Method for preparing lithium carbonate by synergistically treating lithium-containing waste to recover lithium

Abstract

The present application belongs to the technical field of lithium-containing waste treatment, and specifically discloses a method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste. Specifically, lithium amide waste and lithium sulfide waste are mixed with water, and then mixed with hydrogen peroxide solution and sulfuric acid solution to perform acid dissolution reaction, obtaining lithium-containing acid solution and insoluble substances; the lithium-containing acid solution is mixed with lye to perform alkalization reaction, obtaining insoluble impurities and alkalized solution; the alkalized solution is concentrated to obtain concentrated alkalized solution, which is mixed with sodium carbonate solution to perform lithium precipitation reaction, obtaining lithium precipitation mother liquor and lithium carbonate; lithium elements in the lithium precipitation mother liquor are extracted, and the raffinate is evaporated and concentrated to precipitate sodium sulfate and ammonium sulfate; the ammonium sulfate is mixed with lithium iron phosphate waste, and then sequentially subjected to calcination and leaching; the leaching solution is mixed with the lithium-containing acid solution to perform alkalization. The present application has the characteristics of high process integration, high economic value, and less environmental pollution, and conforms to the new concept of green chemical atom economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium-containing waste treatment, and particularly relates to a method for preparing lithium carbonate by synergistically treating lithium-containing waste and recycling lithium. BACKGROUND

[0002] Solid-state electrolyte is a core component of solid-state lithium ion battery, wherein sulfide electrolyte is concerned by people in the industry due to its excellent conductivity, high energy density and long cycle life, and is considered to be the most potential one among solid-state electrolytes. Lithium sulfide is a core material for synthesizing sulfide electrolyte. At present, the main preparation methods of lithium sulfide include mechanical ball milling, high-temperature reduction and solvent method. Waste is inevitably generated in the production process of lithium sulfide. Therefore, the recycling technology of lithium sulfide waste is particularly important.

[0003] Lithium amide is white lusterous crystal or powder with a melting point of 390 DEG C and a density of 1.78 g / cm 3 It is insoluble in kerosene, soluble in liquid ammonia, and soluble in cold water but strongly hydrolyzed in hot water. Lithium amide is mainly used in organic synthesis and drug manufacturing, and is a good hydrogen storage material together with lithium hydride and imino lithium. Lithium amide can be used as a condensation promoter, a reducing agent, a dehydrating agent, a drying agent, a dehalogenating agent, an alkylating agent, an aminolysis reaction agent, an initiator for anion polymerization of ethylene compounds, and can also be used for manufacturing azide compounds and cyanide. In the pharmaceutical industry, it is used as a synthetic catalyst for vitamin A, vitamin D3 and anti-AIDS drugs, and as a high-efficiency catalyst for the production of antioxidants 1010 and 1076. Based on the wide application of lithium amide, many enterprises have built corresponding production lines. However, it is difficult to accurately control the calcination temperature in the actual production process of lithium amide, which leads to the generation of a large amount of lithium amide waste. Therefore, the reprocessing of lithium amide waste is also worth attention.

[0004] With the continuous development of the market, more and more enterprises have entered the lithium iron phosphate battery industry, and the market competition is becoming increasingly fierce. With the increase of the use time of new energy vehicles, the retired amount of lithium iron phosphate batteries is facing explosive growth. Retired lithium iron phosphate batteries will be an important urban mineral, so the recycling of lithium iron phosphate waste is imminent.

[0005] Therefore, how to disclose a treatment method for synergistically treating lithium amide, lithium sulfide and lithium iron phosphate waste and recycling valuable elements therein is particularly important. SUMMARY

[0006] Therefore, the present application provides a method for preparing lithium carbonate by synergistically treating lithium-containing waste and recycling lithium, so as to solve the problem that there is no scheme for synergistically treating lithium amide, lithium sulfide and lithium iron phosphate waste in the prior art.

