Adsorptive removal of sulfamethazine and sulfamethoxazole from aqueous solution by hexadecyl trimethyl ammonium bromide modified activated carbon

Sulfonamide antibiotics are widely detected in soil, surface water, sediments and drinking water due to their stable nature, which has huge potential risks. In this study, we reclaimed activated carbon with hexadecyl trimethyl ammonium bromide (CTAB) modification (MAC) as the adsorbents to remove aqueous sulfamethazine (SMX) and sulfamethoxazole (SMZ). It was best described by the pseudo second-order model for SMX and SMZ on MAC, where the adsorption rate constant k(2) were 0.0039 and 0.0057 g.mg(-1) min(-1), respectively, which indicated that might be the combined effect between in-diffusion, membrane diffusion and surface adsorption. The equilibrium data of SMX and SMZ on MAC were well represented by Freundlich model, while the maximum adsorption capacity of SMX and SMZ by Langmuir model were 16.155 mg g(-1) and 17.513 mg g(-1), respectively. SMX and SMZ sorption on MAC revealed pronounced pH dependence. In addition, HA can inhibit the adsorption of SMX and SMZ on MAC. Cd2+ can promote the sorption ability of SMX on MAC, while Cr6+ inhibits the adsorption of SMX. Adsorption mechanism of SAs on MAC was clarified, where the hydrogen bonding interaction and pi-pi EDA interaction contributed most to SAs adsorption. Well, hydrophobic interaction was considered as another adsorption mechanism for SMZ different from SMX, where it might be one of the reasons that the adsorption capacity of SMZ is higher than that of SMX. This study revealed that MAC may be the efficient and practical adsorbent for SAs removal from aqueous environments.