Removal of diclofenac by cetyltrimethylammonium bromide modified spent bleaching earth carbon loaded with sulfided nano-zero-valent iron: Performance, mechanism insight and toxicity assessment

Diclofenac (DCF), a widely consumed drug, has been frequently detected in water and is toxic to the ecosystem. In this study, a novel complex S-nZVI/[email protected] was obtained through pyrolyzing spent bleaching earth, modifying by cetyltrimethylammonium bromide (CTAB) and loading with sulfided nano-zero-valent iron (S-nZVI). Its removal efficiency for DCF reached up to 83.3%, with the corresponding degradation efficiency of 80.2%. The removal process could be considered as simultaneous occurrence of adsorption that involved electrostatic interactions, hydrogen bonds and π-π interactions and degradation that contained the dominantly reductive and incidentally oxidative dechlorination. According to the intermediates, four possible degradation pathways were proposed. Besides, the toxicity assessment revealed that the degradation process was toxicity-reducing. S-nZVI/[email protected], which showed remarkable removal performance and great environmental suitability, could be promising in DCF treatment.