• Journal of Environmental Science International
• /
• v.15 no.7
• /
• pp.669-676
• /
• 2006

PAHs are major pollutants that are widely distributed in soil and groundwater environment, so that may be regarded as carcinogens. We investigated the degradation kinetics of PAH in aqueous solution when low pressure UV energy and ultrasonic irradiation were applied. Phenanthrene and pyrene were used as model compounds. The degrees of degradation of these compounds with time were analyzed with a GC/MSD (SIM-mode). UV photolysis experiments showed that phenanthrene was reduced by 90 -67% at initial concentrations of 1 ppm to 8ppm whilst it decreased to 50% at 10 ppm. Under the same conditions pyrene was degraded up to about 75% at lower initial concentrations but the reduction efficiency dropped to a level of 34 to 29% at the higher concentrations above 8 ppm. The reaction orders for phenanthrene and pyrene were found to be zero-th and ca. -0.4th order, respectively, thus implying that the reported assumption of pseudo 1st order reaction for some PAHs would be no longer valid. PAH degradation was roughly proportional to the intensity of UV (number of lamps), exhibiting maximum 92.5% of the degradation efficiency. The solution pH was lowered to 4.4 from 6.4 during the experiments partially because the carbons decomposed by the energy reacted with oxygen radicals to produce carbon dioxides. Ultrasonic irradiation on phenanthrene solutions gave relatively poor results which matched to 50 to 70% of degradation efficiency even at 2 ppm of initial concentration. Phenanthrene was found to be degraded more efficiently than pyrene for the two energy sources. Ultrasound also followed the same reaction kinetics as UV energy on PAH degradation.

• Environmental Engineering Research
• /
• v.13 no.4
• /
• pp.197-202
• /
• 2008

This study evaluated the photocatalytic oxidation of BPA using the RPOD reactor under various conditions. This study found that the RPOD was effective for BPA degradation. It could reduce 1 mg/L of BPA by half within 5 min under the optimum conditions. According to the study results, $TiO_2$ coating was important for the BPA oxidation. As the coating thickness increased, the removal efficiency improved. The light source, the light intensity and the drum rotating speed were important for the oxidation. The UV light was more effective for the BPA degradation than the visible light. The removal efficiency improved with increasing intensity. As the drum speed increased, the removal efficiency improved. The maximum speed was 240 rpm in this study. Addition of air and nitrogen was not beneficial for the BPA degradation in this study probably due to enough oxygen in the water.

• Journal of the Korean Ceramic Society
• /
• v.54 no.4
• /
• pp.308-313
• /
• 2017

In this study we examined the photo-degradation efficiency of $CoS_2-G-TiO_2$ nanocomposites under visible light irritation using Reactive Black B (RBB) as standard dye, $CoS_2-G-TiO_2$ nanocomposites synthesized by facial microwave assist technique, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopic analysis. Our results show the efficiency of the $CoS_2-G-TiO_2$ ternary nanocomposite is better than $CoS_2-G$ and $TiO_2-G$ nanocomposite. The degradation efficiency of $CoS_2-G-TiO_2$ nanocomposite was found approximately 89% of Reactive Black B (RBB) degraded after 180 min. Our results will open new way for the development of a new ternary nanocomposite photocatalytic application.

• Journal of Electrochemical Science and Technology
• /
• v.12 no.2
• /
• pp.266-271
• /
• 2021

A commercial PbO₂ electrode was adopted as the anode for the electrochemical degradation of the real textile effluent with the initial COD of 56.0 mg L^-1 and the stainless steel plate as the cathode. The effect of the initial pH, the electrolyte flow rate and the cell voltage on the COD, the current efficiency and the energy consumption were investigated without the addition of NaCl or Na₂SO₄. The experimental results illustrated that the PbO₂ electrode can reduce the COD of the textile effluent from 56.0 mg L^-1 to 26.0 mg L^-1 with the current efficiency of 86.1% and the energy consumption of 17.5 kWh kg^-1 (per kilogram of degraded COD) under the optimal operating conditions. Therefore PbO₂ electrode as the anode was promising to further electrochemically degrade the real textile effluent.

• Journal of Environmental Science International
• /
• v.14 no.7
• /
• pp.699-709
• /
• 2005

This study aimed at improving the $TiO_2$ photocatalytic degradation of HA. In this study, the Degradation of Humic Acid using Jeju Scoria Coated with $WO_3/TiO_2$ in the presence of UV irradiation was investigated as a function of different experimental condition : photocatalyst dosage, $Ca^{2+}\;and\;HCO_{3}_{-}$ addition and pH of the solution. Photodegradation efficiency increased with increasing photocatalyst dosage, the optimum catalyst dosage is 2.5 g/L and Photodegradation efficiency is maximized to $WO_3/TiO_2=3/7$. This indicates that $WO_3$ retains a much higher Lewis surface acidity than $TiO_2,\;and\;WO_3$ has a higher affinity for chemical species having unpaired electrons. The addtion of cation($Ca^{2+}$) in water increased the photodegradaion efficiency. But the addtion of $HCO_{3}^{-}$ ion in water decreased a photodegradation efficiency. Photodegradation efficiency increased with decreasing pH < pzc, the electrostatic repulsion between the HA and the surface of $TiO_2$ decreased.

