A method for separating mixed sulfates

Abstract

This invention belongs to the field of metal ion separation technology, specifically disclosing a method for separating mixed sulfates. In the mixed sulfate separation method provided by this invention, the mixed sulfate is Ni-containing... 2+ Co 2+ Cu 2+ Or Li + K + Na + The specific steps of this invention for obtaining mixed sulfate solutions include: adding a salt phase building agent to the mixed sulfate solution and adjusting the pH to 4-5.5 to obtain a salt phase; mixing the salt phase with an oil phase and a polymer phase to generate a three-phase coexistence system; allowing the phases to separate by standing, and then adjusting the pH to 6-7.5 and allowing it to stand again to obtain a Cu- or Na-rich polymer phase, a Co- or K-rich oil phase, and a Ni- or Li-rich salt phase. This invention utilizes a combination of "multiple driving forces synergistic enhancement, cation-directed selection, and segmented acidity control" to achieve efficient and simultaneous separation of multiple metal ions in sulfate solutions containing nickel, cobalt, copper, lithium, sodium, or potassium.

Description

Technical Field

[0001] This invention relates to the field of metal ion separation technology, and in particular to a method for separating mixed sulfates. Background Technology

[0002] With the rapid expansion of the new energy industry chain, the generation and utilization of sulfate system solutions are showing a trend of "simultaneous expansion at both ends": on the one hand, sulfuric acid leaching is widely used in the resource recycling of waste power batteries and metal-containing solid waste, producing Cu-containing solutions. 2+ / Co 2+ / Ni 2+ Mixed sulfate leachates, etc.; on the other hand, against the backdrop of intensifying supply and demand contradictions in lithium resources, the development and utilization of unconventional lithium resources such as salt lake brines are accelerating, and related processes often form Li... + / Na + / K + The system consists mainly of a mixed sulfate solution and a circulating mother liquor. Although the two systems originate from different sources, they both share common characteristics such as high sulfate content, high ionic strength, complex composition, and the need for selective separation / directional enrichment. Failure to achieve efficient separation and recovery will not only result in resource loss but also significantly increase the pressure on subsequent purification, recycling, and environmental remediation, hindering the economic efficiency and green development of the process.

[0003] To achieve the separation of various sulfates, the industry currently uses four main methods: crystallization, which utilizes differences in solubility but has limited selectivity and is prone to eutectic entrainment; precipitation, which separates by generating sparingly soluble salts but suffers from severe co-precipitation and colloid formation; and adsorption, which relies on ion exchange of materials, but is hampered by high ionic strength and SO42-. 2- Competition weakens capacity and selectivity; extraction methods rely on extractants to achieve ion migration and back-extraction, which has strong selectivity, but the high sulfate hydration energy leads to insufficient extraction driving force, poor separation effect and easy emulsification and loss of organic phase.

[0004] To address the challenges of extracting and separating sulfate ions during the extraction process, as well as the risk of emulsification leading to the formation of a third phase and subsequent organic phase loss, Chinese patents CN114181230A and CN119707997A both employ a macrocyclic organic acceptor to achieve high selectivity and strong binding of target metal ions in sulfate solutions. However, its high molecular weight and strong hydrogen bonds result in high viscosity and low interfacial tension, making subsequent recovery difficult. Chinese patent CN102234721A uses N902 to extract copper, followed by P204 extraction for impurity removal and P507 extraction to separate nickel and cobalt, extracting nickel, cobalt, and copper from the nickel-cobalt material. However, this multiple extraction and separation process is lengthy and requires periodic pH control to ensure smooth extraction. Chinese patent CN111996373A adds a hydroxyoxime extractant to the sulfuric acid leachate for copper extraction; after pretreatment of the raffinate including oxidation and pH adjustment, a co-extraction organic phase is added to complete the cobalt extraction. After separation, cobalt-containing wash water is added to the cobalt-supported co-extraction organic phase for another phase separation, thereby obtaining high-purity copper and cobalt materials. However, when the copper content in the system is high, a third phase is still easily generated. In addition, Chinese patent CN120866636A provides an imidazole derivative-organophosphate combined extractant to extract nickel and cobalt ions from sulfate solutions. However, imidazole and its substituted derivatives are expensive and have complex synthetic routes, making them unsuitable as extractants for large-scale wet recovery systems.

[0005] Therefore, a new method for separating mixed sulfates is needed to achieve the separation of Cu. 2+ Co 2+ Ni 2+ Or Li + Na + K + Efficient separation of metal ions from mixed sulfates. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for separating mixed sulfates. The method utilizes a highly selective extraction system, employing an acidic phosphorus-containing extractant and a carboxylic acid extractant respectively immobilized in immiscible oil and polymer phases. The ionic strength and water activity effects of the salt phases are superimposed to construct a multi-channel selective mass transfer at the three-phase interface, significantly improving extraction efficiency and enabling the separation of Cu... 2+ Co 2+ Ni 2+ Or Li + Na + K + Efficient separation of metal ions from mixed sulfates.

[0007] This invention provides a method for separating mixed sulfates, wherein the mixed sulfates are Ni-containing... 2+ Co 2+ Cu 2+Or Li + K + Na + The separation method for the mixed sulfates includes the following steps:

[0008] S1. Add a salt phase building agent to the mixed sulfate solution and adjust the pH to 4-5.5 to obtain the salt phase;

[0009] S2. Add an oil phase containing a diluent and an acidic phosphorus-containing extractant, and a polymer phase containing a polyether solubilizer and a carboxylic acid extractant to the salt phase of step S1, and mix to generate a three-phase coexistence system.

