Method for refining and defluorinating reverse extraction nickel sulfate solution

Abstract

The invention provides a method for refining and defluorinating a reverse extraction nickel sulfate solution. The problems that a large amount of Na < + > is introduced and loaded metals are easy to dissolve out due to the Tangnan membrane effect exist in the traditional chelating cation defluorination resin treatment; the problems that the multi-cycle defluorination performance of anion defluorination resin is seriously reduced and impurities are introduced due to dissolution of loaded metal in a low-pH environment are solved. According to the method, the high-crosslinking-degree acrylic acid series alkaline anion defluorination resin modified by Zr < 4 + >, Ce < 4 + > and double metal oxides or hydroxides of Zr < 4 + > and Ce < 4 + > is adopted for defluorination refining of the reverse extraction nickel sulfate solution, impurity ions are not introduced, main element loss is not involved, and a back-end nickel product refining link with the high impurity content requirement can be effectively treated. Compared with the prior art, the method has the advantages of simple process, low cost, high value, environmental protection, efficient circulation and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field, and specifically relates to a method for refining and defluorinating a nickel sulfate stripping solution. Background Art

[0002] The main elements in ternary lithium batteries are Ni, Co, Mn, Li, Al, Cu, F, etc. With the continuous development of lithium batteries, the models of ternary lithium batteries have gone through the 333 type, 532 type, 622 type, and 811 type, and the proportion of nickel in the cathode material is 30%, 50%, 60%, and 80% respectively. As the battery formula for new energy vehicles becomes more and more mature, the consumption of nickel will only increase, and the recycling of waste ternary batteries will also become another major source of nickel element recycling.

[0003] After the wet leaching of ternary battery black powder, the leaching solution contains a large amount of fluoride ions. After the traditional process removes impurities from the battery leaching solution by precipitation and extracts valuable metal elements, a large part of the fluoride still enters the nickel salt solution, seriously affecting the product quality of battery-grade nickel sulfate, causing corrosion damage to the subsequent evaporation, concentration, and crystallization process equipment, and posing serious environmental pollution and safety hazards.

[0004] Currently, the main defluorination methods include chemical precipitation method, coagulation precipitation method, adsorption method, volatile stripping method, etc. For product refining, most methods have great limitations. The precipitation / flocculation method (for example, the methods in Patent CN202310195995.0 and Patent CN202411368894.X) requires the introduction of a precipitant, resulting in a large amount of impurity ions and nickel precipitates; in the adsorption method, the cost of the adsorbent is relatively high and it is difficult to be continuously used. The pH of the nickel sulfate stripping solution containing fluorine is 2-4, which will cause a large amount of dissolution of the adsorbent (for example, the aluminum-based adsorbent in Patent CN202411495702.1), and a large amount of inorganic carriers such as calcium and magnesium and some rare earth elements will also be dissolved in the rare earth metal adsorbent (for example, the adsorption of nickel and cobalt by the adsorbent in Patent CN202311455116.X causes losses); the volatile stripping method requires the use of high-temperature and high-acid characteristics to volatilize hydrogen fluoride gas, with complex processes, high energy consumption costs, and inability to deeply remove fluorine. Although these methods can remove fluorine, most of them are only effective for wastewater or the front-end treatment process of battery recycling, and are difficult to work for the subsequent nickel product refining link with high impurity content requirements.

[0005] The defluorination ion exchange resin can deeply remove fluorine, but due to its variety, it is difficult to effectively control the introduction of impurities during the elution and regeneration process. The cationic chelating defluorination resin (for example, the tertiary amine methyl phosphate ion resin in CN202311053010.7) is loaded with metal ions / oxides or hydroxides, and will inevitably adsorb a large amount of Ni when defluorinating the nickel sulfate stripping solution. 2+, during regeneration, it turns into the Al type, Na type or H type, causing a large amount of Na ions in the resin to be replaced and the dissolution of metal complex oxides or hydroxides. This not only reduces the resin performance but also introduces a large amount of Na ions and loaded metal ions. Most of the anion defluorination resins on the market are used for wastewater treatment. After dealing with low pH and high-concentration salt solutions, some loaded metal ions will be introduced into the product solution, resulting in a decline in subsequent defluorination performance.

