Method for recovering lithium from wastewater of a lithium-removing and impurity-removing resin

Abstract

The application provides a method for recovering lithium and removing impurities from resin wastewater resources, and belongs to the technical field of wastewater treatment. The method realizes efficient separation of hydrochloric acid (permeate 1) and lithium, calcium, magnesium and other ions (concentrate 1) in resin desorption liquid through nanofiltration treatment, the permeate 1 can be reused for resin regeneration; the concentrate 1 is subjected to hardening removal and evaporation and then enters a lithium precipitation unit, realizing recovery of lithium resources. At the same time, for resin flushing water, a filtration-two-stage reverse osmosis-electrodialysis step-by-step concentration coupling process is adopted to further enrich the salt-containing concentrated liquid; finally, the electrodialysis concentrated liquid is mixed with the lithium precipitation mother liquor and then is introduced into a bipolar membrane system, so that the lithium precipitation mother liquor is converted into acid and alkali which can be reused at the front end. The whole process route forms a closed loop system of "acid reuse-lithium recovery-water reuse-acid and alkali self-provision", and realizes resource recovery and utilization of all components in the resin wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for resource recovery from wastewater containing lithium extraction and impurity removal resin. Background Technology

[0002] Lithium, as an important strategic resource, has wide applications in new energy batteries, glass and ceramics, nuclear industry, and medicine. Currently, the main lithium extraction routes in China are divided into three major processes: lithium extraction from salt lake brine, lithium extraction from lepidolite mineral leaching, and lithium extraction from underground brine in oil and gas fields. Due to the high content of calcium, magnesium, and iron polyvalent metal ions in the raw water system, the above-mentioned lithium extraction processes generally include ion exchange resin units for calcium and magnesium removal in the refining stage to reduce the scaling risk of subsequent nanofiltration, reverse osmosis, or solvent extraction units.

[0003] However, the selective adsorption of calcium and magnesium ions by existing calcium and magnesium removal resins is not absolute during operation. In systems with high lithium ion concentrations, the resin will inevitably co-adsorb a certain amount of lithium ions. Therefore, the resin acid desorption waste liquid usually exhibits the three characteristics of "high acidity, high hardness, and high salt content". It also contains a considerable concentration of lithium ions as well as other impurity ions and organic matter, making it extremely difficult to treat.

[0004] Furthermore, after the resin becomes saturated with adsorption, it requires high-concentration hydrochloric acid for desorption and regeneration, generating a large amount of resin acid desorption wastewater. Simultaneously, the complete resin regeneration process includes acid desorption rinsing, alkali regeneration, and alkali washing, producing both acidic and alkaline rinsing water. These wastewaters are dispersed and have complex compositions; wastewater treatment and lithium resource recovery have become common technical challenges hindering clean production, cost reduction, and efficiency improvement in the lithium extraction industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method for resource recovery from lithium extraction and impurity removal resin wastewater. The recovery method provided in this application achieves the resource recovery and utilization of all components of the resin wastewater, including acid, lithium, water, and salts.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for resource recovery of lithium extraction and impurity removal resin wastewater, wherein the lithium extraction and impurity removal resin wastewater includes resin acid desorption solution, acidic rinsing water and alkaline rinsing water; The method includes the following steps: The resin acid desorption solution was subjected to nanofiltration to obtain concentrate 1 and permeate 1. The permeate 1 is reused for acid desorption of the lithium extraction and impurity removal resin; After the concentrated liquid 1 is subjected to hardening removal by a double alkali method, the first filtration is used to obtain filtrate 1; The filtrate 1 is evaporated and concentrated to obtain concentrated liquid and condensate; the condensate is directly recycled. The evaporated concentrate was mixed with sodium carbonate and subjected to a lithium precipitation reaction, followed by solid-liquid separation to obtain lithium carbonate and lithium precipitation mother liquor. After mixing acidic and alkaline rinsing water, the pH was adjusted to 6.5-7.2, and then the mixture was filtered a second time to obtain filtrate 2. The filtrate 2 is concentrated by two-stage reverse osmosis to obtain concentrate 2 and permeate 2; the permeate 2 is directly recycled. The concentrate 2 is subjected to electrodialysis to obtain electrodialysis concentrate and fresh water; the fresh water is returned and combined with the filtrate 2 for two-stage reverse osmosis concentration. The electrodialysis concentrate is mixed with the lithium precipitation mother liquor and then subjected to bipolar membrane treatment to obtain acid solution, alkali solution and salt chamber effluent; the salt chamber effluent is returned to be treated with the concentrate 2 for electrodialysis.

[0007] Preferably, the nanofiltration process uses a high-pressure and acid-resistant nanofiltration membrane; the high-pressure and acid-resistant nanofiltration membrane has a precision of 150~300 Da; and the operating pressure of the nanofiltration process is 5~7 MPa.

[0008] Preferably, the alkalis used in the dual-alkali method for hardening include sodium hydroxide and sodium carbonate.

[0009] Preferably, the hardening time of the double alkali method is 0.5~1h.

[0010] Preferably, the temperature of the lithium precipitation reaction is 80~95℃, and the time of the lithium precipitation reaction is 1~2h.

[0011] Preferably, the first filtration includes sequential plate and frame filtration and microfiltration membrane filtration; the filter cloth used for the plate and frame filtration has a pore size of 500~1200 mesh.

[0012] Preferably, the second filtration is microfiltration.

[0013] Preferably, the material of the microfiltration membrane is independently silicon carbide or ceramic; the pore size of the microfiltration membrane is independently 20~100nm; and the operating pressure of the microfiltration membrane is independently 0.3~0.4MPa.

[0014] Preferably, the two-stage reverse osmosis concentration includes a first-stage reverse osmosis and a second-stage reverse osmosis, wherein the operating pressure of the first-stage reverse osmosis is 5~7 MPa and the operating pressure of the second-stage reverse osmosis is 2~4 MPa.

[0015] Preferably, the current density of the electrodialysis treatment is 300~600 A / m 2 .

