obtain a product mainly composed of ammonium oxalate solid and an aqueous phase 6. Add ammonium oxalate to the aqueous phase 6 and return to step (1) to prepare a stripping agent, or return the aqueous phase 6 to step C3 to dissolve the oxalic acid complex solid.

[0152] (4) Washing: The organic phase 1 is washed in two-stage countercurrent with a dilute ammonium oxalate solution having a concentration of 0.1 wt.% and a dilute ammonium sulfate solution having a concentration of 0.1 wt.% at a temperature of 30°C and an O / A ratio of 3:1 (volume ratio). The ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are recovered to obtain a regenerated extractant that can be recycled.

[0153] In this embodiment, the calcium oxalate pre-filtration reduces subsequent precipitation entrainment, not only recovering metal ions such as iron, aluminum, and magnesium, but also obtaining substances such as calcium oxalate and ammonium oxalate through a series of operations, thereby achieving the recycling of multiple substances, enriching the product variety, and increasing the breadth of resource utilization. The recycling of ammonia and aqueous phase and the return of ammonium oxalate to the stripping agent link construct a complete circulation system.

[0154] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0155] Example 6

[0156] like Figure 6 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0157] (1) Stripping: Same as Example 5.

[0158] (2) Enrichment: Same as Example 5.

[0159] (3) Recovery of metal ions:

[0160] The same as Example 5, the only difference is step C5. In step C5 of this embodiment, the aqueous phase 5 returns to step C3 to dissolve the oxalic acid complex solid.

[0161] (4) Washing: Same as Example 5.

[0162] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0163] Example 7

[0164] like Figure 7 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0165] (1) Stripping: Same as Example 5.

[0166] (2) Enrichment: Same as Example 5.

[0167] (3) Recovery of metal ions:

[0168] The same as Example 5, the only difference is step C5. Step C5 of this embodiment is: collecting aqueous phase 5, cooling, crystallizing and filtering to obtain ammonium oxalate solid and aqueous phase 6, aqueous phase 6 returns to step C3 to dissolve the oxalic acid complex solid, the ammonium oxalate solid is acidified and crystallized to obtain oxalic acid, and returns to step (1) to prepare the stripping agent.

[0169] (4) Washing: Same as Example 5.

[0170] In this embodiment, ammonium oxalate is crystallized by cooling instead of concentrating, avoiding pyrolysis (ammonium oxalate loss <1%). Metal ions are recovered through a unique series of operations, including filtration, crystallization by cooling, and the addition of an oxalic acid complex solid. This innovative process effectively separates and recovers metal ions. The aqueous phase after the crystallization by cooling is returned to the ammonia-passing step, further improving material recycling and reducing waste.

[0171] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0172] Example 8

[0173] like Figure 8 As shown, a method for recovering metal cations from an extractant loaded with metal cations comprises the following steps:

[0174] (1) Stripping: A mixed solution of ammonium oxalate and oxalic acid was used as a stripping agent, wherein the concentration of ammonium oxalate was 4.5 wt.%, and the concentration of sulfuric acid was 3.5 wt.%, and the metal ion-loaded extractant was subjected to two-stage three-stage countercurrent stripping. The temperature of each stripping stage was 60°C, and the O / A ratio was 1:3 (volume ratio), to obtain aqueous phase 1 and organic phase 1.

[0175] (2) Enrichment: The aqueous phase 1 is returned to prepare a stripping agent for stripping; the resulting aqueous phase is then returned to the stripping agent for circulation until the total metal ion concentration in the aqueous phase is greater than 80 g / L, or the iron ion concentration is greater than 50 g / L, thereby obtaining an aqueous phase 1 rich in metal ions;

[0176] (3) Recovery of metal ions:

[0177] After A1 and aqueous phase 1 are enriched, gaseous ammonia is introduced to adjust the pH to 11, precipitation occurs, and solid-liquid separation is performed to obtain iron, aluminum, and magnesium hydroxide precipitates and aqueous phase 2;

[0178] A2. Heat aqueous phase 2 to evaporate the ammonia therein to obtain aqueous phase 3. The collected ammonia is returned to step A1 as gaseous ammonia.