• Journal of Korean Society of Water and Wastewater
• /
• v.26 no.1
• /
• pp.37-46
• /
• 2012

The degradation characteristics of TCE by Ferrate(VI) oxidation have been studied. The degradation efficiency of TCE in aqueous solution was investigated at various pH values, Ferrate(VI) doses, initial concentrations of TCE and aqueous solution temperature values. GC-ECD was used to analyze TCE. The optimum conditions of TCE degradation were obtained pH 7.0 and $25^{\circ}C$ in aqueous solution. Also, the experimental results showed that TCE removal efficiency increased with the decrease of initial concentration of TCE. And intermediate products were identified by GC-MS techniques. Ethyl Chloride, Chloroform, Ethylene, 1,2-dichloroethane and 1,1,2-trichloroethane were identified as a reaction intermediate, and $Cl^-$ was identified as an end product.

• Korean Journal of Soil Science and Fertilizer
• /
• v.44 no.2
• /
• pp.316-319
• /
• 2011

Biopiles which offer the potential for cost-effective treatment of contaminated soils are above-ground, engineered systems that use oxygen to stimulate the growth and reproduction of aerobic bacteria for degradation of the petroleum constituents adsorbed to soil in excavated soils. This technology involves heaping contaminated soils into piles and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. Inside the biopile, microbially mediated reactions by blowing or extracting air through the pipes can enhance degradation of the organic contaminants. The influence of a aeration system on the biopile performance was investigated. Air pressure made to compare the efficiency of suction in the pipes showed that there were slightly significant difference between the two piles in the total amount of TPH biodegradation. The normalised degradation rate was, however, considerably higher in the aeration system than in the normal system without aeration, suggesting that the vertical venting method may have improved the efficiency of the biological reactions in the pile.

• Journal of Environmental Science International
• /
• v.22 no.9
• /
• pp.1089-1095
• /
• 2013

The degradation of 3-chlorophenol(3-CP) by various AOPs(Advanced Oxidation Processes) including the ultraviolet / hydrogen peroxide, the Fenton and the ultraviolet(UV)-Fenton process has been conducted. The highest removal efficiency for 3-CP in the aqueous phase was obtained by the UV-Fenton process among the AOPs. In the UV-Fenton process, The removal efficiency of 3-CP decreased with increasing pH in the range of 3 to 6, and it decreased with increasing initial concentration. As the intermediates of 3-CP by UV-Fenton reaction, 3-chlorocatechol, 4-chlorocatechol, and chlorohydroquinone were detected thus the degradation pathways were proposed.

• Journal of Korean Society of Water and Wastewater
• /
• v.29 no.1
• /
• pp.39-46
• /
• 2015

The degradation characteristics of perchloroethylene by ferrate(VI) oxidation have been studied. The degradation efficiency of perchloroethylene in aqueous solution was investigated at various values of ferrate(VI) dosage, pH, initial concentration of perchloroethylene and aqueous solution temperature. GC-ECD has been used to analyze the changes of perchloroethylene concentration. The optimum conditions of perchloroethylene degradation were obtained at pH 7.0 and $25^{\circ}C$ of aqueous solution temperature. Also, the experimental results showed that perchloroethylene removal efficiency increased with the decrease of initial concentration of perchloroethylene. Lastly intermediate products were identified by GC-MS techniques. Trichloroethylene and chloroform were identified as reaction intermediates.

• Journal of Power System Engineering
• /
• v.18 no.6
• /
• pp.84-90
• /
• 2014

The degradation of 2,3-dichlorophenol(2,3-diCP) by various advanced oxidation systems with continuous feeding of hydrogen peroxide including the ultraviolet/hydrogen peroxide, the Fenton and the photo-Fenton process has been conducted. The highest removal efficiency for 2,3-diCP in the aqueous phase was obtained by the photo-Fenton process among the advanced oxidation systems. In the photo-Fenton process, The removal efficiency of 2,3-diCP decreased with increasing pH in the range of 3 to 6, and it decreased with increasing initial concentration. As the intermediates of 2,3-diCP by photo-fenton reaction, 3,4-chlorocatechol and 2,3-dichlorohydroquinone were detected, thus the degradation pathways were proposed.