Method for recovering metal cations from wet-process phosphoric acid

Abstract

The invention relates to a method for recovering metal cations from wet-process phosphoric acid, 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 wet-process phosphoric acid. The method comprises the steps of extraction, washing 1, reverse extraction, metal ion recovery, washing 2 and the like. The specific reverse extraction method is adopted, the metal cations are recovered from the wet-process phosphoric acid, various metal ions can be effectively separated, the recovery rate of all metal elements is high, and the product value is high. And the associated metal elements in the wet-process phosphoric acid can be classified and recycled by adopting one stripping agent, the method is simple and low in cost, and the recycled associated metal elements can be effectively separated and utilized in a high-quality mode.

Description

Technical Field

[0001] The invention relates to a method for recovering metal cations from wet-process phosphoric acid, in particular to a method for recovering metal cations from wet-process phosphoric acid by using a stripping method in a solvent extraction process, and belongs to the technical field of wet-process phosphoric acid. Background Art

[0002] Wet-process phosphoric acid is an important intermediate product for the production of phosphate fertilizers such as diammonium phosphate, monoammonium phosphate, and triple superphosphate, and is also the raw material for food-grade phosphoric acid and industrial-grade phosphoric acid. However, in recent years, with the substantial development and utilization of phosphate rock resources, the quality of phosphate rock has been continuously depleted, resulting in an increase in metal cation impurities such as Fe, Al, Mg, and Ca in wet-process phosphoric acid, which has complicated the processing of subsequent products of wet-process phosphoric acid, and the quality of the products is difficult to meet the requirements of high-quality products, resulting in increased costs.

[0003] The common methods for removing metal cations from phosphoric acid are as follows: 1. Organic solvent extraction. 2. Chemical precipitation. 3. Ion exchange. 4. Membrane separation. The chemical precipitation method has low impurity removal efficiency, introduces alkaline ions to weaken the acidity of the acidic system, and is difficult to separate. The ion exchange method requires a large amount of resin and has high recycling costs. The method uses the difference in the pore size of the separation membrane to selectively pass impurities to achieve the purpose of separation and purification. The cost of this method is relatively high. The product obtained by the organic solvent extraction method has high purity, simple production process and equipment, low energy consumption, good separation effect, high recovery rate, and can be applied continuously.

[0004] Solvent extraction is the mainstream process for wet phosphoric acid purification. Both at home and abroad, a lot of work has been done on the removal of metal ions from phosphoric acid by organic solvent extraction. However, most of them require multiple steps of stripping, low metal ion recovery rate, and difficulty in classified recovery and high-value utilization. Therefore, it is of practical significance to explore the one-step extraction and classified recovery of metal ions from the extractant.

[0005] The invention patent application with application number 201610514424.9 discloses a combined extraction method for producing high-quality phosphoric acid, in which metal cations in crude phosphoric acid are extracted using extractants such as P204, and the raffinate, i.e., the aqueous phase, is used to prepare high-quality phosphoric acid. The extract phase contains a variety of metal cations, and strong acid back extraction is used. The obtained metal cations cannot be separated and can only be used to produce fertilizers or flame retardants. The product application value is not high, and the recovery rate of metal ions is not high. Summary of the invention

[0006] In view of the above defects, the technical problem solved by the present invention is to provide a method for recovering metal cations from wet-process phosphoric acid.

[0007] The method for recovering metal cations from wet-process phosphoric acid of the present invention comprises the following steps:

[0008] (1) Extraction: Extraction of wet-process phosphoric acid, the resulting organic phase is the extractant loaded with metal ions, and the aqueous phase is the purified phosphoric acid;

[0009] (2) Washing 1: washing the metal ion-loaded extractant with dilute phosphoric acid to obtain a washed extractant;

[0010] (3) stripping: using an ammonium oxalate solution or a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent to strip the washed extractant to obtain an aqueous phase 1 and an organic phase 1;

[0011] (4) recovering metal ions: recovering metal ions from the aqueous phase 1;

[0012] (5) Washing 2: Washing the organic phase 1, recovering the ammonium oxalate and ammonium sulfate entrained in the organic phase 1, and obtaining a regenerated extractant, which is returned to step (1) and recycled as an extractant for extracting wet-process phosphoric acid.

