Chromium(VI) Removal by Modified PVP-Coated Silica Gel

Abstract

This research involved the synthesizing of a reactive polymer, long alkyl quaternized poly(4-vinylpyridine) (PVP), and coating it onto the surface of silica gel to produce a granular sorbent to remove Cr(VI) from water. Batch experiments were conducted to determine the kinetics, sorption isotherm, pH effects, and desorption of the sorbed Cr(VI). The research demonstrated that the synthesized PVP-coated silica gel (referred to as coated gel) could successfully remove chromium(VI) from solution. The adsorption of Cr(VI) by the coated gel was strongly influenced by the pH. The maximum sorption occurred at about pH 4.5–5.5 under the test conditions. The removal efficiency was 100% when the initial Cr(VI) concentration was 2.5 mg/L, with 2.5 g/L of coated gel at pH 5.0. The concentrations of Cr(VI) had a pronounced effect on the rate of sorption. Compared with ion exchange, the sorption kinetics of Cr(VI) was fast (about 5 h). The equilibrium sorption data fitted the Langmuir isotherm model. Chromium adsorbed on the coated gel was easily recovered under certain conditions. A continuation of this work dealing with the effects of concentration of Cr(VI) and of other anions on the Cr(VI) removal by PVP-coated silica gel will be published in a subsequent issue.