[0016] This invention provides a method for resource recovery from lithium extraction and impurity removal resin wastewater. Nanofiltration efficiently separates hydrochloric acid (permeate 1) from lithium, calcium, and magnesium ions (concentrate 1) in the resin desorption solution, allowing permeate 1 to be reused for resin regeneration. Concentrate 1, after hardening and evaporation, enters the lithium precipitation unit, achieving lithium resource recovery. The resin rinse water undergoes a staged concentration coupling process of "filtration-two-stage reverse osmosis-electrodialysis" to further enrich the salt-containing concentrate. Finally, the electrodialysis concentrate is mixed with the lithium precipitation mother liquor and introduced into a bipolar membrane system, converting it into acids and alkalis that can be reused in the upstream process. The entire process route forms a closed-loop system of "acid reuse-lithium recovery-water reuse-acid-alkali self-sufficiency," achieving resource recovery and utilization of all components in the resin wastewater. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the lithium extraction and impurity removal wastewater resource recovery method in an embodiment of the present invention. Detailed Implementation

[0018] This invention provides a method for resource recovery of lithium extraction and impurity removal resin wastewater, wherein the lithium extraction and impurity removal resin wastewater includes resin acid desorption solution, acidic rinsing water and alkaline rinsing water; The method includes the following steps: The resin acid desorption solution was subjected to nanofiltration to obtain concentrate 1 and permeate 1. The permeate 1 is reused for acid desorption of the lithium extraction and impurity removal resin; After the concentrated liquid 1 is subjected to hardening removal by a double alkali method, the first filtration is used to obtain filtrate 1; The filtrate 1 is evaporated and concentrated to obtain concentrated liquid and condensate; the condensate is directly recycled. The evaporated concentrate was mixed with sodium carbonate and subjected to a lithium precipitation reaction, followed by solid-liquid separation to obtain lithium carbonate and lithium precipitation mother liquor. After mixing acidic and alkaline rinsing water, the pH was adjusted to 6.5-7.2, and then the mixture was filtered a second time to obtain filtrate 2. The filtrate 2 is concentrated by two-stage reverse osmosis to obtain concentrate 2 and permeate 2; the permeate 2 is directly recycled. The concentrate 2 is subjected to electrodialysis to obtain electrodialysis concentrate and fresh water; the fresh water is returned and combined with the filtrate 2 for two-stage reverse osmosis concentration. The electrodialysis concentrate is mixed with the lithium precipitation mother liquor and then subjected to bipolar membrane treatment to obtain acid solution, alkali solution and salt chamber effluent; the salt chamber effluent is returned to be treated with the concentrate 2 for electrodialysis.

[0019] In this invention, the lithium extraction and impurity removal resin wastewater includes resin acid desorption solution, acidic rinsing water, and alkaline rinsing water.

[0020] As one embodiment of the present invention, the pH of the resin acid desorption solution can be pH≤1. In the embodiments of the present invention, the pH of the resin acid desorption solution can be 0.83 or 0.79.

[0021] In one embodiment of the present invention, the hydrochloric acid content in the resin acid desorption solution can be 4-5%, the lithium ion concentration can be 3-3.5 g / L, the calcium ion concentration can be 0.46-0.55 g / L, and the concentration of other impurity ions such as magnesium and iron can be 0.045-0.055 g / L. In an embodiment of the present invention, the hydrochloric acid content in the resin acid desorption solution is 4.5%, which can also be 4.7%, the lithium ion concentration is 3.1 g / L, which can also be 3.3 g / L, the calcium ion concentration is 0.46 g / L, which can also be 0.5 g / L, and the concentration of other impurity ions such as magnesium and iron is 0.045 g / L, which can also be 0.05 g / L. In another embodiment of the present invention, the resin acid desorption solution can be the desorption waste liquid obtained after desorption of calcium and magnesium removal resin by hydrochloric acid in the lithium extraction and impurity removal process.

[0022] As one embodiment of the present invention, the pH of the acidic rinsing water can be 1.5 to 3.5. In the embodiments of the present invention, the pH of the acidic rinsing water can be 1.5 to 2.5, or even 1.8 to 3.5.

[0023] In one embodiment of the present invention, the hydrochloric acid content in the acidic rinsing water can be 0.1-0.5%, the lithium ion concentration can be 0.3-0.8 g / L, the calcium ion concentration can be 0.03-0.05 g / L, and the concentration of other impurity ions such as magnesium and iron can be 0.015-0.03 g / L. In an embodiment of the present invention, the hydrochloric acid content in the acidic rinsing water is 0.2%, the lithium ion concentration is 0.4 g / L, the calcium ion concentration is 0.04 g / L (or 0.042 g / L), and the concentration of other impurity ions such as magnesium and iron is 0.02 g / L (or 0.029 g / L). In another embodiment of the present invention, the acidic rinsing water can be the rinsing wastewater generated by rinsing the calcium and magnesium removal resin with clean water or recycled water after hydrochloric acid desorption during the lithium extraction and impurity removal process.

[0024] In one embodiment of the present invention, the pH of the alkaline rinsing water can be 10.0 to 11.5. In the embodiments of the present invention, the pH of the alkaline rinsing water can be 10.2 to 11.5, or even 10.5 to 10.9.

[0025] In one embodiment of the present invention, the sodium hydroxide content in the alkaline rinsing water can be 0.1-0.3%, the lithium ion concentration can be 0.01-0.03 g / L, the calcium ion concentration can be 0.002-0.008 g / L, and the concentration of other impurity ions such as magnesium and iron can be 0.001-0.008 g / L. In an embodiment of the present invention, the sodium hydroxide content in the alkaline rinsing water is 0.2%, the lithium ion concentration is 0.02 g / L (or 0.025 g / L), the calcium ion concentration is 0.005 g / L, and the concentration of other impurity ions such as magnesium and iron is 0.001 g / L (or 0.0015 g / L). In another embodiment of the present invention, the alkaline rinsing water can be the rinsing wastewater generated by rinsing the calcium and magnesium resin with clean water or recycled water after the alkali regeneration and alkali washing processes in the lithium extraction and impurity removal process.