[0013] In one embodiment of the present invention, in step (4), metal ions are recovered by method 1, method 2, method 3, or method 4, wherein:

[0014] Method 1 includes the following steps:

[0015] a. Cooling crystallization: Cooling the aqueous phase 1 for crystallization, solid-liquid separation to obtain a mixed sulfate salt of iron, aluminum and magnesium and an aqueous phase 2;

[0016] Method 2 includes the following steps:

[0017] a Cooling crystallization 1: Cooling the aqueous phase 1 for crystallization, and solid-liquid separation to obtain ammonium magnesium sulfate crystals and aqueous phase 2;

[0018] b. Cooling crystallization 2: Cooling the aqueous phase 2 to crystallize, and solid-liquid separation to obtain ammonium aluminum sulfate crystals and aqueous phase 3;

[0019] c. Cooling and crystallizing 3: Cooling the aqueous phase 3 and crystallizing it, and separating the solid and liquid to obtain ammonium ferric sulfate crystals and the aqueous phase 4;

[0020] Method 3 includes the following steps:

[0021] a. Precipitation: pass gaseous ammonia into aqueous phase 1 to adjust the pH, precipitate, separate the solid and liquid, and obtain iron, aluminum and magnesium hydroxide precipitate and aqueous phase 2;

[0022] b. Ammonia evaporation: heating the aqueous phase 2 to evaporate the ammonia gas therein, and returning the collected ammonia gas to step Ⅰ, and returning the aqueous phase 3 as a stripping agent;

[0023] Method 4 includes the following steps:

[0024] a. Precipitation 1: Add ammonia water to aqueous phase 1, adjust the pH, a red precipitate appears, and separate the solid and liquid to obtain Fe(OH)3 precipitate and aqueous phase 2;

[0025] b. Precipitation 2: Add ammonia water dropwise to aqueous phase 2 to adjust the pH, a white precipitate appears, and the solid-liquid separation is performed to obtain Al(OH)3 precipitate and aqueous phase 3;

[0026] c. Precipitation 3: Add aqueous phase 3 dropwise into ammonia water, adjust the pH, a white precipitate appears, and separate the solid and liquid to obtain Mg(OH)2 precipitate and aqueous phase 3.

[0027] In one embodiment of the present invention, in step (1), the extraction is a three-stage countercurrent extraction, the number of stages is 1 to 5. Preferably, the number of stages is 3, the extraction temperature of each stage is 25 to 85°C, and the volume ratio O / A is 1 to 10:1.

[0028] In one embodiment of the present invention, in step (2), two-stage countercurrent washing is performed using dilute phosphoric acid, the concentration of the dilute phosphoric acid is 1 wt.% to 8 wt.% in terms of P2O5, the temperature is 25 to 85°C, and the volume ratio of O / A is 1 to 10:1.

[0029] In one embodiment of the present invention, in step (3), the stripping is a three-stage countercurrent stripping, the number of stages being 1 to 5. In a preferred embodiment, the number of stages of stripping is 3, the stripping temperature of each stage is 25 to 90°C, and the volume ratio O / A is 1 to 10:1.

[0030] In one embodiment of the present invention, in the stripping agent of step (3), the concentration of ammonium oxalate is 1 wt.% to 20 wt.%, and the concentration of ammonium sulfate is 0 wt.% to 35 wt.%.

[0031] Preferably, in method 1 of step (4), the crystallization temperature is -10 to 50°C; in method 2 of step (4), the crystallization temperature of ammonium magnesium sulfate is 20 to 50°C; the crystallization temperature of ammonium aluminum sulfate is 1 to 15°C; and the crystallization temperature of ammonium ferric sulfate is -10 to 0°C.

[0032] Preferably, in method 3 of step (4), in step a, the pH is adjusted to 3.3-12.4; in step b, the temperature of ammonia evaporation is -10-0°C; in method 4 of step (4), in step a, the pH is adjusted to 3.3-3.8, in step b, the pH is adjusted to 4-5, and in step c, the pH is adjusted to 9-12.4.

[0033] In one embodiment of the present invention, in step (5), the organic phase 1 is washed in two-stage countercurrent with dilute ammonium oxalate and dilute ammonium sulfate, the concentration of dilute ammonium oxalate is 0.1wt.% to 5wt.%, the concentration of dilute ammonium sulfate is 0.1wt.% to 5wt.%, the temperature is 30 to 70°C, and the volume ratio O / A is 1 to 10:1.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention adopts a specific stripping method to recover metal cations from wet-process phosphoric acid, various metal ions can be effectively separated, the recovery rate of each metal element is high, and the product value is high.

