采用离子色谱电导检测法测定皮革制品中Cr（Ⅳ），选用Metrohm86I型离子色谱仪，Metrosep A Supp5—150型阴离子分析柱，12．8mmol／LNa2C03＋4．0mmol／LNaHC03淋洗液．在10～100μg／L范围内，Cr（Ⅳ）的浓度与色谱峰面积呈线性关系...采用离子色谱电导检测法测定皮革制品中Cr（Ⅳ），选用Metrohm86I型离子色谱仪，Metrosep A Supp5—150型阴离子分析柱，12．8mmol／LNa2C03＋4．0mmol／LNaHC03淋洗液．在10～100μg／L范围内，Cr（Ⅳ）的浓度与色谱峰面积呈线性关系，线性方程为C×100—2893．72×A＋200．136，相关系数为0．9990，最低检测浓度为4μg／L，低、中、高三个浓度的精密度分别为1．60％、1．05％、0．65％，样品加标回收率分别为91．5％、93．6％和92．3％，本方法可用于皮革中Cr（Ⅵ）的测定．展开更多
The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetic...The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.展开更多
The kinetics and mechanism of lactic acid oxidation in the presence of Mn(II)and Ce(IV)ions by chromic acid were studied spectrophotometrically.The oxidation of lactic acid by Cr(VI)was found to proceed in two measura...The kinetics and mechanism of lactic acid oxidation in the presence of Mn(II)and Ce(IV)ions by chromic acid were studied spectrophotometrically.The oxidation of lactic acid by Cr(VI)was found to proceed in two measurable steps,both of which gave pyruvic acid as the primary product in the absence of Mn(II).2Cr(VI)+2CH3CHOHCOOH→2CH3COCOOH+Cr(V)+Cr(III)Cr(V)+CH3CHOHCOOH→Cr(III)+CH3COCOOH The observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II)and Ce(IV)on the lactic acid oxidation by Cr(VI).The reactivity of lactic acid depends upon the experimental conditions.It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II).It was examined that Cr(III)products resulting from the direct reduction of Cr(VI)by three-equivalent reducing agents.The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid].The activation parameters Ea,ΔH#,and ΔS# were calculated and discussed.展开更多
文摘采用离子色谱电导检测法测定皮革制品中Cr（Ⅳ），选用Metrohm86I型离子色谱仪，Metrosep A Supp5—150型阴离子分析柱，12．8mmol／LNa2C03＋4．0mmol／LNaHC03淋洗液．在10～100μg／L范围内，Cr（Ⅳ）的浓度与色谱峰面积呈线性关系，线性方程为C×100—2893．72×A＋200．136，相关系数为0．9990，最低检测浓度为4μg／L，低、中、高三个浓度的精密度分别为1．60％、1．05％、0．65％，样品加标回收率分别为91．5％、93．6％和92．3％，本方法可用于皮革中Cr（Ⅵ）的测定．
基金Project(50321402) supported by the National Natural Science Foundation of China
文摘The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.
文摘The kinetics and mechanism of lactic acid oxidation in the presence of Mn(II)and Ce(IV)ions by chromic acid were studied spectrophotometrically.The oxidation of lactic acid by Cr(VI)was found to proceed in two measurable steps,both of which gave pyruvic acid as the primary product in the absence of Mn(II).2Cr(VI)+2CH3CHOHCOOH→2CH3COCOOH+Cr(V)+Cr(III)Cr(V)+CH3CHOHCOOH→Cr(III)+CH3COCOOH The observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II)and Ce(IV)on the lactic acid oxidation by Cr(VI).The reactivity of lactic acid depends upon the experimental conditions.It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II).It was examined that Cr(III)products resulting from the direct reduction of Cr(VI)by three-equivalent reducing agents.The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid].The activation parameters Ea,ΔH#,and ΔS# were calculated and discussed.
