Electricity facilitates the lithium sorption from salt-lake brine by H3LiTi5O12 nanoparticles: Kinetics, selectivity and mechanism

The rapid consumption of lithium ion (Li+) battery for electronic devices has significantly increased the demand for lithium resource in recent years. The salt-lake brine is considered as the ideal source for Li+ extraction, but the co-existing cations, such as Na+ and K+ limit its recovery efficiency when the adsorption method is applied. In this study, the H3LiTi5O12 nanoparticles (HTO) with a spinel structure were synthesized as Li+-selective adsorbent. The static adsorption experiments showed that the Li+ absorption capacity of HTO was significantly affected by the pH of bulk solution, and exhibited a high separation factor of Li+/Na+ and Li+/K+ at 37 and 16, respectively. When HTO was mixed with activated carbon (AC) and coated on the cathode plate, the Li+ adsorption kinetics (rate constant) was significantly enhanced from 0.18 to 0.25, due to the accelerated rate of the film diffusion driven by the electric field. Density functional theory (DFT) calculation result showed that applying electricity can strengthen the hydrogen bond between Li and O atom on the HTO (1 1 1) facet. When the AC mixing ratio was increased from 10% to 50%, the Li+ desorption efficiency increased from 47% to 90%, but at the expense of sacrificing the adsorption capacity, which decreased from 18.1 mg/g to 9.8 mg/g. In terms of the overall recovery efficiency of Li from brine, the weight ratio of HTO:AC at 9:1 was suggested for the electro-sorption method. Finally, the Li+ recovery from actual brine was successfully demonstrated, with 7.1 mg/g of adsorption capacity and well stability.