[0036] 2. The present invention adopts a stripping agent to classify and recover the associated metal elements in wet-process phosphoric acid. The method is simple and low in cost, and the recovered associated metal elements can be effectively separated and utilized in high quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a process flow chart of the method for recovering metal cations from wet-process phosphoric acid in Example 1 of the present invention.

[0038] Figure 2 This is a process flow chart of the method for recovering metal cations from wet-process phosphoric acid in Examples 2 to 4 and 9 of the present invention.

[0039] Figure 3 This is a process flow chart of the method for recovering metal cations from wet-process phosphoric acid in Example 5 of the present invention.

[0040] Figure 4 This is a process flow chart of the method for recovering metal cations from wet-process phosphoric acid in Examples 6 to 8 of the present invention. DETAILED DESCRIPTION

[0041] The method for recovering metal cations from wet-process phosphoric acid of the present invention comprises the following steps:

[0042] (1) Extraction: Extraction of wet-process phosphoric acid, the resulting organic phase is the extractant loaded with metal ions, and the aqueous phase is the purified phosphoric acid;

[0043] (2) Washing 1: washing the metal ion-loaded extractant with dilute phosphoric acid to obtain a washed extractant;

[0044] (3) stripping: using an ammonium oxalate solution or a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent to strip the washed extractant to obtain an aqueous phase 1 and an organic phase 1;

[0045] (4) recovering metal ions: recovering metal ions from the aqueous phase 1;

[0046] (5) Washing 2: Washing the organic phase 1, recovering the ammonium oxalate and ammonium sulfate entrained in the organic phase 1, and obtaining a regenerated extractant, which is returned to step (1) and recycled as an extractant for extracting wet-process phosphoric acid.

[0047] In one embodiment of the present invention, in step (4), metal ions are recovered by method 1, method 2, method 3, or method 4, wherein:

[0048] Method 1 includes the following steps:

[0049] a. Cooling crystallization: Cooling the aqueous phase 1 for crystallization, solid-liquid separation to obtain a mixed sulfate salt of iron, aluminum and magnesium and an aqueous phase 2;

[0050] Method 2 includes the following steps:

[0051] a Cooling crystallization 1: Cooling the aqueous phase 1 for crystallization, and solid-liquid separation to obtain ammonium magnesium sulfate crystals and aqueous phase 2;

[0052] b. Cooling crystallization 2: Cooling the aqueous phase 2 to crystallize, and solid-liquid separation to obtain ammonium aluminum sulfate crystals and aqueous phase 3;

[0053] c. Cooling and crystallizing 3: Cooling the aqueous phase 3 and crystallizing it, and separating the solid and liquid to obtain ammonium ferric sulfate crystals and the aqueous phase 4;

[0054] Method 3 includes the following steps:

[0055] a. Precipitation: pass gaseous ammonia into aqueous phase 1 to adjust the pH, precipitate, separate the solid and liquid, and obtain iron, aluminum and magnesium hydroxide precipitate and aqueous phase 2;

[0056] b. Ammonia evaporation: heating the aqueous phase 2 to evaporate the ammonia gas therein, and returning the collected ammonia gas to step Ⅰ, and returning the aqueous phase 3 as a stripping agent;

[0057] Method 4 includes the following steps:

[0058] a. Precipitation 1: Add ammonia water to aqueous phase 1, adjust the pH, a red precipitate appears, and separate the solid and liquid to obtain Fe(OH)3 precipitate and aqueous phase 2;

[0059] b. Precipitation 2: Add ammonia water dropwise to aqueous phase 2 to adjust the pH, a white precipitate appears, and the solid-liquid separation is performed to obtain Al(OH)3 precipitate and aqueous phase 3;

[0060] c. Precipitation 3: Add aqueous phase 3 dropwise into ammonia water, adjust the pH, a white precipitate appears, and separate the solid and liquid to obtain Mg(OH)2 precipitate and aqueous phase 3.

[0061] Step (1) is an extraction process, and conventional methods for extracting metal impurities in wet-process phosphoric acid in the art are applicable to the present invention. In one embodiment of the present invention, the extraction is a multi-stage countercurrent extraction, the number of stages is 1 to 5; preferably the number of stages is 3, and each stage has three stages.

[0062] In a specific embodiment, the extraction temperature of each stage is 25-85° C., and the volume ratio O / A is 1-10:1.