[0010] S3. Allow to stand for 30-60 minutes to separate the phases, allowing Cu to... 2+ Or Na + The preferential complexation and partitioning into the polymer phase are then performed, followed by adjusting the pH of the three-phase system to 6-7.5, and allowing it to stand for 60-120 minutes to allow the Co phases to separate. 2+ or K + Ni is preferentially allocated to the oil phase. 2+ Or Li + Retained in the salt phase, it yields a polymer phase rich in Cu or Na, an oil phase rich in Co or K, and a salt phase rich in Ni or Li.

[0011] According to some embodiments of the present invention, the salt phase building agent includes at least one of ammonium sulfate, sodium sulfate, potassium sulfate, lithium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, aluminum sulfate, ferric sulfate, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, nickel sulfate, cobalt sulfate, sodium bisulfate, or potassium bisulfate.

[0012] According to some embodiments of the present invention, the salt phase building agent is an aqueous solution with a mass fraction of 10wt% to 40wt%; preferably, the mass fraction is 20wt% to 40wt%.

[0013] According to some embodiments of the present invention, when the mixed sulfate system is Ni 2+ Co 2+ Cu 2+ At that time, n(SO4) in the salt phase building agent 2- ):n(Ni 2+ ) = (1.5~3):1; Preferably, n(SO4) 2- ):n(Ni 2+ = (2~3): 1.

[0014] According to some embodiments of the present invention, when the mixed sulfate system is Li + K + Na + At that time, n(SO4) in the salt phase building agent 2-): n(Li + ) = (2~4.5):1; Preferably, n(SO4) 2- ): n(Li + = (3~4.5): 1.

[0015] This invention uses an appropriate amount of salt phase building agent to provide salting-out effect to enhance three-phase separation and inhibit the transfer of Ni / Li to the organic phase, so that Ni / Li is mainly retained in the salt phase. This can maintain stable three-phase stratification and provide a good charge balance environment.

[0016] According to some embodiments of the present invention, in step S1, the pH is adjusted to 4-5, and the pH adjusting agent includes hydrochloric acid, sulfuric acid or nitric acid.

[0017] According to some embodiments of the present invention, in step S2, the temperature of the three-phase mixing is 20~60°C, preferably 40~60°C.

[0018] According to some embodiments of the present invention, in step S2, the salt phase, oil phase and polymer phase are mixed in a volume ratio of 1:(0.3~2):(0.3~2); preferably, they are mixed in a volume ratio of 1:(0.3~1):(0.6~1.5).

[0019] According to some embodiments of the present invention, the diluent includes at least one of anhydrous kerosene, sulfonated kerosene, Shellsol D70, Shellsol D80, Shellsol A150, Shell GTL Solvent GS190, Isopar L, Isopar M, Exxsol D80, Escaid 110, or Solvesso 150ND.

[0020] According to some embodiments of the present invention, the acidic phosphorus-containing extractant includes at least one of Cyanex 272, Cyanex 301, Cyanex 302, D2EHPA, HEHEHP, Ionquest 290, Ionquest 801, DOPA, D2EHPA-type, or EHEHPA.

[0021] According to some embodiments of the present invention, the concentration of the acidic phosphorus-containing extractant in the oil phase is 0.5~2.5 mol / L, preferably 1~2 mol / L; the volume ratio of the diluent to the acidic phosphorus-containing extractant is (2~3):1, preferably (2.5~3):1.

[0022] According to some embodiments of the present invention, when the mixed sulfate system is Ni 2+ Co 2+ Cu 2+At that time, the ratio of n (acidic phosphorus-containing extractant) in the oil phase to n (Co) is: 2+ ) = (1~6):1; Preferably, n (acidic phosphorus-containing extractant):n (Co 2+ = (4~6): 1.

[0023] According to some embodiments of the present invention, when the mixed sulfate system is Li + K + Na + At that time, the ratio of n (acidic phosphorus-containing extractant) in the oil phase to n (K) is: + ) = (4~6):1; Preferably, n (acidic phosphorus-containing extractant):n (K + = (5~6): 1.

[0024] According to some embodiments of the present invention, the polyether solubilizer includes at least one of PEG, mPEG, PPG, PolyTHF or polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer; preferably, the molecular weight of the polyether solubilizer is 600 to 6000.

[0025] According to some embodiments of the present invention, the carboxylic acid extractant includes at least one of Versatic Acid 10, Versatic Acid 911, naphthenic acid, 2-ethylhexanoic acid, neononanoic acid, isononanoic acid, isodecanic acid, n-decanoic acid, lauric acid, oleic acid, or nonanoic acid.

[0026] According to some embodiments of the present invention, the mass fraction of polyether solubilizer in the polymer phase is 10wt%~50wt%, preferably 40wt%~50wt%; the concentration of carboxylic acid extractant is 0.1~1.0mol / L, preferably 0.5~1mol / L; and the volume ratio of polyether solubilizer to carboxylic acid extractant is (2~3):1.

[0027] According to some embodiments of the present invention, when the mixed sulfate system is Ni 2+ Co 2+ Cu 2+ At that time, the ratio of n (carboxylic acid extractant) to n (Cu) in the polymer phase is: 2+ ) = (1~5):1; Preferably, n (carboxylic acid extractant):n (Cu) 2+ = (2~5): 1.

[0028] According to some embodiments of the present invention, when the mixed sulfate system is Li + K + Na + At that time, the oil phase contains n (carboxylic acid extractant): n (Na) +) = (3~5):1; Preferably, n(carboxylic acid extractant):n(Na+) = (4~5):1.

[0029] According to some embodiments of the present invention, the separation method further includes the following steps:

[0030] S4. The polymer phase and oil phase obtained in step S3 are mixed with an acid solution of 1.0~4.0 mol / L respectively, and back-extracted to obtain salt solutions containing Cu or Na, Co or K respectively.

[0031] S5. Adjust the pH of the salt phase obtained in step S3 to 7.5~9.5, add carbonate, and precipitate to obtain a product containing Ni or Li.

