Comparative adsorption performance of oxytetracycline and sulfamethoxazole antibiotic on powder activated carbon and graphene oxide

Antibiotics are frequently detected simultaneously in an aquatic environment since they can cause serious negative effect on human and ecological health. Regarding the adsorptive treatment, the adsorption performance of oxytetracycline (OTC) and sulfamethoxazole (SMX) respected with the adsorption capacities and mechanisms was investigated and compared along with two carbonaceous adsorbents, the commercial powder activated carbon (PAC) and synthesized graphene oxide (GO). Kinetic data fitted well with the pseudo-second-order model. The isothermal adsorption equilibrium could be better described by the nonlinear Sips isotherm model in most of the single antibiotic adsorption on both adsorbents, whereas PAC performed the greater maximum adsorption capacity in both antibiotics than GO. The OTC and SMX adsorption mechanism on PAC could be governed by the combination between hydrogen bonding, pi-pi electron donor-acceptor (EDA) interaction and electrostatic interaction. According to the coadsorption behaviour, the adsorption capacities of OTC were suppressed with the increased ionic strength in the order of decreased OTC adsorption capacities as CO32- > NO3- > Mg2+, while the SMX adsorption capacity was significantly affected by the divalent ions (CO32- and Mg2+). Under the presence of tannic acid as the natural organic matter, the competitive adsorption was exhibited only in the OTC adsorption. More than three successive regeneration cycles for OTC and SMX removal efficiency of PAC slightly decreased around 10-20%. Overall, this study provided a better understanding of their antibiotic adsorptive performance on these adsorbents, which could lead to the improvement and develop their adsorption efficiency.