Effects of photo-Fenton processes on the degradation of ploychlorinated biphenyls in transformer oil

• Main Authors: Wan Jheng Wu, 吳宛錚
• Other Authors: Yaw Jian Lin
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/11699013448141897092

碩士 === 國立屏東科技大學 === 環境工程與科學系 === 94 === Polychlorinated biphenyls（PCBs）are one kind of high stability pollutants in the natural environment and hard to be biodegraded. PCBs have created serious contamination in the environment. Advanced oxidation processes (AOPs) is one of the most effective chemical processes in the treatment of organic xenobiotics. Photo-Fenton method has received significant attention in the recent years. In this study, a circulation reactor was selected to degrade polychlorinated biphenyls in transformer oil using photo-Fenton. In the batch reaction study, the degradation efficiencies of congener 189 and 207 were increased with increasing H2O2 concentrations. The highest degradation rate was the sample using 100 ppm H2O2. However, when the concentration of H2O2 was above 100 ppm, the degradation efficiency of PCBs decreased. In addition, the highest degradation rate was using 12 mg/L ferrous concentration, but the degradation results were decreased when the concentrations of ferrous were above or below 12 mg/L. After extended irradiation, total organic carbon（TOC）mineralization has been significantly reduced only upto 20 min. When the H2O2 was added repeatedly the degradation of PCBs and TOC were not significant increased. That’s because the acetone in the solution demonstrated the effect of inhibition on PCB photodegradation. In the circulation experiment, the best result was the sample using 1500 mL/min circulation rate. When the H2O2 was added repeatedly, the removal rate of PCBs was then inhibited. It was still unable to maintain the ferrous regeneration efficiency when the H2O2 was added step by step. Continuous bubbling of O2 could enhance the PCB degradation. In toxicity test, the toxicity of sample increased during the initial period of reaction. The best degradation efficiency of PCBs, TOC and dechlorination was the samples using O2 bubbling. The degradation pathways for PCB 189 included ortho-, meta- and para-dechlorination. Above all meta- and para-dechlorination were two commonly found dechlorination pathways for the period of 320 min reaction.