[0032] According to some embodiments of the present invention, in step S4, the acid solution is at least one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid; the volume ratio of the acid solution to the polymer phase or oil phase is (0.5~3):1; the back-extraction temperature is 30~60℃ and the contact time is 10~60min, and the back-extraction solution is directly used to obtain salt crystals by evaporation and crystallization.

[0033] According to some preferred embodiments of the present invention, in step S4, the back-extraction temperature is 40~50°C, the contact time is 30~60 min, and the volume ratio of the acid solution to the polymer phase or oil phase is (1.5~2.5):1.

[0034] According to some embodiments of the present invention, in step S5, n(CO3) 2- ):n(Ni 2+ = (1~2): 1 Add carbonate; the carbonate includes ammonium carbonate or ammonium bicarbonate; the precipitation reaction is: stir the reaction at 20~60℃ for 0.5~2h, and separate the solid and liquid to obtain a precipitate containing Ni or Li.

[0035] According to some preferred embodiments of the present invention, in step S5, the pH of the salt phase is adjusted to 8.5-9.5; according to n(CO3) 2- ):n(Ni 2+ ) = (1.5~2):1 Add carbonate; The precipitation reaction is: stir the reaction at 40~60℃ for 1.5~2h.

[0036] The technical principle of this invention lies in achieving efficient and simultaneous separation of multiple metal ions in solutions containing nickel, cobalt, copper, lithium, sodium, and potassium sulfates by combining a combination of "synergistic enhancement of multiple driving forces, cation-directed selection, and segmented acidity control." First, the system significantly enhances the mass transfer and migration capabilities of metal sulfates at the three-phase interface through the superposition of multiple driving forces, including salting-out effect, interfacial potential difference, and polymer network effect. The high ionic strength of the salt phase reduces water activity, increasing the chemical potential difference of metal ions, thereby promoting the separation of Cu... 2+ (Na + ), Co 2+ (K + Selective migration along different interfacial directions, with the salting-out effect and PEG network structure jointly inhibiting emulsification and stabilizing stratification. Secondly, the system achieves directional selection of cations through partitioned functional design: the carboxylic acid extractant in the polymer phase mainly functions as a coordination complex, targeting Cu... 2+ (Na + It has strong affinity; the phosphoric acid extractant in the oil phase mainly uses cation exchange, and is effective against Co. 2+ (K + The selectivity is the highest; while Ni 2+ (Li + Under the competitive coordination of strong hydration and sulfate ions, Cu remains stably in the salt phase. Finally, directional partitioning is achieved through segmented acidity control: under low acidity conditions, Cu... 2+ (Na + Co preferentially complexes into the polymer phase; as the acidity gradually decreases, Co... 2+ (K + The phosphorus extractant is exchanged into the oil phase, while Ni... 2+ Because the migration potential is lowest, it remains in the salt phase. Through the synergistic effect of the above multiple mechanisms, this system can achieve selective migration of Cu(Na), Co(K), and Ni(Li) to the oil phase, polymer phase, and salt phase, respectively, in a single contact process, which not only enhances the extraction driving force but also takes into account separation efficiency and phase stability.

[0037] The beneficial effects of this invention are:

[0038] 1) The method for separating mixed sulfates of the present invention greatly enhances the mass transfer and migration ability of metal sulfates at the three-phase interface through the superposition of multiple driving forces such as salting-out effect, interfacial potential energy difference and polymer network effect, and greatly improves the extraction effect of the extraction system on sulfates.

[0039] 2) The method for separating mixed sulfates of the present invention introduces a three-liquid phase system to achieve the separation of different elements. The polymer phase and the oil phase each perform different selective functions: the carboxylic acid extractant complexes Cu... 2+ (Na + ), phosphoric acid-containing extractant exchange Co 2+(K + ), while Ni 2+ Due to strong hydration and coordination with sulfate, Cu(Na), Co(K), and Ni(Li) are stabilized in the salt phase, thereby achieving the directional distribution of Cu(Na), Co(K), and Ni(Li) to the oil phase, polymer phase, and salt phase, respectively.

[0040] 3) The method for separating mixed sulfates in this invention employs a two-stage programmed acidity adjustment during the extraction process, preferentially extracting Cu under weakly acidic conditions. 2+ (Na + Co is started under weakly acidic conditions. 2+ (K + Extraction, while Ni 2+ (Li + It remains in the aqueous phase throughout, achieving three-dimensional synchronous separation within a single contact.

[0041] 4) The method for separating mixed sulfates of the present invention is stable, produces less emulsification, and can be continuously scaled up. The polymer phase and the phase modifier work together to reduce interfacial tension and increase the phase separation rate, resulting in a clear system interface and strong anti-emulsification properties.

[0042] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0044] Figure 1 This is a schematic diagram of the separation method of copper-cobalt-nickel mixed sulfate in Example 1 of the present invention. Detailed Implementation

[0045] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0046] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0047] Example 1

[0048] This embodiment provides a method for processing Ni-containing... 2+ Co 2+ and Cu 2+The method for separating sulfate solutions involves the following steps:

[0049] 1) Take Ni-containing 2+ Co 2+ and Cu 2+ 1000 mL of a mixed sulfate solution, in which Ni 2+ Co 2+ and Cu 2+ The concentrations were 4.36 g / L, 1.45 g / L, and 1 g / L, respectively;

[0050] 2) Add 30 wt% ammonium sulfate, potassium sulfate, and magnesium sulfate salt phase building agents to the mixed sulfate solution, and control the n(SO4) content in the salt phase building agent. 2- ): n(Ni) in mixed sulfate solution 2+ The ratio of sulfate ions to sodium sulfate is 2.5:1; hydrochloric acid is slowly added to adjust the pH of the system to 4.5, resulting in a high ionic strength aqueous phase (salt phase) containing sulfate ions.