[0026] In this invention, the resin acid desorption solution is preferably filtered and purified before nanofiltration. By filtering and purifying the resin acid desorption solution before nanofiltration, this invention can pre-select fine suspended solids, colloids, resin fragments, and solid impurities in the desorption solution, preventing these solid particles from entering the downstream end and causing membrane surface scratches, pore blockage, and irreversible fouling. This stabilizes the nanofiltration operating flux and extends the service life of the nanofiltration membrane.

[0027] This invention does not impose any particular limitations on the filtration method and apparatus; any conventional filtration method and apparatus capable of removing impurities is acceptable. As one embodiment of this invention, the filtration apparatus can be a precision filter containing a 0.5μm PP filter cartridge.

[0028] After filtration, the present invention performs nanofiltration on the resin acid desorption solution to obtain concentrated solution 1 and permeate 1.

[0029] In this invention, the nanofiltration process preferably uses a high-pressure and acid-resistant nanofiltration membrane; the high-pressure and acid-resistant nanofiltration membrane is preferably a nanofiltration membrane that can withstand 10wt% hydrochloric acid; in the embodiments of this invention, the manufacturer of the high-pressure and acid-resistant nanofiltration membrane is Chengdu Lianjie Fluid Separation Technology Co., Ltd.

[0030] In this invention, the pressure-resistant and acid-resistant nanofiltration membrane preferably has a pressure of 150-300 Da, more preferably 180-250 Da; the operating pressure of the nanofiltration treatment is preferably 5-7 MPa, more preferably 6-6.5 MPa. By controlling the pressure and pressure of the pressure-resistant and acid-resistant nanofiltration membrane, this invention can achieve efficient retention of lithium ions and multivalent ions such as calcium and magnesium while ensuring high hydrochloric acid permeability, thereby accurately achieving effective separation of acid and salt in the acid desorption solution.

[0031] In one embodiment of the present invention, the hydrochloric acid content in the permeate 1 can be 3.5-3.8%, the lithium ion concentration can be 0.09-0.19 g / L, the calcium ion concentration can be 0.001-0.016 g / L, and the concentration of other impurity ions such as magnesium and iron can be 0.001-0.039 g / L. In an embodiment of the present invention, the hydrochloric acid content in the permeate 1 can be 3.6% or 3.8%, the lithium ion concentration can be 0.17 g / L or 0.19 g / L, the calcium ion concentration can be 0.014 g / L or 0.016 g / L, and the concentration of other impurity ions such as magnesium and iron can be 0.0025 g / L or 0.0039 g / L.

[0032] In one embodiment of the present invention, the concentrated solution 1 may contain 7-8% hydrochloric acid, 6-10 g / L lithium ion concentration, 1.37-2.5 g / L calcium ion concentration, and 0.13-0.20 g / L concentration of other impurity ions such as magnesium and iron. In an embodiment of the present invention, the concentrated solution 1 may contain 7.2% hydrochloric acid, or 7.4% lithium ion, 9.02 g / L, or 9.54 g / L calcium ion, 1.37 g / L, or 1.47 g / L magnesium and iron ion, or 0.13 g / L magnesium and iron ion, or 0.14 g / L.

[0033] After obtaining permeate 1, the present invention reuses the permeate 1 for acid desorption of lithium extraction and impurity removal resin.

[0034] In one embodiment of the present invention, hydrochloric acid with a concentration of 6.5-7.5% can be added to the permeate 1 so that the hydrochloric acid concentration in the permeate 1 reaches 4.0-6.0% and can then be directly reused in the acid desorption step of the lithium extraction and impurity removal resin regeneration process.

[0035] After obtaining concentrate 1, the present invention performs a first filtration on concentrate 1 after hardening removal by a double alkali method to obtain filtrate 1.

[0036] In this invention, the turbidity of the filtrate 1 is preferably 0.5~1 NTU.

[0037] In this invention, the alkalis used in the dual-alkali method for hardening preferably include sodium hydroxide and sodium carbonate.

[0038] As one embodiment of the present invention, the preferred method for hardening by the dual alkali method is as follows: first, sodium hydroxide is added to the concentrated solution to adjust the pH, then sodium carbonate is added to carry out a precipitation conversion reaction, and then the solution is allowed to stand and precipitate.

[0039] In this invention, the concentration of sodium hydroxide in the double alkali method for hardening is preferably 7.5-8.5%; and the pH is preferably adjusted to 10-11 after adding sodium hydroxide.

[0040] In this invention, the ratio of the amount of sodium carbonate added to the amount of calcium ions in the concentrate 1 is preferably (1~2):1, more preferably 1.05:1.

[0041] In this invention, the reaction time for precipitation conversion is preferably 0.5-1 h; the settling time is 1.5-2 h. By controlling the parameters of the double-alkali method for hardening, this invention can effectively remove polyvalent impurity ions such as calcium and magnesium from the concentrate 1 while minimizing the co-precipitation loss of lithium ions and ensuring the purity of the lithium carbonate product obtained in the subsequent lithium precipitation process.

[0042] In this invention, the first filtration preferably includes plate and frame filtration and microfiltration performed sequentially.

[0043] In this invention, the pore size of the filter cloth used for the plate and frame filter is preferably 500-1200 mesh, and more preferably 1000 mesh.

[0044] In this invention, the microfiltration membrane is preferably made of silicon carbide or ceramic; the pore size of the microfiltration membrane is preferably 20-100 nm; the operating pressure of the microfiltration membrane is preferably 0.3-0.4 MPa, more preferably 0.35 MPa; and the temperature of the microfiltration membrane is preferably 30-40°C. This invention, by controlling the parameters of the microfiltration membrane, can prevent fine impurities from entering the evaporation and lithium precipitation stages, thus avoiding a decrease in the purity of lithium carbonate.

[0045] In an embodiment of the present invention, the manufacturer of the microfiltration membrane is Chengdu Lianjie Fluid Separation Technology Co., Ltd.

[0046] After obtaining filtrate 1, the present invention evaporates and concentrates filtrate 1 to obtain concentrated evaporation liquid and condensate; the condensate is directly recycled.

