Enhanced Diclofenac Adsorption and Degradation Using Iron-Loaded Modified Spent Bleaching Earth Carbon in the Presence Of Clofibric Acid: Mechanistic Insights and Toxicity Assessment

Pharmaceutical active substances (PhACs), such as diclofenac (DCF) and clofibric acid (CA), have been identified in various water bodies, posing a significant threat to the ecological environment. To address this, a new adsorbent, nZVI/CTAB-SBE@C, was created using industrial waste spent bleaching earth (SBE), modified by cetyltrimethylammonium bromide (CTAB), and loaded with nano zero-valent iron (nZVI). This study explored the impact of CA on the removal capability of nZVI/CTAB-SBE@C for DCF in a co-existing system. The effects of various parameters, such as reaction time, dosage, temperature, actual wastewater, humic acid, and co-existing ions were examined. The results revealed that the presence of CA significantly enhanced the removal efficiency of DCF. Specifically, under conditions of a 2-hour reaction time, an adsorbent dose of 5 g/L, and a temperature of 25℃, the optimal removal rate reached 87.3%. Al3+ notably facilitated the removal rates of DCF and CA. Sixteen intermediate products were detected in the degradation process of DCF. Based on these intermediate products, five potential degradation pathways were proposed: decarboxylation, dechlorination reduction, hydroxylation addition and substitution, and demethylation. The toxicity of DCF degradation intermediates considerably diminished when CA was present. This study explores the transformation of industrial waste into high-performance adsorbents, not only providing an economical solution to PhACs pollution but also contributing to waste reduction and sustainable development.