Reserarch Of Degradation Of Phenol And 2,4-dichlorophenol In Water By Gas Difussion Cathode Method

In recent years, in the field of electrochemical techniques, environmental researchers conducted extensive research. At present,the gas diffusion cathode, as a new type of three-phase electrodes, was able to catalytic hydrodehalo genation and produce an intermediate substance H2O2 by cathodic reduction reaction, as a result, catalytic degradation of organic matter has been gradually attracted attention.This paper used a high-efficient gas diffusion cathode, which was made up of waterproof breathable layer(gas layer), a metal conductive mesh(solid layer) and a catalyst layer(liquid layer), and directly using air as the oxygen source, through degrading phenol and 2,4-dichloro-phenol,established a system of electro-catalytic treatment process, which was based on gas diffusion cathode, then studied the effects of changing the electrode operating conditions for organic contaminants degradation, and speculated the gas diffusion cathode degradation mechanism for phenol and 2,4-dichlorophenol through some analysis method.By designing experiments, this paper investigated the impact of phenol degradation with the cathode gas diffusion and titanium mesh repeat performance test. The results indicated that the optimum conditions of the cathode gas diffusion method for phenol degradation was: at current density 80 m A/cm2, electrolyte concentration 0.2 mol/L, aeration rate 40 m L/min, a fixed p H value of 4. The phenol at 50 mg/L was completely degraded after 40 min, the removal rate of COD reached 89.6% after 2 h, showing a good electrical chemical catal ytic activity. Remaking electrode by high temperature(600 ℃) calcining, results showed that the declining of removal rate by the new electrode was no more than 2%, showing a good repeat performance of titanium mesh.This paper also investigated the 2,4-dichlorophenol degradation by gas diffusion cathode method, the optimum conditions for 2,4-dichlorophenol degradation was at electrode distance 3 cm, current density of 80 m A/cm2, electrolyte concentration 0.2 mol/L, fixed p H of 4, ventilation 60 m L/min. With the 2,4-dichlorophenol concentration of 50 mg/L, after 1h, it could be completely degraded, after 2 h, the removal rate of COD reached 80%. According to the results, after 1 h, the dechlorination almost completed, and chlorine ion concentration in the cathode system reached 0.41 mol/L. By GC-MS analysis, the intermediate product of 2,4-dichlorophenol degradation were 2-chlorophenol, 4-chlorophenol, phenol, bisphenol, benzoquinone, maleic acid and so on.By analysing the surface area, pore volume-diameter and surface area of gas diffusion electrode, different electrode surface morphology and pore size distribution results in differences in the catalytic activity and selectivity electrode, which was the main cause of differences in phenol degradation. At the proportion of 3 of C/PTFE and a hot pressure of 10 MPa, the gas diffusion cathode showed a good performance. By cyclic voltammetry curve analysis, suggesting that the degradation of phenol mainly through the indirect oxidation with formation of hydrogen peroxide and hydroxyl radicals, the degradation of 2,4-dichlorophenol priorly experience reductive dechlorination, forming single-chlorophenol and phenol, then it was degraded under indirect oxidation.