[0047] In one embodiment of the present invention, the evaporation and concentration factor can be 3 times.

[0048] In one embodiment of the present invention, the condensate generated by evaporation can be collected and used as recycled water for the system.

[0049] After obtaining the evaporation concentrate, the present invention mixes the evaporation concentrate with sodium carbonate to carry out a lithium precipitation reaction, followed by solid-liquid separation to obtain lithium carbonate and lithium precipitation mother liquor.

[0050] The present invention does not impose any special limitation on the mixing method of the evaporation concentrate and sodium carbonate. Any conventional mixing method can be used to ensure that the evaporation concentrate and sodium carbonate are mixed evenly.

[0051] In this invention, the preferred temperature for the lithium precipitation reaction is 80-95°C, more preferably 88-90°C; the preferred reaction time is 1-2 hours, more preferably 1.5 hours; and the preferred stirring speed is 200-450 r / min, more preferably 400 r / min. This invention effectively reduces the solubility of lithium carbonate by controlling the reaction parameters, promotes the full crystallization and precipitation of lithium ions, and improves the lithium precipitation recovery rate.

[0052] In this invention, the lithium precipitation mother liquor preferably comprises CO3 at a concentration of 10-35 g / L. 2- OH with a concentration of 0.17~0.29 g / L - Na with a concentration of 45~60 g / L + And Li at a concentration of 1.0~3.0 g / L + .

[0053] In this invention, acidic rinsing water and alkaline rinsing water are mixed and the pH is adjusted to 6.5-7.2 using hydrochloric acid or sodium hydroxide, followed by a second filtration to obtain filtrate 2.

[0054] In one embodiment of the present invention, the pH can be 6.9 or 7.1.

[0055] In this invention, the second filtration is preferably microfiltration; the material of the microfiltration membrane is preferably silicon carbide or ceramic; the pore size of the microfiltration membrane is preferably 20~100nm, more preferably 40nm; the operating pressure of the microfiltration membrane is preferably 0.3~0.4MPa, more preferably 0.35MPa; and the temperature of the microfiltration membrane is preferably 30~40℃. By controlling the parameters of the microfiltration membrane, this invention can effectively intercept suspended solids such as broken resin particles, flocs, and colloids entrained in the water after the acidic and alkaline flushing water are mixed, while simultaneously maintaining the effluent turbidity stably at ≤1NTU. This provides high-quality feed water for the subsequent two-stage reverse osmosis system, ensuring long-term stable operation of the reverse osmosis membrane element and extending its service life.

[0056] In an embodiment of the present invention, the manufacturer of the microfiltration membrane is Chengdu Lianjie Fluid Separation Technology Co., Ltd.

[0057] In this invention, the turbidity of the filtrate 2 is preferably ≤1 NTU.

[0058] After obtaining filtrate 2, the present invention performs two-stage reverse osmosis concentration on filtrate 2 to obtain concentrate 2 and permeate 2; the permeate 2 is directly recycled.

[0059] In this invention, the two-stage reverse osmosis concentration preferably includes a first-stage reverse osmosis and a second-stage reverse osmosis. The preferred operation of the two-stage reverse osmosis concentration is to sequentially process the filtrate 2 through the first-stage reverse osmosis and the second-stage reverse osmosis to obtain concentrate 2 and permeate 2. The permeate from the first-stage reverse osmosis enters the second-stage reverse osmosis for further processing, and the concentrate from the second-stage reverse osmosis is returned to the feed water end of the first-stage reverse osmosis for further processing, forming an internal concentrate circulation. The concentrate from the first-stage reverse osmosis is concentrate 2, and the permeate from the second-stage reverse osmosis is directly reused as permeate 2. In this invention, the preferred operating pressure for the first-stage reverse osmosis is 5-7 MPa, and the preferred operating pressure for the second-stage reverse osmosis is 2-4 MPa. The molecular weight cutoff of the reverse osmosis membrane used for the two-stage reverse osmosis concentration can be ≤50 Da. By controlling the parameters of the two-stage reverse osmosis concentration, this invention enables the first-stage reverse osmosis to complete the main concentration and desalination, and the second-stage reverse osmosis to complete the deep purification, forming a highly efficient desalination system of "concentration-refining-internal circulation". While producing high-quality reclaimed water, it effectively prevents the accumulation of salt in the system and provides a suitable concentrate salt concentration for the subsequent electrodialysis-bipolar membrane coupling process.

[0060] In the embodiments of the present invention, the reverse osmosis membrane used in the two-stage reverse osmosis concentration is manufactured by Chengdu Lianjie Fluid Separation Technology Co., Ltd.

[0061] After obtaining concentrate 2, the present invention performs electrodialysis treatment on concentrate 2 to obtain electrodialysis concentrate and fresh water; the fresh water is returned to be subjected to two-stage reverse osmosis concentration together with the filtrate 2; In this invention, the preferred current density for the electrodialysis treatment is 300~600 A / m. 2 The electrode water used is a sodium sulfate solution with a concentration of 1.0~1.5%.

[0062] In the embodiments of the present invention, the electrodialysis membrane used in the electrodialysis treatment is manufactured by Shandong Tianwei Membrane Technology Co., Ltd.

[0063] After obtaining the electrodialysis concentrate, the present invention mixes the electrodialysis concentrate with the lithium precipitation mother liquor and then performs bipolar membrane treatment to obtain acid solution, alkali solution and salt chamber effluent; the salt chamber effluent is returned to be treated with the concentrate 2 together for electrodialysis treatment.

[0064] This invention does not impose any particular limitation on the mixing method of the electrodialysis concentrate and the lithium precipitation mother liquor, as long as a mixture suitable for bipolar membrane treatment is obtained. In an embodiment of this invention, the electrodialysis concentrate and the lithium precipitation mother liquor are mixed to form a mixture. Hydrochloric acid with a concentration of 6.5-7.5% is added to the mixture to adjust the pH to 4.0-4.6. Air stripping is performed at 40-50°C to remove alkalinity. Then, sodium hydroxide with a concentration of 7.5-8.5% is used to adjust the pH of the mixture back to 6.5-7.0, forming a salt solution with a sodium chloride concentration of 153-156 g / L.