[0006] For the refining and defluorination of nickel sulfate products, not only the defluorination effect but also the refining effect needs to be considered. Therefore, for the nickel sulfate solution that has passed the heavy metal extraction test, a method that can deeply refine and defluorinate without introducing other impurity ions and can be used for a long time is required. Summary of the Invention

[0007] The present invention provides a method for refining and defluorinating a back-extracted nickel sulfate solution, that is, a method for deeply defluorinating and refining nickel sulfate after heavy metal extraction in the wet recovery process of lithium batteries. Since the impurity content of the fluorine-containing back-extracted nickel sulfate solution itself is very low, fluorine can be enriched to prepare high-purity sodium fluoride without introducing impurity cations and anions. Compared with the prior art, this method has the advantages of simple process, low cost, environmental protection, recyclability, high efficiency, etc. The specific scheme is as follows:

[0008] A method for refining and defluorinating a back-extracted nickel sulfate solution, the specific steps are as follows:

[0009] (1) Load the alkaline anion defluorination resin into a resin column, and wash it with sodium hydroxide, sulfuric acid and pure water in sequence until the effluent is clear;

[0010] (2) Take the nickel sulfate back-extracted solution from the workshop. After detecting the ion concentration of the solution, use a pump to make the solution pass through the resin in step (1) for refining and defluorination, and regularly take samples to measure the element concentrations in the effluent;

[0011] (3) When the F concentration in the nickel sulfate solution after refining and defluorination in step (2) is greater than or equal to 5 mg / L, stop adsorption, and perform backwashing and regeneration on the resin. Take samples of the backwashing and regeneration liquid for detection. After complete regeneration, continue to pass the back-extracted nickel sulfate solution for refining; - When the concentration is greater than or equal to 5 mg / L, stop adsorption, and perform backwashing and regeneration on the resin. Take samples of the backwashing and regeneration liquid for detection. After complete regeneration, continue to pass the back-extracted nickel sulfate solution for refining;

[0012] (4) Pump the nickel sulfate solution after refining and defluorination into the MVR system for crystallization to prepare battery-grade nickel sulfate. The condensed water obtained during the evaporation and concentration process can be used as pure water;

[0013] (5) Filter the alkaline washing eluent obtained from the backwashing and regeneration of the resin in step (3), add an alkaline sodium reagent, and use a crystallization process to prepare sodium fluoride with a purity of more than 99%. The low-fluorine alkaline solution after recovering fluorine is used to prepare 2% - 3% wt sodium hydroxide.

[0014] The alkaline anion defluorination resin in step (1) is Zr4+ , Ce 4+ and its bimetallic oxides or hydroxides modified basic anion gel resin; the basic anion defluorination resin is an acrylic basic anion gel resin (quaternary amine, tertiary amine, secondary amine groups), and the crosslinking degree is greater than 12%.

[0015] In the step (2), the concentration of F in the detected ion concentration - is 200 - 300 mg / L, the concentration of Ni 2+ is 110 - 150 g / L, the concentration of Na + is 0.001 - 0.003 g / L, the concentration of Mg 2+ is 0.003 - 0.004 g / L, the concentration of Ca 2+ is less than or equal to 0.002 g / L; the concentrations of the remaining impurity metal ions (such as: Cu, Fe, Al, Mn, Pb, Cr and other ions) are all less than 0.0005 g / L, and the pH value is 2 - 4.

[0016] In the step (2), the flow rate of the nickel sulfate stripping solution is 1 - 3 BV / h.

[0017] In the step (3), the solutions used for backwashing and regeneration are pure water, liquid alkali, pure water, sulfuric acid, pure water in sequence. Further, the mass fraction of the liquid alkali is 2 - 3% wt, and the mass fraction of the sulfuric acid is 1 - 1.7% wt.

[0018] In the step (3), the flow rates of the sulfuric acid and liquid alkali solutions during backwashing and regeneration are 2 - 4 BV / h.

[0019] In the step (3), when the concentration of Na in the final pure water eluate during backwashing and regeneration is ≤ 2 mg / L, it is considered that the backwashing and regeneration are complete.

