Simultaneous removal of cations and anions from waste water by bifunctional mesoporous silica

Abstract

A novel, bifunctional mesoporous silica (Al-SBA-15-G) capable of the simultaneous removal of cations and anions from wastewater was synthesized by the incorporation of aluminum into the framework of SBA-15 followed by the immobilization of melamine-based dendrimer groups onto the surface of the Al-substituted SBA-15. This material was characterized by XRD, SEM, TEM, NH3-TPD, FTIR, and N2 adsorption/desorption. The bifunctional Al-SBA-15-G contains a large amount of aluminum hydroxyl groups and amine groups, which were considered to be responsible for the formation of cation and anion complexes, respectively. Due to the steric effects of the melamine-based dendrimer groups, the aluminum hydroxyl and amine groups on Al-SBA-15-G keep an appropriate distance with a cooperative manner and avoid spontaneous neutralization reactions. The maximum adsorption capacities toward Cu2+ and SO42− of Al-SBA-15-G were 0.763mmol/g and 0.511mmol/g, respectively. A mechanism for the simultaneous adsorption of cations and anions by Al-SBA-15-G is proposed. As a bifunctional adsorbent, Al-SBA-15-G can potentially be used for the simultaneous removal of cations and anions from wastewater.