Adsorption of Clofibric Acid from Aqueous Solution by Graphene Oxide and the Effect of Environmental Factors

Graphene oxide (GO) nanosheets were used as adsorbent material for the removal of clofibric acid (CA) which was difficult to be removed from wastewater by traditional wastewater treatment technique. Adsorption kinetics, adsorption equilibrium, and effect of pH, ionic strength, and humic acid (HA) of the adsorption of CA onto the GO nanosheets in aqueous solution were investigated in detail. Adsorption isotherm studies indicated that the Langmuir isotherm equation fitted the sorption isotherm data better than Freundlich model and the maximum adsorption capacity of GO nanosheets for CA was 994 mg g(-1). In addition, adsorption kinetics data showed that the sorption of CA on GO nanosheets reached equilibration within a few minutes and were well fitted by pseudo second-order model. The results of the effects of environment factors indicated that CA sorption on GO nanosheets was weakly affected by ionic strength and strongly depended on pH and HA because of the structure of CA and the large number of oxygen-containing function groups presented on the surface of GO nanosheets. Besides, the removal efficiency of GO nanosheets for CA was reduced at pH >4 and enhanced at pH <4 in the presence of HA.