Effect of Light Intensity on the Photodegradation of PCB 153 in Aqueous Solution using UV and UV/H₂O₂

摘要

This study examines the photodegradation of PCB 153 under ultraviolet radiation and ultraviolet radiation combined with hydrogen peroxide (H₂O₂) using a batch tubular recirculating photoreactor equipped with 17 W and 24 W UV-C lamps emitting at 254 nm. PCB 153 solutions with various concentration of 50 ppb, 80 ppb and 100 ppb were prepared for experiments conducted under photolysis (UV only) while 25 μL (0.221 mM), 50 μL (0.441 mM), 75 μL (0.662 mM) of 30% (w/w) H₂O₂ were individually added to an 80 ppb PCB 153 solution and used as samples for UV/H₂O₂ experimental runs. Under ultraviolet radiation, the increase of light intensity from 17 W to 24 W increased the degradation from 90.43% to 94.71% of an 80 ppb aqueous PCB 153 solution after 2 hrs of irradiation. The addition of 50 μL (0.441 mM) of 30% wt H₂O₂ resulted into a drastic decrease of the same concentration of PCB 153. After 30 minutes of irradiation using 17 W UV lamp, 95.95% PCB degradation was observed while complete degradation was attained with the 24 W UV lamp. The pH of the solutions was closely monitored and it was observed that it decreases during photodegration. The decrease of the sample's pH was a result of inorganic chlorides and acidic metabolites formation as measured using High Performance Liquid Chromatography (HPLC) - Conductivity Detector. Likewise, the PCB concentration of irradiated samples was measured using Gas Chromatography equipped with Electron Capture Detector (GC-ECD).