[0007] In order to achieve the above object, the present application adopts the following technical solutions:

[0008] A method for preparing lithium carbonate by recovering lithium from lithium-containing waste materials in a cooperative treatment, comprising the following steps:

[0009] 1) mixing lithium amide waste materials, lithium sulfide waste materials and water to obtain a waste material mixture, then mixing the waste material mixture with hydrogen peroxide solution and sulfuric acid solution to obtain an acid dissolution mixture, performing acid dissolution reaction, and after solid-liquid separation, obtaining lithium-containing acid dissolution solution and insoluble materials;

[0010] 2) mixing the lithium-containing acid dissolution solution with lye to perform alkalization reaction, and after the reaction is completed, performing solid-liquid separation to obtain insoluble impurities and alkalization feed liquid;

[0011] 3) concentrating the alkalization feed liquid to obtain concentrated alkalization feed liquid, mixing the concentrated alkalization feed liquid with sodium carbonate solution to perform lithium precipitation reaction, and after the reaction is completed, performing solid-liquid separation to obtain lithium precipitation mother liquor and lithium carbonate;

[0012] 4) extracting lithium elements in the lithium precipitation mother liquor, and obtaining lithium sulfate by sulfuric acid back extraction of the extraction liquid, and evaporating and concentrating the raffinate to stepwise precipitate sodium sulfate and ammonium sulfate;

[0013] 5) mixing ammonium sulfate and lithium iron phosphate waste materials, then performing roasting and leaching in sequence to obtain leaching liquid, and mixing the leaching liquid with the lithium-containing acid dissolution solution in step 2) to perform alkalization reaction.

[0014] Preferably, the mass ratio of the lithium amide waste materials, lithium sulfide waste materials, water, hydrogen peroxide solution and sulfuric acid solution in step 1) is 45-55:45-55:600-1000:80-120:280-320;

[0015] The mass concentration of the hydrogen peroxide solution is 30-60%;

[0016] The mass concentration of the sulfuric acid solution is 80-98%.

[0017] Preferably, the acid dissolution reaction in step 1) is performed for 0.5-2h.

[0018] Preferably, the pH value of the system in the alkalization reaction in step 2) is 10-12;

[0019] The lye includes sodium hydroxide solution;

[0020] The mass concentration of the lye is 30-35%.

[0021] Preferably, the alkalization reaction in step 2) is performed for 0.5-1h.

[0022] Preferably, the mass concentration of Li in the concentrated alkalization feed liquid in step 3) is 15-25g / L.

[0023] The molar ratio of Li in the concentrated alkaline solution to sodium carbonate in the sodium carbonate solution in step 3) is 1.8-2.2:1;

[0024] The mass concentration of the sodium carbonate solution is 200-250 g / L.

[0025] Preferably, the time of the lithium precipitation reaction in step 3) is 0.5-1 h, and the temperature of the lithium precipitation reaction is 80-95 ℃.

[0026] Preferably, the extractant in step 4) comprises an oil phase and an aqueous phase, the volume ratio of the oil phase to the aqueous phase is 0.8-1.5:1; the oil phase comprises a Li alkaline extractant and a diluent, the volume ratio of the Li alkaline extractant to the diluent is 0.8-1.2:1; and the diluent comprises sulfonated kerosene.

[0027] The number of stages of the extraction in step 4) is 3.

[0028] Preferably, the mass ratio of ammonium sulfate to lithium iron phosphate waste in step 5) is 0.6-1:1.

[0029] Preferably, the temperature of the roasting in step 5) is 250-350 ℃, the time of the roasting is 10-15 min, the liquid-solid mass ratio of the leaching is 2-4:1, and the leaching temperature is 40-60 ℃.

[0030] According to the technical solution, compared with the prior art, the application has the following beneficial effects:

[0031] Compared with the prior art, the application utilizes three kinds of lithium-containing waste to cooperatively recover lithium to prepare lithium carbonate. Lithium sulfide and lithium amide waste are cooperatively acid-dissolved to generate lithium sulfate and ammonium sulfate at the same time. The ammonium sulfate is used as a roasting aid of lithium iron phosphate waste. Through roasting and leaching, lithium in the lithium iron phosphate waste is extracted, and the alkalization and impurity removal and the lithium precipitation process are simultaneously completed to obtain the target product lithium carbonate.