[0051] 3) Preparation of oil phase mother liquor: Using anhydrous kerosene as a diluent, add acidic phosphorus-containing extractant Cyanex 272 to achieve an extractant concentration of 1.6 mol / L, while controlling the volume ratio of diluent to extractant at 2.8:1; according to Co... 2+ Molarity meter, so that n(extractant) in the oil phase: n(Co) in the mixed sulfate solution 2+ =4.6:1;

[0052] Preparation of polymer phase mother liquor: Using PEG4000 as a polyether solubilizer (45wt%), add Versatic Acid 10 as a carboxylic acid extractant to achieve an extractant concentration of 0.8mol / L, while controlling the volume ratio of solubilizer to extractant at 2.2:1; according to Cu 2+ Molarity meter, so that n(extractant) in the polymer phase: n(Cu) in the mixed sulfate solution 2+ =3.6:1;

[0053] 4) At 50℃, the salt phase obtained in step 2) is brought into contact and mixed with the oil phase and polymer phase obtained in step 3). The oil phase, polymer phase, and salt phase are taken in a volume ratio of 0.8:1:1. After mixing for 25 min, a stable three-phase coexistence system is formed. Subsequently, it is kept at pH=4.5 for 45 min to allow Cu 2+ The preferential complexation and partitioning into the polymer phase; without disrupting the three-phase system, ammonia water is slowly added dropwise to adjust the pH of the system to 6.8, mixed for 10 min, and allowed to stand for 80 min for phase separation, allowing Co to... 2+ Ni undergoes cation exchange with the extractant in the oil phase and preferentially partitions into the oil phase. 2+Under the inhibition of salting-out, it is mainly retained in the salt phase;

[0054] The resulting phases consist of a Cu-rich polymer phase, a Co-rich oil phase, and a Ni-rich salt phase; the phase distribution ratio is: Cu 2+ The partition ratio in the polymer phase / oil phase / salt phase is approximately 94.6%:2.2%:3.2%; Co 2+ The distribution in the polymer phase / oil phase / salt phase is approximately 3.9%:92.1%:4.0%; Ni 2+ The distribution in the polymer phase / oil phase / salt phase is approximately 1.8%:1.9%:96.3%;

[0055] 5) Perform back-extraction on the three phases separately:

[0056] Acidic back-extraction was performed on the Cu-rich polymer phase by adding 2.5 mol / L sulfuric acid, with the temperature controlled at 45℃ and the contact time at 40 min. The volume ratio of acid phase to polymer phase was 2:1, resulting in a Cu-containing sulfate solution.

[0057] Acidic back-extraction was performed on the Co-rich oil phase by adding 2.5 mol / L sulfuric acid, with the temperature controlled at 45℃ and the contact time at 40 min. The volume ratio of acid phase to oil phase was 2:1, resulting in a Co-containing sulfate solution.

[0058] For the Ni-rich salt phase, adjust the pH to 9.0 with ammonia, then proceed according to n(CO3) 2- ):n(Ni 2+ Ammonium carbonate was added at a ratio of 1.8:1, and the mixture was stirred at 50°C for 1.5 hours. After solid-liquid separation, a nickel-containing precipitate was obtained.

[0059] Cu 2+ The back-extraction rate from the polymer phase to the acid phase was 97.2%, Co 2+ The back-extraction rate from the oil phase to the acid phase is 96.5%; the back-extraction solution can be further evaporated and crystallized to obtain copper sulfate or cobalt sulfate crystals.

[0060] Example 2

[0061] This embodiment provides a method for processing Ni-containing... 2+ Co 2+ and Cu 2+ The method for separating sulfate solutions involves the following steps:

[0062] 1) Take Ni-containing 2+ Co 2+ and Cu 2+ 1000 mL of a mixed sulfate solution, in which Ni 2+ Co 2+ and Cu 2+ The concentrations were 4.36 g / L, 1.45 g / L, and 1 g / L, respectively;

[0063] 2) Add a sodium sulfate and ammonium sulfate phase-forming agent with a mass fraction of 15 wt% to the mixed sulfate solution, and control the n(SO4) content in the salt phase-forming agent. 2- ):n(Ni 2+ The ratio of sulfate to nitric acid was 2.5:1; nitric acid was slowly added to adjust the pH of the system to 5.3, resulting in a salt phase containing sulfate ions.

[0064] 3) Preparation of the oil phase: Using Shellsol D70 as a diluent, add the acidic phosphorus-containing extractant HEHEHP to achieve an extractant concentration of 2.2 mol / L, while controlling the volume ratio of diluent to extractant to be 2:1; according to Co... 2+ Molarity meter, so that n(extractant):n(Co) in the oil phase 2+ = 1.5:1;

[0065] Polymer phase preparation: Using PEG600 as a polyether solubilizer (20 wt%), add 2-ethylhexanoic acid, a carboxylic acid extractant, to achieve an extractant concentration of 0.15 mol / L, while controlling the volume ratio of solubilizer to extractant at 3:1; according to Cu... 2+ Molar ratio meter, so that n(extractant):n(Cu) in the polymer phase 2+ = 1.2:1;

[0066] 4) At 30℃, the salt phase obtained in step 2) is brought into contact and mixed with the oil phase and polymer phase obtained in step 3). The oil phase, polymer phase, and salt phase are taken in a volume ratio of 1.5:0.4:1, and the mixture is stirred for 15 min to form a stable three-phase coexistence system. Then, it is kept at pH=5.3 for 60 min to allow Cu to... 2+ The preferential complexation and partitioning into the polymer phase; without disrupting the three-phase system, sodium hydroxide solution is slowly added dropwise to adjust the pH of the system to 7.4, mixed for 10 min, and allowed to stand for 80 min for phase separation, allowing Co to... 2+ Ni undergoes cation exchange with the extractant in the oil phase and preferentially partitions into the oil phase. 2+ Under the inhibition of salting-out, it is mainly retained in the salt phase;

