Recycling method of potassium sulfate in lithium extraction by lepidolite sulfate method

Abstract

The invention relates to the technical field of chemical metallurgy and efficient utilization of ore lithium resources, in particular to a cyclic utilization method of potassium sulfate in lithium extraction by a lepidolite sulfate method, which comprises the following steps: S1) uniformly mixing lepidolite powder and sulfate containing potassium sulfate to obtain a mixed material; s2) roasting the mixed material for defluorination; s3) carrying out water immersion and filtration to obtain a lithium-containing solution, carrying out carbonization lithium precipitation, and carrying out evaporation concentration on the obtained filtrate to obtain potassium sulfate; s4) mixing solid-phase insoluble slag obtained by water leaching, an acid solution and an additive, stirring, leaching, concentrating, cooling and crystallizing to obtain crystals; s5) mixing the crystal with an aqueous solution of alcohol, heating, stirring and filtering to obtain potassium sulfate; and S6) reusing the potassium sulfate obtained in the step S3) and the step S5) in the step S1). According to the method, the added potassium sulfate and the potassium of the lepidolite are recycled, so that efficient extraction of lithium is realized, and meanwhile, the recycling efficiency of the potassium sulfate in the process of extracting lithium from the lepidolite by the sulfate method is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical metallurgy and efficient utilization of lithium ore resources, and in particular to a method for recycling potassium sulfate in lithium extraction by a lithium mica sulfate method. Background Art

[0002] As one of the important lithium ore resources in my country, lithium mica is one of the important lithium ore resources for the preparation of high-end lithium materials due to its rich reserves and wide distribution. Due to the low grade of lithium oxide in lithium mica (the mass content of Li2O in the concentrate does not exceed 4%), it is often used as flotation tantalum-niobium tailings. At the same time, it coexists with gangue minerals such as potassium / sodium feldspar and quartz, making the efficient extraction of lithium and comprehensive utilization of lithium mica still face severe challenges. The sulfate method has gradually been widely studied due to its high selectivity for lithium extraction, but it still faces problems such as low utilization rate of the potassium sulfate process due to excessive addition of activation aids (mainly potassium sulfate) and accumulation of potassium-containing solid slag. Therefore, improving the recycling efficiency of potassium sulfate is of great significance for lithium extraction from lithium mica sulfate method. Summary of the invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a method for recycling potassium sulfate in lithium extraction by lepidolite sulfate method. The present invention can recycle the added potassium sulfate activation aid and the potassium of the lepidolite itself, thereby achieving efficient extraction of lithium and improving the recycling efficiency of potassium sulfate in the process of lithium extraction by lepidolite sulfate method.

[0004] The present invention provides a method for recycling potassium sulfate in lithium extraction by lepidolite sulfate method, comprising the following steps:

[0005] S1) mixing lepidolite powder and sulfate to obtain a mixed material;

[0006] The sulfate includes a first sulfate and a second sulfate; the first sulfate is potassium sulfate;

[0007] S2) calcining and defluorinating the mixture;

[0008] S3) soaking the material obtained in step S2) in water, filtering to obtain a lithium-containing solution, carbonizing and precipitating lithium, and evaporating and concentrating the obtained filtrate to obtain potassium sulfate;

[0009] S4) mixing the solid insoluble slag obtained by the water immersion, the acid solution and the additive, stirring for leaching, concentrating, cooling and crystallizing to obtain crystals;

[0010] S5) mixing the crystals with an alcohol aqueous solution, heating and stirring, and filtering to obtain potassium sulfate;

[0011] S6) The potassium sulfate obtained in step S3) and step S5) is recycled to step S1).

[0012] Preferably, in step S1), the second sulfate includes at least one of sodium sulfate, ammonium sulfate, ammonium bisulfate, aluminum sulfate, ferrous sulfate, potassium alum and calcium sulfate;

[0013] The mass ratio of the first sulfate to the second sulfate is 1:0.01-5;

[0014] The mass ratio of the lithium mica powder to the sulfate is 1:0.1-3;

[0015] The particle size of the lithium mica powder is 50 to 500 meshes.

[0016] Preferably, in step S2), before the mixed material is subjected to roasting and defluorination, the process further comprises:

[0017] Mixing the mixed material and the auxiliary agent;

[0018] The auxiliary agent comprises at least one of slaked lime, coke, coking coal, chitosan and starch;

[0019] The mass ratio of the lithium mica powder to the auxiliary agent is 1:0.01-5.

