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861.
EunHea Jho Naresh Singhal Susan Turner 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(8):1179-1186
BACKGROUND: Tetrachloroethylene (PCE) and hexachloroethane (HCA) degradation, individually and in mixture, is investigated by Fe(III) or Fe(III)‐citrate initiated Fenton reaction under a range of hydrogen peroxide (H2O2) concentrations to illustrate the applicability and constraints of Fenton chemistry in degrading contaminants in polluted groundwater. RESULTS: In individual solutions Fe(III) rapidly degraded PCE for all H2O2 concentrations, but HCA at ≥ 0.2 mol L?1 H2O2; the apparent PCE degradation rate initially increased but then decreased with increasing H2O2, while the HCA degradation rate was either unaffected or increased. With Fe(III)‐citrate PCE degradation was lower and no HCA degradation occurred. PCE degradation was lower in PCE‐HCA mixture, but the trend with H2O2 concentration was similar to the individual chemical; for HCA the residual was smaller for higher H2O2 concentration, but the apparent degradation rate constant was unaffected. CONCLUSION: Fe(III) catalyzed reactions can potentially degrade chemicals through reductive as well as oxidative transformations. Degradation of chemicals in mixtures occurs at a slower rate due to competition for radical moieties. The Fe(III)‐citrate complex further slowed chemical transformation. This study expands on the use of different forms of iron to catalyze the Fenton reaction to degrade chemicals. Copyright © 2012 Society of Chemical Industry 相似文献
862.
Yeong‐Tarng Shieh Jia‐Cing Jho Tzong‐Liu Wang Chien‐Hsin Yang Chean‐Cheng Su 《Polymer International》2011,60(7):1078-1088
Semi‐crystalline poly(L ‐lactic acid) (PLLA) was physically aged below the glass transition temperature for various times to investigate its amorphous phase behavior. During a differential scanning calorimetry heating scan, dual enthalpy recovery endotherms were found to appear in the glass transition region of PLLA, aged at 52 °C, of a particular degree of crystallinity (Xc) within a definite range. Below the lower Xc limit, only the low endotherm corresponding to the free amorphous phase was observed; above the upper Xc limit, only the high endotherm corresponding to the constrained amorphous phase was observed. Dual tan δ peaks in dynamic mechanical analysis confirmed the coexistence of the dual amorphous phases. Both lower and upper limits of the Xc range increased with an increase in isothermal crystallization temperature from the melt. Long‐term physical aging at 52 °C, which did not affect Xc, allowed the evolution of the free amorphous phase to the constrained amorphous phase in PLLA with Xc within the definite range. The effects of physical aging at various temperatures on the enthalpy recovery endotherms were also investigated. Copyright © 2011 Society of Chemical Industry 相似文献