Degradation Of Aqueous Organic Pollutants By Using Glow Discharge Electrolysis Plasma

The permanent threat to natural environments, resulting from industrial activity, focuses our continuing attention on the development of efficient technologies for the removal of organic pollutants from the environment. In recent years, many papers focus on the advanced oxidation technologies (AOTs) for treating the wastewater, such as wet air oxidation, super critic catalytic wet air oxidations, TiO₂-assisted photocatalytic and electrochemistry, since there are a lot of highly active species, especially ·OH radical, occurring in these processes. Some of these methods have reached the practical application stage. However, the expensive equipment and the significant energy consumption are still a common problem.Glow discharge electrolysis (GDE) is a novel electrochemical process which is used to treat organic pollutants in water. When the applied voltage is sufficiently high, the onset of hydrodynamic instabilities with vapor sheathing the electrode and glow discharges across the vapor sheath and produce various active species in full GDE. Some components, such as hydroxyl radicals, hydrogen peroxide, and aqueous electrons can be transmitted into the solution in vicinity with the solution. They could interact among themselves and with any active substrate in the solution.In the 600V and 30℃, this paper describes the plasma degradation of 1-Naphthylamine, 2,4-Dichlorophenol, alizarin red s, and brilliant green by glow discharge electrolysis. Various influencing factors such as voltage, catalytic action of Fe²⁺ ion, pH of the degradation solution, and the distance between cathode and anode were examined. Chemical oxygen demand (COD), ultraviolet (UV) absorption spectra, atomic force microscopy (AFM), high performance liquid chromatography (HPLC) and gas chromatogram-mass spectrum (GC-MS) are used to monitor the degradation process and to identify the major oxidation intermediates. Degradation pathways of them are proposed on the basis of detection of intermediates. It has been found that all of them underwent a series of intermediate step, which leads to form a number of intermediates, mainly isomeric hydroxybenzenes and aliphatic acids. These products are further oxidized, eventually, mineralized into CO₂, H₂O, and inorganic ions. COD is descended in the presence of Fe²⁺.In treating organic wastewater, the glow discharge electrolysis is a potential technique in future. Generally speaking, the equipment used is cheap in price and operated easily. Moreover, there is no second pollutant and a green chemistry technology observed in the whole degradation process. As a novel technique, the glow discharge electrolysis used in the wastewater treatment would be investigated extremely in future.