[0063] The extractant for extracting metal cations can be commonly used in the art, including but not limited to at least one of P204 (chemical name di(2-ethylhexyl) phosphate), P507 (chemical name 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester), Cynex272 (chemical name di(2,4,4-trimethylpentyl) hypophosphorous acid), DNNSA (chemical name dinonylnaphthalenesulfonic acid), cycloalkane acid and tertiary carbonic acid.

[0064] Step (2) is washing 1, using dilute phosphoric acid to wash the extractant loaded with metal ions and recover the phosphoric acid entrained in the extractant.

[0065] In one embodiment of the present invention, in step (2), two-stage countercurrent washing is performed using dilute phosphoric acid, the concentration of the dilute phosphoric acid is 1 wt.% to 8 wt.% in terms of P2O5, the temperature is 25 to 85°C, and the volume ratio of O / A is 1 to 10:1.

[0066] Step (3) is stripping, which strips out various metal ions from the extractant loaded with metal ions, thereby realizing the separate recovery of metal ions and improving the product value.

[0067] Step (3) using an ammonium oxalate solution or a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent to strip the washed extractant to obtain a stripping solution 1 and an organic phase 1;

[0068] In one embodiment of the present invention, in step (3), the stripping is a three-stage countercurrent stripping, the number of stages being 1 to 5. In a preferred embodiment, the number of stages of stripping is 3, the stripping temperature of each stage is 25 to 90°C, and the volume ratio O / A is 1 to 10:1.

[0069] In one embodiment of the present invention, in the stripping agent, the concentration of ammonium oxalate is 1 wt.% to 20 wt.%, and the concentration of ammonium sulfate is 0 wt.% to 35 wt.%.

[0070] Step (4) is to recover various metal ions from the aqueous phase 1, preferably using method 1 or method 2 or method 3 or method 4.

[0071] In a specific embodiment, method 1 is used to recover metal ions, and the method 1 comprises the following steps:

[0072] a. Cooling crystallization: Cooling the aqueous phase 1 for crystallization, solid-liquid separation to obtain a mixed sulfate salt of iron, aluminum and magnesium and an aqueous phase 2;

[0073] Preferably, in method 1, the crystallization temperature is -10 to 50°C.

[0074] In another specific embodiment, method 2 is used to recover metal ions, and the method 2 comprises the following steps:

[0075] a Cooling crystallization 1: Cooling the aqueous phase 1 for crystallization, and solid-liquid separation to obtain ammonium magnesium sulfate crystals and aqueous phase 2;

[0076] b. Cooling crystallization 2: Cooling the aqueous phase 2 to crystallize, and solid-liquid separation to obtain ammonium aluminum sulfate crystals and aqueous phase 3;

[0077] c. Cooling and crystallizing 3: Cooling the aqueous phase 3 and crystallizing it, and separating the solid and liquid to obtain ammonium ferric sulfate crystals and the aqueous phase 4;

[0078] Preferably, in method 2, the crystallization temperature of ammonium magnesium sulfate is 20 to 50°C; the crystallization temperature of ammonium aluminum sulfate is 1 to 15°C; and the crystallization temperature of ammonium ferric sulfate is -10 to 0°C.

[0079] The solid-liquid separation in methods 1 and 2 can be carried out by conventional separation methods in the art, and only the purpose of separating the crystals from the aqueous phase needs to be achieved. For example, methods such as filtration can be used.

[0080] In another specific embodiment, method 3 is used to recover metal ions, and the method 3 comprises the following steps:

[0081] a. Precipitation: pass gaseous ammonia into aqueous phase 1 to adjust the pH, precipitate, separate the solid and liquid, and obtain iron, aluminum and magnesium hydroxide precipitate and aqueous phase 2;

[0082] b. Ammonia evaporation: heating the aqueous phase 2 to evaporate the ammonia gas therein, and returning the collected ammonia gas to step Ⅰ, and returning the aqueous phase 3 as a stripping agent;

[0083] Preferably, in step a of method 3, the pH is adjusted to 3.3 to 12.4; in step b, the temperature of ammonia evaporation is -10 to 0°C.

[0084] In another specific embodiment, method 4 is used to recover metal ions, and the method 4 comprises the following steps:

[0085] a. Precipitation 1: Add ammonia water to aqueous phase 1, adjust the pH, a red precipitate appears, and separate the solid and liquid to obtain Fe(OH)3 precipitate and aqueous phase 2;

[0086] b. Precipitation 2: Add ammonia water dropwise to aqueous phase 2 to adjust the pH, a white precipitate appears, and the solid-liquid separation is performed to obtain Al(OH)3 precipitate and aqueous phase 3;

[0087] c. Precipitation 3: Add aqueous phase 3 dropwise into ammonia water, adjust the pH, a white precipitate appears, and separate the solid and liquid to obtain Mg(OH)2 precipitate and aqueous phase 3.

