A rapid and sensitive on-line preconcentration method for spectrophotometric determination of chromium (VI) in nature water is described. Preconcentration and determination are based on (i) the quantitative and fast a...A rapid and sensitive on-line preconcentration method for spectrophotometric determination of chromium (VI) in nature water is described. Preconcentration and determination are based on (i) the quantitative and fast adsorption of chromium (VI) on the high surface area nanometer-size TiO2 (anatase) powders, which prepared by a sol-gel method from hydrolysis of TiCI4 and (ii) the quantitative and reproducible elution of Cr (VI) by 2. 0 mol. L-1 HCI. A mini-column system for preconcentration is developed, Cr(VI)on the mini-column is eluted and merged with a stream water and DPCB (1, 5-diphenylcarbazide ) as the chromogenic reagent. The Proposed system permits throughputs of 6 sample h--l (0. 001 μg mL-1 Cr(VI) ) or 20 sample h-1 (0. 1 μg mL-1Cr (VI) . The preconcentration factor is 55. The detection limit is 0. 8 ng·mL-1 Cr(VI). The reproducibility is satisfactory with a relative standard deviation of less than 3. 35% (0. Of μg'mL-1Cr (VI), n = 5).展开更多
Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of th...Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric analysis was conducted to simulate variations in soil dry density, temperature, pH and standing time. The results show that the method used in this paper is simple and effective. The diffusion coefficient of Cr(Ⅵ) in Dalian red clay varies from 1.50×10-7 cm2/s to 2.08×10-7 cm2/s. After 1 000 d diffusion, the concentration of the source solution drops down to 1.27 mg/L from 62.5 mg/L, and the diffusion distance is only 3.5 cm. Under the assumption that diffusion coefficient is constant, the diffusion effect becomes more obvious with lower density, lower temperature, higher pH value, and much more time.展开更多
Cd Se quantum dots（QDs） were synthesized using diphenylcarbazide（DL） to sequester QDs precursors（Cd^（2＋）） in situ. Fluorescence（FL） analysis showed the successive synthesis of QDs could be realized by cappi...Cd Se quantum dots（QDs） were synthesized using diphenylcarbazide（DL） to sequester QDs precursors（Cd^（2＋）） in situ. Fluorescence（FL） analysis showed the successive synthesis of QDs could be realized by capping with DL and the binding between DL and Cd^（2＋）. The average QDs particle size was about 5-20 nm by high-resolution transmission electron microscopy（HRTEM）. Fourier transform infrared（FT-IR） spectra showed that Cd Se QDs could be chemically bonded with DL. The formation of QDs-DL-Cr（Ⅵ） could lower the fluorescence intensity of QDs. In a certain concentration range, the fluorescence intensity and Cr（Ⅵ） concentration presented a linear relationship. As a result, this phenomenon could be used to determine the Cr（Ⅵ） concentration in the range of 0-24 ×10^（-6） mol· L^（-1）.展开更多
文摘A rapid and sensitive on-line preconcentration method for spectrophotometric determination of chromium (VI) in nature water is described. Preconcentration and determination are based on (i) the quantitative and fast adsorption of chromium (VI) on the high surface area nanometer-size TiO2 (anatase) powders, which prepared by a sol-gel method from hydrolysis of TiCI4 and (ii) the quantitative and reproducible elution of Cr (VI) by 2. 0 mol. L-1 HCI. A mini-column system for preconcentration is developed, Cr(VI)on the mini-column is eluted and merged with a stream water and DPCB (1, 5-diphenylcarbazide ) as the chromogenic reagent. The Proposed system permits throughputs of 6 sample h--l (0. 001 μg mL-1 Cr(VI) ) or 20 sample h-1 (0. 1 μg mL-1Cr (VI) . The preconcentration factor is 55. The detection limit is 0. 8 ng·mL-1 Cr(VI). The reproducibility is satisfactory with a relative standard deviation of less than 3. 35% (0. Of μg'mL-1Cr (VI), n = 5).
基金Supported by National Natural Science Foundation of China (No. 50679015).
文摘Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric analysis was conducted to simulate variations in soil dry density, temperature, pH and standing time. The results show that the method used in this paper is simple and effective. The diffusion coefficient of Cr(Ⅵ) in Dalian red clay varies from 1.50×10-7 cm2/s to 2.08×10-7 cm2/s. After 1 000 d diffusion, the concentration of the source solution drops down to 1.27 mg/L from 62.5 mg/L, and the diffusion distance is only 3.5 cm. Under the assumption that diffusion coefficient is constant, the diffusion effect becomes more obvious with lower density, lower temperature, higher pH value, and much more time.
基金Funded by the “Twelfth-Five Year Plan”the National High-tech Research and Development Program of China(863 Project No.2012AA101404)
文摘Cd Se quantum dots（QDs） were synthesized using diphenylcarbazide（DL） to sequester QDs precursors（Cd^（2＋）） in situ. Fluorescence（FL） analysis showed the successive synthesis of QDs could be realized by capping with DL and the binding between DL and Cd^（2＋）. The average QDs particle size was about 5-20 nm by high-resolution transmission electron microscopy（HRTEM）. Fourier transform infrared（FT-IR） spectra showed that Cd Se QDs could be chemically bonded with DL. The formation of QDs-DL-Cr（Ⅵ） could lower the fluorescence intensity of QDs. In a certain concentration range, the fluorescence intensity and Cr（Ⅵ） concentration presented a linear relationship. As a result, this phenomenon could be used to determine the Cr（Ⅵ） concentration in the range of 0-24 ×10^（-6） mol· L^（-1）.
