Evaluation of the adsorption of sulfamethoxazole (SMX) within aqueous influents onto customized ordered mesoporous carbon (OMC) adsorbents: Performance and elucidation of key adsorption mechanisms

Antibiotic resistance genes represent treatment challenges for wastewater treatment systems. These resistance genes are a direct outcome of insufficient treatment of antimicrobial substances within wastewater treatment plants. Thus, this research work concentrated on a typical antibiotic sulfamethoxazole (4-amino-N-[5-methyl-3-isoxazolyl]-benzene sulfonamide or SMX). In this study, the effectiveness of SMX adsorption onto ordered mesoporous carbon (OMC) was first systematically evaluated. SEM, TEM, and BET were used to examine the morphology of OMCs, while XPS, FTIR, and Boehm titration were used to determine the functional groups present on OMCs. The specific surface was found to be 1395.31 m(2)/g for OMC-900. The behavior of adsorbing SMX onto OMCs was evaluated using kinetics and isotherms studies. The influence of solution pH, temperature, coexisting ions, and natural organic matter (NOM) were also evaluated as to their impacts on SMX adsorption. The results revealed that the mesopores in OMC contributed significantly to SMX adsorption capacity. Adsorption achieved equilibrium after 4 h with an adsorption capacity of 334 mg/g. The Pseudo Second Order Kinetic Model provided a good fit for the adsorption kinetic processes of SMX. The Freundlich Isotherm Model, which suggests physical adsorption, provides a better fit for adsorption isotherm data. The adsorption of SMX onto OMC was exothermic and spontaneous, according to thermodynamic analyses. Most importantly, the adsorption mechanisms of SMX onto OMC include hydrogen bonding and electrostatic interaction. Additionally, a key adsorption mechanism was found to be the affinity (pi-pi interactions) between the aromatic structures of OMC and the benzene ring in SMX molecule. This study reports a thorough understanding of adsorption components and mechanisms involved in the adsorption of SMX onto OMCs and also the regeneration of OMCs after adsorption.