• Solar Energy
• /
• v.15 no.2
• /
• pp.65-75
• /
• 1995

We have summarised some important aspects of our recent basic and applied studies in the area of photocatalytic detoxifcation with Degussa P25 titanium dioxide($TiO_2$) being the photocatalyst. Heterogeneousphotocatalytic decompositions of two components such as TCE-chloroform, TCE-phenol and TCE-benzene as well as single component organic, TCE, chloroform and $CCl_4$ were carried out to investigate the effect of additional compound on the TCE decomposition rate. In laboratory experiments, the optimum flow rate of TCE solution was $200cm^3/min$ with annular photoreactor in the presence of 0.1 wt% $TiO_2$ powder under illumination. It was observed that the second compound such as $CHCl_3$, phenol and benzene has a negative effect on the TCE decomposition rate. Result presented that TCE decomposition ratio was increased at low pH in the TCE-phenol two component solution. It could be shown that the photocatalytic reactor exhibits technical feasibility of detoxifying the multicomponent under proper experimental conditions.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.04a
• /
• pp.184-187
• /
• 2003

The preliminary data from the application of the ultrasound to the degradation of TCE were shown. The first order degradation coefficients were are 0.0134 s$^{-1}$ and 0.0151s $^{-1}$ with saturating gas of air and argon, respectively. The pH of the solution went down to 3 and stabilized in each case.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.1
• /
• pp.46-52
• /
• 2008

Oils and chlorinated solvents leaking to the subsurface are entrapped in the soil pore and these are called as nonaqueous phase liquids (NAPL). NAPL entrapped in porous media acts as a continuous source for surface and ground water contamination. This study visualized dissolution of trichloroethylene (TCE) entrapped in porous media and quantified the velocity of TCE dissolution using an image analysis technique. As the water velocity increased, the level of dissolution increased. The results imply that a TCE contaminated region having a high infiltration rate and groundwater velocity may result in severe groundwater contamination. Microscopic images of TCE entrapped in porous media showed that TCE present in the preferential flow paths was easily dissoluted into the water phase. However, TCE present in the stagnant flow region was visualized for long time. The results imply that TCE would be still present in the soil if TCE is detected in goundwater.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.11
• /
• pp.771-780
• /
• 2014

In this study, the various organic supports (i.e., silicone, acrylonitrile-butadiene-styrene, epoxy, and, butadiene rubber) with great sorption capacity of organic contaminants were chosen to develop nano-ZnO/organic composites (NZOCs) and to prevent the detachment of nano-ZnO particles. The water resistance of the developed NZOCs were evaluated, and the feasibility of the developed NZOCs were investigated by evaluating the removal efficiency of 1,1,2-trichloroethylene (TCE) in the aqueous phase. Based on the results from water-resistance experiments, long-term water treatment usage of all NZOCs was found to be feasible. According to the FE-SEM, EDX, and imaging analysis, nano-ZnO/butadiene rubber composite (NZBC) with various sizes and types of porosity and crack was measured to be coated with relatively homogeneously-distributed nano-ZnO particles whereas nano-ZnO/silicone composite (NZSC), nano-ZnO/ABS composite (NZAC), and nano-ZnO/epoxy composite (NZEC) with poorly-developed porosity and crack were measured to be coated with relatively heterogeneously-distributed nano-ZnO particles. The sorption capacity of NZBC was close to 60% relative to the initial concentration, and this result was mainly attributed to the amorphous structure of NZBC, hence the hydrophobic partitioning of TCE to the amorphous structure of NZBC intensively occurred. The removal efficiency of TCE in aqueous phase using NZBC was close to 99% relative to the initial concentration, and the removal efficiency of TCE was improved as the amount of NZBC increased. These results stemmed from the synergistic mechanisms with great sorption capability of butadiene rubber and superior photocatalytic activities of nano-ZnO. Finally, the removal efficiency of TCE in aqueous phase using NZBC was well represented by linear model ($R^2{\geq}0.936$), and the $K_{app}$ values of NZBC were from 2.64 to 3.85 times greater than those of $K_{photolysis}$, indicating that butadiene rubber was found to be the suitable organic supporting materials with enhanced sorption capacity and without inhibition of photocatalytic activities of nano-ZnO.

• Journal of Soil and Groundwater Environment
• /
• v.17 no.5
• /
• pp.49-55
• /
• 2012

A 1.28 L-batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloroethene (TCE) were operated for 120 days and 56 days, respectively, to study the effect of formate as electron donor on anaerobic reductive dechlorination (ARD) of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 ${\mu}mol$ TCE was completely degraded in the presence of 20% hydrogen gas ($H_2$) in less than 8 days by anaerobic dechlorination mixed-culture (300 mg-soluble protein), Evanite Culture with ability to completely degrade tetrachloroethene (PCE) and -TCE to ETH under anaerobic conditions. Once the formate was used as electron donor instead of hydrogen gas in batch or chemostat system, the TCE-dechlorination rate decreased and acetate production rate increased. It indicates that the concentration of hydrogen produced in both systems is possibly more close to threshold for homoacetogenesis process. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. Through the protein monitoring, we confirmed an increase of microbial population during the reactor operation. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 ${\mu}mol/L$) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at 18 days of HRT, but TCE was completely degraded at 36 days of HRT without accumulation of the injected-TCE during the left of experiment period, getting $H_2$ from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after beginning of CFSTR operation, it reached steady-state in the presence of excessive formate. We also evaluated microbial dynamic of the culture at different chemical state in the reactor by DGGE (denaturing gradient gel electrophoresis).

