No abstract

This study examines the photodegradation of PCB 153 under ultraviolet radiation and ultraviolet radiation combined with hydrogen peroxide (H 2 O 2 ) 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 L (0.221 mM), 50 L (0.441 mM), 75 L (0.662 mM) of 30% (w/w) H 2 O 2 were individually added to an 80 ppb PCB 153 solution and used as samples for UV/H 2 O 2 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 H 2 O 2 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).

This study was conducted to optimize the supercritical carbon dioxide (scCO2) extraction of oil from Gliricidia sepium seeds using response surface methodology. Initial experiments were carried out using scCO2 and scCO2 with co-solvent n-hexane to determine the effect of co-solvent addition in oil yield. In order to obtain the maximum yield, experiments were conducted using Response Surface Methodology - Face Centered Central Composite Design (RSM – FCCD) under the following conditions: pressure of 20, 30, and 40 MPa, temperature of 50, 60, and 70°C, and CO2 flow rate of 2, 2.5, and 3 mL/min. A second-order polynomial with extended cubic interaction model was significantly fitted (p < 0.05), and a high coefficient determination value (R2 = 0.98) was recorded. At a constant extraction time of 60 minutes, the best extraction yield (12.12%) was obtained at 60°C, 40 MPa, and 2.5 mL/min. The pressure, temperature, and CO2 flow rate were all found to have a significant effect on the oil yield. The oil was used in biodiesel production and its methyl ester composition was analyzed using Gas Chromatography-Flame Ionization Detector (GC-FID).