Removal of sulfadiazine by ferrate(VI) oxidation and montmorillonite adsorption - synergistic effect and degradation pathways

Antibiotics have been frequently detected in the environment and watercourses which can inspire bacterial resistance and create super-bacteria; resulting in potential adverse impacts on the human health and environment. This work thus investigated the synergistic effect of a combined process (ferrate(VI) oxidation with montmorillonite adsorption), in comparison with either the oxidation or adsorption alone, for the removal of one of antibiotics, sulfadiazine (SDZ). The results manifested that all the three combined processes can promote the removal of SDZ but the simultaneous oxidation and adsorption can achieve the outperforming removal of SDZ (76.20%) in comparison with the oxidation alone (60%) or adsorption alone (10%) for the same given conditions, and the synergistic effect of combined oxidation/adsorption was confirmed. Additionally, the degradation of SDZ by ferrate(VI) fitted in the pseudo-second-order reaction characteristics, and the total reaction rate constant was derived as 2.97*10-4 L2 mg-2 min-1. The study also explored the possible pathways of the SDZ degradation by ferrate(VI) and potential oxidation product formation when an incompletemineralization of SDZ was observed. The oxidation product formed was proposed as a macromolecular-like compound containing RNO2 groups which were oxidized from the initial structure of SDZ containing R-NH2 groups.