Ball milling enhanced magnetic corn straw biochar for peroxyacetic acid activation towards efficient degradation of sulfadiazine

A novel heterogeneous catalyst of ball-milling magnetic corn straw biochar (BMCBC) was the first time synthesized and employed to activate peroxyacetic acid (PAA) for efficiently degrading sulfadiazine (SDZ). The superior porous structure and the magnetic Fe3O4 of BMCBC guaranteed its higher activation efficiency than that of CBC. The results showed that 93% of SDZ was removed by PAA/BMCBC system within 60 min. Solution pH, CO32-, NO3- and Cl- concentrations were the crucial environmental factors affecting the degradation process of SDZ. The electron paramagnetic resonance (EPR), quenching experiments, and Raman spectra analysis indicated that •OH and R-O• were the main contributors to SDZ degradation. The transformed products (TPs) generated in PAA/BMCBC system were less toxic compared to those of SDZ. Three degradation pathways of SDZ were proposed and hydroxylation and S-N bond breakage by •OH and R-O• attacking were the dominant degradation pathways of SDZ in PAA/BMCBC system. Also, PAA/BMCBC system built in this study exhibited excellent removal performance for SDZ in actual waters including river water (84.32%), lake water (73.95%), tap water (93.30%) and drinking water (91.29%). Additionally, BMCBC exhibited satisfactory environmental safety in a wide pH range (from 3 to 11) with low leaching levels of Fe. The good magnetic sensitivity of BMCBC enabled it to be easily collected and it performed outstanding sustainable activation performance for PAA even after five reuse cycles. This study developed a promising method for antibiotics (e.g., SDZ) elimination, in addition to that the resource utilization of agricultural wastes (e.g., corn straw) was achieved.