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 (k f) and pore diffusivity (D p) 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.

The rheological behavior and stability of Mg(OH) 2 suspensions were studied in the presence of sodium polyacrylate with different molecular weights under conditions of different ionic strength and counterion valence (K + and Mg 2+ ). Rheological properties, optical absorbance, and zeta potential measurements were conducted on the Mg(OH) 2 particle suspensions to assess the dispersing ability of the sodium polyacrylate dispersants. Adsorption isotherm measurements were applied to investigate the effect of counterions on the adsorption behavior. The results demonstrate that Mg 2+ ions destabilize the Mg(OH) 2 suspensions more dramatically than K + ions due to the stronger screening effect and special complexation of Mg 2+ ions and carboxyl groups. The effect of molecular weights of NaPA on the rheological properties becomes more pronounced at higher solid loading because the NaPA with a molecular weight of 15,000 g/mol increases the viscosity more obviously than NaPA with a molecular weight of 1200 g/mol. The calculation results of interparticle interaction by the Hamaker 2 program show that the suspensions can achieve good stability with sufficient NaPA dosage, which coincides with the optical absorbance measurement results.

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