[0088] Preferably, in step a of method 4, the pH is adjusted to 3.3-3.8; in step b, the pH is adjusted to 4-5; and in step c, the pH is adjusted to 9-12.4.

[0089] The solid-liquid separation described in the present invention adopts conventional methods in the art. In a specific embodiment, the solid-liquid separation uses a high-speed centrifuge with a rotation speed of 5000 to 8000 rpm for 15 to 30 min.

[0090] Step (5) is washing 2, in which ammonium oxalate and ammonium sulfate entrained in the organic phase 1 are washed and recovered to obtain a regenerated extractant, which is returned to step (1) and recycled as an extractant.

[0091] In one embodiment of the present invention, the organic phase 1 is washed in two-stage countercurrent with dilute ammonium oxalate and dilute ammonium sulfate solutions, the concentration of dilute ammonium oxalate is 0.1wt.% to 5wt.%, the concentration of dilute ammonium sulfate is 0.1wt.% to 5wt.%, the temperature is 30 to 70°C, and the volume ratio O / A is 1 to 10:1.

[0092] The specific implementation modes of the present invention are further described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0093] Example 1

[0094] like Figure 1 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0095] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0096] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0097] (3) Stripping: using a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent, wherein the concentration of ammonium oxalate is 4.5 wt.%, and the concentration of ammonium sulfate is 35 wt.%, and the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping, the temperature of each stripping stage is 60°C, and the ratio of O / A is 1:3 (volume ratio), to obtain an aqueous phase 1 and an organic phase 1.

[0098] (4) Recovery of metal ions: Cooling the aqueous phase 1 to 0°C to obtain a mixed salt of iron, aluminum and magnesium sulfate and the aqueous phase 2. This step simultaneously recovers magnesium, aluminum and iron ions.

[0099] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

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

[0101] Example 2

[0102] like Figure 2 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0103] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0104] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0105] (3) Stripping: using a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent, wherein the concentration of ammonium oxalate is 4.5 wt.%, and the concentration of ammonium sulfate is 35 wt.%, and the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping, the temperature of each stripping stage is 60°C, and the ratio of O / A is 1:3 (volume ratio), to obtain an aqueous phase 1 and an organic phase 1.

[0106] (4) Recovering metal ions: Cooling aqueous phase 1 to 20°C to obtain ammonium magnesium sulfate and aqueous phase 2; cooling aqueous phase 2 to 0°C to obtain ammonium aluminum sulfate and aqueous phase 3; cooling aqueous phase 3 to -10°C to obtain ammonium ferric sulfate; this step recovers magnesium, aluminum, and iron ions separately.

[0107] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0108] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0109] Comparative Example 1

[0110] A method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0111] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0112] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0113] (3) Stripping: Using a 35 wt.% ammonium sulfate solution as a stripping agent, the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping. The stripping temperature of each stage is 60° C., and the O / A ratio is 1:3 (volume ratio), to obtain an aqueous phase 1 and an organic phase 1.

[0114] (4) Recovering metal ions: Cooling aqueous phase 1 to 20°C to obtain ammonium magnesium sulfate and aqueous phase 2; cooling aqueous phase 2 to 0°C to obtain ammonium aluminum sulfate and aqueous phase 3; cooling aqueous phase 3 to -10°C to obtain ammonium iron sulfate; this step recovers magnesium, aluminum, and iron ions separately;

[0115] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0116] This comparative example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0117] Example 3

[0118] like Figure 2 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0119] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0120] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0121] (3) Stripping: using a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent, wherein the concentration of ammonium oxalate is 4.5 wt.%, and the concentration of ammonium sulfate is 25 wt.%, and the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping, the temperature of each stripping stage is 60°C, and the ratio O / A is 1:3 (volume ratio), to obtain an aqueous phase 1 and an organic phase 1.

[0122] (4) Recovering metal ions: Cooling aqueous phase 1 to 30°C to obtain ammonium magnesium sulfate and aqueous phase 2; cooling aqueous phase 2 to 5°C to obtain ammonium aluminum sulfate and aqueous phase 3; cooling aqueous phase 3 to -7°C to obtain ammonium ferric sulfate; this step recovers magnesium, aluminum, and iron ions separately.