[0065] In the embodiments of the present invention, the bipolar membrane used in the bipolar membrane treatment is manufactured by Shandong Tianwei Membrane Technology Co., Ltd., and the water dissociation efficiency of the bipolar membrane is ≥97%.

[0066] In this invention, the acid solution is preferably a hydrochloric acid solution with a concentration of 6.3-7.5%, more preferably a hydrochloric acid solution with a concentration of 6.3-6.5%; the alkali solution is preferably a sodium hydroxide solution with a concentration of 7.5-8.5%, more preferably a sodium hydroxide solution with a concentration of 8.1-8.2%; and the sodium chloride concentration of the effluent from the salt chamber is preferably 20-25 g / L, more preferably 24 g / L.

[0067] In an embodiment of the present invention, the process flow diagram of the lithium extraction and impurity removal wastewater resource recovery method is as follows: Figure 1 As shown, the resin acid desorption solution and resin rinsing water (including acidic and alkaline rinsing water) are used as dual-inlet water sources: the acid desorption solution first passes through a precision filter to remove solid impurities before entering the NF system, where it is separated into permeate 1 rich in hydrochloric acid and concentrate 1 enriched with lithium, calcium, and magnesium ions. Permeate 1 can be reused in the resin acid desorption process, while concentrate 1 undergoes high-density precipitation (dual-alkali hardening), plate and frame filtration, and MF1 system (microfiltration membrane filtration) for hardening and fine filtration. The resulting filtrate is then evaporated and concentrated before entering the lithium precipitation reaction section, where sodium carbonate is added for lithium precipitation. Solid-liquid separation yields lithium carbonate product and lithium precipitation mother liquor. Simultaneously, the acidic and alkaline rinsing water are... The rinse water is mixed and adjusted to neutral in the mixing and conditioning unit, and then enters the two-stage reverse osmosis system after passing through the MF2 system (microfiltration membrane filtration). It produces permeate 2 and concentrate 2, which can be directly reused. Concentrate 2 enters the electrodialysis system for further concentration. The resulting fresh water is returned to the front end of the two-stage reverse osmosis system for recycling treatment. The electrodialysis concentrate is mixed with the aforementioned lithium precipitation mother liquor and sent to the bipolar membrane system for electrolysis to produce acid and alkali solutions that can be reused in the resin regeneration process. The effluent from the salt chamber of the bipolar membrane is returned to the electrodialysis system for further recycling and concentration. Thus, the reuse of acid, the resource recovery of lithium, the purification and reuse of water, and the self-sufficiency of by-product acids and alkalis are realized in the entire process chain, ultimately forming a closed loop of material flow.

