Degradation of trichloroacetic acid by Fe/Ni bimetallic reactive PMS with hierarchical layered structure.

Overuse of chlorinated disinfectants leads to a significant accumulation of disinfection by-products. Trichloroacetic acid (TCA) is a typical carcinogenic disinfection by-product. The efficacy of the conventional degradation process is reduced by the complex nature of its structure, causing a yearly increase in its prevalence within the ecological environment and consequent infliction of significant harm. In this paper, TCA was chosen as the research subject, Fe/Ni bimetallic nanoparticles were employed as the reducing catalyst, ZIF-8@HMON as the catalytic carrier combined with Fe/Ni nanoparticles, and peroxymonosulfate (PMS) was introduced to construct the reducing-advanced oxidation synergistic system and investigated the effect of this system on the degradation performance and degradation pathway of TCA. Various characterization techniques, including TEM, SEM, XRD, FT-IR, XPS, BET, were employed to investigate the morphology, element composition and structure of composite materials analysis. Moreover, the conditions for TCA degradation can be optimized by changing the experimental environment. The results showed that 25 mg of composite catalyst (mole ratio Fe: Ni = 1:1) and 10 mg of PMS effectively degraded TCA within 20-80 mg/L range at pH = 3 and 55 °C, achieving maximum degradation within 20 min. Finally, the potential pathways of TCA degradation were analyzed using EPR and LC-MS, and the corresponding reaction mechanisms were proposed.

Hydrolytic degradation of methoxychlor by immobilized cellulase on LDHs@Fe3O4 nanocomposites.

In this study, we synthesized Fe3O4 using the co-precipitation method and then prepared magnetic carrier LDHs@Fe3O4 by immobilizing layered double hydroxide on Fe3O4 by in situ growth method. Cellulase was immobilized on this magnetic carrier by using glutaraldehyde as a coupling agent, which can be used for degrading Methoxychlor (MXC). The results demonstrated the maximum MXC removal efficiency of 73.4% at 45 °C and pH = 6.0 with excellent reusability. Through kinetic analysis, it was found that the degradation reaction conforms to the Langmuir-Hinshelwood model and is a first-order reaction. Finally, according to the EPR analysis, the active radicals in the system were found to be OH· and the degradation mechanism was proposed in combination with LC-MS. This study provides a feasible method for degrading organochlorine pesticides, which can be used for groundwater purification.