[0032] The specific reaction equation is: 2LiNH2(s)+Li2S(s)+H2O2(aq)+3H2SO4(aq)=2Li2SO4(aq)+(NH4)2SO4(aq)+S(s)+2H2O(aq)

[0033] 2LiFePO4(s)+0.5O2(g)+(NH4)2SO4(s)=2Li2SO4(s)+2FePO4(s)+2NH3(g)+H2O(g)

[0034] Li2SO4(aq)+Na2CO3(aq)=Li2CO3(s)+Na2SO4(aq)

[0035] The present application uses lithium sulfide waste, lithium amide waste and lithium iron phosphate waste as raw materials, generates lithium sulfate and ammonium sulfate from lithium amide and lithium sulfide in sulfuric acid solution, the lithium sulfate is used for producing industrial-grade lithium carbonate, and the ammonium sulfate is used for roasting lithium iron phosphate waste to generate lithium sulfate solution again, realizing the process of simultaneously producing lithium carbonate by synergistically treating three kinds of waste. The process has the characteristics of high process integration, small construction area, high economic value, no waste acid generated in the whole process, less environmental pollution, avoiding single waste treatment, high resource comprehensive utilization rate, and conforms to the new concept of green chemical atom economy. DETAILED DESCRIPTION

[0036] The present application provides a method for preparing lithium carbonate by synergistically treating lithium-containing waste and recovering lithium, comprising the following steps:

[0037] 1) mixing lithium amide waste and lithium sulfide waste with water to obtain a waste mixture, then mixing the waste mixture with hydrogen peroxide solution and sulfuric acid solution to obtain an acid-dissolving mixture, performing acid-dissolving reaction, and after solid-liquid separation, obtaining lithium-containing acid-dissolving solution and insoluble matter;

[0038] 2) mixing the lithium-containing acid-dissolving solution with lye to perform alkalization reaction, and after reaction, performing solid-liquid separation to obtain insoluble impurities and alkalized feed liquid;

[0039] 3) concentrating the alkalized feed liquid to obtain concentrated alkalized feed liquid, mixing the concentrated alkalized feed liquid with sodium carbonate solution to perform lithium precipitation reaction, and after reaction, performing solid-liquid separation to obtain lithium precipitation mother liquor and lithium carbonate;

[0040] 4) extracting lithium elements in the lithium precipitation mother liquor, and obtaining lithium sulfate by sulfuric acid back-extraction of the extraction liquid, and evaporating and concentrating the raffinate to separate out sodium sulfate and ammonium sulfate step by step;

[0041] 5) mixing ammonium sulfate and lithium iron phosphate waste, then sequentially performing roasting and leaching to obtain leaching liquid, and mixing the leaching liquid with the lithium-containing acid-dissolving solution in step 2) to perform alkalization reaction.

[0042] In the present application, the mass ratio of the lithium amide waste, lithium sulfide waste, water, hydrogen peroxide solution and sulfuric acid solution in step 1) is 45-55:45-55:600-1000:80-120:280-320, preferably 48-52:48-52:700-900:90-110:290-310, and further preferably 50:50:800:100:300.

[0043] In the present application, the mass concentration of the hydrogen peroxide solution is 30-60%, and specifically can be 35%, 40%, 45%, 50% or 55%.

[0044] In the present application, the mass concentration of the sulfuric acid solution is 80-98%, and can be specifically 82%, 84%, 85%, 86%, 88%, 90%, 92%, 95%, 96%.

[0045] In the present application, the acid dissolution reaction in step 1) is performed for 0.5-2h, and can be specifically 0.6h, 0.8h, 1h, 1.2h, 1.5h, 1.8h.

[0046] In the present application, the pH value of the system in the alkalization reaction in step 2) is 10-12, and can be specifically 10, 10.5, 11, 11.5, 12.

[0047] In the present application, the alkaline solution comprises a sodium hydroxide solution.

[0048] In the present application, the mass concentration of the alkaline solution is 30-35%, and can be specifically 31%, 32%, 33%, 34%.

[0049] In the present application, the alkalization reaction in step 2) is performed for 0.5-1h, and can be specifically 0.6h, 0.7h, 0.8h, 0.9h.

[0050] In the present application, the mass concentration of Li in the concentrated alkalization feed solution in step 3) is 15-25g / L, and can be specifically 16g / L, 18g / L, 20g / L, 22g / L, 24g / L.

[0051] In the present application, the molar ratio of Li in the concentrated alkalization feed solution to sodium carbonate in the sodium carbonate solution in step 3) is 1.8-2.2:1, preferably 1.9-2.1:1, and further preferably 2:1.

[0052] In the present application, the mass concentration of the sodium carbonate solution is 200-250g / L, and can be specifically 210g / L, 220g / L, 230g / L, 240g / L.

[0053] In the present application, the lithium precipitation reaction in step 3) is performed for 0.5-1h, and can be specifically 0.6h, 0.7h, 0.8h, 0.9h; and the temperature of the lithium precipitation reaction is 80-95℃, and can be specifically 82℃, 84℃, 85℃, 86℃, 88℃, 90℃, 92℃, 94℃.

