Structures of hexamethonium exchanged bentonite and the sorption characteristics for phenol

The role and contribution of siloxane surface and exchanged organic cations on sorption process of organic contaminants is critical for the designing of high efficient organoclay adsorbents. In this study, organobentonites were synthesized using hexamethonium bromide (HM) and tetramethyl ammonium bromide (TMA). And their structures and sorption characteristics for phenol were examined. It was suggested that HM molecules lay parallel to the silicate planes, and were isolated from each other in the interlamellar surfaces. Sorption of phenol by HM-Bent and TMA-Bent were dominanted by adsorption process. At low phenol concentrations, adsorption capacity of phenol on 30HM-Bent is higher than that on 60TMA-Bent, while it is lower at high phenol concentrations. The adsorption capacity of phenol on HM-Bent increased with increasing HM loading under 0.40CEC (cationic exchanged capacity), but which decreased when HM loading over 0.40CEC. The observed results suggested that in HM-Bent, the exposed siloxane surface was the effective adsorption sites for phenol, while the organic cations contributed to enhancing hydrophobic environment and the affinity for organic contaminants.