Abstract: In order to simplify the preparation process and reduce the preparation cost of mercapto bentonite (Bent-SH) for practical application, the bentonite(Bent) was synergistically modified by 3-mercaptopropyltrimethoxysilane (MPS) and sodium silicate. The preparation process of Bent-SH was optimized, the structure of Bent-SH was characterized, and the performance of Bent-SH was measured. The best process is:the solid-liquid ratio of Bent to MPS is 1∶0.05 (g/mL); the mass ratio of Na₂SiO₃ to Bent is 7.0∶100; the solid-liquid ratio is 1∶20 (g/mL); the pH of the modified suspension is 8.0~10.0; the modification time is 5~6 h, and the reaction temperature is room temperature. The gum value, expansion factor and cation exchange capacity of Bent-SH decrease compared with Bent, but the saturated adsorption capacity of Bent-SH for cadmium is 20.86 mg/g, 20 times more than that of Bent. The synergistic modification of sodium silicate and MPS does not change the layer structure of material, but significantly improve the hydrophobicity, dispersity, adsorption capacity and selectivity. The Bent-SH is a promising passivator for heavy metal contaminated soil.

Key words: 3-mercaptopropyltrimethoxysilane, sodium silicate, mercapto bentonite, cadmium