Echelon extraction of valuable components from salt lake brine substrate

Salt fields are indispensable for the salt lake industry, yet their substrates, which are rich in valuable resources accumulated over time by the formation of solid solution enrichment, always stand at a neglected position. In this study, the distribution and occurrence state of elements in the Mahai Salt Lake substrate were comprehensively investigated by multiple characterizations. The substrate was primarily found to consist of calcium-silica‑aluminum minerals, with significant concentrations of lithium (0.0053 %), strontium (0.1130 %), and rubidium (0.0266 %) adsorbed onto these mineralized phases. Besides, an echelon extraction was developed to exploit these valuable resources including hydrochloric acid leaching and segmented calcination-leaching coupled process. It was confirmed that over 95 % of rubidium and 93 % of strontium could be effectively extracted via hydrochloric acid leaching through cation exchange mechanisms. 80 % lithium was extracted by calcination-leaching coupled process with three cycles to conquer the interlayer structure of mineralized lithium, facilitating the occupation of Li⁺ lattice sites by H⁺.