The degradation of diclofenac (DCF), a commonly used nonsteroidal anti-inflammatory drug, by Fe 2+ /chlorine and Fe 2+ /PMS processes was comparatively investigated. The influencing factors of pH, Fe 2+ and oxidant dosage on DCF degradation efficiency were evaluated and optimized. Typically, with an initial solution pH of 5, an Fe 2+ dosage of 70 μM, and a chlorine or PMS dosage of 70 μM, the degradation efficiency of DCF using the Fe 2+ /chlorine and Fe 2+ /PMS processes reached 94.2% and 79.7%, respectively, within 10 min. Quenching tests indicated the coexistence of •OH and RCS in the Fe 2+ /chlorine system, and both SO 4 ●– and •OH were identified in the Fe 2+ /PMS system. In addition, Fe(IV) was also identified to participate in DCF degradation in two systems based on the oxidation of PMSO to PMSO 2 . The degradation products and pathways of DCF were elucidated by LC/TOF/MS analysis and DFT calculations. It was assumed that the degradation pathway of DCF involves hydroxylation, dechlorination, decarboxylation, cleavage of the C-N bond, and chlorine substitution. In addition, trichloromethane (TCM), dichloroacetaldehyde (DCAL), dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) were also detected in the Fe 2+ /chlorine process, and these chlorinated DBPs initially increased and then decreased with prolonged reaction time, indicating that Fe 2+ /chlorine is capable of controlling DBPs formation. Finally, the acute and chronic toxicity of DCF and its degradation products were evaluated by the ECOSAR program.
Chaoqun Tan,Yujie Dong,Lei Shi,Qin Chen,Shengwei Yang,Xiaoyu Liu,Jinfeng Ling,Xuefeng He,Dafang Fu
The degradation of Orange II (Org II) by ferrous activated peroxymonosulfate (PMS) was inspected. The maximum degradation efficiency of 62.3% in 90 min occurred at 0.286 mM [PMS] 0 , corresponding to 1:1 molar ratio of Fe 2+ : PMS. Results show that poor recovery of Fe 2+ accounts for poor degradation in the slow stage. The species of reactive radicals were determined through indirect way by quenching agents, as well as directly by in situ EPR spin trapping tests. Results indicated that hydroxyl radicals instead of sulfate radicals were responsible for Org II degradation. The removal of Org II degradation would increase to 93.3% in 90 min as reaction temperature increased to 60 °C. The activation energy for PMS and Fe 2+ /PMS alone was calculated to be 77.2 kJ/mol and 34.7 kJ/mol, respectively. The removal efficiency of total organic carbon (TOC) was 11.0% and 43.8% when [Fe 2+ ] 0 :[PMS] 0 :[Org II] 0 was 5:5:1 and 34:34:1, respectively. The main degradation products of Org II in system were supposed to be heterocyclic compounds containing a five-atom ring. Results demonstrated that Fe 2+ /PMS technology is promising technology for water pollution.
A phosphomolybdate nanozymes doped with copper and iron particles (Cu,Fe-PMs) with excellent peroxidase (POD)-like activity was prepared by one-step microwave digestion method. It can oxidize the positively charged substrates such as 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂, resulting in the formation of a blue compound. It is noteworthy that the POD-like activity of Cu,Fe-PMs was significantly boosted upon the incorporation of sodium dehydroacetate (DHA). This was attributed to the formation of complex between the Cu,Fe-PMs and DHA. On the one hand, DHA enhances the affinity of Cu,Fe-PMs for the substrate and exhibits superior catalytic properties. On the other hand, DHA also accelerated the valence state transformations between Fe 3+ /Fe 2+ and Cu + /Cu 2+ , increased catalytic active sites and facilitate the generation of more reactive oxygen species (ROS) such as •OH with strong oxidation. Therefore, the current study successfully established a highly sensitive and reliable colorimetric sensor for detecting the DHA content in foods. The results indicated that the absorbance at 652 nm exhibited a linear relationship with DHA concentration within the range of 0.0017—2.5 μg mL −1 , achieving a minimum limit of detection (LOD) as low as 0.83 ng mL −1 . The sensor was successfully applied to detect DHA in actual samples, with recoveries ranging from 91.59% to 103.35% and a relative standard deviation (RSD) not exceeding 3.64%. This demonstrates the reliable performance and consistent reproducibility of the analytical approach. Graphical
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