Preparation of composites of lithium-aluminum layered double hydroxides and biochar and their performance in lithium extraction from aqueous media

Layered lithium aluminum double hydroxides (LiAl-LDH) have significant potential for industrial applications, particularly as adsorbents for lithium extraction from salt lakes. However, their development is constrained by a relatively low adsorption capacity. To address this limitation, a composite material comprising biochar (BC) and lithium aluminum layered double hydroxide (LiAl-LDH@BC) was synthesized via a hydrothermal reaction, using Al(NO 3 ) 3 ·9H 2 O, LiNO 3 , urea, and varying amounts of BC as raw materials. This composite demonstrates excellent Li + adsorption capacity (19.6 mg/g). LiAl-LDH@BC 2.5 was characterized using SEM, XRD, XPS, and other analytical methods. The effects of various adsorption conditions—including adsorption temperature, initial Li + concentration, time, pH, ion interference, and the number of cycles—on the Li + adsorption performance of LiAl-LDH@BC were investigated. The increased specific surface area and the electrostatic adsorption of surface functional groups after composite formation are the primary reasons for the high adsorption capacity. The mechanism of Li + adsorption follows pseudo-first-order kinetics and the Langmuir model, involving both physical and chemical adsorption. This study offers a promising adsorbent for the extraction of Li + from aqueous media. • LiAl-LDH@BC prepared via the hydrothermal method demonstrates excellent lithium ion adsorption capacity. • The doping amount of BC affects the specific surface area and surface charge of LiAl-LDH@BC. • The electrostatic attraction from the surface charge of BC, combined with adsorption by the vacancies in the LDH structure, work together to enhance the adsorption performance.