Papers by Keyword: Trichloroethylene (TCE)

Abstract: The removal of trichloroethylene (TCE) by corona discharge plasma was investigated. The influences of initial concentration, gas flow rate, injection of water vapor and ozone (O₃) on removal efficiency were discussed. The results show that removal efficiency reduces with the initial concentration and gas flow rate increasing. A proper quantity of water vapor injection can improve the removal efficiency, but which is not always increased, due to the electronegative characteristic of water molecule. The maximum removal efficiency of 90.7% can be obtained in wet air flow with relative humidity of 70.6%. The removal efficiency increases obviously with O₃ injection. The decomposition products are 2,2-Dichloroacetyl chloride (CHCl₂COCl), carbonyl chloride (COCl₂), hydrogen chloride (HCl) and carbon dioxide (CO₂), based on which the decomposition mechanism is discussed. The oxygen chain reaction is the primary decomposition mechanism, and high energy electrons and active oxygen species play a leading role in the decomposition process. Therefore, removal efficiency of TCE can be improved greatly when water vapor and O₃ is injected.

Abstract: The adsorption of trichloroethylene (TCE) and Cd²⁺ combined contamination in the groundwater by attapulgite were studied, and the effects of pH, dosage of attapulgite and adsorption time on adsorption were investigated, equilibrium of the adsorptions processes were further conducted. Results showed that the adsorption rate of TCE affected little by the pH; TCE adsorption equilibrium reached after 3d, the removal rate was 71.34%; when attapulgite dosage was 0.03g, the adsorption rate was up to more than 51.08%. Freundlich isotherm was best fitted the adsorption process of TCE. Compound contamination of TCE and Cd²⁺ decreased the removal rate of TCE; but was in line with Freundlich adsorption isotherm.

Abstract: Trichloroethylene is one of chlorinated organic compounds widely used as a solvent and degreasing agent in industry. Because of uninformed disposal in the past, trichloroethylene has become one of major contaminant in environment, and this situation has brought about a serious public concern for its toxicity. A promising approach to solving this problem is bioremediation using degrading-bacteria. A bacterium(strain TC-1) was isolated from environment, which could degrade trichloroethylene. It was preliminary identified as the genus of Sporosarcina sp.. The results showed that the optimal degradation temperature, degradation time, rotary speed and the initial pH of fermentation medium were 25°C, 60 h, 180 rpm and 7.5 respectively, the ratio of degradation reached 95.56% under this conditions.

Abstract: The modified oil sludge (MOS) was a novel sorbent in groundwater remediation, and it has a carbon content of 37-50% and a huge adsorption capacity after its pyrolytic treatment. This study highlights the adsorption potential of MOS to remove organic contaminants in groundwater. Batch-type experiments about the adsorption and desorption characteristics of MOS to MTBE, TCE and benzene were conducted. Results showed that the adsorption removal rate of TCE and benzene were up to 99%, and was lower for MTBE (88-93%) due to its high water solubility, but the maximum adsorption capacity of MOS to MTBE was still larger (14.3-33.3 mg/g). The desorption quantities of TCE and benzene was 0.4% and 1%, respectively; but was larger for MTBE (10%), and similar trend was also found for the desorption hysteresis coefficient.

Abstract: The activities of nitrifying bacteria and organic utilizing bacteria against TCE in sludge was investigated using three series of Membrane bioreactors, and the results indicated that, the removal efficiencies of COD decreased gradually, but was not affected severely with TCE inhibition, good organics removal efficiencies was possibly realized, while the ammonia removal efficiencies dropped sharply due to the severe inhibition of TCE against nitrifying bacteria, the degree of TCE inhibition against nitrifying bacteria increased with the TCE concentration, but low-concentration TCE addition seems act as a chronic toxicity to the sludge activity, However, the nitrifying bacteria was gradually adapted to the TCE inhibition and its activities could be entirely resumed, and the ability of the nitrifying sludge to tolerate TCE could be satisfactory maintained either after the stop of TCE addition, therefore, TCE could be degradated partly by the nitrification processes, when the TCE was added intermittently and continuously into the Membrane reactors, simultaneously, a good performance of nitrification and organic utilization processes was possibly maintained stably.

Abstract: The effect of TCE cometabolism degradation with glucose as electron donor on reduction progress was investigated with enriched nitrate, sulfate, trivalent iron and their mixtures under anoxic or anaerobic conditions. The removal effect of TCE was found to be better in anoxic environment; TCE degradation was inhibited by the addition of trivalent iron salts and the mixed salts under anoxic condition or strongly inhibited by nitrate under anaerobic condition; promoted by the addition of trivalent iron salts under anaerobic condition; little inhibited by the addition of nitrate and sulfate under anoxic condition or sulfate and the mixed salts under anaerobic condition.

Abstract: In this study, a trichloroethylene (TCE)-spill site was selected to assess the feasibility of enhanced in situ anaerobic bioremediation of TCE-contaminated groundwater using hydrogen as the electron donor produced from nanoscale zero-valent iron (nZVI). Results of hydrogen production experiments show that nZVI had a good efficiency on hydrogen production. Results of microcosm study show that indigenous microorganisms were capable of degrading TCE under anaerobic reductive dechlorinating conditions. Compared to the live control and autoclaved control microcosms, microcosms with hydrogen addition significantly enhanced the TCE removal rates. Results imply that nZVI can be applied as the source of hydrogen to bioremediate TCE-contaminated groundwater under anaerobic conditions. Except for the biotic mechanism, the supplied nZVI can also cause the TCE degradation via abiotic mechanism through oxidation-reduction process. For field application, if proper doses of iron nanoparticles can be applied in the mid- or downgradient areas, both chemical and biological mechanisms can enhance the removal of the contaminants and their byproducts. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site. The nZVI treatment scheme would be expected to provide a more cost-effective alternative to remediate chlorinated-solvent contaminated aquifers.

Abstract: In this paper, exfoliated graphite supported nanoscale Fe-Cu is synthesized by aqueous-phase reductive method. The effect trichloroethene (TCE) reduction by the supported nanoscale Fe-Cu bimetal is researched in the batch experiments. Kinetics studies show that the reduction of TCE process obeys pseudo-second-order kinetics. The kinetic constants of TCE reduction by supported nano bimetal are measured at different nano Fe0 dosage and Cu content on bimetal in this study. When the dosage of supported nano Fe0 in bimetal with 4wt% Cu is 1.25g/L in reaction solution, the kSA of dechlorination reaction for TCE is higher than other nano Fe0 dosage. The dechlorination speed becomes lower as well as kSA and kobs decreasing with increasing the Fe0 dosage. Supported Fe-Cu bimetal with 4wt% Cu content exhibits the best dehalogenation effect than those with other contents of Cu. The generation of H2 and effect of Cu analysis influence the TCE dechloriation and hydrogenation in the surface of bimetal to a different extent. Excess nano Fe0 existing in the reaction system can generate plenty of H2 as well as increasing the solution pH value so that decrease the surface concentration of bimetal reactive sites and then hinder the TCE dechlorination in surface of bimetal. Cu as catalysis metal could accelerate the process of TCE dechlorination and hydrogenation.