Enhanced lithium-ion adsorption by recyclable lithium manganese oxide-sepiolite composite microsphere from aqueous media: Fabrication, structure, and adsorption characteristics

Abstract

A novel spherical structure, hydrogen-substituted lithium manganese oxide (LMO)-sepiolite (HMO-SEP) composite assembled from nanorods was fabricated via hydrothermal method combined with solid-phase method. The structure and composition of the as-prepared HMO-SEP was analyzed by a series of characterization techniques, and its adsorption behavior and characteristics for Li+ adsorption from aqueous media and recyclability were investigated in detail. The as-prepared HMO-SEP showed a typical IV-type gas adsorption isotherm with H3-type hysteresis loop at high P/P0, with a specific surface area of 46.49 m2/g and a pore size of 18.31 nm. The isotherm adsorption data of Li+ adsorption by HMO-SEP conform well to the Langmuir model, and the maximum adsorption capacity of Li+ reached 52.41 mg/g at 298 K. Kinetic studies showed that the adsorption process complies well with the pseudo-second-order model, reaching adsorption equilibrium within 8 h. The adsorption of Li+ by the resulting HMO-SEP is a spontaneous endothermic process with increasing entropy, with an adsorption ΔH of 21.9432 kJ/mol and an adsorption activation energy of 19.8092 kJ/mol. A suitable amount of SEP could improve the microstructure of the HMO-SEP through the interface effect between SEP and LMO. Such effect could enlarge the specific surface area and pore volume and improve the ion transport channels, thus enhancing the adsorption capacity towards Li+, stability, and recycling performance. The resulting HMO-SEP possesses excellent selective adsorption performance for Li+, even under high concentrations of Na+, K+, Ca2+, and Mg2+, stability, and regeneration–recycling performance. It has excellent potential for efficient use in the extraction of Li+ from aqueous media.