[0054] In the present application, the extractant in step 4) comprises an oil phase and a water phase, the volume ratio of the oil phase and the water phase is 0.8-1.5:1, preferably 0.9-1.2:1, and further preferably 1:1; the oil phase comprises a Li basic extractant and a diluent, the volume ratio of the Li basic extractant and the diluent is 0.8-1.2:1, preferably 0.9-1.1:1, and further preferably 1:1; the diluent comprises sulfonated kerosene.

[0055] In the present application, the number of stages of the extraction in step 4) is 3 stages.

[0056] In the present application, the raffinate in step 4) is concentrated by evaporation, preferably to 38°Bé, and sodium sulfate is precipitated at 80-90℃, and ammonium sulfate is precipitated at 50-60℃.

[0057] In the present application, the temperature for precipitating sodium sulfate can be specifically 82℃, 84℃, 85℃, 86℃, or 88℃, and the temperature for precipitating ammonium sulfate can be specifically 52℃, 54℃, 55℃, 56℃, or 58℃.

[0058] In the present application, the mass ratio of ammonium sulfate to lithium iron phosphate waste in step 5) is 0.6-1:1, preferably 0.7-0.9:1, and further preferably 0.8:1.

[0059] In the present application, the temperature for the roasting in step 5) is 250-350℃, and can be specifically 260℃, 280℃, 300℃, 320℃, or 340℃; the roasting time is 10-15min, and can be specifically 11min, 12min, 13min, or 14min; the liquid-solid mass ratio for the leaching is 2-4:1, preferably 2.5-3.5:1, and further preferably 3:1; and the leaching temperature is 40-60℃, and can be specifically 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, or 58℃.

[0060] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0061] Embodiment 1

[0062] Step A: acid dissolution of lithium amide and lithium sulfide waste, 50 g of lithium amide waste and 50 g of lithium sulfide waste were taken into a reaction vessel, while stirring, 800 g of deionized water was added, and at the same time, 300 g of 98% mass concentration H2SO4 solution and 100 g of 50% mass concentration H2O2 solution were added, after 1 hour of reaction, the lithium-containing acidified slurry was obtained and solid-liquid separation was carried out, obtaining a lithium-containing acid solution and a sulfur single element precipitate, which can be further purified and refined into sulfur.

[0063] Step B: alkalization, the lithium-containing acid solution obtained in step A was adjusted to pH 12 with a 32% mass concentration sodium hydroxide solution, and after stirring for 1 h, filtration was carried out with a sand core funnel with a pore size of 2 μm, to obtain insoluble impurities (lithium iron phosphate leaching solution returned mainly as iron hydroxide) and alkalized liquor.

[0064] Step C: lithium precipitation, the alkali-removing solution obtained in step B was concentrated to a Li mass concentration of 20 g / L, and a 230 g / L mass concentration sodium carbonate solution was added at 95°C (the molar ratio of Li in the concentrated alkali liquor to sodium carbonate in the sodium carbonate solution was 1.95:1), and after stirring for 1 h, filtration was carried out to obtain a lithium precipitation mother liquor and crude lithium carbonate, and the crude lithium carbonate was filtered, washed and dried to obtain 278 g of industrial-grade lithium carbonate (including the conversion amount of the raw material lithium iron phosphate), with a main content of 99.1%.

[0065] Step D: extraction, the lithium precipitation mother liquor obtained in step C was subjected to Li extraction, the volume ratio of oil phase to water phase was 1:1, the oil phase included HB121 basic extractant and sulfonated kerosene in a volume ratio of 1:1, and after three-stage countercurrent extraction at room temperature, the lithium extraction rate was 99.5%. The raffinate was evaporated and concentrated, and when the boiling point was 38°Bé, 435 g of sodium sulfate was precipitated at 85°C, and 327 g of ammonium sulfate was precipitated at 55°C.

[0066] Step E: roasting, 327 g of ammonium sulfate obtained in step D was roasted with 409 g of lithium iron phosphate waste, i.e. the mass ratio of ammonium sulfate to lithium iron phosphate waste was 0.8:1, and roasting was carried out at 300°C for 10 min, after roasting and cooling, the leaching was carried out with 3 times the mass of water at 50°C, and 1150 g of leaching solution was obtained, which was recycled to step B for lithium precipitation, and the above operation was recycled.

