Self-endowed magnetic photocatalysts derived from iron-rich sludge and its recycling in photocatalytic process for tetracycline degradation

The disposal of iron-rich sludge by landfill or incineration poses environmental risks and wastes resources. The utilization of iron-rich sludge for magnetic material preparation offers a sustainable and resource-efficient solution for its disposal. Herein, self-endowed magnetic photocatalysts were initially prepared by pyrolysis using iron-rich sludge without any additives. The photocatalysts performance were evaluated for tetracycline degradation, with the highest degradation rate of 95.3 % at a concentration of 10 mg·L^-1 (pH = 7) within 5 h being achieved for the photocatalyst prepared at 800 °C. The reactive radical species in the photocatalysis process were confirmed to be •OH and O₂^•- activated by ferrous oxygen species under light irradiation. Furthermore, quinone-like structures induced bound persistent free radicals, which emerged as the predominant factors influencing ¹O₂ formation. The employed photocatalyst can be efficiently separated and recovered owing to its magnetism. This work presents an economic solution for antibiotic removal using waste iron-rich sludge.