Provided is a solid electrolyte which contains a composition expressed by 3LiOH.Math.Li.sub.2SO.sub.4. The solid electrolyte has a lithium ion conductivity of 0.110.sup.6 S/cm or more at 25 C. and an activation energy of 0.6 eV or more.

Provided is a solid electrolyte which contains a composition expressed by 3LiOH.Math.Li.sub.2SO.sub.4. The solid electrolyte has a lithium ion conductivity of 0.110.sup.6 S/cm or more at 25 C. and an activation energy of 0.6 eV or more.

A process for recovering lithium phosphate and lithium sulfate from a lithium-bearing solution, such as a brine or pregnant process liquor is described. The process includes adding phosphate to the lithium-bearing solution to precipitate lithium phosphate and then separating the resulting lithium phosphate precipitate from the solution. 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 first step of the process.

A process for recovering lithium phosphate and lithium sulfate from a lithium-bearing solution, such as a brine or pregnant process liquor is described. The process includes adding phosphate to the lithium-bearing solution to precipitate lithium phosphate and then separating the resulting lithium phosphate precipitate from the solution. 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 first step of the process.

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.

A method for preparing nickel/manganese/lithium/cobalt sulfate and tricobalt tetraoxide from battery wastes adopts the following process: dissolving battery wastes with acid, removing iron and aluminum, removing calcium, magnesium and copper, carrying extraction separation, and carrying out evaporative crystallization to prepare nickel sulfate, manganese sulfate, lithium sulfate, cobalt sulfate or/and tricobalt tetraoxide. By using the method, multiple metal elements, such as nickel, manganese, lithium and cobalt, can be simultaneously recovered from the battery wastes, the recovered products are high in purity and can reach battery grade, battery-grade tricobalt tetraoxide can also be directly produced. The method is simple in process, low in energy consumption and free in exhaust gas pollution, and can realize zero release of wastewater.

A method for preparing nickel/manganese/lithium/cobalt sulfate and tricobalt tetraoxide from battery wastes adopts the following process: dissolving battery wastes with acid, removing iron and aluminum, removing calcium, magnesium and copper, carrying extraction separation, and carrying out evaporative crystallization to prepare nickel sulfate, manganese sulfate, lithium sulfate, cobalt sulfate or/and tricobalt tetraoxide. By using the method, multiple metal elements, such as nickel, manganese, lithium and cobalt, can be simultaneously recovered from the battery wastes, the recovered products are high in purity and can reach battery grade, battery-grade tricobalt tetraoxide can also be directly produced. The method is simple in process, low in energy consumption and free in exhaust gas pollution, and can realize zero release of wastewater.

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.