[0067] Example 2

[0068] Step A: acid dissolution of lithium amide and lithium sulfide waste, 50 g of lithium amide waste and 50 g of lithium sulfide waste were taken into a reaction vessel, while stirring, 600 g of deionized water was added, and at the same time, 300 g of 98% mass concentration H2SO4 solution and 100 g of 50% mass concentration H2O2 solution were added, after 1 hour of reaction, the lithium-containing acidified slurry was obtained and solid-liquid separation was carried out, obtaining a lithium-containing acid solution and a sulfur single element precipitate, which can be further purified and refined into sulfur.

[0069] Step B: alkalization, the lithium-containing acid solution obtained in step A was adjusted to pH 12 with a 32% mass concentration sodium hydroxide solution, and after stirring for 1 h, filtration was carried out with a sand core funnel with a pore size of 5 μm, to obtain insoluble impurities (lithium iron phosphate leaching solution returned mainly as iron hydroxide) and alkalized liquor.

[0070] Step C: lithium precipitation, the alkalization and impurity removal solution obtained in step B was concentrated to a Li mass concentration of 18 g / L, and a 230 g / L mass concentration sodium carbonate solution was added at 95°C (the molar ratio of Li in the concentrated alkalized liquor to sodium carbonate in the sodium carbonate solution was 2:1), and after stirring for 1 h, filtration was carried out to obtain a lithium precipitation mother liquor and crude lithium carbonate, and the crude lithium carbonate was filtered, eluted and dried to obtain 278 g of industrial grade lithium carbonate (including the conversion amount of the raw material lithium iron phosphate), with a main content of 99.1%.

[0071] Step D: extraction, the lithium precipitation mother liquor obtained in step C was subjected to Li extraction, the volume ratio of oil phase to water phase was 1:1, the oil phase included 1.2:1 volume ratio of HB121 basic extractant and sulfonated kerosene, and after three-stage countercurrent extraction at room temperature, the lithium extraction rate was 99.3%. The raffinate was evaporated and concentrated, and when the boiling point was 38°Bé, 395 g of sodium sulfate was precipitated at 80°C, and 295 g of ammonium sulfate was precipitated at 55°C.

[0072] Step E: roasting, 295 g of ammonium sulfate obtained in step D was roasted with 295 g of lithium iron phosphate waste, i.e. the mass ratio of ammonium sulfate to lithium iron phosphate waste was 1:1, and roasting was carried out at 280°C for 10 min, after roasting and cooling, 2.5 times the mass of water was used for leaching at 50°C, and 575 g of leaching solution was obtained, which was recycled to step B for lithium precipitation and used in the above operation.

[0073] Example 3

[0074] Step A: acid dissolution of lithium amide and lithium sulfide waste, 50 g of lithium amide waste and 50 g of lithium sulfide waste were taken into a reaction vessel, 1000 g of deionized water was added while stirring, and 300 g of 98% mass concentration H2SO4 solution and 100 g of 50% mass concentration H2O2 solution were added, after 1 hour of reaction, the lithium-containing acidified slurry was obtained and solid-liquid separation was carried out, obtaining a lithium-containing acid solution and elemental sulfur precipitate, and the elemental sulfur can be further purified and refined into sulfur.

[0075] Step B: alkalization, the lithium-containing acid solution obtained in step A was adjusted to pH 11 with a 32% mass concentration sodium hydroxide solution, and after stirring for 0.5 h, filtration was carried out with a sand core funnel with a pore size of 3 μm to obtain insoluble impurities (lithium iron phosphate leaching solution returned mainly as iron hydroxide) and alkalized liquor.

[0076] Step C: lithium precipitation, the alkali-removing solution obtained in step B was concentrated to a Li mass concentration of 23 g / L, and a 230 g / L mass concentration sodium carbonate solution was added at 95°C (the molar ratio of Li in the concentrated alkali liquor to sodium carbonate in the sodium carbonate solution was 1.95:1), and after stirring for 1 h, filtration was carried out to obtain a lithium precipitation mother liquor and crude lithium carbonate, and the crude lithium carbonate was filtered, eluted and dried to obtain 267 g of industrial-grade lithium carbonate (including the conversion amount of the raw material lithium iron phosphate), with a main content of 99.3%.

