Degradation of sulfamethazine using sludge-derived photocatalysts from dyeing industry and livestock farm: preparation and mechanism

Excess sludge disposal and management has become a global issue of scientific and public concern owing to its high yield and toxicity. In this study, for the first time, we prepared industrial and livestock sludge-derived photocatalysts using dyeing sludge and swine sludge as raw materials, respectively, using a facile pyrolysis coupled ball-milling process without additives. The photocatalytic performances of the two types of photo -catalysts were evaluated using sulfamethazine as the target contaminant. The surface morphology and functional groups of the catalysts were analyzed using field-emission scanning electron microscopy combined with energy -dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The sulfamethazine removal rate was 91.5 % under optimal conditions. Degradation intermediates were detected, and a possible degradation pathway was proposed. Major reactive oxygen species in the photocatalytic systems were investigated using electron spin resonance spectroscopy and radical trapping experiments. The results revealed that.O2- and h+ played main roles in the degradation of SMZ. Furthermore, a pilot-scale experimental setup was designed and manufactured to realize pilot-scale production. Economic analysis of the pilot-scale experiment suggested that the developed photocatalysts are comparatively suitable for practical applications.