Method for removing phosphorus from cobalt sulfate solution

Abstract

The invention provides a method for removing phosphorus from a cobalt sulfate solution. The method comprises the following steps: providing a cobaltous sulfate solution to be treated; the method comprises the following steps: mixing a to-be-treated cobaltous sulfate solution, a composite polymer soluble ferric salt and a coagulant aid, carrying out precipitation reaction, and separating to obtain phosphorus-containing slag and cobaltous sulfate primary purified liquid; a deep phosphorus removal adsorbent is adopted to adsorb trace phosphorus in the cobalt sulfate primary purification liquid, then trace iron in the cobalt sulfate primary purification liquid generates precipitates in an oxygen-containing atmosphere, and after separation, a cobalt sulfate secondary purification liquid is obtained. According to the method, firstly, the synergistic effect of the composite polymer soluble ferric salt and the coagulant aid is adopted, and primary efficient removal of phosphorus is achieved; then, a deep phosphorus removal adsorbent is used for directionally adsorbing trace phosphorus in the cobalt sulfate primary purification liquid, so that deep removal of phosphorus is further realized; and finally, the residual trace iron is precipitated and separated in the oxygen-containing atmosphere, so that the purity of the secondary purified cobalt sulfate liquid is further guaranteed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrometallurgy, and particularly relates to a method for removing phosphorus from a cobalt sulfate solution. BACKGROUND

[0002] The laterite nickel ore is generally treated by a hydrometallurgical process such as high-pressure acid leaching (HPAL), in which nickel, cobalt, iron and other metals are simultaneously leached, and then separated and enriched through neutralization, precipitation, extraction and other processes to obtain a crude cobalt sulfate solution. However, the laterite nickel ore is generally associated with apatite and other phosphorus-containing minerals, and in the leaching process, phosphorus will inevitably enter the solution system. Although the foregoing multi-step purification is performed, the crude cobalt sulfate solution still often contains a high concentration of phosphorus impurities, which becomes a key bottleneck restricting the production of high-quality cobalt products.

[0003] Therefore, how to achieve deep removal of phosphorus from the cobalt sulfate solution is a technical problem to be solved. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for removing phosphorus from a cobalt sulfate solution. The present application proposes a "step-by-step purification and phosphorus removal" strategy. First, a composite high-molecular soluble iron salt and a coagulant are used in cooperation to convert most of the phosphorus impurities in the cobalt sulfate solution into stable and easily separated phosphorus-containing residues, thereby achieving preliminary and efficient removal of phosphorus. Then, a deep phosphorus removal adsorbent is used to adsorb the trace phosphorus in the primary purified cobalt sulfate solution, thereby further achieving deep removal of phosphorus. Finally, the residual trace iron is precipitated and separated in an oxygen-containing atmosphere, thereby further ensuring the purity of the secondary purified cobalt sulfate solution. Therefore, this process not only solves the problem of deep removal of phosphorus from the high-phosphorus cobalt sulfate solution produced in the hydrometallurgical process of the laterite nickel ore, effectively improving the quality of the cobalt sulfate, but also simultaneously removes the iron impurities in the solution, with excellent impurity removal effect. The entire process is simple to operate and has significant industrial application value and economic benefits.

[0005] To achieve the purpose of the present application, the following technical solutions are adopted:

[0006] The present application provides a method for removing phosphorus from a cobalt sulfate solution, which comprises the following steps:

[0007] A cobalt sulfate solution to be treated is provided.

[0008] The cobalt sulfate solution to be treated, a composite high-molecular soluble iron salt and a coagulant are mixed to perform a precipitation reaction, and after separation, a phosphorus-containing residue and a primary purified cobalt sulfate solution are obtained.

[0009] Trace amounts of phosphorus in the primary cobalt sulfate purification solution are adsorbed using a deep phosphorus removal adsorbent. Then, trace amounts of iron in the cobalt sulfate purification solution are precipitated in an oxygen-containing atmosphere. After separation, a secondary cobalt sulfate purification solution is obtained.