• Journal of Korean Society for Atmospheric Environment
• /
• v.17 no.1
• /
• pp.97-104
• /
• 2001

Decomposition of trichloroethlyene(TCE) in electron beam irradiation was examined on order to obtain information on the treatment of VOC in air. Air containing vaporized TCE has been studied in a flow reactor with different reaction environments, at various initial TCE concentration and in the presence and absence of water vapor. Maximum decomposition was observed in oxygen reaction environment and the degree of decomposition was about 99% at 20kGy for 2,000ppm initial TCE. The concentration of TCE exponentially decreased with dose in air and pure oxygen. The effect of water vapor on TCE decomposition efficiency was examined. The decomposition rate of TCE in the presence of water vapor (5,600 ppm) was approximately 10% higher than that in the absence of water vapor. Dichloroacetic acid, dichloroacethyl chloride and dichloroethyl ester acid were identified as primary products of this reaction adn were decomposed and oxidized to yield CO and $CO_2$. Perchloroethylene, hexachloroethane, chloroform and carbon tetrachloride were also observed as highly chlorinat-ed by products.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.11
• /
• pp.753-759
• /
• 2014

This paper describes the development of a piezoelectric flextensional transducer, which aims to effectively degrade the TCE contained in aqueous solution. In order to adjust the 1st flextensional resonant frequency and output displacement of the flextensional transducer, the effect of the geometrical variations on performance was analyzed using the finite element analysis (FEM). The results indicated that the effect of external shell's thickness and curvature were most significant, and experimental fabrication and characterization of a transducer was performed to confirm the results. To prove the capacity to degrade the TCE contained in aqueous solution, 50 and 100 ppm of TCE were prepared in sealed chamber, and investigated the removal rate of TCE through the time and initial concentration.

• Microbiology and Biotechnology Letters
• /
• v.22 no.2
• /
• pp.203-209
• /
• 1994

The bacterial strain which utilizes phenol and degrade TCE was isolated from an industrial waste site. The bacterial strain was named as T5-7 and identified as an Acinetobacter species. After phenol-induction, the strain T5-7 removed TCE efficiently without cell growth. So, it seems that TCE degradation was not related to cell growth. TCE degradation increased when initial cell concentrations of phenol-grown T5-7 were high. In the presence of phenol, initial degradation of TCE was delayed but total amount of degradation was not affected at final stage. The strain cultured in 0.1% yeast extract did not degrade TCE, which indicates that phenol induction was essential to the TCE degradation.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.5
• /
• pp.971-980
• /
• 2000

Mixed methanotrophs (MM) secreting soluble methane monooxygenase(sMMO) were immobilized on celite R-635 to degrade trichloroethylene(TCE) in methanotrophic consortium biofilm reactor(MCBR) system. Further neutralization of celite R-635 was not needed for immobilization because effluent pH was stabilized at neutral after 4 hour washing. It took 130 days to develop biofilm on celite R-635 and the color of the celite changed gradually from white to red. After biofilm developed, influent methane and oxygen were decreased from 2.5~4 and 8~10 ppm to 0.5~1 and 1~2 ppm, respectively, With influent 2 ppm of TCE and 10 hours of retention time, 79.9% of TCE was degraded in the MCBR system.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.3 no.1
• /
• pp.3-13
• /
• 1993

This study was conducted at seven degreasing processes in plating plants located in Seoul, Incheon, Ansan, and Taejeon areas from July 21 to august 27, 1992. This study was performed to assess the TWA exposures to trichloroethylene (TCE) and evaluate factors affecting TCE concentrations in degreasing process. Two-Point Eddy Diffusional Model suggested by Wadden et al. was employed to calculalte emission factors according to degreaser type. Results are summarized as follows. 1. The TWA exposures of the degreasing operators ranged from 1.4 ppm to 123 ppm, and those of three plants out of seven were exceeding 50 ppm of both the Korean and U.S. OSHA standards. Degreasing assistant of Plant B, was exposed to 59 ppm. 2. The average concentrations at the distance 0, 1.5, 3.0 m from the degreasers were 1.014, 24, and 18 ppm, respectively, and showed a signifficant difference by distance (p<0.01). 3. The emission of TCE was reduced by installing local exhaust systems, condensers, and refrigeration lines at the degreasers (p<0.01). 4. The major factors related to exposure of operators were workload (r=.9621. p<0.01) and dimensions of degreansing room(r=-.8667, p<0.05). 5. If the air in degreasing room is mixed violently by other factors in addition to diffusion, the emission factors can not be evaluated because the important hypothesis of the Two-Point Eddy Diffusional Model can not be accepted. 6. The ultrasonic degreaser without the local exhaust ststem, condenser, and refrigeration lines emitted TCE three times greater than the ultrasonic degreaser with condenser and refrigeration 1ines only.