Synthesis, Adsorption Properties and Stability of Cr-Doped Lithium Ion Sieve in Salt Lake Brine

Li1.6Mn1.6−xCrxO4 was synthesized by hydrothermal reaction followed by acid leaching to form lithium ion sieve. The structure, morphology and composition were examined using X-ray diffraction, SEM and EDS. The influences of Cr doping content and hydrothermal temperature on Li+ adsorption capacity and manganese dissolution ratio were investigated. The result indicates that Cr is incorporated into the spinel structure with cell contraction when x ≤ 0.08. Li1.6Mn1.6−xCrxO4 shows Li+ adsorption capacity of 31.67 mg/g and Mn dissolution ratio of 2.1% when x is 0.016 at 270 °C. After 20 cycles in salt lake brine, the Mn dissolution ratio and Li adsorption capacity is 0.35% and 25.5 mg/g, respectively. The Cr-doped ion-sieve shows improved adsorption capacity, retention and structural stability compared with the undoped lithium ion-sieve. The adsorption process for the Cr-doped ion-sieve follows a pseudo-second-order kinetic model.