Selective recovery of lithium from geothermal water by EGDE cross-linked spherical CTS/LMO

As a new-type liquid lithium resource, the recovery of lithium from geothermal water is of great significance due to the increasing importance of lithium in modern industry. In this work, different lithium manganese oxides (LM0s), including LiMn2O4, Li1.66Mn1.66O4, and Li4Mn5O12, were synthesized and applied for selective recovery of lithium from geothermal water. It was found that the powdery Li4Mn5O12 exhibits high performances for low concentrations of Li+ and was then successfully granulated using chitosan (CTS) at a mass ratio of CTS/LMO = 3:2. The hydrophily of CTS leaded to a serious dissolution loss of CTS/LMO under acidic conditions, but it was successfully solved by direct cross-link of the spherical material using ethylene glycol diglycidyl ether (EGDE), by which the dissolution loss in 0.25 mol/L HCl was decreased from 27.65% to no more than 0.6%. The equilibrium adsorption capacity of Li+ in geothermal water reached 8.98 mg/g at 303.15 K, while the attenuation of adsorption capacity was no more than 1.1% after five times adsorption-desorption cycles. The separation factors between Li+ and other ions were all higher than 51 with a distribution coefficient of Li+ reaching up to 1113.27 mL/g. All these properties demonstrate that the developed material has high selectivity and stability, and can be used as a candidate for selective recovery of lithium from geothermal water or other solutions.