[0010] This invention proposes a "stepwise purification and phosphorus removal" strategy. First, a composite polymeric soluble iron salt and a coagulant aid work synergistically to convert most phosphorus impurities in the cobalt sulfate solution into stable and easily separable phosphorus-containing slag, achieving preliminary and efficient phosphorus removal. Subsequently, a deep phosphorus removal adsorbent is used to directionally adsorb trace amounts of phosphorus in the primary cobalt sulfate purification solution, further achieving deep phosphorus removal. Finally, residual trace iron is precipitated and separated in an oxygen-containing atmosphere, further ensuring the purity of the final secondary cobalt sulfate purification solution. Therefore, this process not only solves the problem of deep phosphorus removal from high-phosphorus cobalt sulfate solutions produced during the hydrometallurgical process of laterite nickel ore, effectively improving the quality of cobalt sulfate, but also simultaneously removes iron impurities from the solution, demonstrating excellent impurity removal performance. The entire process is simple to operate and has significant industrial application value and economic benefits.

[0011] It should be noted that the cobalt sulfate solution to be processed comes from the crude cobalt sulfate solution obtained in the hydrometallurgical process of laterite nickel ore.

[0012] Preferably, the phosphorus content in the cobalt sulfate solution to be treated is 10-460 mg / L, for example, it can be 10 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 450 mg / L or 460 mg / L, etc.

[0013] Preferably, the molar ratio of iron ions in the composite polymer soluble iron salt to phosphate ions in the cobalt sulfate solution to be treated is (2-3):1, for example, it can be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, etc.

[0014] Preferably, the composite polymeric soluble iron salt includes any one or a combination of at least two of polyferric sulfate, polyferric chloride, polyferric silicate sulfate, or polydimethyldiallylammonium chloride.

[0015] Preferably, the composite polymeric soluble iron salt is a combination of polyferric sulfate and polyferric chloride.

[0016] In this invention, polyferric sulfate and polyferric chloride work synergistically. On the one hand, polyferric sulfate possesses a high binding capacity and strong coordination ability for phosphate ions, enabling it to efficiently capture high concentrations of phosphorus in cobalt sulfate solutions and generate stable ferric phosphate precipitates. On the other hand, polyferric chloride can rapidly adsorb free phosphate ions in the solution and release high-charge sites, promoting the aggregation of fine precipitate particles formed by polyferric sulfate and phosphate ions, thus increasing the precipitate particle size. This solves the problem of poor precipitate aggregation and difficult solid-liquid separation when polyferric sulfate is used alone. The synergistic effect of these two technologies significantly improves the phosphorus removal rate while reducing the total amount of composite polymeric soluble iron salt used. This avoids excessive co-precipitation of iron and cobalt ions and shortens the solid-liquid separation time due to the increased precipitate particle size. Furthermore, this composite polymeric soluble iron salt has stronger anti-interference capabilities, adapting to interference from trace impurity ions in cobalt sulfate solutions, ensuring stable high-phosphorus removal performance, laying a low-phosphorus foundation for subsequent deep phosphorus removal adsorbent treatment, and reducing the amount of adsorbent used in the deep treatment stage.

[0017] Preferably, the mass ratio of the polyferric sulfate to the polyferric chloride is (2-4):1, for example, it can be 2:1, 3:1 or 4:1, etc.

[0018] In this invention, an appropriate mass ratio allows polyferric sulfate to fully utilize its high phosphorus binding capacity, avoiding insufficient binding capacity and incomplete phosphorus removal due to an excessively high proportion of polyferric chloride. Simultaneously, the appropriate proportion of polyferric chloride promotes the aggregation of fine polyferric sulfate-phosphate precipitates through its high charge density. Under this mass ratio, the synergistic effect of the two is more balanced, resulting in superior phosphorus removal.