[0179] A3, aqueous phase 3 is concentrated and crystallized (60-70°C) and filtered to obtain ammonium oxalate solid and aqueous phase 4. Aqueous phase 4 is returned to step (1) for use in preparing a stripping agent.

[0180] A4. Add sulfuric acid to the ammonium oxalate solid for acidification and crystallization, and filter to obtain oxalic acid solid (purity ≥98%) and acidified mother liquor. The acidified mother liquor is collected and returned to the subsequent step (5) for recycling as a stripping agent.

[0181] (4) Washing: The organic phase 1 is washed in two-stage countercurrent with a 3.5 wt.% dilute oxalic acid solution at 30°C and an O / A ratio of 3:1 (volume ratio) to obtain an organic phase 2 and an acid phase. The acid phase is returned and recycled as a dilute oxalic acid solution.

[0182] (5) Ammonium stripping: A mixed solution of ammonium oxalate, oxalic acid and sulfuric acid is used as stripping agent 1, wherein the ammonium oxalate concentration is 4.5 wt.%, the sulfuric acid concentration is 3.5 wt.%, and the oxalic acid concentration is 3.5 wt.%. The organic phase 2 is subjected to two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 60 ° C, and the phase O / A is 1:3 (volume ratio). The regenerated extractant is obtained and can be recycled. The obtained acid phase is returned to be used as stripping agent 1 for recycling.

[0183] In this embodiment, washing and stripping complement "rough cleaning" and "deep regeneration"—the former removes surface impurities, while the latter, through strong chemical reactions, strips away deeply complexed metal ions and restores the extractant's activity. This combination ensures: ① a metal ion recovery rate >99.9% (avoiding recycling losses); ② stable performance of the regenerated extractant (extraction rate <5% difference from fresh extractant); and ③ a fully closed-loop stripping agent cycle (100% acid phase reuse and no wastewater discharge), achieving the goal of "efficient recovery + green recycling."

[0184] This embodiment utilizes a double stripping process in series to completely regenerate the extractant (metal residue <0.005%), followed by acidification and crystallization to co-produce oxalic acid (purity >98%). The resulting product diversity includes ammonium oxalate solid and oxalic acid solid obtained from the aqueous phase through concentration, cooling, and crystallization, increasing product diversity and improving the economic efficiency of the process. The stripping agent's recycling design is more complex and sophisticated, with some returning to the stripping step and some used in the subsequent ammonium stripping phase separation step, thereby improving the stripping agent's efficiency.

[0185] This embodiment recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0186] Table 1 Stripping rate and recovery rate of metal ions in each embodiment and comparative example

[0187]

[0188]

[0189] The stripping rate is calculated as the ratio of the mass of the stripped material to the mass of the material previously extracted into the organic phase. The recovery rate is calculated as the ratio of the mass of the recovered target metal ion to the total mass of the metal ion in the original wet-process phosphoric acid extractant.

[0190] Energy consumption calculation

[0191] The main links involving energy consumption in the process of the present invention include:

[0192] Stripping heating: the heat consumption of heating the stripping agent to a specified temperature (such as 60°C).

[0193] Circulation enrichment: electricity consumption for circulating pumping of the aqueous phase.

[0194] Precipitation and ammonia evaporation: energy consumption for ammonia stirring and ammonia evaporation heating.

[0195] Concentration crystallization: heat consumption of evaporating solvent by concentrating the aqueous phase.

[0196] Washing and stripping equipment: power consumption of equipment such as agitators and centrifuges.

[0197] 1. Stripping heating energy consumption

[0198] Formula: Q stripping heating = m·c·ΔT

[0199] m: Mass of stripping agent (kg), calculated by volume (L) × density (about 1.05 kg / L, approximate value for dilute solution).

[0200] c: Specific heat capacity of the solution (approximately 4.2 kJ / (kg·℃), approximate value for dilute aqueous solution).

[0201] ΔT: Temperature change (e.g. heating from 25°C to 60°C, ΔT = 35°C).

