Disclosed by the invention is a method for preparing lithium carbonate from lithium ore, comprising the steps of: preparing lithium sulfate leachate from lithium ore concentrate, removing Fe.sup.2+ and Al.sup.3+ from the lithium sulfate leachate by adding alkali, removing Ca.sup.2+ and Mg.sup.2+ from the lithium sulfate leachate by an ion exchange method, adding a saturated solution of soda ash into the obtained concentrated solution of lithium sulfate leachate, precipitating lithium carbonate, filtering and separating the lithium carbonate precipitate, washing with hot water and drying to obtain a finished lithium carbonate product. The invention saves the production cost, and obviously improves the purity of lithium carbonate as a final product. In addition, disclosed by the invention is also a system for realizing the method for preparing lithium carbonate from lithium ore.

The present disclosure relates to processes for treating an aqueous composition comprising lithium sulfate and sulfuric acid. The processes comprise evaporatively crystallizing the aqueous composition comprising lithium sulfate and sulfuric acid under conditions to obtain crystals of lithium sulfate monohydrate and a lithium sulfate-reduced solution; and optionally separating the crystals of the lithium sulfate monohydrate from the lithium sulfate-reduced solution. The processes optionally further comprise concentrating the lithium sulfate-reduced solution under conditions to obtain an acidic condensate and a concentrate comprising sulfuric acid.

The present disclosure relates to processes for treating an aqueous composition comprising lithium sulfate and sulfuric acid. The processes comprise evaporatively crystallizing the aqueous composition comprising lithium sulfate and sulfuric acid under conditions to obtain crystals of lithium sulfate monohydrate and a lithium sulfate-reduced solution; and optionally separating the crystals of the lithium sulfate monohydrate from the lithium sulfate-reduced solution. The processes optionally further comprise concentrating the lithium sulfate-reduced solution under conditions to obtain an acidic condensate and a concentrate comprising sulfuric acid.

A process for recovering lithium phosphate and lithium sulfate from a lithium-bearing silicate is described. The process includes adding from 800 kg/t to 1600 kg/t of sulfuric acid to a slurry of the lithium-bearing silicate and from 40 kg/t to 600 kg/t of a source of fluoride to produce a leach mixture and heating said leach mixture. A lithium-bearing solution is then separated from the leach mixture and its pH is increased sequentially to pH 3.5 to 4, pH 5.5 to 6 then pH 10.5 to 11 to precipitate, respectively, a first, second and third set of impurities therefrom. The first, second and third sets of impurities are separated from the lithium-bearing solution and lime is added to maintain a soluble Ca concentration of at least 30 mg/L. The lithium-bearing solution is then softened by adding a two sequential amounts of phosphate to precipitate fluorapatite and apatite, respectively. A third amount of phosphate is added to produce a lithium phosphate precipitate which is then separated. The separated lithium phosphate precipitate is then digested in sulphuric acid to produce a digestion mixture from which a lithium sulfate precipitate is separated. An alkali metal hydroxide is added to the separated solution to produce an alkali metal phosphate solution and this is recycled for use as phosphate in the process.

A process for recovering lithium phosphate and lithium sulfate from a lithium-bearing silicate is described. The process includes adding from 800 kg/t to 1600 kg/t of sulfuric acid to a slurry of the lithium-bearing silicate and from 40 kg/t to 600 kg/t of a source of fluoride to produce a leach mixture and heating said leach mixture. A lithium-bearing solution is then separated from the leach mixture and its pH is increased sequentially to pH 3.5 to 4, pH 5.5 to 6 then pH 10.5 to 11 to precipitate, respectively, a first, second and third set of impurities therefrom. The first, second and third sets of impurities are separated from the lithium-bearing solution and lime is added to maintain a soluble Ca concentration of at least 30 mg/L. The lithium-bearing solution is then softened by adding a two sequential amounts of phosphate to precipitate fluorapatite and apatite, respectively. A third amount of phosphate is added to produce a lithium phosphate precipitate which is then separated. The separated lithium phosphate precipitate is then digested in sulphuric acid to produce a digestion mixture from which a lithium sulfate precipitate is separated. An alkali metal hydroxide is added to the separated solution to produce an alkali metal phosphate solution and this is recycled for use as phosphate in the process.

A process for generating a metal sulfate that involves crystallizing a metal sulfate from an aqueous solution to form a crystallized metal sulfate in a mother liquor with uncrystallized metal sulfate remaining in the mother liquor; separating the crystallized metal sulfate from the mother liquor; basifying a portion of the mother liquor to convert the uncrystallized metal sulfate to a basic metal salt; and using the basic metal salt upstream of crystallizing the metal sulfate. So crystallized, the generated metal sulfate may be battery-grade or electroplating-grade.

Systems and methods of producing potassium sulfate can involve converting a mixed salts feed stream into a conversion end slurry in a conversion unit, the mixed salts feed comprising at least one potassium-containing salt, at least one chloride-containing salt, at least one magnesium-containing salt and at least one sulfate-containing salt and the conversion end slurry comprising schoenite; separating conversion end slurry into a conversion end solids stream and a conversion brine; leaching the conversion end solids stream in a crystallization unit to produce a potassium sulfate product stream comprising potassium sulfate and a crystallizer mother liquor comprising magnesium sulfate and potassium sulfate; collecting heat generated in the conversion unit by a heat pump; and providing at least a portion of the heat collected to the crystallization unit to regulate a temperature of the potassium sulfate product stream and the crystallizer mother liquor stream contained in the crystallization unit.

Systems and methods of producing potassium sulfate can involve converting a mixed salts feed stream into a conversion end slurry in a conversion unit, the mixed salts feed comprising at least one potassium-containing salt, at least one chloride-containing salt, at least one magnesium-containing salt and at least one sulfate-containing salt and the conversion end slurry comprising schoenite; separating conversion end slurry into a conversion end solids stream and a conversion brine; leaching the conversion end solids stream in a crystallization unit to produce a potassium sulfate product stream comprising potassium sulfate and a crystallizer mother liquor comprising magnesium sulfate and potassium sulfate; collecting heat generated in the conversion unit by a heat pump; and providing at least a portion of the heat collected to the crystallization unit to regulate a temperature of the potassium sulfate product stream and the crystallizer mother liquor stream contained in the crystallization unit.

The present specification provides a method for preparing a solid electrolyte for a secondary battery, comprising the steps of: (S1) preparing a material composition comprising phosphorus (P) sulfide, a lithium halide and lithium sulfide; (S2) mechanically milling the material composition in a milling container; and (S3) calcining a compound obtained after the milling step, wherein the calcination step (S3) performs purging using gas.

The present specification provides a method for preparing a solid electrolyte for a secondary battery, comprising the steps of: (S1) preparing a material composition comprising phosphorus (P) sulfide, a lithium halide and lithium sulfide; (S2) mechanically milling the material composition in a milling container; and (S3) calcining a compound obtained after the milling step, wherein the calcination step (S3) performs purging using gas.