[0068] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0069] Example 1 A method for resource recovery of lithium extraction and impurity removal resin wastewater, wherein the lithium extraction and impurity removal resin wastewater comprises resin acid desorption solution, acidic rinsing water, and alkaline rinsing water; The acid desorption solution contains 4.5% hydrochloric acid, 3.3 g / L lithium ions, 0.5 g / L calcium ions, and 0.05 g / L magnesium, iron, and other impurity ions; the pH of the acid desorption solution is 0.83. The acidic rinsing water contains 0.2% hydrochloric acid, 0.4 g / L lithium ions, 0.04 g / L calcium ions, and 0.02 g / L magnesium, iron, and other impurity ions; the pH of the acidic rinsing water is 1.9. The alkaline rinsing water contains 0.2% sodium hydroxide, 0.02 g / L lithium ions, 0.005 g / L calcium ions, and 0.0015 g / L magnesium, iron, and other impurity ions; the pH of the alkaline rinsing water is 10.6. The acid desorption solution was treated by passing it through a 0.5 μm cartridge-type precision filter (made of PP), and then subjected to nanofiltration at an operating pressure of 6 MPa. The nanofiltration process used a high-pressure, acid-resistant nanofiltration membrane (150 Da precision) to obtain permeate 1 and concentrate 1. Permeate 1 contained 3.6% hydrochloric acid, 0.17 g / L lithium ions, 0.014 g / L calcium ions, and 0.0025 g / L magnesium, iron, and other impurity ions. / L; the concentrated solution 1 contains 7.4% hydrochloric acid, 9.54 g / L lithium ions, 1.47 g / L calcium ions, and 0.14 g / L magnesium, iron, and other impurity ions; the volume of the permeate 1 is 66.7% of the volume of the acid desorption solution; hydrochloric acid with a concentration of 6.5-7.5% is added to the permeate 1 so that the hydrochloric acid concentration in the permeate 1 reaches 4.0-6.0%, and then it is directly reused in the acid desorption step of the lithium extraction and impurity removal resin regeneration process; First, sodium hydroxide with a concentration of 7.5-8.5% was added to concentrate 1 to adjust the pH of the concentrate to 11. Then, sodium carbonate was added according to the molar ratio of calcium ions to carbonate ions in concentrate 1 (1:1). The reaction time was 0.5 h, and after the reaction was completed, the solution was allowed to stand and precipitate for 1.5 h. The precipitate was separated into solid and liquid components by plate and frame filtration with a filter cloth pore size of 1200 mesh to obtain filtrate and filter residue. The filter residue was recycled as solid waste. The filtrate was then filtered through a microfiltration membrane to obtain filtrate 1. The microfiltration membrane used was a silicon carbide membrane with a pore size of 100 nm, an operating pressure of 0.35 MPa, and a temperature of 40 °C. The turbidity of filtrate 1 was 0.6 NTU. The filtrate 1 was evaporated and concentrated by a factor of 3 to obtain the evaporated concentrate and condensate. The lithium ion concentration in the evaporated concentrate was 25 g / L. The condensate generated during evaporation was collected and reused as system makeup water. The concentrated evaporation solution was fed into a lithium precipitation unit, where sodium carbonate was added to initiate a lithium precipitation reaction (resulting in a lithium to carbonate ratio of 2:1.1). The parameters for the lithium precipitation reaction were: reaction temperature 85°C, stirring speed 400 r / min, and reaction time 1.5 h. After the reaction was complete, solid-liquid separation was performed to obtain lithium carbonate and lithium precipitation mother liquor. The composition of the lithium precipitation mother liquor was CO3. 2- (Concentration of 25 g / L), OH - (Concentration is 0.19 g / L), Na + (Concentration of 49 g / L) and Li + (Concentration is 1.8 g / L); Acidic and alkaline rinsing water were mixed and the pH was adjusted to 7.1 using hydrochloric acid or sodium hydroxide to obtain mixed water (salt concentration of 18 g / L, conductivity of 31580 μs / cm). The mixed water was then subjected to a second filtration to obtain filtrate 2. The membrane used in the second filtration was a silicon carbide membrane with a pore size of 100 nm, an operating pressure of 0.35 MPa, and a temperature of 40 °C. The turbidity of filtrate 2 was 1.0 NTU. Filtrate 2 is sequentially treated by first-stage and second-stage reverse osmosis to obtain concentrate 2 and permeate 2. The permeate from the first-stage reverse osmosis enters the second-stage reverse osmosis for further treatment, while the concentrate from the second-stage reverse osmosis is returned to the feed water end of the first-stage reverse osmosis for further treatment, forming an internal concentrate circulation. The concentrate from the first-stage reverse osmosis is concentrate 2; the permeate from the second-stage reverse osmosis is directly reused as permeate 2. The operating pressure of the first-stage reverse osmosis is 5~7MPa, the operating pressure of the second-stage reverse osmosis is 2~4MPa, and the molecular weight cutoff of the reverse osmosis membrane is ≤50Da. After two-stage reverse osmosis treatment, the salt concentration in concentrate 2 is 72g / L, and the conductivity is 90300μs / cm; the salt concentration in the first-stage reverse osmosis permeate is 0.25g / L, and the conductivity is 1052μs / cm; the salt concentration in the second-stage reverse osmosis concentrate is 2.38g / L, and the conductivity is 12460μs / cm; and the salt concentration in permeate 2 is 0.01g / L, and the conductivity is 16μs / cm. The concentrate 2 was subjected to electrodialysis to obtain an electrodialysis concentrate and fresh water. The current density of the electrodialysis treatment was 400 A / m³. 2 The electrode water used is a 1.0% sodium sulfate solution; the salt concentration in the electrodialysis concentrate is 158 g / L and the conductivity is 187300 μs / cm; the salt concentration in the fresh water is 23 g / L and the conductivity is 35680 μs / cm; the fresh water is returned to the two-stage reverse osmosis system and continues to undergo two-stage reverse osmosis concentration treatment together with the filtrate 2; The electrodialysis concentrate was mixed with the above lithium precipitation mother liquor to form a mixture. 7.5% hydrochloric acid was added to the mixture to adjust the pH to 4.2. Air was blown off at 45°C to remove alkalinity. Then, 7.8% sodium hydroxide was used to adjust the pH of the mixture back to 6.8 to form a salt solution with a sodium chloride concentration of 156 g / L. The above-mentioned salt solution was passed through a bipolar membrane system for electrolysis. After bipolar membrane treatment, acid, alkali, and salt chamber effluent were obtained. The acid solution was hydrochloric acid with a concentration of 6.5%; the alkali solution was sodium hydroxide with a concentration of 8.2%; and the sodium chloride concentration of the salt chamber effluent was 25 g / L. The hydrochloric acid and sodium hydroxide produced by the bipolar membrane system were recycled to the acid desorption and alkali regeneration steps in the lithium extraction and impurity removal resin regeneration process, respectively; the salt chamber effluent was returned to the electrodialysis system and, together with concentrate 2, underwent further electrodialysis concentration treatment.