[0202] Example (taking Example 1 as an example):

[0203] Stripping agent volume = 1000L (assuming), then:

[0204] Q=1000L×1.05kg / L×4.2kJ / (kg·℃)×35℃=154,350kJ

[0205] 2. Energy consumption of ammonia evaporation

[0206] Formula: Q ammonia vaporization = mH2O·ΔH vaporization

[0207] mH2O: The mass of evaporated water (kg), which can be estimated from the volume of the water phase and the evaporation amount.

[0208] ΔHvaporization: Heat of vaporization of water (about 2260 kJ / kg at 100°C).

[0209] Example:

[0210] The amount of water evaporated = 500kg, then: Q = 500kg × 2260kJ / kg = 1,130,000kJ

[0211] 3. Equipment power consumption

[0212] Formula: W = P·tP: Equipment power (kW), such as agitator power of 10kW and pump power of 5kW.

[0213] t: running time (hours).

[0214] Example:

[0215] Total equipment power = 15 kW, operating time = 10 hours, then: W = 15 kW × 10 h = 150 kWh = 540,000 kJ According to the above calculation method, the energy consumption reduction ratio of each embodiment and the purity of each product are calculated and shown in Table 2.

[0216] Table 2

[0217]

[0218] Among them, the traditional process refers to the process of CN119265410A and CN119503888A, and the specific steps are as follows:

[0219] (1) Single stripping: Use a single acid (such as sulfuric acid, hydrochloric acid) or use different stripping agents in stages (such as sulfuric acid first and then oxalic acid) to strip the metal ion-loaded extractant. The stripping stage is usually single or two stages, and the stripping temperature and phase ratio are roughly controlled (such as temperature 40-70 ° C, phase ratio O / A = 1:1-4).

[0220] (2) Direct precipitation: After stripping, the aqueous phase is directly passed through ammonia or a precipitant is added to adjust the pH to achieve metal ion precipitation. There is a lack of a cyclic enrichment process, and the metal ion concentration is low (usually <30 g / L).

[0221] (3) Non-closed-loop treatment: The mother liquor after precipitation is directly discharged or simply treated, and the stripping agent and ammonium salt are not recycled; the ammonia evaporation process consumes high energy and the ammonia gas is not recovered.

[0222] (4) Extractant regeneration: The organic phase is simply washed with water or diluted acid, and the residual metal ions and reagents are not completely removed. The metal residue in the regenerated extractant is high (>0.1%), and the extraction efficiency is significantly reduced.

[0223] Purity detection method:

[0224] Purity of hydroxide precipitate: The content of main components was determined by X-ray diffraction (XRD) and chemical titration.

[0225] Purity of ammonium oxalate / ammonium sulfate / oxalic acid: determined by high performance liquid chromatography (HPLC) or acid-base titration, and impurity content by atomic absorption spectroscopy (AAS).

[0226] Metal residues in regenerated extractant: detected by inductively coupled plasma mass spectrometry (ICP-MS).

[0227] Energy consumption comparison basis:

[0228] In traditional processes, ammonia distillation accounts for approximately 35% to 40% of total energy consumption. This invention significantly reduces energy consumption by reducing the number of stripping steps through cyclic enrichment, eliminating ammonia distillation (as in Example 2), and optimizing the crystallization process. For example, Example 2 eliminates the ammonia distillation step, directly reducing energy consumption by 40% compared to traditional processes.

[0229] It can be seen that the metal ion purity of the iron, aluminum and magnesium hydroxide precipitates of Examples 1 to 8 of the present invention is all greater than 99%. The low-temperature precipitation (25°C) in Example 2 can inhibit the decomposition of ammonium oxalate, further improving the purity of the precipitate. In Examples 1, 4, 5 and 6, the purity of the ammonium oxalate solid is ≥95%, among which the purity of Example 4 can reach 99.5% (determined by high-performance liquid chromatography or titration) through graded concentration and low-temperature crystallization. The purity of the oxalic acid solid obtained by acidification crystallization in Example 7 is ≥98% (determined by acidity titration and impurity content analysis).