[0123] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0124] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0125] Example 4

[0126] like Figure 2 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0127] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0128] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0129] (3) Stripping: using a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent, wherein the concentration of ammonium oxalate is 4.5 wt.%, and the concentration of ammonium sulfate is 15 wt.%, and the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping, the temperature of each stripping stage is 60°C, and the ratio of O / A is 1:3 (volume ratio), to obtain an aqueous phase 1 and an organic phase 1.

[0130] (4) Recovering metal ions: Cooling aqueous phase 1 to 40°C to obtain ammonium magnesium sulfate and aqueous phase 2; cooling aqueous phase 2 to 10°C to obtain ammonium aluminum sulfate and aqueous phase 3; cooling aqueous phase 3 to -5°C to obtain ammonium ferric sulfate; this step recovers magnesium, aluminum, and iron ions separately.

[0131] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0132] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0133] Example 5

[0134] like Figure 3 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0135] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0136] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0137] (3) Stripping: using ammonium oxalate solution as stripping agent, wherein the concentration of ammonium oxalate is 4.5 wt.%, and subjecting the metal ion-loaded extractant to two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 60°C, the ratio of O / A is 1:3 (volume ratio), and an aqueous phase 1 and an organic phase 1 are obtained.

[0138] (4) Recovering metal ions: passing gaseous ammonia into aqueous phase 1, adjusting the pH to 11, causing precipitation, and solid-liquid separation to obtain iron, aluminum and magnesium hydroxide precipitates and aqueous phase 2; heating aqueous phase 2 to evaporate the ammonia therein, and the collected ammonia is returned to step a.

[0139] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0140] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0141] Example 6

[0142] like Figure 4 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0143] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0144] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0145] (3) Stripping: using ammonium oxalate solution as stripping agent, wherein the concentration of ammonium oxalate is 4.5 wt.%, and subjecting the metal ion-loaded extractant to two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 60°C, the ratio of O / A is 1:3 (volume ratio), and an aqueous phase 1 and an organic phase 1 are obtained.

[0146] (4) Recovering metal ions: adding ammonia water to the aqueous phase 1 and adjusting the pH to 3.7, a red precipitate appears, and solid-liquid separation is performed to obtain Fe(OH)3 precipitate and aqueous phase 2; adding ammonia water to the aqueous phase 2 and adjusting the pH to 5, a white precipitate appears, and solid-liquid separation is performed to obtain Al(OH)3 precipitate and aqueous phase 3; adding ammonia water to the aqueous phase 3 and adjusting the pH to 12.4, a white precipitate appears, and solid-liquid separation is performed to obtain Mg(OH)2 precipitate and aqueous phase 3;

[0147] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0148] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0149] Example 7

[0150] like Figure 1 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0151] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0152] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0153] (3) Stripping: using a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent, wherein the concentration of ammonium oxalate is 8.0 wt.%, and subjecting the metal ion-loaded extractant to two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 60°C, the ratio of O / A is 1:3 (volume ratio), and an aqueous phase 1 and an organic phase 1 are obtained.

[0154] (4) Recovering metal ions: adding ammonia water to the aqueous phase 1 and adjusting the pH to 3.5, a red precipitate appears, and solid-liquid separation is performed to obtain Fe(OH)3 precipitate and aqueous phase 2; adding ammonia water to the aqueous phase 2 and adjusting the pH to 4.7, a white precipitate appears, and solid-liquid separation is performed to obtain Al(OH)3 precipitate and aqueous phase 3; adding ammonia water to the aqueous phase 3 and adjusting the pH to 10, a white precipitate appears, and solid-liquid separation is performed to obtain Mg(OH)2 precipitate and aqueous phase 3;

[0155] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0156] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0157] Example 8

[0158] like Figure 1 As shown, a method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0159] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0160] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0161] (3) Stripping: using ammonium oxalate solution as stripping agent, wherein the concentration of ammonium oxalate is 12.0 wt.%, the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping, the stripping temperature of each stage is 60°C, the ratio of O / A is 1:3 (volume ratio), and aqueous phase 1 and organic phase 1 are obtained.