[0019] Preferably, the composite polymeric soluble iron salt is a combination of polyferric sulfate and polydimethyldiallyl ammonium chloride.

[0020] In this invention, in the combination of polyferric sulfate and polydimethyldiallyl ammonium chloride, polyferric sulfate mainly plays the role of charge neutralization and precipitation, while polydimethyldiallyl ammonium chloride has extremely strong adsorption and bridging ability. The combination of the two can not only efficiently precipitate ferric phosphate, but also form larger and denser precipitate particles, which greatly improves the efficiency of subsequent solid-liquid separation, making the obtained cobalt sulfate purified liquid clearer and the phosphorus-containing slag easier to filter.

[0021] Preferably, the mass ratio of the polyferric sulfate and polydimethyldiallylammonium chloride is (5-10):1, for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0022] In this invention, under a suitable mass ratio, polyferric sulfate can fully exert its high binding capacity for phosphate, ensuring efficient capture of high concentrations of phosphorus in the solution. At the same time, polydimethyldiallylammonium chloride, as a cationic polymeric flocculant, can enhance the agglomeration of fine precipitate particles formed by polyferric sulfate and phosphate through adsorption bridging, thereby significantly increasing the precipitate particle size.

[0023] Preferably, the coagulant aid comprises polyacrylamide.

[0024] In this invention, polyacrylamide is used as a coagulant aid, which can further enhance the agglomeration effect of the precipitate particles generated by the composite polymer soluble iron salt, accelerate the solid-liquid separation speed, reduce the suspension residue of fine precipitate particles, avoid the loss caused by the encapsulation of cobalt ions, ensure the stability of cobalt recovery rate, and reduce the water content of the precipitate residue, thereby reducing the cost of subsequent slag treatment.

[0025] Preferably, the mass ratio of the composite polymeric soluble iron salt to the coagulant is (30-50):1, for example, it can be 30:1, 35:1, 40:1, 45:1 or 50:1, etc.

[0026] Preferably, during the precipitation reaction, the pH of the reaction system is 4-5, for example, it can be 4, 4.5 or 5.

[0027] Preferably, during the precipitation reaction, the reaction temperature is 40-80℃, for example, 40℃, 50℃, 60℃, 70℃ or 80℃, and the holding time is 1-3h, for example, 1h, 2h or 3h.

[0028] Preferably, the phosphorus content in the primary cobalt sulfate purification solution is ≤12mg / L, for example, it can be 12mg / L, 11mg / L, 10mg / L, 8mg / L, 6mg / L, 4mg / L or 2mg / L, etc., and the iron content is ≤5mg / L, for example, it can be 5mg / L, 4mg / L, 3mg / L, 2mg / L or 1mg / L, etc.

[0029] Preferably, the deep phosphorus removal adsorbent comprises calcium hydroxyphosphate.

[0030] In this invention, hydroxyapatite is used as a deep phosphorus removal adsorbent, which can accurately capture free phosphate ions in the solution and does not react with cobalt ions, thus deeply removing trace amounts of phosphorus from the secondary purification solution. At the same time, hydroxyapatite has strong stability in acidic systems and will not dissolve and release calcium ions to introduce new impurities, ensuring the purity of the purification solution. In addition, the adsorption residue particles formed after adsorption are uniform and can be filtered and separated simultaneously with the iron hydroxide precipitate generated in the subsequent oxygen-containing atmosphere, without the need for additional separation steps.

[0031] Preferably, based on the mass of the cobalt sulfate primary purification solution, the amount of hydroxyapatite added is 0.1-0.5 wt%, for example, it can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%.

[0032] Preferably, during the adsorption process, the temperature is 40-80℃, for example, 40℃, 50℃, 60℃, 70℃ or 80℃, and the time is 1-3h, for example, 1h, 2h or 3h.