[0230] Regenerated extractant performance

[0231] The extraction rates of the regenerated extractants of Examples 1 to 8 of the present invention differ by less than 5% from those of the new extractants, and the metal residues are less than 0.005% (determined by extraction efficiency test and atomic absorption spectroscopy), indicating that they have stable performance and can be recycled.

[0232] It can be seen that the process of the present invention has advantages in stripping rate (increased by 7-8%), recovery rate (increased by 12-13%) and energy consumption reduction (40%). At the same time, the product purity meets battery-grade standards (such as ammonium oxalate, oxalic acid, etc.), which meets the requirements of green chemistry and industrial applications.

Claims

1. A method for recovering metal cations from an extractant loaded with metal cations, characterized in that: The following steps are involved: a. Stripping: Stripping the metal cation-loaded extractant with a stripping agent to obtain an aqueous phase 1 and an organic phase 1; the acid is oxalic acid or sulfuric acid; the aqueous phase 1 is subjected to the following steps b and c, and the organic phase 1 is subjected to the following step d; The stripping agent is an ammonium oxalate solution, or a mixed solution of ammonium oxalate and an oxygen-containing acid / salt, wherein the oxygen-containing acid / salt is oxalic acid, sulfuric acid or a sulfate, and the sulfate is lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate or ammonium sulfate; b. Cyclic enrichment: specifically includes the following operations: 1) returning the aqueous phase 1 to prepare a stripping agent for stripping in step a; 2) Repeat step 1) until the iron ion concentration in the aqueous phase 1 is ≥50 g / L or the total metal ion concentration is ≥80 g / L, thereby obtaining an aqueous phase 1 rich in metal ions; c. Recovering metal ions: recovering metal ions from the aqueous phase 1 rich in metal ions; d. Washing: Using a stripping agent diluted 10 times or more as a washing agent, washing the organic phase 1, recovering the ammonium oxalate and / or ammonium sulfate entrained in the organic phase 1, and obtaining a wet-process phosphoric acid regeneration extractant.

2. The method for recovering metal cations from a metal cation-loaded extractant according to claim 1, wherein: In step a, the stripping agent is 1 wt.% to 14 wt.% ammonium oxalate solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 1 wt.% to 20 wt.% sulfuric acid solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 1 wt.% to 10 wt.% oxalic acid solution, or a mixed solution of 1 wt.% to 14 wt.% ammonium oxalate solution and 8 wt.% to 35 wt.% sulfate solution; Preferably, the stripping agent is a 3wt.% to 8wt.% ammonium oxalate solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and a 3.5wt.% to 10wt.% sulfuric acid solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and a 3.5wt.% to 5wt.% oxalic acid solution, or a mixed solution of a 3wt.% to 8wt.% ammonium oxalate solution and an 8wt.% to 20wt.% sulfate solution.

3. The method for recovering metal cations from a metal cation-loaded extractant according to claim 1, wherein: In step a, the stripping is a two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 25-80°C, and the volume ratio O / A is 1:1-5; preferably, the stripping temperature of each stage is 60°C, and the volume ratio O / A is 1:2-3.