[0020] Preferably, in step S2), the temperature of the calcination defluorination is 680-1100°C and the time is 10min-5h;

[0021] The particle size of the material obtained in step S2) is 50 to 500 meshes.

[0022] Preferably, in step S3), the liquid-to-solid ratio of the water immersion is 0.5 to 20:1;

[0023] The water immersion is performed at a temperature of 25 to 90° C. and for a time of 10 to 180 minutes.

[0024] Preferably, in step S3), the carbonization of lithium precipitate comprises:

[0025] After adjusting the pH value of the lithium-containing solution to not exceed 13.0, NaCO3 is added to carbonize and precipitate lithium;

[0026] The reagent used to adjust the pH value of the lithium-containing solution includes ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate;

[0027] The molar ratio of the amount of NaCO3 added to the lithium ions in the lithium-containing solution is 0.5 to 3:1;

[0028] The temperature of the carbonized lithium precipitate is 25-100° C. and the time is 0.5-5 hours.

[0029] Preferably, in step S4), the acid solution comprises one of a sulfuric acid solution, a hydrochloric acid solution and an acetic acid solution;

[0030] The concentration of the acid solution is 0.1 to 3 mol / L;

[0031] The additive comprises at least one of potassium sulfate, ammonium sulfate, ammonium bisulfate, aluminum sulfate, potassium sulfate, potassium alum and calcium sulfate;

[0032] The mass ratio of the solid insoluble slag, the acid solution and the additive is 0.1-1:0.01-2:0.01-1.

[0033] Preferably, in step S4), the stirring leaching temperature is 25 to 90° C. and the time is 10 to 180 min;

[0034] The temperature of the cooling crystallization is -10 to 25°C.

[0035] Preferably, in step S5), the alcohol includes one of methanol, ethanol, n-butanol and ethylene glycol;

[0036] The volume concentration of the alcohol aqueous solution is 10% to 70%.

[0037] Preferably, in step S5), the crystals are mixed with an aqueous solution of alcohol at a liquid-to-solid ratio of 0.1-10:10-0.1;

[0038] The heating and stirring is performed at a temperature of 25 to 90° C. and for a time of 0.5 to 3 hours.

[0039] The present invention provides a method for recycling potassium sulfate in lithium extraction by lithium mica sulfate method, comprising the following steps: S1) mixing lithium mica powder and sulfate to obtain a mixed material; the sulfate includes a first sulfate and a second sulfate; the first sulfate is potassium sulfate; S2) roasting and defluorinating the mixed material; S3) water leaching the material obtained in step S2), filtering to obtain a lithium-containing solution, carbonizing and precipitating lithium, and evaporating and concentrating the obtained filtrate to obtain potassium sulfate; S4) mixing the solid phase insoluble slag, acid solution and additives obtained by the water leaching, stirring and leaching, concentrating, cooling and crystallizing to obtain crystals; S5) mixing the crystals with an aqueous solution of alcohol, heating and stirring, filtering, and obtaining potassium sulfate; S6) reusing the potassium sulfate obtained in step S3) and step S5) in step S1). The present invention utilizes lattice activation in the process of roasting lithium mica and sulfate to replace lithium and convert it into soluble lithium sulfate. Among them, the potassium sulfate reaction has high efficiency in selective lithium extraction, but usually requires excessive addition. The present invention recycles the excess potassium sulfate and the potassium that enters the lithium mica lattice respectively. The insoluble potassium-containing phase generated by the reaction product of lithium mica and potassium sulfate is recovered by acid leaching, and after potassium alum is crystallized and precipitated, alcohol precipitation double decomposition is introduced to recover the potassium sulfate that enters the lithium mica lattice, and the recovered potassium sulfate enters the next activation roasting cycle. The key point of the present invention is that the added potassium sulfate can be fully recovered, and the potassium of the lithium mica itself can also be utilized, so as to improve the recycling efficiency of potassium sulfate and reduce the consumption of potassium sulfate, which is beneficial to the comprehensive utilization of potassium-containing solid phase slag in the lithium mica sulfate process, and the amount of solid waste generated is relatively small. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of the recycling process of potassium sulfate in lithium extraction using the lepidolite sulfate method provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The present invention provides a method for recycling potassium sulfate in lithium extraction by lepidolite sulfate method, comprising the following steps:

[0043] S1) mixing lepidolite powder and sulfate to obtain a mixed material;

[0044] The sulfate includes a first sulfate and a second sulfate; the first sulfate is potassium sulfate;

[0045] S2) calcining and defluorinating the mixture;

[0046] S3) soaking the material obtained in step S2) in water, filtering to obtain a lithium-containing solution, carbonizing and precipitating lithium, and evaporating and concentrating the obtained filtrate to obtain potassium sulfate;

[0047] S4) mixing the solid insoluble slag obtained by the water immersion, the acid solution and the additive, stirring for leaching, concentrating, cooling and crystallizing to obtain crystals;

[0048] S5) mixing the crystals with an alcohol aqueous solution, heating and stirring, and filtering to obtain potassium sulfate;

[0049] S6) The potassium sulfate obtained in step S3) and step S5) is recycled to step S1).

[0050] Regarding step S1):

[0051] Raw material mixing:

[0052] Mixing the lepidolite powder and the sulfate to obtain a mixed material;

[0053] The sulfate includes a first sulfate and a second sulfate; the first sulfate is potassium sulfate.

[0054] In certain embodiments of the present invention, the second sulfate is selected from at least one of sodium sulfate, ammonium sulfate, ammonium bisulfate, aluminum sulfate, ferrous sulfate, potassium alum and calcium sulfate.

[0055] The mass ratio of the first sulfate to the second sulfate is 1:0.01-5, such as 1:0.4, 1:1.

[0056] The mass ratio of the lithium mica powder to the sulfate is 1:0.1-3, for example 1:1.

[0057] The particle size of the lepidolite powder is 50-500 meshes, such as 150 meshes. The lepidolite powder is obtained by crushing and grinding lepidolite concentrate.

[0058] Regarding step S2):

[0059] Roasting:

[0060] The mixed material is calcined for defluorination.

[0061] In certain embodiments of the present invention, before the mixed material is subjected to calcination and defluorination, the method further comprises:

[0062] The mixed material and the auxiliary agent are mixed uniformly.

[0063] The auxiliary agent is selected from at least one of slaked lime, coke, coking coal, chitosan and starch. The mass ratio of the lithium mica powder to the auxiliary agent is 1:0.01-5, such as 1:1, 1:2.

[0064] In certain embodiments of the present invention, the temperature of the calcination defluorination is 680-1100° C., such as 900° C., 1100° C.; and the time is 10 min-5 h, such as 0.5 h, 3 h.

[0065] Regarding step S3):

[0066] Leaching:

[0067] The material obtained in step S2) is immersed in water, filtered to obtain a lithium-containing solution, carbonized and precipitated lithium, and the obtained filtrate is evaporated and concentrated to obtain potassium sulfate.

[0068] The particle size of the material obtained in step S2) is 50 to 300 meshes.

[0069] In certain embodiments of the present invention, the liquid-to-solid ratio of the water immersion is 0.5-20:1, such as 5:1. The temperature of the water immersion is 25-90°C, such as 80°C, and the time is 10-180 min, such as 60 min.

[0070] In certain embodiments of the present invention, the carbonized lithium precipitate comprises:

[0071] After adjusting the pH value of the lithium-containing solution to not exceed 13.0, NaCO3 is added to carbonize and precipitate lithium.

[0072] The reagent used to adjust the pH value of the lithium-containing solution includes ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate, and the pH value of the lithium-containing solution is adjusted to 13.

[0073] The molar ratio of the added amount of NaCO3 to the lithium ions in the lithium-containing solution is 0.5 to 3:1, such as 1.1:1.

[0074] The temperature of the carbonized lithium precipitate is 25-100° C., such as 50° C., and the time is 0.5-5 hours, such as 1 hour.

[0075] After the carbonization and precipitation of lithium, the method further includes: solid-liquid separation, which can be specifically filtration. The obtained solid substance is lithium carbonate; the obtained filtrate is evaporated and concentrated to obtain potassium sulfate.

[0076] Regarding step S4):

[0077] Alum:

[0078] The solid insoluble slag obtained by water immersion, the acid solution and the additive are mixed, stirred for leaching, concentrated, cooled and crystallized to obtain crystals.

