Insights into lithium adsorption by coal-bearing strata kaolinite

The sharp increase in the demand for lithium (Li) for high-energy-storage battery materials due to its high specific energy and low negative chemical potential render Li a geopolitically significant resource. It is urgent to develop a low-cost, efficient method to improve lithium extraction. Herein, Li ion (Li+) adsorption in coal-bearing strata kaolinite (CSK) was studied. The effects of pre-activation acid leaching (meta-kaolinite/H2SO4, MK-HS) and dimethyl sulfoxide intercalation (coal-bearing strata kaolinite/dimethyl sulfoxide, CSK-DMSO) on the Li+ adsorption capacity were studied under the same adsorption conditions. The results indicated that the adsorption was completed in 60 min under alkaline conditions (pH = 8.5), a high solution concentration (400 mg/L), and a low dosage (1 g/100 mL); and the comprehensive adsorption capacity is MK-HS > CSK-DMSO > CSK. Furthermore, the DMSO intercalation caused the interlayer spacing of the CSK to increase, which provided more space for Li+ to enter and increase the adsorption capacity. After thermal pre-activation and acid leaching, structural failure and lattice collapse resulted in the presence of more micropores in the MK-HS, which resulted in a 10-fold increase in its specific surface area and caused coordination bond changes (Al(VI) to Al(IV)) and leaching of aluminum (Al) from the lattice. It is proposed that these structural changes greatly improve the activity of CSK so that Li+ cannot only adsorb onto the surface and between the layers but can also enter the lattice defects, which results in the MK-HS having the best adsorption performance. Combined with the adsorption kinetics analysis, the adsorption methods of CSK and two modified materials include physical adsorption and chemical adsorption. In this study, the adsorption capacity of CSK and its modified products to Li were explored, providing a new option for the reuse of CSK and the extraction of Li.