[0033] Preferably, the phosphorus content in the cobalt sulfate secondary purification solution is <1 mg / L, for example, it can be 0.8 mg / L, 0.6 mg / L, 0.4 mg / L or 0.2 mg / L, etc.

[0034] Preferably, the method includes the following steps:

[0035] (1) Provide a cobalt sulfate solution to be treated, wherein the phosphorus content in the cobalt sulfate solution to be treated is 10-460 mg / L.

[0036] (2) Under stirring conditions, the cobalt sulfate solution to be treated, the composite polymer soluble iron salt and the coagulant are mixed, the pH of the reaction system is adjusted to 4-5, and the reaction temperature is controlled at 40-80℃. The precipitation reaction is carried out for 1-3 hours. After the reaction is completed, the mixture is filtered to obtain phosphorus slag and cobalt sulfate primary purification liquid.

[0037] The molar ratio of iron ions in the composite polymeric soluble iron salt to phosphate ions in the cobalt sulfate solution to be treated is (2-3):1; the composite polymeric soluble iron salt is a combination of polyferric sulfate and polyferric chloride with a mass ratio of (2-4):1, or a combination of polyferric sulfate and polydimethyldiallylammonium chloride with a mass ratio of (5-10):1; the coagulant aid includes polyacrylamide, and the mass ratio of the composite polymeric soluble iron salt to the coagulant aid is (30-50):1; the phosphorus content in the primary cobalt sulfate purification solution is ≤12mg / L, and the iron content is ≤5mg / L.

[0038] (3) Under the condition of 40-80℃, the trace phosphorus in the cobalt sulfate purification solution is adsorbed by a deep phosphorus removal adsorbent for 1-3h. Then, in an oxygen-containing atmosphere with an oxygen concentration of 5-8vol% (e.g., 5vol%, 3vol%, 7vol%, or 8vol%), the pH of the cobalt sulfate purification solution is adjusted to 5-5.5 (e.g., 5, 5.1, 5.2, 5.3, 5.4, or 5.5) so that the trace iron is precipitated. After separation, the cobalt sulfate secondary purification solution is obtained.

[0039] The deep phosphorus removal adsorbent is hydroxyapatite; based on the mass of the primary cobalt sulfate purification solution, the amount of hydroxyapatite added is 0.1-0.5 wt%; the phosphorus content in the secondary cobalt sulfate purification solution is <1 mg / L.

[0040] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention proposes a "stepwise purification and phosphorus removal" strategy. First, a composite polymeric soluble iron salt and a coagulant aid work synergistically to convert most phosphorus impurities in the cobalt sulfate solution into stable and easily separable phosphorus-containing slag, achieving preliminary and efficient phosphorus removal. Subsequently, a deep phosphorus removal adsorbent is used to directionally adsorb trace amounts of phosphorus in the primary cobalt sulfate purification solution, further achieving deep phosphorus removal. Finally, residual trace iron is precipitated and separated in an oxygen-containing atmosphere, further ensuring the purity of the final secondary cobalt sulfate purification solution. Therefore, this process not only solves the problem of deep phosphorus removal from high-phosphorus cobalt sulfate solutions produced during the hydrometallurgical process of laterite nickel ore, effectively improving the quality of cobalt sulfate, but also simultaneously removes iron impurities from the solution, demonstrating excellent impurity removal performance. The entire process is simple to operate and has significant industrial application value and economic benefits. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Example 1

[0045] This embodiment provides a method for removing phosphorus from a cobalt sulfate solution, the method comprising the following steps:

[0046] (1) Provide a cobalt sulfate solution to be treated, wherein the cobalt content in the cobalt sulfate solution is 82.58 mg / L and the phosphorus content is 20.8 mg / L.

