The electrochemical behavior of Pd(Ⅱ) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid has been studied on Pt working electrodes at 298 K by cyclic voltammetry(CV), polarization curve and galvanostatic transient techniques.Cycli...The electrochemical behavior of Pd(Ⅱ) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid has been studied on Pt working electrodes at 298 K by cyclic voltammetry(CV), polarization curve and galvanostatic transient techniques.Cyclic voltammogram of Pd(II) in [EMIm]NTf2consists of two cathodic current peaks located at 1.37 V(E pc2),corresponding to Pd2+/Pd+, and at 0.69 V(E pc1) corresponding to Pd+/Pd. The transfer coefficient α was calculated by the Tafel extrapolation from the polarization curves to be 0.306, which is in agreement with the value reported in an aqueous solution system. For Rh(Ⅲ) in [EMIm]NTf2, a cathodic current peak(E pc) was observed at-0.39 V, corresponding to Rh3+/Rh, and two oxidation peaks were observed at-0.13 V(E pa1) and0.37 V(E pa2) during the reverse scan. A significantly negative shift in the cathodic peak potential was observed with the increase of the scan rate, indicating that the reduction of Pd(II) and Rh(Ⅲ) on the Pt electrode involves kinetic complications. By using the galvanostatic transient technique, the diffusion coefficients of Pd(II) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid solution were found to be ～ 10-7cm2/s. The potential difference between the reduction of Pd(II) to Pd and the reduction of Rh(Ⅲ) to Rh obtained from the CV curves of the Pd(II) and Rh(Ⅲ) co-existing [EMIm]NTf2solution is found to be about 0.74 V, which makes it possible to electrodeposit Pd(II) and Rh(Ⅲ) separately.展开更多
The adsorption behavior of241Am(Ⅲ) and Eu(Ⅲ) by silica/polymer-based iso Hex-BTP adsorbent(iso HexBTP/Si O2-P) was investigated by a batch experiment method. iso Hex-BTP/Si O2-P exhibited high affinity and selectivi...The adsorption behavior of241Am(Ⅲ) and Eu(Ⅲ) by silica/polymer-based iso Hex-BTP adsorbent(iso HexBTP/Si O2-P) was investigated by a batch experiment method. iso Hex-BTP/Si O2-P exhibited high affinity and selectivity for241Am(Ⅲ) over152Eu(Ⅲ) in 2–4 mol/dm3 nitric acid solutions. Within the experimental contact time range of 0.5–24 h, iso Hex-BTP/Si O2-P showed high selectivity for241Am(Ⅲ) compared to152Eu(Ⅲ) in3 mol/dm3 nitric acid solution. However, the adsorption kinetics of241Am(Ⅲ) and152Eu(Ⅲ) was slow. Eu(Ⅲ)adsorption followed the pseudo-second-order kinetic model, indicating chemical adsorption as the rate-limiting step of the adsorption process. And the adsorption agreed well with the Langmuir adsorption model at various temperatures. The adsorption kinetics and isotherm data indicated that the equilibrium adsorption capacity, the adsorption rate, the maximum adsorption capacity and the adsorption affinity, increased with temperature. The thermodynamic parameters, negative change in Gibbs free energy, and positive change in enthalpy and entropy,suggested that the adsorption of Eu(Ⅲ) was spontaneous and endothermic process with an increase of entropy.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.91026019 and 91126006)
文摘The electrochemical behavior of Pd(Ⅱ) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid has been studied on Pt working electrodes at 298 K by cyclic voltammetry(CV), polarization curve and galvanostatic transient techniques.Cyclic voltammogram of Pd(II) in [EMIm]NTf2consists of two cathodic current peaks located at 1.37 V(E pc2),corresponding to Pd2+/Pd+, and at 0.69 V(E pc1) corresponding to Pd+/Pd. The transfer coefficient α was calculated by the Tafel extrapolation from the polarization curves to be 0.306, which is in agreement with the value reported in an aqueous solution system. For Rh(Ⅲ) in [EMIm]NTf2, a cathodic current peak(E pc) was observed at-0.39 V, corresponding to Rh3+/Rh, and two oxidation peaks were observed at-0.13 V(E pa1) and0.37 V(E pa2) during the reverse scan. A significantly negative shift in the cathodic peak potential was observed with the increase of the scan rate, indicating that the reduction of Pd(II) and Rh(Ⅲ) on the Pt electrode involves kinetic complications. By using the galvanostatic transient technique, the diffusion coefficients of Pd(II) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid solution were found to be ～ 10-7cm2/s. The potential difference between the reduction of Pd(II) to Pd and the reduction of Rh(Ⅲ) to Rh obtained from the CV curves of the Pd(II) and Rh(Ⅲ) co-existing [EMIm]NTf2solution is found to be about 0.74 V, which makes it possible to electrodeposit Pd(II) and Rh(Ⅲ) separately.
基金Supported by National Natural Science Foundation of China(Nos.11305102,91126006,21261140335 and 91226111)Doctoral Fund of Ministry of Education of China(No.20130073110046)
文摘The adsorption behavior of241Am(Ⅲ) and Eu(Ⅲ) by silica/polymer-based iso Hex-BTP adsorbent(iso HexBTP/Si O2-P) was investigated by a batch experiment method. iso Hex-BTP/Si O2-P exhibited high affinity and selectivity for241Am(Ⅲ) over152Eu(Ⅲ) in 2–4 mol/dm3 nitric acid solutions. Within the experimental contact time range of 0.5–24 h, iso Hex-BTP/Si O2-P showed high selectivity for241Am(Ⅲ) compared to152Eu(Ⅲ) in3 mol/dm3 nitric acid solution. However, the adsorption kinetics of241Am(Ⅲ) and152Eu(Ⅲ) was slow. Eu(Ⅲ)adsorption followed the pseudo-second-order kinetic model, indicating chemical adsorption as the rate-limiting step of the adsorption process. And the adsorption agreed well with the Langmuir adsorption model at various temperatures. The adsorption kinetics and isotherm data indicated that the equilibrium adsorption capacity, the adsorption rate, the maximum adsorption capacity and the adsorption affinity, increased with temperature. The thermodynamic parameters, negative change in Gibbs free energy, and positive change in enthalpy and entropy,suggested that the adsorption of Eu(Ⅲ) was spontaneous and endothermic process with an increase of entropy.