[0079] In certain embodiments of the present invention, the acid solution is selected from one of a sulfuric acid solution, a hydrochloric acid solution and an acetic acid solution. The concentration of the acid solution is 0.1 to 3 mol / L, such as 0.2 mol / L or 1 mol / L.

[0080] The additive is selected from at least one of potassium sulfate, sodium sulfate, ammonium sulfate, ammonium hydrogen sulfate, aluminum sulfate, ferrous sulfate, potassium alum and calcium sulfate.

[0081] The mass ratio of the solid insoluble slag, the acid solution and the additive is 0.1-1:0.01-2:0.01-1, such as 1:1:0.5, 1:2:1.

[0082] The stirring leaching is performed at a temperature of 25 to 90° C., such as 50° C. or 80° C., and for a time of 10 to 180 min, such as 30 min or 180 min.

[0083] The concentration is evaporation concentration; the temperature of the evaporation concentration is 30-100° C., such as 80° C.; the time is 30-180 min, such as 120 min.

[0084] The temperature of the cooling crystallization is -10 to 25°C, such as -5°C or 5°C.

[0085] The solid phase insoluble slag is mainly a new phase of aluminosilicate containing potassium. Potassium and aluminum are dissolved out after acid dissolution, and then cooled and crystallized to form double salt potassium alum crystals.

[0086] Regarding step S5):

[0087] Alcohol analysis:

[0088] The crystals are mixed with an alcohol aqueous solution, heated and stirred, and filtered to obtain potassium sulfate.

[0089] In certain embodiments of the present invention, the alcohol is selected from one of methanol, ethanol, n-butanol and ethylene glycol. The volume concentration of the alcohol aqueous solution is 10% to 70%, such as 70%.

[0090] The crystals are mixed with an aqueous solution of alcohol in a liquid-to-solid ratio of 0.1-10:10-0.1; for example, 5:1.

[0091] The heating and stirring is performed at a temperature of 25 to 90° C., such as 80° C., and for a time of 0.5 to 3 h, such as 3 h.

[0092] Alcohol precipitation can precipitate potassium sulfate crystals that were originally soluble in water and generated by the double decomposition of potassium alum crystals, while aluminum chloride is soluble in alcohol. The double decomposition product potassium sulfate can be separated by filtering, which is beneficial to the subsequent circulation of potassium sulfate.

[0093] Regarding step S6):

[0094] cycle:

[0095] The potassium sulfate obtained in step S3) and step S5) is recycled to step S1) and used as the first sulfate (potassium sulfate).

[0096] Figure 1 A schematic diagram of the recycling process of potassium sulfate in lithium extraction using the lepidolite sulfate method provided in accordance with an embodiment of the present invention.

[0097] The present invention utilizes the lattice activation of lithium mica and sulfate roasting process to replace lithium and convert it into soluble lithium sulfate. Among them, potassium sulfate reaction has high efficiency in selective lithium extraction, but usually needs to be added in excess. The present invention recovers the excess potassium sulfate and the potassium that enters the lithium mica lattice respectively and recycles them. The insoluble potassium-containing phase generated by the reaction product of lithium mica and potassium sulfate is recovered by acid leaching, and after potassium alum is crystallized and precipitated, alcohol precipitation and double decomposition are introduced to recover the potassium sulfate that enters the lithium mica lattice, and the recovered potassium sulfate enters the next activation roasting cycle. The key point of the present invention is that the added potassium sulfate can be fully recovered, and the potassium of the lithium mica itself can also be used at the same time, so as to improve the recycling efficiency of potassium sulfate and reduce the consumption of potassium sulfate, which is beneficial to the comprehensive utilization of potassium-containing solid phase slag in the lithium mica sulfate process, and the amount of solid waste generated is relatively small.

[0098] The potassium sulfate circulation process of the present invention does not require obtaining high-purity potassium sulfate, and the impurities in the reaction system can be circulated and enriched and then removed in an open circuit.

