Adsorption and Desorption Behavior of Lithium Ion in Spherical PVC–MnO2 Ion Sieve

A spherical PVC–MnO2 ion sieve of 2.0–3.5 mm diameter was prepared by the antisolvent method using synthesized Li4Mn5O12 ultrafine powder as the precursor, poly(vinyl chloride) as the binder, and N-methyl-2-pyrrolidone as solvent. Batch experiments of the adsorption capacity (isotherm) and adsorption rate of Li+ on the spherical PVC–MnO2 ion sieve were studied. Spherical PVC–MnO2 had a high adsorption capacity for Li+, and the isotherm data were well fitted by the Langmuir model; the adsorption kinetics were well described by the Lagergren equation. Furthermore, a mathematical model was set up to calculate the film mass transfer coefficient (kf) and pore diffusivity (Dp) of the adsorbent. Continuous flow experiments for study of Li+ adsorption breakthrough and the subsequent desorption (elution) in a PVC–MnO2 packed column were carried out employing six feed solutions of various pH values and concentrations of Li+, Na+, K+, and Mg2+ for simulating brine samples of various salt lakes and/or seawaters. After the adsorption treatment to concentrate the Li+ on PVC–MnO2, the column was regenerated by 1.0 mol/L HCl which supplied H+ to accomplish elution of the adsorbed Li+ by ion exchange. The experimental results demonstrate that PVC–MnO2 had high selectivity for Li+ and that its adsorption of Li+ from the feed were little affected by Na+, K+, and Mg2+ also present in the feed solution. Spherical PVC–MnO2 is an attractive medium for large scale lithium extraction from brine or seawater.