Degradation of polychlorinated biphenyls using UV/H2O2: Effects of initial oxidant and PCB concentrations

In this study, the degradation of polychlorinated biphenyls (PCBs) using UV/H2O2 system was investigated. The effects of initial H2O and PCB concentrations were studied using batch tubular reactor equipped with a 254 nm low-pressure Hg lamp. Samples were withdrawn from the reactor at desired time intervals. The temperature and pH of the solution were continuously monitored. Initial H2O concentrations of 8.8mM, 17.64mM, 22.05mM, 24.71mM, 26.47mM abd 35.29mM were used to determine the optimum oxidant concentration while initial PCB concentrations of 40ppm, 20ppm, 10ppm, 5ppm and 1 ppm were employed to study the effect of this parameter on PCB degradation.Results show that there is an optimum H2O2 concentration that maybe used beyond which no significant increase in the degree of degradation was achieved. The highest PCB degradation efficiencies of85.69% after 60 minutes and 94% after 300minutes were obtained at a peroxide concentration of 22.05mM and PCB concentration of about 40 ppm. The initial concentration of PCBs at the given optimum peroxide concentration obtained also proved to have a significant effect on the degradation of the compound. Results indicate that, wth the initial PCB concentrations employed, PCB photodegadation increases as the initial concentration increases.The use of UV/H2O2 for PCB degradation seems very promising in the treatment of wastewater containing PCBs. The results of this study are highly significant in performing a kinetic analysis on PCB degradation

Degradation of polychlorinated biphenyls (PCBs) in water matrix using UV/H2O2: Effect of initial PCB concentration and analysis of reaction products

This study investigated the effect of the different initial concentrations of polychlorinated biphenyls (PCBs) on its degradation in water matrix using UV/H2O2 and on the formation of reaction intermediates or products. Simulated PCB-contaminated water solution was subjected to irradiation with 17 W, 254 nm wavelength UV lamp in a batch tubular reactor. The ratio of oxidant to PCBs, in terms of Aroclor 1260, was based on 2,800uL H2O2 is to 40 ppm PCB. Samples were extracted from the matrix by solid-phase extraction (SPE) method using C18 cartridges with hexane and ethyl acetate as solvents. The samples were analyzed using Gas Chromatography-Electron Capture Detector System (GC-ECD) to determine the concentration of PCBs in the samples and pH was monitored every sampling time. The analysis of chloride (Cl) ion concentration in the samples was done using Argentometric titration. Determination of reaction intermediates and products was carried out with 40 ppm PCB concentration using Gas Chromatography-Mass Spectroscopy (GC-MS) system. A decrease in pH in the early stages of degradation was observed and the higher the initial concentration of PCB the greater was the drop in pH . The PCB degradation profile showed that from 1 to 40 ppm initial concentration, the degradation efficiency of UV/H2O2 increased with increasing initial PCB concentration. At 80 ppm. however, it was observed that there was a decrease in concentration of PCBs in the solution and showed the preferential attack of the UV/H2O2 to PCBs over long chain saturated alkanes or waxes which contained the PCBs