[0099] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0100] In order to further illustrate the present invention, a method for recycling potassium sulfate in lithium extraction by a lithium mica sulfate method provided by the present invention is described in detail below in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0101] Example 1

[0102] Method for recycling potassium sulfate in lithium extraction from lepidolite sulfate:

[0103] 1) Grinding: crushing and grinding the lithium mica concentrate to a particle size of 150 mesh to obtain lithium mica powder;

[0104] 2) Mixing: uniformly mixing the lepidolite powder, potassium sulfate and sodium sulfate in a mass ratio of 1:0.7:0.3 to obtain a mixed material;

[0105] 3) Calcination: After mixing the mixture with chitosan (the mass ratio of the lithium mica powder to chitosan is 1:1), the mixture is activated and calcined at 900° C. for 0.5 h for defluorination;

[0106] 4) Leaching: the material obtained in step 3) (particle size of 50-300 mesh) is immersed in water at a liquid-to-solid ratio of 5:1 (the immersion temperature is 80°C and the time is 60 min), filtered to obtain a lithium-containing solution, the pH value is adjusted to 13 with sodium hydroxide, sodium carbonate is added (the molar ratio of the addition amount of NaCO3 to the lithium ions in the lithium-containing solution is 1.1:1), lithium is carbonized and precipitated at 50°C for 1 hour, filtered, and the solid substance obtained is lithium carbonate; the obtained filtrate is evaporated and concentrated to obtain potassium sulfate;

[0107] 5) Alum formation: the solid insoluble residue obtained by water leaching in step 4) is put into a 0.2 mol / L sulfuric acid solution (acid solution), potassium sulfate additive is added, stirred and leached at 50° C. for 3 h, evaporated and concentrated at 80° C. for 2 h, cooled and crystallized at -5° C. to obtain double salt potassium alum crystals;

[0108] The mass ratio of the solid insoluble slag, the acid solution and the additive is 1:1:0.5.

[0109] 6) Alcohol precipitation: adding the double salt potassium alum crystals into a 70% by volume ethylene glycol aqueous solution at a liquid-solid ratio of 5:1, heating and stirring at 80° C. for 3 h, filtering, and obtaining potassium sulfate.

[0110] 7) Recycling: The potassium sulfate obtained in step 4) and step 6) is recycled to step 2). According to the test, the recovery rate of lithium is 91%, the recovery rate of potassium sulfate is 82%, and the amount of solid waste generated is 9% (based on the ore sample).

[0111] Comparative Example 1 (without additives)

[0112] The difference from Example 1 is:

[0113] In step 3), calcination: the mixed material is activated and calcined at 900° C. for 0.5 h for defluorination.

[0114] The remaining steps and parameters are the same as those in Example 1.

[0115] According to the test, the recovery rate of lithium is 79%, the recovery rate of potassium sulfate is 68%, and the amount of solid waste generated is 17% (based on the ore sample).

[0116] Comparative Example 2

[0117] The difference from Example 1 is that steps 5) and 6) are not included:

[0118] Method for recycling potassium sulfate in lithium extraction from lepidolite sulfate:

[0119] 1) Grinding: crushing and grinding the lithium mica concentrate to a particle size of 150 mesh to obtain lithium mica powder;

[0120] 2) Mixing: uniformly mixing the lepidolite powder, potassium sulfate and sodium sulfate in a mass ratio of 1:0.7:0.3 to obtain a mixed material;

[0121] 3) Calcination: After mixing the mixture with chitosan (the mass ratio of the lithium mica powder to chitosan is 1:1), the mixture is activated and calcined at 900° C. for 0.5 h for defluorination;

[0122] 4) Leaching: the material obtained in step 3) (particle size of 50-300 mesh) is immersed in water at a liquid-to-solid ratio of 5:1 (the immersion temperature is 80°C and the time is 60 min), filtered to obtain a lithium-containing solution, the pH value is adjusted to 13 with sodium hydroxide, sodium carbonate is added (the molar ratio of the addition amount of NaCO3 to the lithium ions in the lithium-containing solution is 1.1:1), lithium is carbonized and precipitated at 50°C for 1 hour, filtered, and the solid substance obtained is lithium carbonate; the obtained filtrate is evaporated and concentrated to obtain potassium sulfate;

[0123] 5) Recycling: The potassium sulfate obtained in step 4) is recycled to step 2). According to the test, the recovery rate of lithium is 87%, the recovery rate of potassium sulfate is 46%, and the amount of solid waste generated is 34% (based on the ore sample).

[0124] Example 2 (changing the second sulfate and auxiliary agent)

[0125] The difference from Example 1 is:

[0126] In step 2), mixing: the lepidolite powder, potassium sulfate and ammonium sulfate are uniformly mixed in a mass ratio of 1:0.7:0.3 to obtain a mixed material.