[0070] Example 2 A method for resource recovery of lithium extraction and impurity removal resin wastewater, wherein the lithium extraction and impurity removal resin wastewater comprises resin acid desorption solution, acidic rinsing water, and alkaline rinsing water; The acid desorption solution contains 4.7% hydrochloric acid, 3.1 g / L lithium ions, 0.46 g / L calcium ions, and 0.045 g / L magnesium, iron, and other impurity ions; the pH of the acid desorption solution is 0.79. The acidic rinsing water contains 0.2% hydrochloric acid, 0.4 g / L lithium ions, 0.042 g / L calcium ions, and 0.029 g / L magnesium, iron, and other impurity ions; the pH of the acidic rinsing water is 2.1. The alkaline rinsing water contains 0.2% sodium hydroxide, 0.025 g / L lithium ions, 0.005 g / L calcium ions, and 0.001 g / L magnesium, iron, and other impurity ions; the pH of the alkaline rinsing water is 10.7. The acid desorption solution was treated by passing it through a 0.5 μm cartridge-type (PP) precision filter, and then subjected to nanofiltration at an operating pressure of 6.5 MPa. The nanofiltration process used a high-pressure, acid-resistant nanofiltration membrane (200 Da precision) to obtain permeate 1 and concentrate 1. Permeate 1 contained 3.8% hydrochloric acid, 0.19 g / L lithium ions, 0.016 g / L calcium ions, and 0.003 g / L magnesium, iron, and other impurity ions. 9 g / L; the concentrated solution 1 contains 7.2% hydrochloric acid, 9.02 g / L lithium ions, 1.37 g / L calcium ions, and 0.13 g / L magnesium, iron, and other impurity ions; the volume of the permeate 1 is 70% of the volume of the acid desorption solution; hydrochloric acid with a concentration of 6.5-7.5% is added to the permeate 1 so that the hydrochloric acid concentration in the permeate 1 reaches 4.0-6.0%, and then it is directly reused in the acid desorption step of the lithium extraction and impurity removal resin regeneration process; First, sodium hydroxide with a concentration of 7.5-8.5% was added to concentrate 1 to adjust the pH of the concentrate to 11. Then, sodium carbonate was added according to the molar ratio of calcium ions to carbonate ions in concentrate 1 of 1:1.05. The reaction time was 0.5 h, and after the reaction was completed, the solution was allowed to stand and precipitate for 1.5 h. The precipitate was separated into solid and liquid by plate and frame filtration with a filter cloth pore size of 1000 mesh to obtain filtrate and filter residue. The filter residue was recycled as solid waste. The filtrate was then filtered through a microfiltration membrane to obtain filtrate 1. The microfiltration membrane used was a silicon carbide membrane with a pore size of 100 nm, an operating pressure of 0.3 MPa, and a temperature of 35 °C. The turbidity of filtrate 1 was 0.7 NTU. The filtrate 1 was evaporated and concentrated by a factor of 3 to obtain the evaporated concentrate and condensate. The lithium ion concentration in the evaporated concentrate was 26.98 g / L. The condensate generated during evaporation was collected and reused as makeup water for the system. The concentrated evaporation solution was fed into a lithium precipitation unit, where sodium carbonate was added to initiate a lithium precipitation reaction (resulting in a lithium to carbonate ratio of 2:1.1). The parameters for the lithium precipitation reaction were: reaction temperature 86°C, stirring speed 400 r / min, and reaction time 1.5 h. After the reaction was complete, solid-liquid separation was performed to obtain lithium carbonate and lithium precipitation mother liquor. The composition of the lithium precipitation mother liquor was CO3. 2-(Concentration is 26g / L), OH - (Concentration is 0.2 g / L), Na + (Concentration of 52 g / L) and Li + (Concentration is 1.7 g / L); Acidic and alkaline rinsing water were mixed and the pH was adjusted to 6.9 to obtain mixed water (salt concentration of 16 g / L, conductivity of 30460 μs / cm). The mixed water was then subjected to a second filtration to obtain filtrate 2. The membrane used for the second filtration was a silicon carbide membrane with a pore size of 40 nm, an operating pressure of 0.35 MPa, and a temperature of 35 °C. The turbidity of filtrate 2 was 0.2 NTU. Filtrate 2 is sequentially treated by first-stage and second-stage reverse osmosis to obtain concentrate 2 and permeate 2. The permeate from the first-stage reverse osmosis enters the second-stage reverse osmosis for further treatment, while the concentrate from the second-stage reverse osmosis is returned to the feed water end of the first-stage reverse osmosis for further treatment, forming an internal concentrate circulation. The concentrate from the first-stage reverse osmosis is used as concentrate 2, and the permeate from the second-stage reverse osmosis is used as permeate 2 for direct reuse. The operating pressure of the first-stage reverse osmosis is 5~7MPa, and the operating pressure of the second-stage reverse osmosis is 2~4MPa. The molecular weight cutoff of the reverse osmosis membrane is ≤50Da. After two-stage reverse osmosis treatment, the salt concentration in concentrate 2 is 70g / L, and the conductivity is 91260μs / cm; the salt concentration in the first-stage reverse osmosis permeate is 0.23g / L, and the conductivity is 996μs / cm; the salt concentration in the second-stage reverse osmosis concentrate is 2.21g / L, and the conductivity is 11460μs / cm; and the salt concentration in permeate 2 is 0.01g / L, and the conductivity is 15μs / cm. The concentrate 2 was subjected to electrodialysis to obtain an electrodialysis concentrate and fresh water. The current density of the electrodialysis treatment was 400 A / m³. 2 The electrode water used is a 1.0% sodium sulfate solution; the salt concentration in the electrodialysis concentrate is 153 g / L and the conductivity is 175460 μs / cm; the salt concentration in the fresh water is 24 g / L and the conductivity is 46250 μs / cm; the fresh water is returned to the two-stage reverse osmosis system and continues to undergo two-stage reverse osmosis concentration treatment together with the filtrate 2; The electrodialysis concentrate was mixed with the above lithium precipitation mother liquor to form a mixture. 7.5% hydrochloric acid was added to the mixture to adjust the pH to 4.6. Air was blown off at 46°C to remove alkalinity. Then, 7.8% sodium hydroxide was used to adjust the pH of the mixture back to 7 to form a salt solution with a sodium chloride concentration of 153 g / L. The above-mentioned salt solution was passed into a bipolar membrane system for electrolysis. After bipolar membrane treatment, acid, alkali, and salt chamber effluent were obtained. The acid solution was hydrochloric acid with a concentration of 6.3%; the alkali solution was sodium hydroxide with a concentration of 8.1%; and the sodium chloride concentration of the salt chamber effluent was 24 g / L. The hydrochloric acid and sodium hydroxide produced by the bipolar membrane system were recycled to the acid desorption and alkali regeneration steps in the lithium extraction and impurity removal resin regeneration process, respectively. The salt chamber effluent was returned to the electrodialysis system and, together with concentrate 2, underwent further electrodialysis concentration treatment.

[0071] Comparative Example 1 A method for resource recovery of lithium extraction and impurity removal resin wastewater, wherein the lithium extraction and impurity removal resin wastewater comprises resin acid desorption solution, acidic rinsing water, and alkaline rinsing water; The acid desorption solution contains 4.8% hydrochloric acid, 3.2 g / L lithium ions, 0.51 g / L calcium ions, and 0.049 g / L magnesium, iron, and other impurity ions; the pH of the acid desorption solution is 0.76. The acidic rinsing water contains 0.2% hydrochloric acid, 0.4 g / L lithium ions, 0.04 g / L calcium ions, and 0.019 g / L magnesium, iron, and other impurity ions; the pH of the acidic rinsing water is 2.2. The alkaline rinsing water contains 0.17% sodium hydroxide, 0.03 g / L lithium ions, 0.002 g / L calcium ions, and 0.002 g / L magnesium, iron, and other impurity ions; the pH of the alkaline rinsing water is 10.4. The method for recycling lithium extraction and impurity removal resin wastewater is the same as in Example 1, except that the resin acid desorption liquid is not treated by nanofiltration, but directly undergoes a double alkali hardening process, and the alkali consumption is recorded.