[0047] (2) Under stirring conditions, the cobalt sulfate solution to be treated, the composite polymer soluble iron salt and the coagulant are mixed, the pH of the reaction system is adjusted to 4.5, and the reaction temperature is controlled at 60°C for 1.5 h of precipitation reaction. After the reaction is completed, the mixture is filtered to obtain phosphorus slag and cobalt sulfate primary purification liquid.

[0048] The molar ratio of iron ions in the composite polymeric soluble iron salt to phosphate ions in the cobalt sulfate solution to be treated is 2:1; the composite polymeric soluble iron salt is a combination of polyferric sulfate and polyferric chloride with a mass ratio of 3:1; the coagulant is polyacrylamide, and the mass ratio of the composite polymeric soluble iron salt to the coagulant is 35:1; the phosphorus content in the primary cobalt sulfate purification solution is 7.61 mg / L, and the iron content is 1.58 mg / L.

[0049] (3) At a temperature of 65°C, a deep phosphorus removal adsorbent is used to adsorb trace amounts of phosphorus in the cobalt sulfate purification solution for 1.5 hours. Then, in an oxygen-containing atmosphere with an oxygen concentration of 6.5 vol%, the pH of the cobalt sulfate purification solution is adjusted to 5.2, so that trace amounts of iron precipitate. After separation, a secondary cobalt sulfate purification solution is obtained.

[0050] The deep phosphorus removal adsorbent is hydroxyapatite; based on the mass of the primary cobalt sulfate purification solution, the amount of hydroxyapatite added is 0.1 wt%; the phosphorus content in the secondary cobalt sulfate purification solution is 0.65 mg / L.

[0051] Example 2

[0052] This embodiment provides a method for removing phosphorus from a cobalt sulfate solution, the method comprising the following steps:

[0053] (1) Provide a cobalt sulfate solution to be treated, wherein the cobalt content in the cobalt sulfate solution is 95.14 mg / L and the phosphorus content is 11.5 mg / L.

[0054] (2) Under stirring conditions, the cobalt sulfate solution to be treated, the composite polymer soluble iron salt and the coagulant are mixed, the pH of the reaction system is adjusted to 4, and the reaction temperature is controlled at 40°C for 1 hour of precipitation reaction. After the reaction is completed, the mixture is filtered to obtain phosphorus slag and cobalt sulfate primary purification liquid.

[0055] The molar ratio of iron ions in the composite polymeric soluble iron salt to phosphate ions in the cobalt sulfate solution to be treated is 2:1; the composite polymeric soluble iron salt is a combination of polyferric sulfate and polyferric chloride with a mass ratio of 2:1; the coagulant is polyacrylamide, and the mass ratio of the composite polymeric soluble iron salt to the coagulant is 30:1; the phosphorus content in the primary cobalt sulfate purification solution is 3.31 mg / L, and the iron content is 2.15 mg / L.

[0056] (3) Under the condition of 50℃, the trace phosphorus in the cobalt sulfate purification solution is adsorbed by a deep phosphorus removal adsorbent for 1 hour. Then, in an oxygen-containing atmosphere with an oxygen concentration of 5 vol%, the pH of the cobalt sulfate purification solution is adjusted to 5 so that the trace iron is precipitated. After separation, the cobalt sulfate secondary purification solution is obtained.

[0057] The deep phosphorus removal adsorbent is hydroxyapatite; based on the mass of the primary cobalt sulfate purification solution, the amount of hydroxyapatite added is 0.1 wt%; the phosphorus content in the secondary cobalt sulfate purification solution is 0.58 mg / L.

[0058] Example 3

[0059] This embodiment provides a method for removing phosphorus from a cobalt sulfate solution, the method comprising the following steps:

[0060] (1) Provide a cobalt sulfate solution to be treated, wherein the cobalt content in the cobalt sulfate solution is 68.37 mg / L and the phosphorus content is 460 mg / L.