[0127] 3) Calcination: After the mixed material is mixed with starch (the mass ratio of the lithium mica powder to starch is 1:1), activation calcination is performed at 900° C. for 0.5 h to defluorinate.

[0128] The remaining steps and parameters are the same as those in Example 1.

[0129] According to the test, the recovery rate of lithium was 89%, the recovery rate of potassium sulfate was 84%, and the amount of solid waste generated was 19% (based on the ore sample).

[0130] Example 3 (changing the second sulfate and auxiliary agent)

[0131] The difference from Example 1 is:

[0132] In step 2), mixing: the lepidolite powder, potassium sulfate and calcium sulfate are uniformly mixed in a mass ratio of 1:0.7:0.3 to obtain a mixed material.

[0133] 3) Calcination: After the mixed material is mixed with coke (the mass ratio of the lithium mica powder to the coke is 1:1), activation calcination is performed at 900° C. for 0.5 h for defluorination.

[0134] The remaining steps and parameters are the same as those in Example 1.

[0135] After testing, the recovery rate of lithium was 87%, the recovery rate of potassium sulfate was 72%, and the amount of solid waste generated was 43% (based on the ore sample).

[0136] Comparative Example 3 (the auxiliary agent is calcium oxide)

[0137] The difference from Example 1 is:

[0138] In step 2), mixing: the lepidolite powder, potassium sulfate and calcium sulfate are uniformly mixed in a mass ratio of 1:0.7:0.3 to obtain a mixed material.

[0139] 3) Calcination: After the mixed material is mixed with calcium oxide (the mass ratio of the lithium mica powder to calcium oxide is 1:1), activation calcination is performed at 900° C. for 0.5 h to defluorinate.

[0140] The remaining steps and parameters are the same as those in Example 1.

[0141] According to the test, the recovery rate of lithium is 81%, the recovery rate of potassium sulfate is 74%, and the amount of solid waste generated is 65% (based on the ore sample).

[0142] Embodiment 4 (changing the proportion of each component in the mixture)

[0143] The difference from Example 1 is:

[0144] In step 2), mixing: the lepidolite powder, potassium sulfate and sodium sulfate are uniformly mixed in a mass ratio of 1:0.5:0.5 to obtain a mixed material.

[0145] The remaining steps and parameters are the same as those in Example 1.

[0146] According to the test, the recovery rate of lithium is 83%, the recovery rate of potassium sulfate is 68%, and the amount of solid waste generated is 16% (based on the ore sample).

[0147] Embodiment 5 (changing the proportion of each component in the mixture)

[0148] The difference from Example 1 is:

[0149] In step 2), mixing: the lepidolite powder, potassium sulfate and sodium sulfate are uniformly mixed in a mass ratio of 1:0.5:0.5 to obtain a mixed material.

[0150] 3) Calcination: After the mixture is mixed with chitosan (the mass ratio of the lepidolite powder to chitosan is 1:2), activation calcination is performed at 900° C. for 0.5 h to defluorinate.

[0151] The remaining steps and parameters are the same as those in Example 1.

[0152] According to the test, the recovery rate of lithium is 89%, the recovery rate of potassium sulfate is 78%, and the amount of solid waste generated is 11% (based on the ore sample).

[0153] Comparative Example 4 (Changing Calcination Parameters)

[0154] The difference from Example 1 is:

[0155] 3) Calcination: The mixture is activated and calcined at 650° C. for 3 h for defluorination.

[0156] The remaining steps and parameters are the same as those in Example 1.

[0157] After testing, the recovery rate of lithium was 53%, the recovery rate of potassium sulfate was 32%, and the amount of solid waste generated was 73% (based on the ore sample).

[0158] Example 6 (Changing Calcination Parameters)

[0159] The difference from Example 1 is:

[0160] 3) Calcination: Calcinate the mixture at 1100° C. for 0.5 h to remove fluorine.

[0161] The remaining steps and parameters are the same as those in Example 1.

[0162] According to the test, the recovery rate of lithium was 83%, the recovery rate of potassium sulfate was 69%, and the amount of solid waste generated was 14% (based on the ore sample).

[0163] Example 7

[0164] The difference from Example 1 is:

[0165] 5) Alum formation: the solid insoluble residue obtained by water leaching in step 4) is put into a 1 mol / L hydrochloric acid solution (acid solution), and after adding ammonium sulfate as an additive, it is stirred and leached at 80° C. for 90 min, concentrated, and cooled and crystallized at 5° C. to obtain double salt potassium alum crystals;

[0166] The mass ratio of the solid insoluble slag, the acid solution and the additive is 1:2:1.