4. The method for recovering metal cations from a metal cation-loaded extractant according to claim 1, wherein: In step c, metal ions are recovered from the metal ion-rich aqueous phase 1 using method A, method B or method C. The method A is: A1. Precipitation: Ammonia gas is passed through the metal ion-rich aqueous phase 1 to adjust the pH to 8-11, preferably to 11, to cause precipitation, and solid-liquid separation to obtain a hydroxide precipitate of iron, aluminum and magnesium and an aqueous phase 2; A2, ammonia evaporation: Heat aqueous phase 2 to evaporate the ammonia gas therein to obtain aqueous phase 3. The collected ammonia gas is returned to step A1 for use as gaseous ammonia; aqueous phase 3 is returned to step a for preparation of a stripping agent or aqueous phase 3 is subjected to step A3; A3, treatment of aqueous phase 3: aqueous phase 3 is concentrated, crystallized and filtered to obtain ammonium oxalate solid and aqueous phase 4; The aqueous phase 4 is concentrated, crystallized and filtered to obtain ammonium sulfate solid, and the mother liquor is returned to the aqueous phase 3; or the aqueous phase 4 is returned to step a for preparing a stripping agent; The method B is: B1. Precipitation: Crystallize and filter the metal ion-rich aqueous phase 1, dissolve the resulting oxalate, pass ammonia gas, adjust the pH to 8-11, preferably to 11, precipitate, separate the solid and liquid, and obtain the iron, aluminum and magnesium hydroxide precipitate and aqueous phase 2; B2, cooling crystallization: Aqueous phase 2 is concentrated, crystallized, and filtered to obtain ammonium oxalate solid. The crystallization mother liquor is returned to be combined with aqueous phase 1 from the recycling enrichment step; or aqueous phase 2 is collected and returned to step B1 for dissolving oxalate; The method C is: After C1 and aqueous phase 1 are enriched, calcium oxalate and aqueous phase 2 are obtained by filtration; aqueous phase 2 is returned to step a to prepare a stripping agent; or aqueous phase 2 is subjected to step C2; or part of aqueous phase 2 is returned to step a to prepare a stripping agent, and part of aqueous phase 2 is subjected to step C2; C2, aqueous phase 2 is cooled, crystallized and filtered to obtain aqueous phase 3 and oxalic acid complex, aqueous phase 3 is returned to step C1 and filtered together with the enriched aqueous phase 1; C3. After the oxalic acid complex is dissolved, ammonia gas is passed through to adjust the pH to 8-11, preferably to 11, and precipitation occurs. Solid-liquid separation is performed to obtain iron, aluminum and magnesium hydroxide precipitates and aqueous phase 4; C4, heating aqueous phase 4 to evaporate the ammonia therein to obtain aqueous phase 5, and the collected ammonia is returned to step C3 to be used as gaseous ammonia; C5, collecting aqueous phase 5, concentrating, crystallizing, and filtering to obtain ammonium oxalate solid and aqueous phase 6; adding ammonium oxalate to aqueous phase 6 and returning to step a for preparing a stripping agent, or returning aqueous phase 6 to step C3 for dissolving the oxalic acid complex; Alternatively, the aqueous phase 5 is collected, cooled, crystallized, and filtered to obtain crude ammonium oxalate and aqueous phase 6. The crude ammonium oxalate is acidified and crystallized to obtain oxalic acid, which is returned to step (1) to prepare a stripping agent. The aqueous phase 6 is returned to step C3 to dissolve the oxalic acid complex. Alternatively, the aqueous phase 5 is returned to step C3 to dissolve the oxalic acid complex.

5. The method for recovering metal cations from a metal cation-loaded extractant according to claim 1, wherein: The detergent in step d is the stripping agent in step a diluted 10 times.

6. The method for recovering metal cations from an extractant loaded with metal cations according to any one of claims 1 to 4, characterized in that: The step d is replaced by: d1. Washing: Washing the organic phase 1 with an oxalic acid solution to obtain an organic phase 2 and an acid phase, and returning the acid phase to the oxalic acid solution; e. Reverse extraction of ammonium phase separation: Use a mixed solution of ammonium oxalate, oxalic acid or sulfuric acid as a reverse extraction agent to reverse extract the organic phase 2 to obtain a wet-process phosphoric acid regeneration extractant.

7. The method for recovering metal cations from a metal cation-loaded extractant according to claim 6, wherein: In step d1, the concentration of the oxalic acid solution is 0.9 wt.% to 4.5 wt.%.

8. The method for recovering metal cations from a metal cation-loaded extractant according to claim 6, wherein: In step e, two-stage three-stage countercurrent stripping of the organic phase 2 is adopted, the stripping temperature of each stage is 30-80°C, and the volume ratio O / A is 1:2-4; preferably, the stripping temperature of each stage is 60°C, and the volume ratio O / A is 1:

3.

9. The method for recovering metal cations from a metal cation-loaded extractant according to claim 1, wherein: The metal cation-loaded extractant is the extractant obtained after extraction, washing and phase separation using dilute phosphoric acid during the wet-process phosphoric acid production process.

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