Preparation and performance optimization of SA/LiAl-LDHs composite gel for lithium extraction from concentrated seawater

To achieve efficient recovery of lithium resources from concentrated seawater, an aluminum-based lithium adsorbent （LiAl-LDHs） was prepared via the co-precipitation method in this work. Using sodium alginate （SA） as the binder, composite gel particles （GLDHs） with high selectivity, excellent stability, and easy applicability were fabricated through CaCl₂ cross-linking and granulation. Its lithium extraction performance and mechanism were evaluated through static/dynamic adsorption experiments, and the process parameters were optimized. The results showed that the GLDHs-20 beads with a LiAl-LDHs loading of 20% had an adsorption capacity of 6.53 mg·g⁻¹, and the adsorption conformed to the pseudo-second-order kinetic model （dominated by chemical adsorption）; under the optimal process conditions （aspect ratio of 2∶1, adsorption flow rate of 10 mL·min⁻¹, feed volume of 10 BV, desorption solution temperature of 25 ℃, desorption flow rate of 5 mL·min⁻¹, desorption solution volume of 2.5 BV）, the lithium recovery rate reached 81.34%; it exhibited excellent selectivity in a high Na⁺/K⁺ coexistence system, and the recovery rate still exceeded 70% after 15 cycles. The research conclusions indicate that GLDHs-20 is a promising industrial-grade lithium adsorbent suitable for lithium extraction from concentrated seawater, which contributes to promoting the sustainable utilization of resources and the development of new technologies related to environmental protection.