REMOVAL OF CIPROFLOXACIN AND CARBAMAZEPINE BY GRAPHENE OXIDE MODIFIED BI-FUNCTIONAL GROUP MESOPOROUS SILICA

Abstract

The purpose of this study was to investigate the adsorption mechanism of ciprofloxacin (CIP) and carbamazepine (CBZ) on graphene oxide modified bi-functional mesoporous silica. Hexagonal Mesoporous silica (HMS) was synthesized and modified surface functional group with two different types of organosilanes, i.e. amino-, mercapto- and amino- + mercapto- functional groups (A-HMS, M-HMS, A5M5, respectively). Then synthesized adsorbents were modified by graphene oxide (GO) as GO-A-HMS and GO-A5M5 in order to enhance the adsorption capacity by π-π interaction and hydrophobicity. The physicochemical properties of the synthesized adsorbents were characterized by various techniques. The adsorption kinetic and adsorption isotherm were performed to investigate the mechanism in batch experiment. According to the kinetic study, the pseudo-second-order kinetic model gave the best correlation with experimental results for all adsorbents and intraparticle diffusion were suggested to be the rate limiting step for both CIP and CBZ. The presence of GO on A-HMS can enhance CIP adsorption capacity, on the other hand, mercapto functional group on GO-A5M5 are supposed to be the key functional group for CBZ adsorption. The adsorption isotherms were well-fitted with Freundlich isotherm model as multilayer adsorption. Electrostatic interaction was proved by the decrease of CIP and CBZ adsorption capacity with the increasing of pH. The lower adsorption capacities of CIP and CBZ on GO modified HMS (GO-A-HMS and GO-A5M5) in binary-solute solution than single-solute solution were observed. The competitive adsorption of CIP was supposed to relate with π-π interaction and electrostatic interaction. In contrast, the hydrophobic interaction might play the key role for CBZ adsorption mechanism.