[0020] In the step (5), the basic sodium reagent added to the alkali washing eluate is liquid alkali sodium hydroxide, and the addition amount is 1.1 - 1.3 times the concentration of F ions in the alkali washing eluate.

[0021] Traditional chelating cation defluorination resin treatment has problems such as introducing a large amount of Na + and the easy dissolution of the loaded metal due to the Donnan membrane effect; it avoids the problems of serious decline in the defluorination performance in multiple cycles and impurity introduction caused by the dissolution of the loaded metal in the anion defluorination resin due to the low pH environment. In the present invention, the present invention uses Zr 4+ , Ce 4+ and its bimetallic oxides or hydroxides modified highly crosslinked acrylic basic anion defluorination resin to carry out defluorination and refining on the stripped nickel sulfate solution, without introducing impurity ions and without involving the loss of main elements, and can effectively treat the refined nickel product link at the back end with high requirements for impurity content. Compared with the prior art, this method has the advantages of simple process, low cost and high value, environmental protection, and efficient recycling.

[0022] The present invention relates to a method for refining nickel sulfate by defluorination in the back-end of nickel sulfate recovery from batteries. The pH of the back-extracted nickel sulfate solution is 2-4, and the metal cations are at a relatively low level after extraction and impurity removal. The Ce 4+ or Zr 4+ has the remaining loaded defluorinating metal ions such as Ce 3+ , La 3+ , Al 3+ , Mn 2+ , Ca 2+ , Mg 2+ etc. with a lower dissolution pH; the basic nitrogen-containing groups on the acrylic basic anion resin are more than those on the styrene-based anion resin, resulting in a larger number of positively charged groups. The characteristics of high cross-linking degree and gel-type structure make the metal loading more secure and difficult to dissolve. The organic charged functional groups weaken the mass transfer reaction between cations and the internal substances of the resin. The above characteristics can effectively avoid the influence of the dissolution of the loaded metal on the components of the defluorinated liquid and the significant reduction of the defluorination performance of the resin.

[0023] The present invention has the following advantages:

[0024] (1) It overcomes the problems that chelating cation defluorination resins will inevitably introduce a large amount of Na + and the problem that the loaded metal is easily dissolved due to the Donnan membrane effect, and avoids the problems of the decline of defluorination performance and the introduction of impurities caused by the dissolution of the loaded metal in the anion defluorination resin due to the low pH environment.

[0025] (2) The depth of defluorination in the refining of nickel sulfate is up to 0.1 mg / L, effectively maintaining the F-ion concentration in the defluorinated liquid after the refining of nickel sulfate below 5 mg / L. Except for the reduction of the defluoride ion concentration in the solution before and after the refining of the back-extracted nickel sulfate by defluorination, the cation concentration remains basically unchanged, and no other anions except sulfate are introduced. The refining effect is better after multiple cycles of regeneration.

[0026] (3) The operation of the present invention is simple, the industrial application has a large amount of nickel sulfate treatment, is green and environmentally friendly, has a good effect on refining and removing F ions, the impurity content in the regeneration washing liquid is low, and it can be recycled without secondary pollution.

[0027] (4) The present invention is used for the refining of the back-end nickel sulfate solution. The impurities in the back-end solution are less except for the main product, and it can be used to recycle and prepare high-purity sodium fluoride by-products, improving the overall industrial value. Description of the Drawings

[0028] Figure 1 It is the data of the cation concentrations in the defluorinated liquid after the refining of the back-extracted nickel sulfate by defluorination in Example 1 of the present invention.

[0029] Figure 2 It is the data of the cycle performance of the defluorination cycle of the back-extracted nickel sulfate by defluorination in Example 1 of the present invention. Detailed implementation manners

[0030] Example 1

[0031] A certain volume of new Zr-modified acrylic basic anion gel resin with a crosslinking degree of 14% was filled into a resin column, and it was successively washed with 2% wt sodium hydroxide, 1% wt sulfuric acid, and pure water until the effluent was clear. Take the nickel sulfate stripping solution from the extraction workshop, and sample and detect the concentrations of Ni 4+ 、F 2+ 、F, - 、Na + 、Na, 4+ 、Zr - and other plasma concentrations, and then use a pump to make the solution pass through the resin at 2 BV / h for refining and defluorination, and regularly sample and measure the concentrations of various elements in the effluent; when the F

[0032] concentration in the nickel sulfate solution after refining and defluorination is greater than or equal to 5 mg / L, stop adsorption, and regenerate the resin; the solutions used for backwashing and regeneration are successively pure water, 2% wt liquid caustic soda, pure water, 1% wt sulfuric acid, and pure water; the flow rates of liquid caustic soda and sulfuric acid are 2 BV / h, sample the concentrations of various ions in the regenerated liquid, and perform multi-cycle refining and defluorination after complete regeneration.

