Sorptive Removal of Ionizable Antibiotic Sulfamethazine from Aqueous Solution by Graphene Oxide-coated Biochar Nanocomposites: Influencing Factors and Mechanism

Significant concerns have been raised over antibiotics pollution in aquatic environments in recent years. In this study, sorption of sulfamethazine (SMT) by novel graphene oxide-coated biochar nanocomposites (GO-BC) based on graphene oxide (GO) with bamboo sawdust biochar (BC) was investigated. In comparison with the original BC, the sorption capacity of GO-BC for SMT increased by 1.14 times. Sorption of SMT onto GO-BC was proved to be dominantly by chemisorption, and Freundlich isotherm described the sorption adequately. It was found that variation of pH and ionic strength obviously affected the sorption of SMT, and GO-BC had a good sorption effect on SMT at pH 3.0-6.0 and lower ionic strength. Obvious enhancement (by 30%) in sorption of SMT on GO-BC was observed, which might be attributed to the increase of functional groups on the surface of GO-BC. Moreover, the main sorption mechanism for SMT was π-π electron-donor-acceptor interaction, while auxiliary sorption mechanisms were inferred as pore-filling, cation exchange, hydrogen bonding interaction and electrostatic interaction. The results indicated that GO-BC sorption was an efficient way for the removal of SMT.