[0162] (4) Recovering metal ions: adding ammonia water to the aqueous phase 1 and adjusting the pH to 3.3, a red precipitate appears, and solid-liquid separation is performed to obtain Fe(OH)3 precipitate and aqueous phase 2; adding ammonia water to the aqueous phase 2 and adjusting the pH to 4, a white precipitate appears, and solid-liquid separation is performed to obtain Al(OH)3 precipitate and aqueous phase 3; adding ammonia water to the aqueous phase 3 and adjusting the pH to 9, a white precipitate appears, and solid-liquid separation is performed to obtain Mg(OH)2 precipitate and aqueous phase 3;

[0163] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0164] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0165] Example 9

[0166] A method for recovering metal cations from wet-process phosphoric acid comprises the following steps:

[0167] (1) Extraction: The wet-process phosphoric acid was subjected to three-stage three-stage countercurrent extraction. The extraction temperature of each stage was 60° C. and the O / A ratio was 4:1 (volume ratio).

[0168] (2) Washing 1: The metal ion-loaded extractant is first subjected to two-stage countercurrent washing with dilute phosphoric acid having a concentration of 1 wt.% P2O5 at a temperature of 50°C and an O / A ratio of 3:1 (volume ratio) to recover the phosphoric acid entrained in the extractant and improve the yield of P2O5 in the phosphoric acid purification process.

[0169] (3) Stripping: Using a 4.5 wt.% ammonium oxalate solution as a stripping agent, the metal ion-loaded extractant is subjected to two-stage three-stage countercurrent stripping. The stripping temperature of each stage is 60° C., and the O / A ratio is 1:3 (volume ratio), to obtain an aqueous phase 1 and an organic phase 1.

[0170] (4) Recovering metal ions: Cooling aqueous phase 1 to 20°C to obtain ammonium magnesium sulfate and aqueous phase 2; cooling aqueous phase 2 to 0°C to obtain ammonium aluminum sulfate and aqueous phase 3; cooling aqueous phase 3 to -10°C to obtain ammonium iron sulfate; this step recovers magnesium, aluminum, and iron ions separately;

[0171] (5) Washing 2: Using a 0.1 wt.% dilute ammonium oxalate solution and a 0.1 wt.% dilute ammonium sulfate solution, the organic phase 1 is washed in two-stage countercurrent at a temperature of 30° C. and a phase 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, which can be recycled.

[0172] This example recovers metal cations, and its stripping rate and recovery rate are shown in Table 1.

[0173] Table 1 Stripping rate and recovery rate of metal ions in each embodiment and comparative example

[0174]

[0175]

[0176] In the above table, the stripping rate is calculated as: the ratio of the mass of the substance stripped out to the mass of the substance previously extracted into the organic phase. The recovery rate is calculated as: the ratio of the mass of the substance recovered after extraction and stripping to the mass of the substance in the previous raw material.

[0177] It can be seen that in step (3), using ammonium oxalate and ammonium sulfate as stripping agents can improve the stripping rate and recovery rate of metal ions, which are higher than those of the embodiment in which only ammonium oxalate is used as the stripping agent. However, as the concentration of ammonium oxalate increases, the stripping rate also gradually increases. In comparative example 1 in which only ammonium sulfate is used as the stripping agent, iron ions are basically not stripped out. When ammonium oxalate and ammonium sulfate are used as stripping agents, the stripping rate of metal ions is significantly improved, and increases with the increase in the amount of ammonium sulfate added.

Claims

1. A method for recovering metal cations from wet-process phosphoric acid, characterized in that: The following steps are involved: (1) Extraction: Extraction of wet-process phosphoric acid, the resulting organic phase is the extractant loaded with metal ions, and the aqueous phase is the purified phosphoric acid; (2) Washing 1: washing the metal ion-loaded extractant with dilute phosphoric acid to obtain a washed extractant; (3) stripping: using an ammonium oxalate solution or a mixed solution of ammonium oxalate and ammonium sulfate as a stripping agent to strip the washed extractant to obtain an aqueous phase 1 and an organic phase 1; (4) recovering metal ions: recovering metal ions from the aqueous phase 1; (5) Washing 2: Washing the organic phase 1, recovering the ammonium oxalate and ammonium sulfate entrained in the organic phase 1, and obtaining a regenerated extractant, which is returned to step (1) and recycled as an extractant for extracting wet-process phosphoric acid.