[0033] Pump the liquid after refining and defluorination into the MVR system for crystallization to prepare battery-grade nickel sulfate. The alkali washing eluate (the alkali washing eluate after the resin is eluted with liquid caustic soda) is filtered, and liquid caustic soda with 1.1 times the molar amount of F ions is added, and the crystallization process is used to prepare high-purity sodium fluoride.

[0034] The data of the liquid before and after refining and defluorination of the stripped nickel sulfate, the washing liquid, and the cycle recyclability in Example 1 are shown in Table 1.

[0035]

[0036]

[0037] Example 2

[0038] A certain volume of new Ce-modified acrylic basic anion gel resin with a crosslinking degree of 15% was filled into a resin column, and it was successively washed with 2% wt sodium hydroxide, 1% wt sulfuric acid, and pure water until the effluent was clear. The nickel sulfate stripping solution in Example 1 was refined and defluorinated at 3 BV / h, and regularly sample and measure the concentrations of various elements in the effluent; when the F 4+ concentration in the nickel sulfate solution after refining and defluorination is greater than or equal to 5 mg / L, stop adsorption, and regenerate the resin. The backwashing and regeneration solutions are successively pure water, 2% wt liquid caustic soda, pure water, 1% wt sulfuric acid, and pure water; the flow rates of liquid caustic soda and sulfuric acid are 2 BV / h, sample each regenerated liquid to detect Ni - 、F 2+ 、F,- , Na + , Ce 4+ plasma concentration, backwashing and regeneration are completed for multi-cycle refined defluorination.

[0039] The liquid after refined defluorination of nickel sulfate is pumped into the MVR system for crystallization to prepare battery-grade nickel sulfate. The alkali washing eluate is filtered and then 1.2 times the amount of liquid alkali in terms of the amount of F ions is added, and the crystallization process is used to prepare high-purity sodium fluoride.

[0040] The data of the liquid before and after back-extraction and refined defluorination of nickel sulfate, the washing liquid, and the cycle recyclability in Example 2 are shown in Table 2.

[0041] Table 2 Data table of back-extraction, refined defluorination and regeneration of nickel sulfate in Example 2

[0042]

[0043] Example 3

[0044] A certain volume of quaternary Ce, Zr bimetal oxide modified acrylic basic anion gel resin with a crosslinking degree of 16% is loaded into the resin column, and it is washed with 2% wt sodium hydroxide, 1% wt sulfuric acid, and pure water in sequence until the effluent is clear. The back-extracted nickel sulfate solution from the workshop is taken for refined defluorination at a rate of 1 BV / h, and the ion concentrations in the original solution and the effluent are sampled and measured; when the F - concentration is greater than or equal to 5 mg / L, the adsorption is stopped, and the resin is regenerated. The backwashing and regeneration solutions are pure water, 3% wt liquid alkali, pure water, 1.5% wt sulfuric acid, and pure water in sequence; the flow rates of liquid alkali and sulfuric acid are 4 BV / h, and the ion concentrations of each regeneration liquid are sampled and detected, and backwashing and regeneration are completed for multi-cycle refined defluorination.

[0045] The liquid after refined defluorination of nickel sulfate is pumped into the MVR system for crystallization to prepare battery-grade nickel sulfate. The alkali washing eluate is filtered and then 1.2 times the amount of liquid alkali in terms of the amount of F ions is added for crystallization to prepare sodium fluoride with high purity.

[0046] The data of the liquid before and after back-extraction and refined defluorination of nickel sulfate, the washing liquid, and the cycle recyclability in Example 3 are shown in Table 3.

