In this study, the kinetics and mechanism of the iridium（ Ⅲ ） -catalyzed oxidation of ethanol amine（EAN） by cerium（Ⅳ） in a sulfuric acid medium was investigated using titrimetric technique of redox in a temper...In this study, the kinetics and mechanism of the iridium（ Ⅲ ） -catalyzed oxidation of ethanol amine（EAN） by cerium（Ⅳ） in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298--313 K. It was found that the reaction is of first order with respect to Ce（ Ⅳ ） and It（ Ⅲ ）, and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order （ [EAN ] 〉〉 [ Ce （ Ⅳ） ] ） rate constant koba decreases with the increase of [ H^＋ ] and [ HSO^-4 ]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of koba on the concentration of hydrogen sulfate, Ce（SO4）2 was found to be the kinetically active species. The rate constants of the rote-determining step together with the activation parameters were evaluated.展开更多
Tributyl phosphate （TBP） solvent was used for impregnation into Amberlite XAD-16 nonionic polymeric resin beads using the wet method to prepare solvent impregnated resin （SIR）. Undiluted TBP in a ratio to the resi...Tributyl phosphate （TBP） solvent was used for impregnation into Amberlite XAD-16 nonionic polymeric resin beads using the wet method to prepare solvent impregnated resin （SIR）. Undiluted TBP in a ratio to the resin support （volume to mass） of 6.0 at room temperature （RT） in 24 h was impregnated the resin with a mass ratio of 1.944, while the prepared gross sample of SIR at the ratio of solvent to resin of 3.0 was impregnated with a mass ratio of 1.88. Cerium（Ⅳ） oxide concentrate, prepared from crude Egyptian monazite sand, containing 37% cerium, 1.6% thorium and about 40% the other trivalent rare earth oxides, was used to prepare cerium（Ⅳ） nitrate solution for extraction using the prepared SIR. The impregnated resin was satisfactory for Ce（Ⅳ） extraction from nitric acid medium at room temperature. Cerium loading capacity of the impregnated resin reached 95.6% of the calculated theoretical capacity （173 g/kg （Ce/SIR）） under the conditions of 51.57 g/L cerium and 2.48 g/L thorium, 5.0 mol/L free nitric acid, solution to resin ratio of 10.0 and contacting the phases for 5.0 min. The loading capacity reached 98.75% when cerium concentration was increased to 91.43 g/L under the same conditions.展开更多
A new chemiluminescence (CL) method for the determination of tetracycline and oxytetracycline is developed, hased on the CL reaction of tetracycline and oxytetracycline with Ru(bipy)_3~2+ and Ce(IV). In sulfuric acid ...A new chemiluminescence (CL) method for the determination of tetracycline and oxytetracycline is developed, hased on the CL reaction of tetracycline and oxytetracycline with Ru(bipy)_3~2+ and Ce(IV). In sulfuric acid medium, the CL emission is generated upon continuous oxidation of Ru(bipy)_3~2+ by cerium (IV ). The emission intensity is greatly enhanced when tetracycline and oxytetracycline are introduced into the reaction system after acid degradation. Under the optimum conditions, the calibration curves are linear over the range of 8. 0 X 10^-8^-4. 0 X 10^-6 mol/L for tetracycline and of 2. 0 X 10^-7~4. 0 X 10^-5 mol/L for oxytetracycline, with the detection limits are 4. 2 X 10^-8 mol/L for tetracycline and 1. 5 X 10^-7 mol/L for oxytetracycline, respectively. The proposed method was used for the determination of tetracycline and oxytetracycline in pharmaceutical formulations with good results.展开更多
The solubility product constant of cerium(Ⅳ) phosphate according to the concentration of phosphate detected by spectrophotometer at pH=0.4 and 20 ℃ were determined. The solubility product constant of cerium(Ⅳ) phos...The solubility product constant of cerium(Ⅳ) phosphate according to the concentration of phosphate detected by spectrophotometer at pH=0.4 and 20 ℃ were determined. The solubility product constant of cerium(Ⅳ) phosphate is 2.915×10 -34. The reliability of determination data is proved by s=0.004 and CV=1.30%. The result indicate that solubility product constant of cerium(Ⅳ) phosphate is effected by temperature and acidity significantly. Therefore, temperature and acidity increase over a particular range could result in an increase of solubility of cerium(Ⅳ) phosphate.展开更多
基金Supported by the Doctoral Foundation of Education Department of Hebei Province(NoB2004205) Hebei University Re-search Foundation(No2003Z09)
文摘In this study, the kinetics and mechanism of the iridium（ Ⅲ ） -catalyzed oxidation of ethanol amine（EAN） by cerium（Ⅳ） in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298--313 K. It was found that the reaction is of first order with respect to Ce（ Ⅳ ） and It（ Ⅲ ）, and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order （ [EAN ] 〉〉 [ Ce （ Ⅳ） ] ） rate constant koba decreases with the increase of [ H^＋ ] and [ HSO^-4 ]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of koba on the concentration of hydrogen sulfate, Ce（SO4）2 was found to be the kinetically active species. The rate constants of the rote-determining step together with the activation parameters were evaluated.