[0072] The results showed that when the acid desorption solution was directly subjected to the dual-alkali hardening process, the consumption of sodium hydroxide and sodium carbonate was 1.5 to 2 times that in Example 1. This is because the acid desorption solution contains a large amount of free hydrochloric acid. When alkali is added directly for neutralization, sodium hydroxide first reacts with the hydrochloric acid, consuming a large amount of alkali solution. In contrast, in Example 1, the acid desorption solution was first treated with nanofiltration, and more than 75% of the hydrochloric acid was separated and recovered as permeate 1, with only concentrate 1 entering the hardening process, significantly reducing the amount of alkali required to neutralize the free acid. Therefore, it is evident that the present application's method of first treating the acid desorption solution with nanofiltration not only recovers hydrochloric acid resources but also significantly reduces the alkali consumption and operating costs of the subsequent hardening process.

[0073] Comparative Example 2 A method for resource recovery of lithium extraction and impurity removal resin wastewater, wherein the lithium extraction and impurity removal resin wastewater includes resin acid desorption solution, acidic rinsing water and alkaline rinsing water; The acid desorption solution contains 4.8% hydrochloric acid, 3.2 g / L lithium ions, 0.51 g / L calcium ions, and 0.049 g / L magnesium, iron, and other impurity ions; the pH of the acid desorption solution is 0.76. The acidic rinsing water contains 0.18% hydrochloric acid, 0.5 g / L lithium ions, 0.039 g / L calcium ions, and 0.03 g / L magnesium, iron, and other impurity ions; the pH of the acidic rinsing water is 2.3. The alkaline rinsing water contains 0.18% sodium hydroxide, 0.03 g / L lithium ions, 0.004 g / L calcium ions, and 0.001 g / L magnesium, iron, and other impurity ions; the pH of the alkaline rinsing water is 10.3. The method for recycling the wastewater from the lithium extraction and impurity removal resin is the same as in Example 1, except that the two-stage reverse osmosis system is replaced with a single-stage reverse osmosis system, and the conductivity and salt concentration of the product water are recorded.

[0074] The results show that when using a single-stage reverse osmosis system, the permeate conductivity is ≥500 μS / cm, and the salt concentration is high, failing to meet the pure water standard. If this permeate is directly reused in the lithium extraction system, salt will continuously accumulate within the system, affecting the resin adsorption capacity and the operating efficiency of subsequent membrane treatment units, thus failing to meet the system reuse requirements. In contrast, the two-stage reverse osmosis system used in Example 1 has a permeate conductivity of only 16 μS / cm and a salt concentration of 0.01 g / L, meeting the pure water standard and allowing for direct reuse in the production system. Therefore, this application's use of a two-stage reverse osmosis system instead of a conventional single-stage reverse osmosis system effectively ensures the quality of the permeate and prevents salt accumulation within the system, providing a key technological guarantee for achieving zero wastewater discharge and resource reuse.

[0075] As can be seen from Examples 1-2 and Comparative Examples 1-2, the various process steps in the lithium extraction and impurity removal resin wastewater resource recovery method provided by the present invention are mutually synergistic and indispensable, forming an organic whole technical solution.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for resource recovery from lithium extraction and impurity removal resin wastewater, characterized in that, The lithium extraction and impurity removal resin wastewater includes resin acid desorption solution, acidic rinsing water, and alkaline rinsing water; The method includes the following steps: The resin acid desorption solution was subjected to nanofiltration to obtain concentrate 1 and permeate 1. The permeate 1 is reused for acid desorption of the lithium extraction and impurity removal resin; After the concentrated liquid 1 is subjected to hardening removal by a double alkali method, the first filtration is used to obtain filtrate 1; The filtrate 1 is evaporated and concentrated to obtain concentrated liquid and condensate; the condensate is directly recycled. The evaporated concentrate was mixed with sodium carbonate and subjected to a lithium precipitation reaction, followed by solid-liquid separation to obtain lithium carbonate and lithium precipitation mother liquor. After mixing acidic and alkaline rinsing water, the pH was adjusted to 6.5-7.2, and then the mixture was filtered a second time to obtain filtrate 2. The filtrate 2 is concentrated by two-stage reverse osmosis to obtain concentrate 2 and permeate 2; the permeate 2 is directly recycled. The concentrate 2 is subjected to electrodialysis to obtain electrodialysis concentrate and fresh water; the fresh water is returned and combined with the filtrate 2 for two-stage reverse osmosis concentration. The electrodialysis concentrate is mixed with the lithium precipitation mother liquor and then subjected to bipolar membrane treatment to obtain acid solution, alkali solution and salt chamber effluent; the salt chamber effluent is returned to be treated with the concentrate 2 for electrodialysis.

2. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The nanofiltration process uses a high-pressure and acid-resistant nanofiltration membrane; the precision of the high-pressure and acid-resistant nanofiltration membrane is 150~300 Da; the operating pressure of the nanofiltration process is 5~7 MPa.

3. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The alkalis used in the dual-alkali method for hardening include sodium hydroxide and sodium carbonate.

4. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1 or 3, characterized in that, The hardening time for the double alkali method is 0.5~1h.

5. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The lithium precipitation reaction is carried out at a temperature of 80~95℃ for 1~2 hours.

6. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The first filtration includes sequential plate and frame filtration and microfiltration membrane filtration; the filter cloth used for the plate and frame filtration has a pore size of 500~1200 mesh.

7. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The second filtration is microfiltration membrane filtration.

8. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 6 or 7, characterized in that, The microfiltration membrane is made of silicon carbide or ceramic; the pore size of the microfiltration membrane is 20~100nm; and the operating pressure of the microfiltration membrane is 0.3~0.4MPa.

9. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The two-stage reverse osmosis concentration includes a first-stage reverse osmosis and a second-stage reverse osmosis. The operating pressure of the first-stage reverse osmosis is 5~7 MPa, and the operating pressure of the second-stage reverse osmosis is 2~4 MPa.

10. The method for resource recovery of lithium extraction and impurity removal resin wastewater according to claim 1, characterized in that, The current density of the electrodialysis treatment is 300~600 A / m. 2 .

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