[0047] Table 3 Data table of back-extraction, refined defluorination and regeneration of nickel sulfate in Example 3

[0048]

[0049] Comparative Example 1

[0050] A certain volume of commercially available ZGF860 defluorination resin (styrene-divinylbenzene backbone with active aluminum cations resin) is placed in the resin column. The nickel sulfate back-extracted solution from the extraction workshop is taken, and Ni 2+ , F - , Na+ and Al 3+ The plasma concentration was measured, and then the solution was pumped through the resin at a flow rate of 2 BV / h for refined defluorination. The resin was regenerated according to the self-regeneration method of the commercially available resin, and samples were taken regularly to measure the concentrations of various elements in the effluent and the regenerant.

[0051] The data of the liquid before and after refined defluorination, the washing liquid, and the cycle recyclability of Comparative Example 1 are shown in Table 4.

[0052] Table 4 Data of refined defluorination and regeneration of nickel sulfate stripping in Comparative Example 1

[0053]

[0054] Comparative Example 2

[0055] A certain volume of commercially available LX869 defluorination resin (macroporous resin with Zr loaded on a styrene-divinylbenzene backbone) was placed in a resin column. The nickel sulfate stripping solution from the extraction workshop was taken, and the concentrations of Ni 4+ , F 2+ , Na - , Zr + and other plasma concentrations were measured. Then, the solution was pumped through the resin at a flow rate of 2 BV / h for refined defluorination. The resin was regenerated according to the self-regeneration method of the commercially available resin, and repeated multi-cycle tests were carried out. Samples were taken regularly to measure the concentrations of various elements in the effluent and the regenerant. 4+ The data of the liquid before and after refined defluorination, the washing liquid, and the cycle recyclability of Comparative Example 2 are shown in Table 5.

[0056] Table 5 Data of refined defluorination and regeneration of nickel sulfate stripping in Comparative Example 2

[0057] Table 5 Data of refined defluorination and regeneration of nickel sulfate stripping in Comparative Example 2

[0058]

[0059]

[0060] In the process of using the LX869 defluorination resin in Comparative Example 2, a small amount of Ni ions will be adsorbed. During the pickling process with 1 wt%, Zr elements will dissolve out. If a lower concentration of pickling is used, a large amount of turbid precipitation will occur during the caustic washing process, and a small amount of Zr will dissolve out. A large amount of Na ions will appear in the 4 BV effluent after regeneration and reuse, seriously affecting the product quality. And this phenomenon becomes more serious after continuous use for 5 cycles, and the defluorination performance drops severely.

[0061] Comparative Example 3

[0062] Taking the nickel sulfate stripping solution in Example 2 as the experimental object, the concentrations of Ni 2+ , F - , Na + , Zr4+ The plasma concentration was measured, and then commercially available zirconium hydroxide defluorination agent powder was added thereto. The dosage was 100 times the concentration of F ions in the solution. The mixture was stirred and reacted for 1 h, filtered, washed, and the concentrations of various elements in the defluorinated solution were measured. The used defluorination agent was regenerated and recycled using 2 wt% liquid caustic soda.

[0063] The fluoride ion concentration in nickel sulfate after the first treatment was 3 - 4 mg / L. Ca in the treated solution was detected 2+ The concentration reached 0.0075 g / L, and a small amount of Zr 4+ was 0.0015 g / L. Ni 2+ residual precipitate would appear during the regeneration process, and Na 2+ would be introduced into the new defluorinated and refined solution. After using it for three cycles, the defluorination effect decreased significantly, only reaching 12 mg / L. There would be obvious losses during the transfer of the defluorination agent, along with yellow oil droplets enriched.

[0064] From the defluorination effect and regeneration data of the stripping nickel sulfate refining in Examples 1 - 3 and Comparative Examples 1 - 3 above, it can be seen that the present invention can ensure effective deep defluorination of stripping nickel sulfate without introducing impurity ions, without involving the loss of main elements, and truly achieve the refinement of the backend product; compared with general defluorination resins on the market, there is no Na ion replacement and dissolution of some loaded metal ions, making the subsequent MVR process simpler and more secure; the enriched F - is used to prepare high - purity sodium fluoride, improving the additional economic value of the product. The nitrogen - containing groups on its acrylate - based basic anion resin are more than those on the styrene - based anion resin. The characteristics of high cross - linking degree and gel - type structure make the metal loading more secure and difficult to dissolve. The organic charged functional groups weaken the mass transfer reaction between cations and the internal substances of the resin, which can effectively avoid the influence of Ni loss, dissolution of loaded metals, and significant reduction of the defluorination performance of the resin.

