Synergistic adsorption and degradation of diclofenac by zero-valent iron modified spent bleaching earth carbon: Mechanism and toxicity assessment

Diclofenac (DCF) is a drug compound that exists widely in water bodies, which may pose a threat to the ecological environment. In this study, spent bleaching earth (SBE) was pyrolyzed, modified with cetyltrimethylammonium bromide (CTAB) and loaded with zero-valent iron (nZVI) to obtain CTAB-SBE@C-nZVI. The effects of CTAB concentration, Fe-0 loading, CTAB-SBE@C-nZVI dosage, and initial pH value on the removal efficiency of DCF were studied. The results showed that the DCF removal efficiency could reach a maximum of 87.0% with 2.0 g/L dosage of the optimal material, which was prepared under the conditions of 30 mmol/L CTAB concentration, 25% Fe-0 loading, and initial pH 5. It indicated that the strong adsorption of the material and the reduction effect of nZVI can achieve high-efficiency removal of DCF. Based on the detected reaction inter-mediate products, four possible degradation paths were inferred. The toxicity assessment of DCF and its intermediates manifested that the degradation of DCF by CTAB-SBE@C-nZVI was a process of gradual dechlorination and toxicity reduction. CTAB-SBE@C-nZVI displayed excellent DCF removal efficiency, good stability and environmental friendliness, achieving wastes treat wastes and exhibiting good prospects.

Automated summary

In this study, spent bleaching earth (SBE) was modified and loaded with zero-valent iron (nZVI) to remove diclofenac (DCF) from water bodies. The removal efficiency of DCF reached a maximum of 87.0% under optimal conditions. Four possible degradation paths were inferred based on detected reaction intermediate products. The toxicity assessment showed that CTAB-SBE@C-nZVI can gradually dechlorinate DCF and reduce its toxicity. This study demonstrates the potential and environmental friendliness of using CTAB-SBE@C-nZVI for waste treatment.