Periodate activation by mulukhiyah stalks and potato peels-derived biochars for the efficient degradation of sulfamethazine

In this study, two biochars were derived from potato peels and mulukhiyah stalks and employed for activating periodate (PI) to efficiently degrade sulfamethazine (SMZ). The two biochars were characterized indicating the high carbon content and surface area of mulukhiyah-derived biochar (MBC) compared to potato-derived biochar (PBC). Different oxidants such as persulfate, hydrogen peroxide, and periodate were used with MBC and PBC. MBC/PI system showed the highest degradation performance. High degradation efficiency of SMZ could be achieved under neutral condition, and the optimum operating conditions were MBC dose of 0.42 g/L and PI concentration of 2.8 mM at SMZ concentration of 6.7 mg/L. The synthesized MBC exhibited high stability under repetitive runs, where the degradation percentages were 99.7%, 99.3%, 98.6%, 98.3%, and 97.88% in five succeeding runs. Trapping experiments showed that iodate radicals and singlet oxygen contributed greatly more than other radicals to the degradation of SMZ. The degradation pathway was proposed indicating the conversion of SMZ to simpler by-products. Organic matter in different water matrices showed a high inhibitory effect on SMZ degradation compared to inorganic salts. This study paves the way for scaling-up the periodate-activated systems using the synthesized biochar (MBC) due to its low-cost, high surface area, excellent stability, and potential to efficiently activate periodate.