PROCESS OF EXTRACTING MONOHYDRATE OF HIGH-PURITY LITHIUM HYDROXIDE FROM MATERIALS CONTAINING LITHIUM CARBONATE Russian patent published in 2003 - IPC

FIELD: chemical technology of production of inorganic compounds. SUBSTANCE: invention refers to processes of extraction of monohydrate of high-purity lithium hydroxide from materials containing lithium carbonate or technical lithium. Lithium carbonate is solved in sulfuric acid formed in anode chamber of membrane electrolyzer with obtainment of solution of lithium sulfate. Solution of lithium sulfate with concentration 180-200 kg/cu.m (3.3-3.6 kg eq/cu.m) displays high conduction and allows process of conversion of lithium sulfate to hydroxide to be conducted in electrolyzer with current density 5.0-15.0 A/dm and voltage drop across cell 4.7-5.1 V. Under conditions of membrane electrolysis formed solution of lithium hydroxide (catolyte) includes impurities of bivalent and trivalent metals contained in technical lithium carbonate or waste carrying Li₂CO₃. Solution of lithium hydroxide and lithium carbonate won within scope of technological process is utilized to purify anolyte from impurities. Concentration of lithium hydroxide in catolyte is kept at level 35.0-45.0 kg/cu.m. It is achieved when concentration of acid in anolyte equals 0.6-1.0 kg eq/cu.m. Keeping concentration of LiOH at level of 35.0-45.0 kg/cu.m is determined by least summary expenses on process of electrolysis and evaporation of solutions of LiOH. Content of impurities Na⁺ and K⁺ is maintained at level of 0.35-1.2 relative per cent in solutions of lithium hydroxide by extraction of portion of mother liquor. Monohydrate of lithium hydroxide formed in this case contains ≤0,060 mas.% of sodium (potassium) which can be washed out under conditions of counterflush prior to winning high-purity LiOH.H₂O. Carbon dioxide at stage of neutralization of sulfuric acid by lithium carbonate is used for reclamation of lithium from mother liquors with production of lithium carbonate which is utilized in technological circuit to purify anolyte or is returned for operation of neutralization of sulfuric acid. EFFECT: potential for entrainment of technical lithium carbonate and waste containing lithium carbonate in process of extraction of high-purity monohydrate of lithium hydroxide. 4 cl, 6 dwg, 4 tbl