Separation of K2CO3 from Li+ Brine with Aid of CO2 and Trace of Metastable Quaternary System Li+–K+–CO32−–HCO3−–H2O

It is of importance to reclaim single-salt of potash from Li + -type brines of low concentration. In this work the potassium salts KHCO 3 was efficiently separated from the lithium carbonate-type brines with the aid of CO 2 carbonation. The phase field was provided in which the precipitation of KHCO 3 occurs and single-salt of potassium can be obtained. The low concentration of [Li + ] was also successfully concentrated to a high level (8.1 g/L), and this concentration can be used as sources for Li + -salts production using pre-developed strategies, which looks forward wider applications of the lithium resources of natural brine. This state-of-art was traced via isotherm evaporation on the quaternary system of Li + –K + –CO 3 2− –H 2 O at 298.15 K in which the carbonation steps were performed by CO 2 . Metastable phase diagram was found to consist of three invariant points, seven univariant curves, and four crystallization fields corresponding to Li 2 CO 3 , KHCO 3 , potassium carbonate sesquihydrate (K 2 CO 3 ⋅ 3/2H 2 O), and a potassium carbonate and potassium bicarbonate double salt (K 2 CO 3 ⋅ 2 KHCO 3 ⋅ 1.5H 2 O). There was no crystallization field corresponding to LiHCO 3 . The pH-composition diagram and density-composition diagram were also plotted. This work was carried out in aim of extracting/separating single salts of alkali metals from carbonate-type brines of west China.