Kinetics, isotherm and thermodynamic studies of S2− adsorption by (SBA-15)-Hg (II)

Abstract

The nano-mesoporous material SBA (Santa Barbara Amorphous)-15 was synthesized using the hydrothermal method. Hg2+ was adsorbed by SBA-15 and then the S2− in the aqueous phase by (SBA-15)-Hg(II), with the hope that materials with better S2− adsorption properties can be obtained. The relevant materials were characterized by X-ray diffraction, scanning electron microscopy, 77 K nitrogen adsorption-desorption, and related product characteristics were determined. In this work, the adsorption conditions of S2− onto (SBA-15)-Hg(II) were optimized. Adsorption efficiency reached about 92% and the adsorption capacity 55.02 mg/g. Studies of the system's adsorption kinetics showed that the pseudo-second-order equation applies. The thermodynamic results indicated that ΔG0 < 0, ΔH0 = −28.56 kJ/mol, ΔS0 = −81.136 J/(mol·K), and that adsorption is exothermic, enthalpy decreases and the reaction is spontaneous. This accords with Freundlich isothermal adsorption equation.