[0067] The resulting phases consist of a Cu-rich polymer phase, a Co-rich oil phase, and a Ni-rich salt phase; the phase distribution ratio is: Cu 2+ The distribution in the polymer phase / oil phase / salt phase is approximately 88.4%:4.6%:7.0%; Co 2+ The distribution in the polymer phase / oil phase / salt phase is approximately 6.0%:82.0%:12.0%; Ni 2+ The distribution in the polymer phase / oil phase / salt phase is approximately 4.0%:5.0%:91.0%;

[0068] 5) Perform back-extraction on the three phases separately:

[0069] Acid back-extraction was performed on the Cu-rich polymer phase by adding 1 mol / L sulfuric acid, with the temperature controlled at 30℃ and the contact time at 15 min. The volume ratio of the acid phase to the polymer phase was 1:1, resulting in a Cu-containing sulfate solution.

[0070] Acid back-extraction was performed on the Co-rich oil phase by adding 1 mol / L sulfuric acid, with the temperature controlled at 30℃ and the contact time at 15 min. The volume ratio of the acid phase to the oil phase was 1:1, resulting in a Co-containing sulfate solution.

[0071] The pH of the Ni-rich salt phase was adjusted to 7.8 with ammonia, and then n(CO3) was added. 2- ):n(Ni 2+ Ammonium carbonate was added at a ratio of 1.1:1, and the mixture was stirred at 25°C for 0.8 hours. After solid-liquid separation, a nickel-containing precipitate was obtained.

[0072] Cu 2+ The back-extraction rate from the polymer phase to the acid phase was 91%, Co 2+ The back-extraction rate from the oil phase to the acid phase was 90.2%.

[0073] Example 3

[0074] This embodiment provides a method for processing Li-containing... + K + Na + The method for separating sulfate solutions involves the following steps:

[0075] 1) Take Li-containing + K + Na + 1000 mL of sulfate solution, containing Li + K + and Na + The concentrations were 4.36 g / L, 1.45 g / L, and 1 g / L, respectively.

[0076] 2) Add 30 wt% ammonium sulfate, potassium sulfate, and magnesium sulfate salt phase building agents to the above solution, and control the n(SO4) content in the salt phase building agent. 2- ):n(Li + The ratio of sulfate to 3.5:1 was used; hydrochloric acid was slowly added to adjust the pH of the system to 4.5, resulting in a high ionic strength salt phase containing sulfate.

[0077] 3) Preparation of the oil phase: Using anhydrous kerosene as a diluent, add acidic phosphorus-containing extractant Cyanex 272 to achieve an extractant concentration of 1.6 mol / L, while controlling the volume ratio of diluent to extractant at 2.8:1; according to K... + Molarity meter, so that n(extractant):n(K) in the oil phase + =5:1;

[0078] Polymer phase preparation: Using PEG4000 as a polyether solubilizer (45 wt%), add Versatic Acid 10, a carboxylic acid extractant, to achieve an extractant concentration of 0.8 mol / L, while controlling the volume ratio of solubilizer to extractant at 3:1; according to Na... + Molar ratio meter, so that n(extractant):n(Na) in the polymer phase + =4:1;

[0079] 4) At 50℃, the salt phase obtained in step 2) is brought into contact and mixed with the oil phase and polymer phase obtained in step 3). The oil phase, polymer phase, and salt phase are taken in a volume ratio of 1:1.5:1. After mixing for 35 min, a stable three-phase coexistence system is formed. Subsequently, the mixture is kept at pH=4.5 for 50 min to allow Na... + The preferential complexation and partitioning into the polymer phase; without disrupting the three-phase system, ammonia water is slowly added dropwise to adjust the pH of the system to 7, mixed for 10 minutes, and allowed to stand for 80 minutes to separate the phases, allowing K to... + It undergoes cation exchange with the extractant in the oil phase and preferentially partitions into the oil phase, while Li + Under the inhibition of salting-out, it is mainly retained in the salt phase;

[0080] The resulting phases consist of a Na-rich polymer phase, a K-rich oil phase, and a Li-rich salt phase; the three phase distribution ratio is: Na + The partition ratio in the polymer phase / oil phase / salt phase is approximately 92.6%:2.2%:5.2%; K + The distribution in the polymer phase / oil phase / salt phase is approximately 3.2%:90.8%:6.0%; Li + The distribution in the polymer phase / oil phase / salt phase is approximately 1.4%:2.9%:95.7%;

[0081] 5) Perform back-extraction on the three phases separately:

[0082] Acidic back-extraction was performed on the Na-rich polymer phase by adding 2.5 mol / L sulfuric acid, with the temperature controlled at 45℃ and the contact time at 40 min. The volume ratio of acid phase to polymer phase was 2.5:1, resulting in a Na-containing sulfate solution.

[0083] Acidic back-extraction was performed on the K-rich oil phase by adding 2.5 mol / L sulfuric acid, with the temperature controlled at 45℃ and the contact time at 40 min. The volume ratio of acid phase to oil phase was 2.5:1, resulting in a K-containing sulfate solution.

[0084] The pH of the Li-rich salt phase was adjusted to 9.0 with ammonia, and then n(CO3) was added. 2- ):n(Li +Ammonium carbonate was added at a ratio of 1.5:1, and the mixture was stirred at 50°C for 1.5 hours. After solid-liquid separation, a Li-containing precipitate was obtained.

[0085] Na + The back-extraction rate from the polymer phase to the acid phase was 98.4%, K + The back-extraction rate from the oil phase to the acid phase is 95.2%; the back-extraction solution can be further evaporated and crystallized to obtain sodium sulfate or potassium sulfate crystals.