文摘Tributyl phosphate （TBP） solvent was used for impregnation into Amberlite XAD-16 nonionic polymeric resin beads using the wet method to prepare solvent impregnated resin （SIR）. Undiluted TBP in a ratio to the resin support （volume to mass） of 6.0 at room temperature （RT） in 24 h was impregnated the resin with a mass ratio of 1.944, while the prepared gross sample of SIR at the ratio of solvent to resin of 3.0 was impregnated with a mass ratio of 1.88. Cerium（Ⅳ） oxide concentrate, prepared from crude Egyptian monazite sand, containing 37% cerium, 1.6% thorium and about 40% the other trivalent rare earth oxides, was used to prepare cerium（Ⅳ） nitrate solution for extraction using the prepared SIR. The impregnated resin was satisfactory for Ce（Ⅳ） extraction from nitric acid medium at room temperature. Cerium loading capacity of the impregnated resin reached 95.6% of the calculated theoretical capacity （173 g/kg （Ce/SIR）） under the conditions of 51.57 g/L cerium and 2.48 g/L thorium, 5.0 mol/L free nitric acid, solution to resin ratio of 10.0 and contacting the phases for 5.0 min. The loading capacity reached 98.75% when cerium concentration was increased to 91.43 g/L under the same conditions.
基金the National Natural Science Foundation of China the Natural Science Foundation of Hubei Province
文摘A new chemiluminescence (CL) method for the determination of tetracycline and oxytetracycline is developed, hased on the CL reaction of tetracycline and oxytetracycline with Ru(bipy)_3~2+ and Ce(IV). In sulfuric acid medium, the CL emission is generated upon continuous oxidation of Ru(bipy)_3~2+ by cerium (IV ). The emission intensity is greatly enhanced when tetracycline and oxytetracycline are introduced into the reaction system after acid degradation. Under the optimum conditions, the calibration curves are linear over the range of 8. 0 X 10^-8^-4. 0 X 10^-6 mol/L for tetracycline and of 2. 0 X 10^-7~4. 0 X 10^-5 mol/L for oxytetracycline, with the detection limits are 4. 2 X 10^-8 mol/L for tetracycline and 1. 5 X 10^-7 mol/L for oxytetracycline, respectively. The proposed method was used for the determination of tetracycline and oxytetracycline in pharmaceutical formulations with good results.
文摘The solubility product constant of cerium(Ⅳ) phosphate according to the concentration of phosphate detected by spectrophotometer at pH=0.4 and 20 ℃ were determined. The solubility product constant of cerium(Ⅳ) phosphate is 2.915×10 -34. The reliability of determination data is proved by s=0.004 and CV=1.30%. The result indicate that solubility product constant of cerium(Ⅳ) phosphate is effected by temperature and acidity significantly. Therefore, temperature and acidity increase over a particular range could result in an increase of solubility of cerium(Ⅳ) phosphate.
