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Comparison of photodegradation performance of 1,1,1 - trichloroethane in aqueous solution with the addition of H2O2 or S2O82 – oxidants / Xiaogang Gu in Industrial & engineering chemistry research, Vol. 51 N° 21 (Mai 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 21 (Mai 2012) . - pp. 7196-7204 Titre : Comparison of photodegradation performance of 1,1,1 - trichloroethane in aqueous solution with the addition of H2O2 or S2O82 – oxidants Type de document : texte imprimé Auteurs : Xiaogang Gu, Auteur ; Shuguang Lu, Auteur ; Zhaofu Qiu, Auteur Année de publication : 2012 Article en page(s) : pp. 7196-7204 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Oxidant  Hydrogen  peroxide  Aqueous  solution  Photochemical  degradation Résumé : The chemical oxidation of 1,1,1-trichloroethane (TCA), a widely detected groundwater pollutant, by UV/H2O2 and UV/S2O82― processes was investigated. The effects of various factors were evaluated, including peroxide/TCA molar ratio, solution pH, C― and HCO3― anions, and humic acid (HA). The results showed that TCA oxidation fit to a pseudo-first-order kinetic model. The optimum H2O2/TCA molar ratio was 5:1, with TCA removal of 54.2% in 60 min. In the UV/S2O82― process, higher molar ratios (from 1/1 to 10/1) resulted in higher TCA oxidation rates, and TCA could be completely removed after 60 min with a S2O82―/TCA molar ratio of 3/1. In addition, acidic conditions were favorable for TCA removal in the UV/S2O82― process, while maximum TCA removal was observed at pH 6 in the UV/H2O2 process. Both Cl― and HCO3― anions adversely affected TCA oxidation performance, and higher concentration of HA resulted in a lag phase for TCA oxidation in both processes. Several reaction intermediates, including 1,1,1,2-tetrachloroethane, carbon tetrachloride, chloroform, tetrachloroethylene, 1,1-dichloroethylene, and tri- and dichloroacetic acids, were first identified during TCA oxidation by S2O82― chemistry, while only monochloroacetic acid was detected in the UV/H2O2 process. The results indicated that the UV/S2O82― process was much more effective than the UV/H2O2 process, but the latter was more environmentally friendly because fewer toxic intermediates were produced. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25948460 [article] Comparison of photodegradation performance of 1,1,1 - trichloroethane in aqueous solution with the addition of H2O2 or S2O82 – oxidants [texte imprimé] / Xiaogang Gu, Auteur ; Shuguang Lu, Auteur ; Zhaofu Qiu, Auteur . - 2012 . - pp. 7196-7204. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 21 (Mai 2012) . - pp. 7196-7204 Mots-clés : Oxidant  Hydrogen  peroxide  Aqueous  solution  Photochemical  degradation Résumé : The chemical oxidation of 1,1,1-trichloroethane (TCA), a widely detected groundwater pollutant, by UV/H2O2 and UV/S2O82― processes was investigated. The effects of various factors were evaluated, including peroxide/TCA molar ratio, solution pH, C― and HCO3― anions, and humic acid (HA). The results showed that TCA oxidation fit to a pseudo-first-order kinetic model. The optimum H2O2/TCA molar ratio was 5:1, with TCA removal of 54.2% in 60 min. In the UV/S2O82― process, higher molar ratios (from 1/1 to 10/1) resulted in higher TCA oxidation rates, and TCA could be completely removed after 60 min with a S2O82―/TCA molar ratio of 3/1. In addition, acidic conditions were favorable for TCA removal in the UV/S2O82― process, while maximum TCA removal was observed at pH 6 in the UV/H2O2 process. Both Cl― and HCO3― anions adversely affected TCA oxidation performance, and higher concentration of HA resulted in a lag phase for TCA oxidation in both processes. Several reaction intermediates, including 1,1,1,2-tetrachloroethane, carbon tetrachloride, chloroform, tetrachloroethylene, 1,1-dichloroethylene, and tri- and dichloroacetic acids, were first identified during TCA oxidation by S2O82― chemistry, while only monochloroacetic acid was detected in the UV/H2O2 process. The results indicated that the UV/S2O82― process was much more effective than the UV/H2O2 process, but the latter was more environmentally friendly because fewer toxic intermediates were produced. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25948460