[0086] For Li + K + Na + In this invention, a mixed sulfate system is described. The invention utilizes the three-phase phase separation behavior induced by high sulfate ionic strength and the differences in extraction and complexation capabilities among different phases under segmented pH control to achieve Li… + K + Na + The targeted allocation was achieved by first constructing a high-salt system by adding salt-phase building agents such as ammonium sulfate, potassium sulfate, and magnesium sulfate, thereby increasing the SO42- content. 2- / Li + This creates a sulfate environment with high ionic strength and low water activity in the system, providing a basis for salting out the three phases to coexist stably, and also amplifying the Li... + K + Na + Differences in hydration capacity (Li + >Na + >K + This enhances the relative strength of the salt's hydration of the Li ion. + The retention tendency was observed; subsequently, an oil phase and a polymer phase were introduced. The former provided a low-polarity acidic extraction environment, while the latter provided a moderately polar complexing environment that combined polyether solubilization and carboxylic acid coordination capabilities. Under the pH conditions of the first acidity window, the polyether oxygen and carboxylic acid sites in the polymer phase exhibited a high degree of Na+ retention. + It exhibits preferential complexation, making Na + First it enters the polymer phase, while Li + Due to the high hydration energy and high cost of desolvation, the extractant remains primarily in the salt phase under high sulfate salting-out conditions. By adjusting the pH to the second acidity window without disrupting the three-phase structure, the system's acidity decreases, increasing the deprotonation of the acidic phosphorus-containing extractant and enhancing its cation exchange capacity in the oil phase. At this point, K, with its weaker hydration and lower interphase migration resistance, becomes more readily available. + It is more likely to exchange with the oil phase extractant and preferentially enter the oil phase, while Li + It remains in the salt phase due to strong hydration and salt phase stabilization, thus forming Na. + Migration to the polymer phase, K + Migration to the oil phase, Li +The distribution of salt phases was investigated; finally, acid back-extraction was performed on the Na-rich polymer phase and the K-rich oil phase, essentially utilizing H₂ under high acidity conditions. + Reverse displacement of the complexed cation, Na + and K + The solution is switched back to an aqueous sulfate phase, while the Li-rich salt phase is improved by increasing the pH and introducing CO3. 2- Make Li + It precipitates as a low-solubility carbonate.

[0087] Comparative Example 1

[0088] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0089] This comparative example is basically the same as Example 1, except that in step 4) of this comparative example, no polymer phase is added for mixing, and only the salt phase and oil phase are contacted and mixed for separation. The steps and conditions are the same as those in Example 1.

[0090] Separation results: Co 2+ It accounts for 86.8% of the oil phase, Ni 2+ It accounts for 84.1% of the salt phase, while Cu 2+ It is impossible to achieve directional distribution to the polymer phase; and obvious emulsification occurs.

[0091] Comparative Example 2

[0092] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0093] This comparative example is basically the same as Example 1, except that Versatic Acid 10 is not added when preparing the polymer phase in step 3) of this comparative example, and only PEG4000 (45wt%) is used to construct the polymer phase. The remaining steps and conditions are the same as those in Example 1.

[0094] Separation results: Cu 2+ The partition ratio in the polymer phase / oil phase / salt phase is approximately 43.7%:5.8%:50.5%, Co 2+ Ni accounts for 90.4% of the oil phase. 2+ It accounts for 95.0% of the salt phase.

[0095] Comparative Example 3

[0096] This comparative example provides a comparison of Ni-containing... 2+ Co2+ and Cu 2+ A method for separating sulfate solutions.

[0097] This comparative example is basically the same as Example 1, except that in step 3) of this comparative example, PEG400 is used instead of PEG4000 to prepare the polymer phase, and the remaining steps and conditions are the same as those in Example 1.

[0098] Separation results: Cu 2+ It accounts for 79.2% of the polymer phase, Co 2+ Ni accounts for 87.1% of the oil phase. 2+ It accounts for 91.5% of the salt phase.

[0099] Comparative Example 4

[0100] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0101] This comparative example is basically the same as Example 1, except that in step 3) of this comparative example, the concentration of Cyanex272 in the oil phase is changed from 1.6 mol / L to 0.8 mol / L. The other steps and conditions are the same as in Example 1.

[0102] Separation results: Cu 2+ It accounts for 93.1% of the polymer phase, Co 2+ Its proportion in the oil phase decreased to 69.4%, Ni 2+ It accounts for 95.6% of the salt phase.

[0103] Comparative Example 5

[0104] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0105] This comparative example is basically the same as Example 1, except that in step 2) of this comparative example, the mass fraction of inorganic salt in the salt phase is changed from 30wt% to 5wt%, and the remaining steps and conditions are the same as in Example 1.

[0106] Separation results: Cu 2+ It accounts for 85.6% of the polymer phase, Co 2+ It accounts for 76.8% of the oil phase, Ni 2+ It accounts for 82.4% of the salt phase.

[0107] Comparative Example 6

[0108] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0109] This comparative example is basically the same as Example 1, except that in step 4) of this comparative example, instead of maintaining the pH at 4.5 for 45 minutes, the system is directly adjusted to pH 6.8 after mixing and maintained for 125 minutes for separation. The remaining steps and conditions are the same as in Example 1.

[0110] Separation results: Cu 2+ Its proportion in the polymer phase decreased to 71.8%, Co 2+ It accounts for 87.5% of the oil phase, Ni 2+ The salt phase accounted for 88.7%; the system showed slight turbidity.

[0111] Comparative Example 7

[0112] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0113] This comparative example is basically the same as Example 1, except that in step 4) of this comparative example, the separation is maintained only at pH=4.5, and the pH is not adjusted to 6.8 for the second separation. The remaining steps and conditions are the same as in Example 1.

[0114] Separation results: Cu 2+ It accounts for 92.8% of the polymer phase, Co 2+ Ni accounts for only 41.6% of the oil phase. 2+ It accounts for 94.2% of the salt phase.

