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Identification of sulfate and hydroxyl radicals in thermally activated persulfate / Chenju Liang in Industrial & engineering chemistry research, Vol. 48 N° 11 (Juin 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5558–5562 Titre : Identification of sulfate and hydroxyl radicals in thermally activated persulfate Type de document : texte imprimé Auteurs : Chenju Liang, Auteur ; Hsin-Wey Su, Auteur Année de publication : 2009 Article en page(s) : pp. 5558–5562 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Thermal  activation  Persulfate  degradation  Chemical  probe  method Résumé : Thermal activation can induce persulfate (S2O82−) degradation to form sulfate radicals (SO4−•) that can undergo radical interconversion to form hydroxyl radicals (HO•) under alkaline conditions. The radicals SO4−•/HO• can be present either individually or simultaneously in the persulfate oxidation system. To identify the active radical species, a chemical probe method was developed. An excess of probe compounds was added to the system, and differences between the reactivity of the probes and the potential radical species were observed. The usage of various probes, including tert-butyl alcohol, phenol, and nitrobenzene (NB), for simultaneously identifying SO4−•/HO• was investigated. NB can only react with radicals: it cannot react with persulfate. The reaction rate of NB with HO• is 3000−3900 times greater than that of NB with SO4−•, which is a good candidate for use as a probe for differentiating between SO4−•/HO• reactivity. Furthermore, the effects of pH on the formation of SO4−•/HO• were demonstrated by the degradation kinetics of NB at varying pH values. The results indicated that SO4−• is the predominant radical at pH <7; both SO4−• and HO• are present at pH 9; HO• is the predominant radical at a more basic pH (i.e., pH 12). The use of chemical probe NB is a suitable compound for differentiating HO•/SO4−• reactivity. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9002848 [article] Identification of sulfate and hydroxyl radicals in thermally activated persulfate [texte imprimé] / Chenju Liang, Auteur ; Hsin-Wey Su, Auteur . - 2009 . - pp. 5558–5562. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5558–5562 Mots-clés : Thermal  activation  Persulfate  degradation  Chemical  probe  method Résumé : Thermal activation can induce persulfate (S2O82−) degradation to form sulfate radicals (SO4−•) that can undergo radical interconversion to form hydroxyl radicals (HO•) under alkaline conditions. The radicals SO4−•/HO• can be present either individually or simultaneously in the persulfate oxidation system. To identify the active radical species, a chemical probe method was developed. An excess of probe compounds was added to the system, and differences between the reactivity of the probes and the potential radical species were observed. The usage of various probes, including tert-butyl alcohol, phenol, and nitrobenzene (NB), for simultaneously identifying SO4−•/HO• was investigated. NB can only react with radicals: it cannot react with persulfate. The reaction rate of NB with HO• is 3000−3900 times greater than that of NB with SO4−•, which is a good candidate for use as a probe for differentiating between SO4−•/HO• reactivity. Furthermore, the effects of pH on the formation of SO4−•/HO• were demonstrated by the degradation kinetics of NB at varying pH values. The results indicated that SO4−• is the predominant radical at pH <7; both SO4−• and HO• are present at pH 9; HO• is the predominant radical at a more basic pH (i.e., pH 12). The use of chemical probe NB is a suitable compound for differentiating HO•/SO4−• reactivity. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9002848

Oxidative degradation of MTBE by pyrite - activated persulfate / Chenju Liang in Industrial & engineering chemistry research, Vol. 49 N° 18 (Septembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 18 (Septembre 2010) . - pp. 8858–8864 Titre : Oxidative degradation of MTBE by pyrite - activated persulfate : proposed reaction pathways Type de document : texte imprimé Auteurs : Chenju Liang, Auteur ; Yi-Yu Guo, Auteur ; Yi-Chi Chien, Auteur Année de publication : 2010 Article en page(s) : pp. 8858–8864 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Oxidative  degradation Résumé : This bench-scale study investigated the feasibility of activated persulfate (S2O82−) oxidation of methyl tert-butyl ether (MTBE), using pyrite (FeS2) as the source of ferrous ion activators. Under the FeS2-activated S2O82− condition, the sulfate free radical (SO4−•) is the predominant reactive species generated. The oxidation reactions were able to completely degrade MTBE when given sufficient doses of FeS2 and S2O82− and sufficient reaction time (e.g., 3 g FeS2/L and 5 g Na2S2O8/L within 4 h) and exhibited generation and subsequent degradation of the primary MTBE degradation intermediate products including tert-butyl formate, tert-butyl alcohol, methyl acetate, and acetone. The detailed reaction mechanism proposed for a SO4−•-driven oxidation process in this paper indicates that the destruction of MTBE most likely happens through α-hydrogen abstraction via attack of the SO4−• at the intermediate methoxy group. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100740d [article] Oxidative degradation of MTBE by pyrite - activated persulfate : proposed reaction pathways [texte imprimé] / Chenju Liang, Auteur ; Yi-Yu Guo, Auteur ; Yi-Chi Chien, Auteur . - 2010 . - pp. 8858–8864. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 18 (Septembre 2010) . - pp. 8858–8864 Mots-clés : Oxidative  degradation Résumé : This bench-scale study investigated the feasibility of activated persulfate (S2O82−) oxidation of methyl tert-butyl ether (MTBE), using pyrite (FeS2) as the source of ferrous ion activators. Under the FeS2-activated S2O82− condition, the sulfate free radical (SO4−•) is the predominant reactive species generated. The oxidation reactions were able to completely degrade MTBE when given sufficient doses of FeS2 and S2O82− and sufficient reaction time (e.g., 3 g FeS2/L and 5 g Na2S2O8/L within 4 h) and exhibited generation and subsequent degradation of the primary MTBE degradation intermediate products including tert-butyl formate, tert-butyl alcohol, methyl acetate, and acetone. The detailed reaction mechanism proposed for a SO4−•-driven oxidation process in this paper indicates that the destruction of MTBE most likely happens through α-hydrogen abstraction via attack of the SO4−• at the intermediate methoxy group. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100740d

Treatment of trichloroethylene by adsorption and persulfate oxidation in batch studies / Chenju Liang in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8373–8380 Titre : Treatment of trichloroethylene by adsorption and persulfate oxidation in batch studies Type de document : texte imprimé Auteurs : Chenju Liang, Auteur ; Ya-Ting Lin, Auteur ; Wu-Hang Shih, Auteur Année de publication : 2010 Article en page(s) : pp. 8373–8380 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Trichloroethylene  Activated  carbon Résumé : For remediation of trichloroethylene (TCE) contaminated groundwater, activated carbon (AC) has been used to adsorb and reduce the TCE concentration and to manage contaminant migration. Additionally, AC may also act as an activator of the electron-transfer mediator in activating persulfate anion (S2O82−) to generate sulfate radical (SO4−·) for contaminant destruction. The objective of the present research was to examine the combined use of AC and persulfate to treat TCE. The degradation of persulfate in the presence of AC follows a first-order kinetic behavior, and the faster persulfate degradation is observed when elevated AC dosage is used. Higher initial persulfate concentration results in a decrease of the persulfate degradation rate. Upon persulfate oxidation, the AC surface properties are altered including: an increase in acidity of surface concentration, a decrease in pHzpc, and a slight decrease in the surface area. The results of a study of adsorption kinetics and isotherms suggest that the adsorption behavior for the original AC fits the pseudo-second-order kinetic model while the pseudo-first-order kinetic model is suitable for predicting oxidized AC performance. During the persulfate oxidation of TCE with AC as an activator, studies show that TCE removal can be a net result of adsorption and oxidation, in which a partial mineralization of TCE to release chloride occurs. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900841k [article] Treatment of trichloroethylene by adsorption and persulfate oxidation in batch studies [texte imprimé] / Chenju Liang, Auteur ; Ya-Ting Lin, Auteur ; Wu-Hang Shih, Auteur . - 2010 . - pp. 8373–8380. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8373–8380 Mots-clés : Trichloroethylene  Activated  carbon Résumé : For remediation of trichloroethylene (TCE) contaminated groundwater, activated carbon (AC) has been used to adsorb and reduce the TCE concentration and to manage contaminant migration. Additionally, AC may also act as an activator of the electron-transfer mediator in activating persulfate anion (S2O82−) to generate sulfate radical (SO4−·) for contaminant destruction. The objective of the present research was to examine the combined use of AC and persulfate to treat TCE. The degradation of persulfate in the presence of AC follows a first-order kinetic behavior, and the faster persulfate degradation is observed when elevated AC dosage is used. Higher initial persulfate concentration results in a decrease of the persulfate degradation rate. Upon persulfate oxidation, the AC surface properties are altered including: an increase in acidity of surface concentration, a decrease in pHzpc, and a slight decrease in the surface area. The results of a study of adsorption kinetics and isotherms suggest that the adsorption behavior for the original AC fits the pseudo-second-order kinetic model while the pseudo-first-order kinetic model is suitable for predicting oxidized AC performance. During the persulfate oxidation of TCE with AC as an activator, studies show that TCE removal can be a net result of adsorption and oxidation, in which a partial mineralization of TCE to release chloride occurs. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900841k