[0061] (2) Under stirring conditions, the cobalt sulfate solution to be treated, the composite polymer soluble iron salt and the coagulant are mixed, the pH of the reaction system is adjusted to 5, and the reaction temperature is controlled at 80°C for 3 hours of precipitation reaction. After the reaction is completed, the mixture is filtered to obtain phosphorus slag and cobalt sulfate primary purification liquid.

[0062] The molar ratio of iron ions in the composite polymeric soluble iron salt to phosphate ions in the cobalt sulfate solution to be treated is 3:1; the composite polymeric soluble iron salt is a combination of polyferric sulfate and polyferric chloride with a mass ratio of 4:1; the coagulant is polyacrylamide, and the mass ratio of the composite polymeric soluble iron salt to the coagulant is 50:1; the phosphorus content in the primary cobalt sulfate purification solution is 11.05 mg / L, and the iron content is 3.56 mg / L.

[0063] (3) Under the condition of 80℃, the trace phosphorus in the cobalt sulfate purification solution is adsorbed by a deep phosphorus removal adsorbent for 3 hours. Then, in an oxygen-containing atmosphere with an oxygen concentration of 8 vol%, the pH of the cobalt sulfate purification solution is adjusted to 5.5 so that the trace iron is precipitated. After separation, the cobalt sulfate secondary purification solution is obtained.

[0064] The deep phosphorus removal adsorbent is hydroxyapatite; based on the mass of the primary cobalt sulfate purification solution, the amount of hydroxyapatite added is 0.5 wt%; the phosphorus content in the secondary cobalt sulfate purification solution is 0.81 mg / L.

[0065] Example 4

[0066] The difference between this embodiment and Embodiment 1 is that the composite polymeric soluble iron salt is replaced by a combination of polyferric sulfate and polydimethyldiallyl ammonium chloride, and the mass ratio of polyferric sulfate to polydimethyldiallyl ammonium chloride is 7.5:1.

[0067] The remaining methods and parameters are consistent with those in Example 1.

[0068] Example 5

[0069] The difference between this embodiment and Embodiment 1 is that the composite polymeric soluble iron salt is replaced by a combination of polyferric sulfate and polydimethyldiallyl ammonium chloride, and the mass ratio of polyferric sulfate to polydimethyldiallyl ammonium chloride is 5:1.

[0070] The remaining methods and parameters are consistent with those in Example 1.

[0071] Example 6

[0072] The difference between this embodiment and Embodiment 1 is that the composite polymeric soluble iron salt is replaced by a combination of polyferric sulfate and polydimethyldiallyl ammonium chloride, and the mass ratio of polyferric sulfate to polydimethyldiallyl ammonium chloride is 10:1.

[0073] The remaining methods and parameters are consistent with those in Example 1.

[0074] Example 7

[0075] The difference between this embodiment and Embodiment 1 is that the mass ratio of polyferric sulfate and polyferric chloride is 1:1.

[0076] The remaining methods and parameters are consistent with those in Example 1.

[0077] Example 8

[0078] The difference between this embodiment and Embodiment 1 is that the mass ratio of polyferric sulfate to polyferric chloride is 5:1.

[0079] The remaining methods and parameters are consistent with those in Example 1.

[0080] Example 9

[0081] The difference between this embodiment and Embodiment 4 is that the mass ratio of the polyferric sulfate and polydimethyldiallyl ammonium chloride is 4:1.

[0082] The remaining methods and parameters are consistent with those in Example 4.

[0083] Example 10

[0084] The difference between this embodiment and Embodiment 4 is that the mass ratio of the polyferric sulfate and polydimethyldiallyl ammonium chloride is 11:1.

[0085] The remaining methods and parameters are consistent with those in Example 4.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is that the polyferric chloride is replaced with an equal mass of polyferric sulfate, that is, a single polymeric soluble iron salt is used.

[0088] The remaining methods and parameters are consistent with those in Example 1.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is that the polyferric sulfate is replaced with an equal mass of polyferric chloride, that is, a single polymeric soluble iron salt is used.