[0077] Step D: extraction, the lithium precipitation mother liquor obtained in step C was subjected to Li extraction, the volume ratio of oil phase to water phase was 1:1, the oil phase included 0.8:1 volume ratio of HB121 basic extractant and sulfonated kerosene, and after three-stage countercurrent extraction at room temperature, the lithium extraction rate was 99.2%. The raffinate was evaporated and concentrated, and when the Baume degree was 38°Bé, 408 g of sodium sulfate was hot-dissolved at 82°C, and 276 g of ammonium sulfate was dissolved at 57°C.

[0078] Step E: roasting, 276 g of ammonium sulfate obtained in step D was roasted with 307 g of lithium iron phosphate waste at a mass ratio of 0.9:1, and after roasting at 300°C for 10 min, the roasting was cooled, 3 times the mass of water was used for leaching at 50°C, and 895 g of leaching solution was obtained, which was recycled to step B for lithium precipitation and used in the above operation.

[0079] The analysis data of the industrial-grade lithium carbonate obtained in examples 1-3 of the present application are shown in Table 1.

[0080] Table 1 Analysis data of industrial-grade lithium carbonate

[0081]

[0082]

[0083] As can be seen from Table 1, the lithium carbonate prepared in Examples 1-3 all meet the requirements of industrial grade.

[0084] The various embodiments in the specification are described in progressive order, each embodiment highlighting a difference from the other embodiments, and the same or similar parts between the embodiments can be mutually referred to.

[0085] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will accord with the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material, characterized by, Comprise the following steps: 1) mixing lithium amide waste, lithium sulfide waste and water to obtain a waste mixture, then mixing the waste mixture with hydrogen peroxide solution and sulfuric acid solution to obtain an acid dissolution mixture, carrying out acid dissolution reaction, and after solid-liquid separation, obtaining a lithium-containing acid dissolution solution and insoluble matter; 2) mixing the lithium-containing acid dissolution solution with lye, carrying out alkalization reaction, and after reaction is completed, carrying out solid-liquid separation to obtain insoluble impurities and alkalization liquor; 3) concentrating the alkalization liquor to obtain concentrated alkalization liquor, mixing the concentrated alkalization liquor with sodium carbonate solution to carry out lithium precipitation reaction, and after reaction is completed, carrying out solid-liquid separation to obtain lithium precipitation mother liquor and lithium carbonate; 4) extracting lithium elements in the lithium precipitation mother liquor, and obtaining lithium sulfate by sulfuric acid back extraction of the extract, and evaporating and concentrating the raffinate to stepwise precipitate sodium sulfate and ammonium sulfate; 5) mixing ammonium sulfate and lithium iron phosphate waste, then carrying out roasting and leaching in sequence to obtain leaching liquor, and mixing the leaching liquor with the lithium-containing acid dissolution solution in step 2) to carry out alkalization reaction. The mass ratio of the lithium amide waste, lithium sulfide waste, water, hydrogen peroxide solution and sulfuric acid solution in step 1) is 45-55:45-55:600-1000:80-120:280-320. The pH value of the system in the alkalization reaction in step 2) is 10-12.

2. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 1, characterized in that, The mass concentration of the hydrogen peroxide solution in step 1) is 30-60%. The mass concentration of the sulfuric acid solution is 80-98%.

3. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 2, characterized in that, The time of the acid dissolution reaction in step 1) is 0.5-2h.

4. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste materials according to any one of claims 1-3, characterized in that, The lye in step 2) comprises sodium hydroxide solution. The mass concentration of the lye is 30-35%.

5. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 4, characterized in that, The time of the alkalization reaction in step 2) is 0.5-1h.

6. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 5, characterized in that, The mass concentration of Li in the concentrated alkalization liquor in step 3) is 15-25g / L. The molar ratio of Li in the concentrated alkalization liquor to sodium carbonate in the sodium carbonate solution in step 3) is 1.8-2.2:

1. The mass concentration of the sodium carbonate solution is 200-250g / L.

7. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 5 or 6, characterized in that, The time of the lithium precipitation reaction in step 3) is 0.5-1h, and the temperature of the lithium precipitation reaction is 80-95℃.

8. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 7, characterized in that, The number of stages of the extraction in step 4) is 3.

9. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 8, characterized in that, The mass ratio of ammonium sulfate to lithium iron phosphate waste in step 5) is 0.6-1:

1.

10. The method for preparing lithium carbonate by synergistically treating and recovering lithium from lithium-containing waste material according to claim 9, characterized in that, The temperature of the roasting in step 5) is 250-350℃, the time of the roasting is 10-15min, the liquid-solid mass ratio of the leaching is 2-4:1, and the leaching temperature is 40-60℃.

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