Efficient Degradation Of Organic Pollutions By Contact Glow Discharge And Its Mechanism Study

Recently, due to some outstanding advantages of degradation of pollution water using contact glow discharge electrolysis (CGDE), CGDE exhibits favorable application perspective. Currently, as a branch of plasma technology, the study of degradation of pollution water using CGDE are widely and deeply exploring. As a newly developped technology, CGDE has the advantage of high efficiency, good fidelity and could degrade nearly all sorts of organic pollutants without selectivity. Compared with the technology of high pressure pulsed corona discharge, the electromagnetism on CGDE is comparatively low and also the equipment is much simple, cheaper and efficient. So the technology of CGDE is more practical in on situ water treatment and has potential in being widely used industrialization.In this dissertation, CGDE has been used in degradation of azo dye polluted water. The methyl organe (MO) and phenol in aqueous solution were used as simulation system and followed works have been done:First, the degradation of methyl orange (MO) in a neutral phosphate buffer solution was investigated by means of contact glow discharge electrolysis (CGDE). The effects on the degradation of MO by applied potentials, initial concentration of MO and the treatment time were studied in detail;Second, the enhanced degradation of methyl orange in aqueous solution has been achieved by means of contact glow discharge electrolysis (CGDE) through adding a small amount of Fe2+ to the solution. The catalytic effects of Cu2+ and Ce3+ were also studied. Finally, the amount of hydroxyl radicals produced by CGDE were measured by decolour UV-vis spectrometer.Results showed that the methyl oranges were degraded and eventually decomposed into inorganic carbon when CGDE was conducted under the applied DC voltage of 480 V and current of ca. 80 mA. As the intermediate products, some phenolic compounds were detected as well as carboxylic acids. Experimental results showed that the oxidation process followed a first-order reaction law. On the basis of analyzing the ultraviolet (UV) spectra of the solution and the intermediate products from High Pressure Liquid Chromatography-Mass Spectrum (HPLC-MS), reaction pathway was proposed.By adding a small amount of Fe2+ in solution, methyl orange has been degraded and eventually decomposed into inorganic carbon when CGDE was carried out under the applied DC voltage of 480 V and current of 65-80 mA. Experimental results show that the oxidation process follows a first-order rate law. The degradation rate increases almost eight times in the presence of Fe2+ than that of in the absence of Fe2+ and 91.6 % degradation rate has been achieved in 20 mintues. A reaction pathway has been proposed based on analysis of the ultraviolet (UV) spectra of the solution and intermediate products from High Performance Liquid Chromatography-Mass Spectrometry (HCLP-MS). The increasement of hydroxyl radicals promoted by the Fe2+ catalyst is considered to be the key step to enhance the entire oxidation process. During the mechanism study, the methyl violet was used as probe molecule. The amount of hydroxyl radicals that produced by CGDE infered from the amount of degradation rate of methyl violet under different electrochemical conditions were determined. At same time, the changes of the amount of hydroxyl radicals by adding Fe2+ were determined and found that the amount of hydroxyl radicals produced by CGDE increased five times than that of no Fe2+ in solution. Through measuring the changes of amount of hydroxy peroxide and hydroxyl radicals during the treatment of pehnol using CGDE, it was found that the hydroxyl radicals play a key role in degradation of organic polluted water.