Li+ adsorption performance and mechanism using lithium/aluminum layered double hydroxides in low grade brines

Lithium/aluminum layered double hydroxides (Li/Al-LDHs) without elution damage, have been regarded as the most applicable adsorbents in the industrial lithium extraction from brines, while the low adsorption capacity and unclear adsorption/desorption mechanism are restraining their lithium extraction performance. In this study, Li/Al-LDHs with regular two-dimensional hexagonal flats, prepared by a simple coprecipitation method, demonstrated the highest Li+ adsorption capacity reported of 7.27 mg/g in the Qarhan Salt Lake old brine with an ultrahigh Mg2+/Li+ ratio at room temperature. Besides, the Li/Al-LDHs had a great adsorption selectivity to Li+ with the ion selective sequence of Li+ > Na+ > K+ > Ca2+ ≫ Mg2+, and the separation factor between Li+ and Mg2+ (αMgLi) reached up to 125. The adsorption capacity of Li/Al-LDHs exceeded 7.0 mg/g after 12 adsorption-desorption cycles, showing a great stability on the adsorption performance and crystal structure. In addition, the adsorption-desorption column experiments manifested that the Li+ adsorbed on the Li/Al-LDHs could be eluted completely by neutral water and the Mg2+/Li+ ratio in the eluent reduced significantly to <0.43 from 301.58.