Sedimentation based process development for Li2CO3 and Mg–K–Ca–PO4–SO4 fertilizer recovery from Aral Sea brine
Аннотация
The high salinity of Aral Sea water, as well as high amounts of accompanying magnesium, potassium, and sulfate ions, significantly limit the rational use of these waters for lithium extraction. The effective separation of these impurities is a complex scientific and technological task that requires selective and economically justified solutions. The current study evaluates the feasibility of Aral Sea water purification using a chemical precipitation method for the removal of magnesium and potassium compounds and sulfate ions. The method is based on the selective precipitation of magnesium and potassium in the form of double phosphate salt KMgPO4 using sodium hydrogen phosphate as the precipitating agent, with the precipitation of sulfate ions as calcium sulfate dihydrate. The key process variables, including reagent proportions, pH, temperature, and precipitation time, were examined and optimized to achieve maximum purification efficiency. The removal efficiency under the established optimal conditions reached 97.1% for magnesium compounds, 96.3% for potassium, and 93.4% for sulfate ions. The precipitates obtained had stable phase composition and good filtration properties, thus improving the technological feasibility of the proposed method. The findings confirm the high efficiency of the proposed method and its great potential for deep purification of highly mineralized waters.