[0115] Comparative Example 8

[0116] This comparative example provides a comparison of Ni-containing... 2+ Co 2+ and Cu 2+ A method for separating sulfate solutions.

[0117] This comparative example is basically the same as Example 1, except that in step 4), the volume ratio of oil phase: polymer phase: salt phase is changed from 0.8:1:1 to 1.5:2.5:2.5. The remaining steps and conditions are the same as in Example 1.

[0118] Separation results: Cu 2+ It accounts for 68.9% of the polymer phase, Co 2+Ni accounts for only 90.2% of the oil phase. 2+ It accounts for 89.5% of the salt phase.

[0119] Comparative Example 9

[0120] This comparative example provides a comparison of Li-containing... + Na + and K + A method for separating sulfate solutions.

[0121] This comparative example is basically the same as Example 3, except that in step 4) of this comparative example, no polymer phase is added for mixing, and only the salt phase and oil phase are contacted and mixed for separation. The steps and conditions are the same as those in Example 3.

[0122] Separation results: Na + It accounts for 89.74% of the oil phase, Li + It accounts for 94.15% of the salt phase, while K + It is impossible to achieve directional distribution to the polymer phase; and obvious emulsification occurs.

[0123] Comparative Example 10

[0124] This comparative example provides a comparison of Li-containing... + Na + and K + A method for separating sulfate solutions.

[0125] This comparative example is basically the same as Example 3, except that Versatic Acid 10 is not added when preparing the polymer phase in step 3) of this comparative example, and only PEG4000 (45wt%) is used to construct the polymer phase. The remaining steps and conditions are the same as those in Example 3.

[0126] Separation result: K + The distribution ratio in the polymer phase / oil phase / salt phase is approximately 40.6%:6.49%:52.91%, Na + It accounts for 90.5% of the oil phase, Li + It accounts for 93.76% of the salt phase.

[0127] Comparative Example 11

[0128] This comparative example provides a comparison of Li-containing... + Na + and K + A method for separating sulfate solutions.

[0129] This comparative example is basically the same as Example 3, except that in step 3) of this comparative example, PEG400 is used instead of PEG4000 to prepare the polymer phase, and the remaining steps and conditions are the same as those in Example 3.

[0130] Separation result: K + It accounts for 79.86% of the polymer phase, Na + It accounts for 90.5% of the oil phase, Li + It accounts for 93.4% of the salt phase.

[0131] Comparative Example 12

[0132] This comparative example provides a comparison of Li-containing... + Na + and K + A method for separating sulfate solutions.

[0133] This comparative example is basically the same as Example 3, except that in step 3) of this comparative example, the concentration of Cyanex272 in the oil phase is changed from 1.6 mol / L to 0.8 mol / L. The other steps and conditions are the same as in Example 3.

[0134] Separation result: K + It accounts for 88.31% of the polymer phase, Na + Its proportion in the oil phase decreased to 57.14%, Li + It accounts for 94.56% of the salt phase.

[0135] In summary, the present invention utilizes a highly selective extraction system, employing an acidic phosphorus-containing extractant and a carboxylic acid extractant respectively immobilized in the immiscible oil phase and polymeric phase. The superimposed ionic strength and water activity effects of the salt phase construct a multi-channel selective mass transfer at the three-phase interface, significantly improving extraction efficiency and achieving extraction of Ni-containing extracts. 2+ Co 2+ Cu 2+ Or Li + K + Na + Efficient separation of mixed sulfate solutions.

[0136] In Comparative Examples 1 and 9, the lack of a polymer phase resulted in Cu... 2+ (K + It cannot achieve directional distribution to the polymer phase, and cannot achieve Ni 2+ Co 2+ Cu 2+ Or Li + Na + and K +Good separation of mixed sulfates; in Comparative Examples 2 and 10, the lack of the carboxylic acid extractant Versatic Acid 10 resulted in a relative decrease in polymer concentration compared to Cu. 2+ (or K) + The complexing / exchange capacity of Cu is insufficient. 2+ (or K) + Cu is difficult to preferentially extract into the polymer phase; in Comparative Examples 3 and 11, due to the small molecular weight of the polymer, the polarity / viscosity and phase stability of the polymer phase are insufficient, making it prone to entrainment or insufficient driving force for interphase mass transfer. 2+ (or K) + The enrichment capacity decreases, making it impossible to achieve Ni enrichment. 2+ Co 2+ Cu 2+ Or Li + Na + and K + Good separation of mixed sulfates; in Comparative Examples 4 and 12, the low concentration of the oil phase extractant led to Co... 2+ (or Na + Insufficient extraction capacity and partition ratio make it difficult to achieve selective transfer in the second step, thus preventing the realization of Ni. 2+ Co 2+ Cu 2+ Or Li + Na + and K + Good separation of mixed sulfates; in Comparative Example 5, the reduced concentration of the salt phase building agent resulted in insufficient ionic strength and salting-out effect, Ni 2+ Difficult to exist in the salt phase, unable to realize Ni 2+ Co 2+ Cu 2+ Or Li + Na + and K + Good separation of mixed sulfates; in Comparative Example 6, the omission of the preliminary extraction step in the three-liquid-phase system led to Cu... 2+ (or K) + The lack of pre-enrichment led to competitive extraction and mutual interference during subsequent staged pH adjustments, preventing the achievement of Ni extraction. 2+ Co 2+ Cu 2+ Or Li + Na + and K + Good separation of mixed sulfates; in Comparative Example 7, the second extraction step of the three-liquid-phase system was neglected, resulting in Co... 2+ (or Na + Unable to enter the oil phase in a specific direction, thus failing to achieve Ni 2+ Co 2+ Cu 2+Or Li + Na + and K + Good separation of mixed sulfates; in Comparative Example 8, due to an unreasonable three-phase ratio, the volume fraction of the three phases deviated from the stable region, resulting in insufficient mass transfer contact or increased entrainment / emulsification, thus failing to achieve Ni 2+ Co 2+ Cu 2+ Or Li + Na + and K + Good separation of mixed sulfates.

