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

Abstract

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 photocatalysts 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.