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 the Freundlich isothermal adsorption equation. HIGHLIGHTS Under the optimized adsorption conditions, the adsorption rate of S2− reached 92% and the adsorption capacity reached 55.02 mg/g.; The adsorption process of S2− by the (SBA-15)-Hg(II) is in accordance with the quasi-second-order kinetic equation in kinetic aspect, and the adsorption isotherm is in accordance with the Freundlich model.;

Keywords

• adsorption
• hg2+
• mesoporous material
• sba-15
• s2−