[0065] The above embodiments are only used to explain the inventive concept of the present invention, rather than limiting the protection scope of the rights of the present invention. Any non - substantial modification made to the present invention using this concept shall fall within the protection scope of the present invention.

Claims

1. A method for refining and removing fluorine by stripping nickel sulfate solution, characterized in that: The specific steps are as follows: (1) Load the alkaline anion defluorination resin into the resin column and wash it with sodium hydroxide, sulfuric acid and pure water in sequence until the effluent is clear; (2) taking the nickel sulfate stripping solution from the workshop, detecting the ion concentration of the solution, and then using a pump to pass the solution through the resin in step (1) for purification and defluorination, and taking samples at regular intervals to determine the concentration of each element in the effluent; (3) After the nickel sulfate in step (2) is refined and fluorinated, the F - When the concentration is greater than or equal to 5 mg / L, the adsorption is stopped, and the resin is backwashed and regenerated. The backwash regeneration liquid is sampled and tested. After the regeneration is complete, the nickel sulfate solution is continued to be stripped for refining; (4) The refined and defluorinated nickel sulfate solution is pumped into the MVR system for crystallization to prepare battery-grade nickel sulfate. The condensed water obtained during the evaporation and concentration process can be used as pure water; (5) The alkaline washing eluate obtained in the resin backwash regeneration in step (3) is filtered and then added with an alkaline sodium reagent to prepare sodium fluoride with a purity of more than 99% by a crystallization process. The low-fluorine alkaline solution after fluorine recovery is used to prepare 2%~3% wt Sodium hydroxide.

2. The method for refining and removing fluorine from a stripping nickel sulfate solution according to claim 1, characterized in that: In the step (1), the alkaline anion defluorination resin is Zr 4+ 、Ce 4+ and double metal oxide or hydroxide modified alkaline anion gel resin.

3. A method for refining and removing fluorine from a stripping nickel sulfate solution as claimed in claim 2, characterized in that: The alkaline anion defluorination resin is Zr 4+ Modified acrylic alkaline anionic gel resin with a cross-linking degree greater than 12%.

4. The method for refining and removing fluorine from a stripping nickel sulfate solution according to claim 1, characterized in that: In the step (2), the ion concentration of F - The concentration is 200~300mg / L, Ni 2+ The concentration is 110~150g / L, Na + The concentration is 0.001~0.003g / L, Mg 2+ The concentration is 0.003~0.004g / L, Ca 2+ The concentration is less than or equal to 0.002g / L; the concentrations of other impurity metal ions are all less than 0.0005g / L, and the pH value is 2~4.

5. The method for refining and removing fluorine from a stripping nickel sulfate solution according to claim 1, characterized in that: The flow rate of the nickel sulfate stripping solution in step (2) is 1-3 BV / h.

6. The method for refining and removing fluorine from a stripping nickel sulfate solution according to claim 1, characterized in that: The solutions used in the backwash regeneration in step (3) are pure water, liquid alkali, pure water, sulfuric acid, pure water, and the mass fraction of the liquid alkali is 2-3%. wt , sulfuric acid mass fraction is 1~1.7% wt .

7. A method for refining and removing fluorine from a stripping nickel sulfate solution as claimed in claim 6, characterized in that: During backwash regeneration in step (3), the flow rate of sulfuric acid and liquid alkali solution is 2-4 BV / h.

8. The method for refining and removing fluorine from a stripping nickel sulfate solution according to claim 1, characterized in that: When the Na concentration in the final pure water elution effluent during the backwash regeneration process in step (3) is ≤2 mg / L, the backwash regeneration is considered to be complete.

9. The method for refining and removing fluorine from a stripping nickel sulfate solution according to claim 1, characterized in that: The alkaline sodium reagent added to the alkaline washing solution in step (5) is liquid sodium hydroxide, and the amount added is 1.1 to 1.3 times the F ion concentration in the alkaline washing solution.

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