[0167] The remaining steps and parameters are the same as those in Example 1.

[0168] According to the test, the recovery rate of lithium was 83%, the recovery rate of potassium sulfate was 57%, and the amount of solid waste generated was 21% (based on the ore sample).

[0169] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. 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 invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for recycling potassium sulfate in lithium extraction by lepidolite sulfate method, comprising the following steps: S1) mixing lepidolite powder and sulfate to obtain a mixed material; The sulfate includes a first sulfate and a second sulfate; the first sulfate is potassium sulfate; S2) calcining and defluorinating the mixture; S3) soaking the material obtained in step S2) in water, filtering to obtain a lithium-containing solution, carbonizing and precipitating lithium, and evaporating and concentrating the obtained filtrate to obtain potassium sulfate; S4) mixing the solid insoluble slag obtained by the water immersion, the acid solution and the additive, stirring for leaching, concentrating, cooling and crystallizing to obtain crystals; S5) mixing the crystals with an alcohol aqueous solution, heating and stirring, and filtering to obtain potassium sulfate; S6) The potassium sulfate obtained in step S3) and step S5) is recycled to step S1).

2. The recycling method according to claim 1, characterized in that: In step S1), the second sulfate includes at least one of sodium sulfate, ammonium sulfate, ammonium bisulfate, aluminum sulfate, ferrous sulfate, potassium alum and calcium sulfate; The mass ratio of the first sulfate to the second sulfate is 1:0.01-5; The mass ratio of the lithium mica powder to the sulfate is 1:0.1-3; The particle size of the lithium mica powder is 50 to 500 meshes.

3. The recycling method according to claim 1, characterized in that: In step S2), before the mixed material is subjected to calcination and defluorination, the process further comprises: Mixing the mixed material and the auxiliary agent; The auxiliary agent comprises at least one of slaked lime, coke, coking coal, chitosan and starch; The mass ratio of the lithium mica powder to the auxiliary agent is 1:0.01-5.

4. The recycling method according to claim 1, characterized in that: In step S2), the temperature of the calcination defluorination is 680-1100°C and the time is 10min-5h; The particle size of the material obtained in step S2) is 50 to 500 meshes.

5. The recycling method according to claim 1, characterized in that: In step S3), the liquid-to-solid ratio of the water immersion is 0.5 to 20:1; The water immersion is performed at a temperature of 25 to 90° C. and for a time of 10 to 180 minutes.

6. The recycling method according to claim 1, characterized in that: In step S3), the carbonization of lithium precipitate comprises: After adjusting the pH value of the lithium-containing solution to not exceed 13.0, NaCO3 is added to carbonize and precipitate lithium; The reagent used to adjust the pH value of the lithium-containing solution includes ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate; The molar ratio of the amount of NaCO3 added to the lithium ions in the lithium-containing solution is 0.5 to 3:1; The temperature of the carbonized lithium precipitate is 25-100° C. and the time is 0.5-5 hours.

7. The recycling method according to claim 1, characterized in that: In step S4), the acid solution includes one of a sulfuric acid solution, a hydrochloric acid solution and an acetic acid solution; The concentration of the acid solution is 0.1 to 3 mol / L; The additive comprises at least one of potassium sulfate, ammonium sulfate, ammonium bisulfate, aluminum sulfate, potassium sulfate, potassium alum and calcium sulfate; The mass ratio of the solid insoluble slag, the acid solution and the additive is 0.1-1:0.01-2:0.01-1.

8. The recycling method according to claim 1, characterized in that: In step S4), the stirring leaching temperature is 25 to 90° C. and the time is 10 to 180 min; The temperature of the cooling crystallization is -10 to 25°C.

9. The recycling method according to claim 1, characterized in that: In step S5), the alcohol includes one of methanol, ethanol, n-butanol and ethylene glycol; The volume concentration of the alcohol aqueous solution is 10% to 70%.

10. The recycling method according to claim 1, characterized in that: In step S5), the crystals are mixed with an aqueous solution of alcohol at a liquid-to-solid ratio of 0.1-10:10-0.1; The heating and stirring is performed at a temperature of 25 to 90° C. and for a time of 0.5 to 3 hours.

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