Degradation of phenol in wastewater by cathodic microarc plasma electrolysis

Degradation of 2,4-dichlorophenol by cathodic microarc plasma electrolysis: characteristics and mechanisms

In this work, we used cathodic microarc plasma electrolysis (CMPE) to degrade 2,4-dichlorophenol (2,4-DCP) in simulated wastewater. By investigating and comparing the removal efficiencies and chemical oxygen demand (COD) during the degradation process, higher bath voltage and alkaline condition were considered as more suitable for the 2,4-DCP decomposition. Higher initial 2,4-DCP concentration was attributed to the increase in the utilisation of the energy input. The plasma characteristics during CMPE were studied by optical emission spectroscopy (OES). It was found that the 2,4-DCP directly participated in the plasma discharge process. Furthermore, by studying the evolution of intermediate products at different experimental parameters, it was found that the existence of Cl^- played an important role in the opening of benzene ring, which activated the ortho-substitutions of hydroxyl, meanwhile accelerated the p-substitutions. The instantaneous high temperature and high pressure and the Cl^- that were generated and driven by cathodic plasma made the decomposition of 2,4-DCP much quicker.

Decomposition of n-hexane using a dielectric barrier discharge plasma

In this study, we investigated the decomposition characteristics of n-hexane by a dielectric barrier discharge (DBD) plasma. In order to accomplish this, the factors influencing these decomposition characteristics such as background gases (air, N₂, and He), residence time (1-10 s), initial n-hexane concentration (10-50 ppm), relative humidity (2.5%, 40%, and 70%), and power (50-80 W) were evaluated. As a result, the decomposition efficiency of n-hexane at N₂ atmosphere was found to be lower than those at air and He atmosphere. The removal efficiency of n-hexane was increased when the residence time, relative humidity, and power increased, and when the initial concentration decreased. The concentrations of CO, CO₂, and aerosol increased as the specific energy density increased. However, the O₃ level increased up to a certain point, then decreased. Various hydrocarbons such as acetone, pentanal, nonanal, etc. were also detected as by-products and their decomposition and recombination pathways were suggested.

Degradation of bromobenzene via external electric field

Bromobenzene is one of the organic pollutants that damage the natural environment and poses a serious threat to human health. Therefore, it is meaningful to study its degradation characteristics under the electric field. In this paper, density functional theory (DFT) at BPV86/6-311G (d, p) level are employed for the study of C–Br bond distance, total energy, charge distribution, dipole moment, lowest unoccupied molecular orbital (LUMO) level, highest occupied molecular orbital (HOMO) level, energy gap and potential energy surface (PES) of bromobenzene in external electric field ([Formula: see text]15.43[Formula: see text]V[Formula: see text][Formula: see text][Formula: see text]nm[Formula: see text]–15.43[Formula: see text]V[Formula: see text][Formula: see text][Formula: see text]nm[Formula: see text]). It shows that as the electric field increases, the C–Br bond tends to break. The changes in the HOMO level and the LUMO level result in a rapid drop in the energy gap. In addition, the dissociation barrier gradually decreases. When the applied electric field reaches 15.43[Formula: see text]V[Formula: see text][Formula: see text]nm[Formula: see text], the dissociation barrier disappears completely, which means that the C–Br bond is broken and bromobenzene is degraded.