[0091] The remaining methods and parameters are consistent with those in Example 1.

[0092] Comparative Example 3

[0093] The difference between this comparative example and Example 1 is that step (3) is not performed.

[0094] The remaining methods and parameters are consistent with those in Example 1.

[0095] Performance testing

[0096] The phosphorus content of the cobalt sulfate secondary purification solution provided in the above examples and comparative examples was tested by inductively coupled plasma mass spectrometry, and the phosphorus removal rate was calculated as follows: phosphorus removal rate = (initial phosphorus concentration in the cobalt sulfate solution to be treated - residual phosphorus concentration in the cobalt sulfate secondary purification solution) ÷ initial phosphorus concentration in the cobalt sulfate solution to be treated × 100%.

[0097] The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100] analyze:

[0101] As shown in Table 1, this invention proposes a "stepwise purification and phosphorus removal" strategy. First, a composite polymeric soluble iron salt and a coagulant aid work synergistically to convert most phosphorus impurities in the cobalt sulfate solution into stable and easily separable phosphorus-containing slag, achieving preliminary and efficient phosphorus removal. Then, a deep phosphorus removal adsorbent is used to directionally adsorb trace amounts of phosphorus in the primary cobalt sulfate purification solution, further achieving deep phosphorus removal. Finally, residual trace iron is precipitated and separated in an oxygen-containing atmosphere, further ensuring the purity of the final secondary cobalt sulfate purification solution. Therefore, this process not only solves the problem of deep phosphorus removal from high-phosphorus cobalt sulfate solutions produced during the hydrometallurgical process of laterite nickel ore, effectively improving the quality of cobalt sulfate, but also simultaneously removes iron impurities from the solution, demonstrating excellent impurity removal performance.

[0102] As can be seen from the comparison between Example 1 and Examples 7-8, if the mass ratio of polyferric sulfate to polyferric chloride is too small, it will not be conducive to the precipitation reaction that plays a major role, thus affecting the phosphorus removal rate; if the mass ratio of polyferric sulfate to polyferric chloride is too large, it will not be conducive to the effective separation of precipitates, thus affecting the phosphorus removal rate.

[0103] A comparison of Examples 4 and 9-10 shows that if the mass ratio of polyferric sulfate to polydimethyldiallyl ammonium chloride is too small, it is not conducive to the restabilization and dispersion of colloids, thus affecting the phosphorus removal rate; if the mass ratio of polyferric sulfate to polydimethyldiallyl ammonium chloride is too large, it is not conducive to the effective flocculation process, thus affecting the phosphorus removal rate.

[0104] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, if only a single polymeric soluble iron salt, namely single polyferric sulfate or single polyferric chloride, is used to remove phosphorus, it is not conducive to cost control and the phosphorus removal rate is poor.

[0105] As can be seen from the comparison between Example 1 and Comparative Example 3, if only one-step purification and phosphorus removal is used, directional adsorption cannot be carried out, which is not conducive to the deep removal of phosphorus.

[0106] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for removing phosphorus from a cobalt sulfate solution, characterized by, The method comprises the following steps: Providing a to-be-treated cobalt sulfate solution; Mixing the to-be-treated cobalt sulfate solution, a composite high-molecular soluble iron salt and a coagulant aid, performing a precipitation reaction, and separating to obtain a phosphorus-containing residue and a cobalt sulfate primary purification solution; Using a deep phosphorus removal adsorbent to adsorb trace phosphorus in the cobalt sulfate primary purification solution, and then making trace iron in the cobalt sulfate purification solution generate a precipitate in an oxygen-containing atmosphere, and separating to obtain a cobalt sulfate secondary purification solution.

