Synthesis of Inorganic Sorbents Based on Manganese Oxides for Lithium Extraction from Natural Brines

The most acceptable method when processing natural brines found in Kazakhstan and extracting lithium, should be considered the sorption process using inorganic sorbents, in particular, those based on manganese oxides. Two sorbents were synthesized and passed four preparation stages. Stage I -obtaining a hydrated oxide manganese compound. Stage II -obtaining intermediate lithium-containing products in two ways: autoclaving commercial manganese dioxide with a lithium hydroxide solution LiOH∙Н2Оand treatment of a previously obtained hydrated oxide manganese compound with lithium hydroxide LiOH∙Н2О, which included holding in a drying oven in a wet state. Stage III -calcining the precursors. The calcined products are represented by the main phases of lithium-manganese oxides Li1.27Mn1.73O4and Li1.6Mn1.6O4. The batches of intermediate lithium-containing products resulting from the two methods are precursor substances (precursors) of sorbents and to obtain them, it is necessary to acidize the precursors, which is the last IV stage. Precursors are acidized in order to remove lithium with the formation of very small free vacancies in the sorbent structure, which can only be occupied by lithium during sorption. The sorbents obtained by the two methods consist mainly of manganese oxide compounds Mn2.03O4and MnO2; a phase of manganese hydroxide Mn(OH)2is present in the second case. The manganese content in sorbents is kept at the level of Mn ~54 %, and the residual lithium content is 1 %. The developed sorbents showed the maximum lithium holding capacity of 29.07 and 36.97 mg/g, respectively, when extracted from brine with a pH 7.3