2. The method for recovering metal cations from wet-process phosphoric acid according to claim 1, characterized in that: In step (4), metal ions are recovered by method 1, method 2, method 3, or method 4, wherein: Method 1 includes the following steps: a. Cooling and crystallizing: Cooling and crystallizing the aqueous phase 1, and separating the solid and liquid to obtain a mixed sulfate salt of iron, aluminum and magnesium and the aqueous phase 2; Method 2 includes the following steps: a Cooling crystallization 1: Cooling the aqueous phase 1 for crystallization, and solid-liquid separation to obtain ammonium magnesium sulfate crystals and aqueous phase 2; b. Cooling crystallization 2: Cooling the aqueous phase 2 to crystallize, and solid-liquid separation to obtain ammonium aluminum sulfate crystals and aqueous phase 3; c. Cooling and crystallizing 3: Cooling the aqueous phase 3 and crystallizing it, and separating the solid and liquid to obtain ammonium ferric sulfate crystals and the aqueous phase 4; Method 3 includes the following steps: a. Precipitation: pass gaseous ammonia into aqueous phase 1 to adjust the pH, precipitate, separate the solid and liquid, and obtain iron, aluminum and magnesium hydroxide precipitate and aqueous phase 2; b. Ammonia evaporation: heating the aqueous phase 2 to evaporate the ammonia gas therein, and returning the collected ammonia gas to step a, and returning the aqueous phase 3 as a stripping agent; Method 4 includes the following steps: a. Precipitation 1: Add ammonia water dropwise to aqueous phase 1 to adjust the pH, a red precipitate appears, and solid-liquid separation is performed to obtain Fe(OH)3 precipitate and aqueous phase 2; b. Precipitation 2: Add ammonia water dropwise to aqueous phase 2 to adjust the pH, a white precipitate appears, and the solid-liquid is separated to obtain Al(OH)3 precipitate and aqueous phase 3; c. Precipitation 3: Add aqueous phase 3 dropwise into ammonia water, adjust the pH, a white precipitate appears, and separate the solid and liquid to obtain Mg(OH)2 precipitate and aqueous phase 3.

3. The method for recovering metal cations from wet-process phosphoric acid according to claim 1, characterized in that: In step (1), the extraction is a three-stage countercurrent extraction with 1 to 5 stages; preferably 3 stages, the extraction temperature of each stage is 25 to 85° C., and the volume ratio O / A is 1 to 10:

1.

4. The method for recovering metal cations from wet-process phosphoric acid according to claim 1, characterized in that: In step (2), two-stage countercurrent washing is performed using dilute phosphoric acid, the concentration of which is 1 wt.% to 8 wt.% in terms of P2O5, the temperature is 25 to 85°C, and the volume ratio of O / A is 1 to 10:

1.

5. The method for recovering metal cations from wet-process phosphoric acid according to claim 1, characterized in that: In step (3), the stripping is a three-stage countercurrent stripping with several stages, the number of stages is 1 to 5; preferably the number of stages is 3, the stripping temperature of each stage is 25 to 90° C., and the volume ratio O / A is 1 to 10:

1.

6. The method for recovering metal cations from wet-process phosphoric acid according to claim 1, characterized in that: In step (3), in the stripping agent, the concentration of ammonium oxalate is 1 wt.% to 20 wt.%, and the concentration of ammonium sulfate is 0 wt.% to 35 wt.%.

7. The method for recovering metal cations from wet-process phosphoric acid according to claim 2, characterized in that: In method 1 of step (4), the crystallization temperature is -10 to 50°C; in method 2 of step (4), the crystallization temperature of ammonium magnesium sulfate is 20 to 50°C, the crystallization temperature of ammonium aluminum sulfate is 1 to 15°C, and the crystallization temperature of ammonium ferric sulfate is -10 to 0°C.

8. The method for recovering metal cations from wet-process phosphoric acid according to claim 2, characterized in that: In method 3 of step (4), in step a, the pH is adjusted to 3.3-12.4; in step b, the temperature of ammonia evaporation is -10-0°C; in method 4 of step (4), in step a, the pH is adjusted to 3.3-3.8, in step b, the pH is adjusted to 4-5, and in step c, the pH is adjusted to 9-12.

4.

9. A method for recovering metal cations from wet-process phosphoric acid according to claim 1, characterized in that: In step (5), the organic phase 1 is washed in two-stage countercurrent with dilute ammonium oxalate and dilute ammonium sulfate, the concentration of dilute ammonium oxalate is 0.1wt.% to 5wt.%, the concentration of dilute ammonium sulfate is 0.1wt.% to 5wt.%, the temperature is 30 to 70°C, and the volume ratio O / A is 1 to 10:1.

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