Enhancing the adsorption behavior and mechanism of Sr(ii) by functionalized montmorillonite with different 3-aminopropyltriethoxysilane (APTES) ratios

Abstract

Modified calcium saturated montmorillonite (Mt) was prepared at different 3-aminopropyltriethoxysilane (APTES) loadings through grafting. The as-products were characterized by XRD, FTIR and elemental analysis. Surface analysis such as acidity was examined at different H⁺ concentrations, showing that the release of OH⁻ from the modified samples increased in the following order: APTES_4.0CEC–Mt > APTES_3.0CEC–Mt > APTES_2.0CEC–Mt > APTES_1.0CEC–Mt. Batch experiments were conducted and different conditions (pH, temperature and co-existing ions) were used to evaluate the adsorption capacity of the modified samples. The study developed a new way to confirm the mechanism, which indicated that ligand adsorption was the dominant sorption mechanism for Sr(II) uptake onto APTES–Mts. In general, APTES grafted montmorillonite possessed a higher efficiency of Sr(II) uptake and showed great potential for Sr(II)-rich wastewater treatment.