Fabrication of Fe-doped lithium-aluminum-layered hydroxide chloride with enhanced reusable stability inspired by computational theory and its application in lithium extraction

Abstract

Lithium-aluminum-layered double hydroxide chloride (Li-Al-Cl LDH) is one of the most promising adsorbents for lithium extraction from low-grade salt lake brine, but achieving its high reusable stability with high adsorption performance is still a huge challenge. Here, a novel strategy combining simulation with a “one-pot” reaction was proposed to prepare Fe-doped lithium-aluminum-layered double hydroxide chloride (Li-Al-Fe-Cl LDH). More specifically, the geometric parameters and binding energy of aluminum-based adsorbent clusters have been investigated to predict the relative structural stability of adsorbents by density functional theory (DFT). The simulation results showed that Fe-doping increases the binding energy of the host layers, thus enhancing the structural stability of the adsorbent. Inspired by the computational theory result, Li-Al-Fe-Cl LDH was synthesized by a facile “one-pot” reaction method with excellent reusable stability and adsorption performance. The Li-Al-Fe-Cl LDH was characterized by XRD, FTIR, SEM, EDS, BET-BJH, and pHZPC. The Li+ adsorption capacity of Li-Al-Fe-Cl LDH was up to 11.3 mg/g, about 13% higher than Li-Al-Cl LDH. After 30 cycles, the decrease in lithium adsorption capacity of Li-Al-Fe-Cl LDH was 2.5%, far lower than 28.5% of Li-Al-Cl LDH. The Li-Al-Fe-Cl LDH had an excellent adsorption selectivity to Li+ with the ion-selective sequence of Li+>>Mg2+> Na+>K+>Ca2+, and the separation factor between Li+ and Mg2+ reached up to 35.83. The pseudo-second-order and the Langmuir model adequately described the adsorption kinetics and isotherms of Li-Al-Fe-Cl LDH for Li+ adsorption, respectively. The thermodynamic study proved that the Li+ adsorption of Li-Al-Fe-Cl LDH was an endothermic process. Moreover, the adsorption selectivity mechanism of Li-Al-Fe-Cl LDH is the interfacial effects of limited geometric pores and the dehydration of hydrated ions.