Recovery of lithium from a synthetic solution using spodumene leach residue

There exist active adsorption sites in the spodumene leach residue (SLR), the solid waste of spodumene after high-temperature roasting and leaching. It is potential for SLR to selectively adsorb Li+ from brine because of the “memory effect”. Lithium ion adsorption isotherm and adsorption rate of SLR were studied. Effects of adsorption temperature and initial pH of solution on lithium adsorption performance were investigated. Physicochemical properties of SLR before and after adsorption were characterized via powder X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). Adsorption mechanism of SLR for lithium ion in the liquid solution was discussed. Results show that the major component of SLR is aluminosilicate (HAlSi2O6), whose theoretical lithium adsorption uptake of HAlSi2O6 is 37 mg/g. Lithium adsorption behavior of SLR could be well described by the pseudo-second-order kinetic model and Langmuir isotherm, indicating adsorption process conforms to a monolayer chemical adsorption, that is a H+-Li+ exchange process. Adsorption capacity and adsorption rate of SLR could be effectively enhanced with the increase of adsorption temperature, initial Li+ concentration and pH value. Lithium uptake of SLR in Li+ solution (C0 = 500 mg/L, pH = 12.95, at 90 °C for 36 h) reached 25.40 mg/g, which was 68.65% of its theoretical uptake. SLR exhibits an excellent adsorption stability, whose uptake remains above 17 mg/g in 100 mg/L Li+ solution after 5 cycles.