Microwave-Synthesized Mn-Based Li-Rich Ion Sieves for Selective Lithium Recovery from High Mg/Li Brines

The most proven lithium resources are stored in salt lakes, yet their efficient extraction faces challenges due to the lack of high-performance adsorbents. Here, lithium-rich ion sieves (M-LMO-t) were successfully synthesized via a microwave-assisted hydrothermal method, significantly reducing the reaction time and optimizing the pore structure. Systematic evaluation of microwave irradiation time revealed its impact on particle size distribution, manganese dissolution, and lithium adsorption capacity. M-LMO-1, synthesized in 1 h, exhibited optimal properties: a small average particle size (69.1 nm), low Mn3+ content (13.04%), and enhanced lithium adsorption capacity (38.4 mg·g–1) in alkaline LiCl solution (C0 = 350 mg·L–1, pH = 12), outperforming conventional H-LMO (31.3 mg·g–1, 16.59% Mn3+). Remarkably, M-LMO-1 showed exceptional structural stability, with manganese dissolution reduced to 2.06% during acid pickling (vs 6.85% for H-LMO). Over ten adsorption–desorption cycles, M-LMO-1 maintained a high capacity (25.7 mg·g–1) and a low dissolution rate (0.93%). From high Mg/Li brine in the Yi Li Ping Salt Lake, M-LMO-1 achieved an impressive capacity (36.4 mg·g–1) with excellent Li+ selectivity. This work not only advances efficient lithium extraction technologies but also establishes M-LMO-1 as a highly promising candidate for practical lithium extraction, offering superior performance, stability, and selectivity.