Efficient oxidative degradation of 2-chlorophenol and 4-chlorophenol over supported CuO-based catalysts

Enhanced permanganate oxidation of phenolic pollutants by alumina and potential industrial application

In this study, we found that alumina (Al2O3) may improve the degradation of phenolic pollutants by KMnO4 oxidation. In KMnO4/Al2O3 system, the removal efficiency of 2,4-Dibromophenol (2,4-DBP) was increased by 26.5%, and the apparent activation energy was decreased from 44.5 kJ/mol to 30.9 kJ/mol. The mechanism of Al2O3-catalytic was elucidated by electrochemical processes, X-ray photoelectron spectroscopy (XPS) characterization and theoretical analysis that the oxidation potential of MnO4- was improved from 0.46 V to 0.49 V. The improvement was attributed to the formation of coordination bonds between the O atoms in MnO4- and the empty P orbitals of the Al atoms in Al2O3 crystal leading to the even-more electron deficient state of MnO4-. The excellent reusability of Al2O3, the good performance on degradation of 2,4-DBP in real water, the satisfactory degradation of fixed-bed reactor, and the enhanced removal of 6 other phenolic pollutants demonstrated that the KMnO4/Al2O3 system has satisfactory potential industrial application value. This study offers evidence for the improvement of highly-efficient MnO4- oxidation systems.

Zn-CNTs-Cu catalytic in-situ generation of H2O2 for efficient catalytic wet peroxide oxidation of high-concentration 4-chlorophenol

4-chlorophenol (4-CP) with high concentration is difficult to degrade thoroughly by traditional treatment methods due to its high biotoxicity and refractory to bio-degradation. A novel catalytic wet peroxide oxidation (CWPO) system based on Zn-CNTs-Cu catalysts through the in-situ generation of H₂O₂ was constructed and investigated for the degradation of high-concentration 4-CP for the first time. Zn-CNTs-Cu composite was prepared by the infiltration melting-chemical replacement method. The operational factors effect, mechanism, and pathways of Zn-CNTs-Cu/O₂ system for high concentration of 4-CP degradation were systematically performed and discussed. At the optimal experimental conditions, the degradation efficiency of 4-CP through CWPO system with Zn-CNTs-Cu/O₂ achieved 100 %, which was 689 % higher than that of wet oxidation system with O₂ alone. According to the mainly in-situ generated H₂O₂, the strong oxidative OH radical and wet-oxidation effect of O₂, high concentration of 4-CP degraded into small molecular organic matter, even been mineralized into carbon dioxide and water in the Zn-CNTs-Cu/O₂ based CWPO system. Overall, Zn-CNTs-Cu/O₂ CWPO system can efficiently degrade high-concentration 4-CP through the in-situ generation of H₂O₂ without extra replenishment, and it provides a novel method and strategy to the efficient treatment of refractory chlorophenols wastewater.

2-Chlorophenol degradation by catalytic wet air oxidation using copper supported on TiO2-CeO2-ZrO2

In this work, we describe the morphological, electronic and catalytic properties of support TiO₂-CeO₂-ZrO₂, prepared by sol-gel method, which was impregnated with copper at 5 and 10% by weight, in order to obtain efficient catalysts in the catalytic wet air oxidation (CWAO) of 2-cp. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM-EDS), UV-Vis diffuse reflectance spectroscopy (DRS) and nitrogen physisorption by the Brunauer-Emmett-Teller (BET) method. The activity of the materials used in this study revealed that without the presence of Cu, the SCO₂ is low and with a content of 10% this metal shows the best catalytic behaviour; conversely, a reaction mechanism is proposed that describes the complete oxidation of 2-cp in this case.

A new combined green method for 2-Chlorophenol removal using cross-linked Brassica rapa peroxidase in silicone oil

This study proposes a new technique to treat waste air containing 2-Chlorophenol (2-CP), namely an integrated process coupling absorption of the compound in an organic liquid phase and its enzymatic degradation. Silicone oil (47V20) was used as an organic absorbent to allow the volatile organic compound (VOC) transfer from the gas phase to the liquid phase followed by its degradation by means of Cross-linked Brassica rapa peroxidase (BRP) contained in the organic phase. An evaluation of silicone oil (47V20) absorption capacity towards 2-CP was first accomplished by determining its partition coefficient (H) in this solvent. The air-oil partition coefficient of 2-CP was found equal to 0.136 Pa m(3) mol(-1), which is five times lower than the air-water value (0.619 Pam(3) mol(-1)). The absorbed 2-CP was then subject to enzymatic degradation by cross-linked BRP aggregates (BRP-CLEAs). The degradation step was affected by four parameters (contact time; 2-CP, hydrogen peroxide and enzyme concentrations), which were optimized in order to obtain the highest conversion yield. A maximal conversion yield of 69% and a rate of 1.58 mg L(-1) min(-1)were obtained for 100 min duration time when 2-CP and hydrogen peroxide concentrations were respectively 80 mg L(-1) and 6 mM in the presence of 2.66 UI mL(-1) BRP-CLEAs. The reusability of BRP-CLEAs in silicone oil was assessed, showing promising results since 59% of their initial efficiency remained after three batches.