2. The method of claim 1, wherein, The to-be-treated cobalt sulfate solution has a phosphorus content of 10-460 mg / L.

3. The method according to claim 1 or 2, characterized in that, The molar ratio of iron ions in the composite high-molecular soluble iron salt to phosphate in the to-be-treated cobalt sulfate solution is (2-3):

1. Preferably, the composite high-molecular soluble iron salt comprises any one or a combination of at least two of polyferric sulfate, polyferric chloride, polyferric silicate sulfate or polydimethyldiallylammonium chloride.

4. The method of claim 3, wherein, The composite high-molecular soluble iron salt is a combination of polyferric sulfate and polyferric chloride. Preferably, the mass ratio of polyferric sulfate to polyferric chloride is (2-4):

1.

5. The method of claim 3, wherein, The composite high-molecular soluble iron salt is a combination of polyferric sulfate and polydimethyldiallylammonium chloride. Preferably, the mass ratio of polyferric sulfate to polydimethyldiallylammonium chloride is (5-10):

1.

6. The method according to any one of claims 1 to 5, characterized in that, The coagulant aid comprises polyacrylamide. Preferably, the mass ratio of the composite high-molecular soluble iron salt to the coagulant aid is (30-50):

1.

7. The method according to any one of claims 1 to 6, characterized in that, During the precipitation reaction, the pH of the reaction system is 4-5. Preferably, during the precipitation reaction, the reaction temperature is 40-80°C, and the holding time is 1-3 h.

8. The method according to any one of claims 1 to 7, characterized in that, The cobalt sulfate primary purification solution has a phosphorus content of ≤12 mg / L and an iron content of ≤5 mg / L.

9. The method according to any one of claims 1 to 8, characterized in that, The deep phosphorus removal adsorbent comprises calcium hydroxyphosphate. Preferably, the addition amount of the calcium hydroxyphosphate is 0.1-0.5 wt% based on the mass of the cobalt sulfate primary purification solution. Preferably, during the adsorption, the temperature is 40-80°C, and the time is 1-3 h. Preferably, the cobalt sulfate secondary purification solution has a phosphorus content of <1 mg / L.

10. The method according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: (1) providing a to-be-treated cobalt sulfate solution, the to-be-treated cobalt sulfate solution having a phosphorus content of 10-460 mg / L; (2) mixing the to-be-treated cobalt sulfate solution, a composite high-molecular soluble iron salt and a coagulant aid under stirring, adjusting the pH of the reaction system to 4-5, and controlling the reaction temperature to be 40-80°C, performing a precipitation reaction for 1-3 h, filtering after the reaction is completed, and obtaining a phosphorus-containing residue and a cobalt sulfate primary purification solution; The molar ratio of iron ions in the composite high-molecular soluble iron salt to phosphate in the cobalt sulfate solution to be treated is (2-3):1; the composite high-molecular soluble iron salt is a combination of polymeric ferric sulfate and polymeric ferric chloride with a mass ratio of (2-4):1, or a combination of polymeric ferric sulfate and polydimethyl diallyl ammonium chloride with a mass ratio of (5-10):1; the coagulant aid comprises polyacrylamide, and the mass ratio of the composite high-molecular soluble iron salt to the coagulant aid is (30-50):1; the phosphorus content in the primary purified cobalt sulfate solution is ≤12 mg / L, and the iron content is ≤5 mg / L; (3) under the condition that the temperature is 40-80℃, the trace phosphorus in the cobalt sulfate purified solution is adsorbed by a deep phosphorus removal adsorbent for 1-3h, then the pH of the cobalt sulfate purified solution is adjusted to 5-5.5 in an oxygen-containing atmosphere with an oxygen concentration of 5-8vol%, so that trace iron generates a precipitate, and the secondary purified cobalt sulfate solution is obtained after separation; The deep phosphorus removal adsorbent is calcium hydroxyphosphate; the addition amount of the calcium hydroxyphosphate is 0.1-0.5wt% based on the mass of the primary purified cobalt sulfate solution; the phosphorus content in the secondary purified cobalt sulfate solution is <1mg / L.

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