The thermally activated persulfate （PS） degradation of carbon tetrachloride （CT） in the presence of formic acid （FA） was investigated. The results indicated that CT degradation followed a zero order kinetic mode...The thermally activated persulfate （PS） degradation of carbon tetrachloride （CT） in the presence of formic acid （FA） was investigated. The results indicated that CT degradation followed a zero order kinetic model, and CO2^- was responsible for the degradation of CT confirmed by radical scavenger tests. CT degradation rate increased with increasing PS or FA dosage, and the initial CT had no effect on CT degradation rate. However, the initial solution pH had effect on the degradation of CT, and the best CT degradation occurred at initial pH 6. Cl^- had a negative effect on CT degradation, and high concentration of Cl^- displayed much strong inhibition. Ten mmol·L^-1HCO3^- promoted CT degradation, while 100mmol·L^-1NO3^- inhibited the degradation of CT, but SO4^2- promoted CT degradation in the presence of FA. The measured Cl^- concentration released into solution along with CT degradation was 75.8% of the total theoretical dechlorination yield, but no chlorinated intermediates were detected. The split of C-Cl was proposed as the possible reaction pathways in CT degradation. In conclusion, this study strongly demonstrated that the thermally activated PS system in the presence of FA is a promising technique in in situ chemical oxidation （ISCO） remediation for CT contaminated site.展开更多
Trichloroethene （TCE） degradation by Fe（III）- activated calcium peroxide （CP） in the presence of citric acid （CA） in aqueous solution was investigated. The results demonstrated that the presence of CA enhanced...Trichloroethene （TCE） degradation by Fe（III）- activated calcium peroxide （CP） in the presence of citric acid （CA） in aqueous solution was investigated. The results demonstrated that the presence of CA enhanced TCE degradation significantly by increasing the concen- tration of soluble Fe（III） and promoting H202 generation. The generation of HO· and O2^-· in both the CP/Fe（III） and CP/Fe（III）/CA systems was confirmed with chemical probes. The results of radical scavenging tests showed that TCE degradation was due predominantly to direct oxidation by HO·, while O2^-· strengthened the generation of HO· by promoting Fe（III） transformation in the CP/Fe （III）/CA system. Acidic pH conditions were favorable for TCE degradation, and the TCE degradation rate decreased with increasing pH. The presence of Cl·-, HCO3·-, and humic acid （HA） inhibited TCE degradation to different extents for the CP/Fe（III）/CA system. Analysis of Cl·- production suggested that TCE degradation in the CP/Fe （III）/CA system occurred through a dechlorination process. In summary, this study provided detailed information for the application of CA-enhanced Fe（III）-activated calcium peroxide for treating TCE contaminated groundwater.展开更多
基金This study was financially supported by a grant from the National Natural Science Foundation of China （Grant Nos. 41373094 and 51208199）.
文摘The thermally activated persulfate （PS） degradation of carbon tetrachloride （CT） in the presence of formic acid （FA） was investigated. The results indicated that CT degradation followed a zero order kinetic model, and CO2^- was responsible for the degradation of CT confirmed by radical scavenger tests. CT degradation rate increased with increasing PS or FA dosage, and the initial CT had no effect on CT degradation rate. However, the initial solution pH had effect on the degradation of CT, and the best CT degradation occurred at initial pH 6. Cl^- had a negative effect on CT degradation, and high concentration of Cl^- displayed much strong inhibition. Ten mmol·L^-1HCO3^- promoted CT degradation, while 100mmol·L^-1NO3^- inhibited the degradation of CT, but SO4^2- promoted CT degradation in the presence of FA. The measured Cl^- concentration released into solution along with CT degradation was 75.8% of the total theoretical dechlorination yield, but no chlorinated intermediates were detected. The split of C-Cl was proposed as the possible reaction pathways in CT degradation. In conclusion, this study strongly demonstrated that the thermally activated PS system in the presence of FA is a promising technique in in situ chemical oxidation （ISCO） remediation for CT contaminated site.
基金This study was financially supported by the National Natural Science Foundation of China （Grant Nos. 41373094 and 51208199）, China Postdoctoral Science Foundation （No. 2015M570341） and the Fundamental Research Funds for the Central Universities （No. 22A2015 14057）. The contributions of Dr. Mark Brusseau were supported by the NIEHS Superfund Research Program （P42 ES04940）.
文摘Trichloroethene （TCE） degradation by Fe（III）- activated calcium peroxide （CP） in the presence of citric acid （CA） in aqueous solution was investigated. The results demonstrated that the presence of CA enhanced TCE degradation significantly by increasing the concen- tration of soluble Fe（III） and promoting H202 generation. The generation of HO· and O2^-· in both the CP/Fe（III） and CP/Fe（III）/CA systems was confirmed with chemical probes. The results of radical scavenging tests showed that TCE degradation was due predominantly to direct oxidation by HO·, while O2^-· strengthened the generation of HO· by promoting Fe（III） transformation in the CP/Fe （III）/CA system. Acidic pH conditions were favorable for TCE degradation, and the TCE degradation rate decreased with increasing pH. The presence of Cl·-, HCO3·-, and humic acid （HA） inhibited TCE degradation to different extents for the CP/Fe（III）/CA system. Analysis of Cl·- production suggested that TCE degradation in the CP/Fe （III）/CA system occurred through a dechlorination process. In summary, this study provided detailed information for the application of CA-enhanced Fe（III）-activated calcium peroxide for treating TCE contaminated groundwater.