[0137] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for separating mixed sulfates, characterized in that, The mixed sulfate is Ni-containing 2+ Co 2+ Cu 2+ Or Li + K + Na + The separation method for the mixed sulfates includes the following steps: S1. Add a salt phase building agent to the mixed sulfate solution and adjust the pH to 4-5.5 to obtain the salt phase; S2. Add an oil phase containing a diluent and an acidic phosphorus-containing extractant, and a polymer phase containing a polyether solubilizer and a carboxylic acid extractant to the salt phase of step S1, and mix to generate a three-phase coexistence system. S3. Allow to stand for 30-60 minutes to separate the phases, allowing Cu to... 2+ Or Na + The preferential complexation and partitioning into the polymer phase are then performed, followed by adjusting the pH of the three-phase system to 6-7.5, and allowing it to stand for 60-120 minutes to allow the Co phases to separate. 2+ or K + Ni is preferentially allocated to the oil phase. 2+ Or Li + Retained in the salt phase, it yields a polymer phase rich in Cu or Na, an oil phase rich in Co or K, and a salt phase rich in Ni or Li.

2. The method for separating mixed sulfates according to claim 1, characterized in that, The salt phase building agent includes at least one of ammonium sulfate, sodium sulfate, potassium sulfate, lithium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, aluminum sulfate, ferric sulfate, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, nickel sulfate, cobalt sulfate, sodium bisulfate, or potassium bisulfate; the salt phase building agent is an aqueous solution with a mass fraction of 10wt% to 40wt%. When the mixed sulfate system is Ni 2+ Co 2+ Cu 2+ At that time, n(SO4) in the salt phase building agent 2- ):n(Ni 2+ ) = (1.5~3): 1; When the mixed sulfate system is Li + K + Na + At that time, n(SO4) in the salt phase building agent 2- ): n(Li + = (2~4.5):

1.

3. The method for separating mixed sulfates according to claim 1, characterized in that, The diluent includes at least one of anhydrous kerosene, sulfonated kerosene, Shellsol D70, Shellsol D80, Shellsol A150, Shell GTL Solvent GS190, Isopar L, Isopar M, Exxsol D80, Escaid 110, or Solvesso 150ND; The acidic phosphorus-containing extractant includes at least one of Cyanex 272, Cyanex 301, Cyanex 302, D2EHPA, HEHEHP, Ionquest 290, Ionquest 801, DOPA, D2EHPA-type, or EHEHPA.

4. The method for separating mixed sulfates according to claim 3, characterized in that, The concentration of the acidic phosphorus-containing extractant in the oil phase is 0.5~2.5 mol / L, and the volume ratio of the diluent to the acidic phosphorus-containing extractant is (2~3):1; When the mixed sulfate system is Ni 2+ Co 2+ Cu 2+ At that time, the ratio of n (acidic phosphorus-containing extractant) in the oil phase to n (Co) is: 2+ ) = (1~6): 1; When the mixed sulfate system is Li + K + Na + At that time, the ratio of n (acidic phosphorus-containing extractant) in the oil phase to n (K) is: + = (4~6):

1.

5. The method for separating mixed sulfates according to claim 1, characterized in that, The polyether solubilizer includes at least one of PEG, mPEG, PPG, PolyTHF, or polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer; The carboxylic acid extractant includes at least one of Versatic Acid 10, Versatic Acid 911, naphthenic acid, 2-ethylhexanoic acid, neononanoic acid, isononanoic acid, isodecanic acid, n-decanoic acid, lauric acid, oleic acid, or nonanoic acid.

6. The method for separating mixed sulfates according to claim 5, characterized in that, The polymer phase contains a polyether solubilizer with a mass fraction of 10wt%~50wt%, a carboxylic acid extractant concentration of 0.1~1.0mol / L, and a volume ratio of polyether solubilizer to carboxylic acid extractant of (2~3):1; When the mixed sulfate system is Ni 2+ Co 2+ Cu 2+ At that time, the ratio of n (carboxylic acid extractant) to n (Cu) in the polymer phase is: 2 + ) = (1~5): 1; when the mixed sulfate system is Li + K + Na + At that time, the oil phase contains n (carboxylic acid extractant): n (Na) + = (3~5):

1.

7. The method for separating mixed sulfates according to claim 1, characterized in that, In step S2, the salt phase, oil phase and polymer phase are mixed at a volume ratio of 1:(0.3~2):(0.3~2).

8. The method for separating mixed sulfates according to claim 1, characterized in that, The separation method further includes the following steps: S4. The polymer phase and oil phase obtained in step S3 are mixed with an acid solution of 1.0~4.0 mol / L respectively, and back-extracted to obtain salt solutions containing Cu or Na, Co or K respectively. S5. Adjust the pH of the salt phase obtained in step S3 to 7.5~9.5, add carbonate, and precipitate to obtain a product containing Ni or Li.

9. The method for separating mixed sulfates according to claim 8, characterized in that, In step S4, the acid solution is at least one of hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid; the volume ratio of the acid solution to the polymer phase or oil phase is (0.5~3):1; the back-extraction temperature is 30~60℃ and the contact time is 10~60min; the back-extraction solution is directly crystallized by evaporation to obtain salt crystals.

10. The method for separating mixed sulfates according to claim 8, characterized in that, In step S5, press n(CO3) 2- ):n(Ni 2+ = (1~2): 1 Add carbonate; the carbonate includes ammonium carbonate or ammonium bicarbonate; the precipitation reaction is: stir the reaction at 20~60℃ for 0.5~2h, and separate the solid and liquid to obtain a precipitate containing Ni or Li.

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