Convenient synthesis of granulated Li/Al-layered double hydroxides/chitosan composite adsorbents for lithium extraction from simulated brine with a high Mg2+/Li+ ratio
Liqin Zhao, Xiaojie Zhang, Keyi Liu, Xin Liu, Yuefa Gong, Hong Peng, Wei Qi
Abstract
Lithium/aluminum layered double hydroxides (LDH) have been industrially applied to extract lithium from salt-lake brine. Different from traditional granulation methods, chitosan with high hydrophilicity was used as the binder of LDH in this work, and LDH/chitosan composite hydrogel granules (CLDH) with a diameter of about 1–2 mm were successfully prepared. The new granulation method is simple, cost-effective, and does not require the use of organic solvents . The chemical composition and structure of CLDH were characterized by techniques such as FTIR, XRD, FESEM, TEM, TGA, and XPS. In simulated brine with a Mg 2+ /Li + ratio of 102, the maximum saturated adsorption capacity of lithium on CLDH-3 reached 12.5 mg g −1 (pH = 6.5), but it took 24 h to reach adsorption equilibrium. During the three successive cycles for the extraction of Li + from simulated brine by the CLDH-3 column at the flow rate of 1 mL min −1 , the adsorption capacities of Li + on CLDH-3 in the three cycles were 15.4, 15.9 and 12.1 mg g −1 , respectively. Moreover, deionized water (30 °C) was used as the eluent to recover lithium adsorbed on the CLDH-3 column, and the lithium recovery efficiencies reached 50.7 %, 53.6 %, and 62.8 % of the column adsorption capacities over the three cycles, respectively, and the Mg/Li ratios in the eluents were 0.47, 0.71, and 0.50, respectively. Overall, CLDH-3 exhibits good reusability, mechanical strength, structural stability, and selectivity in the process of lithium extraction from simulated salt-lake brine, and has potential industrial application value.