Oxidation of 1,1,1 - trichloroethane stimulated by thermally activated persulfate / Xiaogang Gu in Industrial & engineering chemistry research, Vol. 50 N° 19 (Octobre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 19 (Octobre 2011) . - pp. 11029–11036 Titre : Oxidation of 1,1,1 - trichloroethane stimulated by thermally activated persulfate Type de document : texte imprimé Auteurs : Xiaogang Gu, Auteur ; Shuguang Lu, Auteur ; Lin Li, Auteur Année de publication : 2011 Article en page(s) : pp. 11029–11036 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Oxidation  Trichloroethane Résumé : In this study, thermally activated persulfate (PS) to stimulate the oxidation of 1,1,1-trichloroethane (TCA) in groundwater remediation was investigated. The effects of various factors including temperature; initial TCA concentration; PS/TCA molar ratio; solution pH; and common constituents in groundwater such as Cl–, HCO3–, SO42–, and NO3– anions and humic acid (HA) were evaluated. The experimental results showed that TCA can be completely oxidized in 2 h at 50 °C with a PS/TCA molar ratio of 100/1, indicating the effectiveness of thermally activated PS oxidation for TCA removal. TCA oxidation was fitted with a pseudo-first-order kinetic model, and the rate constant was found to increase with increasing temperature and PS/TCA molar ratio, but to decrease with increasing initial TCA concentration. In addition, acidic conditions were favorable to TCA removal and elevating, the initial solution pH value (from pH 3 to 11) decreased the TCA degradation rate. Anions Cl– and HCO3– had negative effects on TCA removal, whereas the effects of both SO42– and NO3– were negligible. With 5–10 mg L–1 concentrations of HA in solution, an inhibitive effect was observed, indicating that dissolved organic matter consumed some of the oxidant. However, the anticipated effective thermally activated PS oxidation of TCA in groundwater from a real contaminated site was not achieved because of the complex solution matrix. On the other hand, the TCA degradation mechanism derived from GC/MS analytical results confirmed formic acid, dichloromethane, and trichloromethane as the primary intermediates, and therefore, two TCA decomposition pathways were proposed. In conclusion, thermally activated PS oxidation is a highly promising technique for TCA-contaminated groundwater remediation, but more complex constituents in in situ groundwater should be carefully considered for its practical application. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201059x [article] Oxidation of 1,1,1 - trichloroethane stimulated by thermally activated persulfate [texte imprimé] / Xiaogang Gu, Auteur ; Shuguang Lu, Auteur ; Lin Li, Auteur . - 2011 . - pp. 11029–11036. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 19 (Octobre 2011) . - pp. 11029–11036 Mots-clés : Oxidation  Trichloroethane Résumé : In this study, thermally activated persulfate (PS) to stimulate the oxidation of 1,1,1-trichloroethane (TCA) in groundwater remediation was investigated. The effects of various factors including temperature; initial TCA concentration; PS/TCA molar ratio; solution pH; and common constituents in groundwater such as Cl–, HCO3–, SO42–, and NO3– anions and humic acid (HA) were evaluated. The experimental results showed that TCA can be completely oxidized in 2 h at 50 °C with a PS/TCA molar ratio of 100/1, indicating the effectiveness of thermally activated PS oxidation for TCA removal. TCA oxidation was fitted with a pseudo-first-order kinetic model, and the rate constant was found to increase with increasing temperature and PS/TCA molar ratio, but to decrease with increasing initial TCA concentration. In addition, acidic conditions were favorable to TCA removal and elevating, the initial solution pH value (from pH 3 to 11) decreased the TCA degradation rate. Anions Cl– and HCO3– had negative effects on TCA removal, whereas the effects of both SO42– and NO3– were negligible. With 5–10 mg L–1 concentrations of HA in solution, an inhibitive effect was observed, indicating that dissolved organic matter consumed some of the oxidant. However, the anticipated effective thermally activated PS oxidation of TCA in groundwater from a real contaminated site was not achieved because of the complex solution matrix. On the other hand, the TCA degradation mechanism derived from GC/MS analytical results confirmed formic acid, dichloromethane, and trichloromethane as the primary intermediates, and therefore, two TCA decomposition pathways were proposed. In conclusion, thermally activated PS oxidation is a highly promising technique for TCA-contaminated groundwater remediation, but more complex constituents in in situ groundwater should be carefully considered for its practical application. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201059x