Lithium extraction process from low grade Na+/K+ brines dependent on high layer charge layered double hydroxides

To meet the rigorous separation demand for lithium in monovalent ion systems, high layer charge layered double hydroxides (H-LDHs) were used to extract lithium resource from Na+/K+ brines dependent on a stronger Li+ adsorption effect than conventional Li/Al-LDHs. Adsorption kinetics, isotherms and selectivity of H-LDHs were thoroughly investigated and it was found that H-LDHs had a high selectivity to Li+, and could extract the low concentration Li+ in 3 M Na+/K+ brines in <30 min. Additionally, the effects of desorption temperature and initial Li+ concentration in the eluent were explored in detail. It could be clearly seen that the Li+ desorption rate was increased with less Li+ in the eluent and higher desorption temperature, and the Li/Al molar ratios of H-LDHs dramatically decreased after desorption as the initial Li+ concentration in the eluent was lower than 100 mg/L. Under optimal conditions, the Li+ adsorption capacities of H-LDHs always maintained >4.0 mg/g in 10 adsorption-desorption cycles, reflecting a great stability on the adsorption performance and the crystal structure. These experimental results confirmed great potential application prospects of H-LDHs in lithium extraction from Na+/K+ brines.