Solvent extraction of neodymium（III） from acidic nitrate medium using Cyanex 921 in kerosene

The extraction of neodymium(Ⅲ) from acidic nitrate medium was investigated using Cyanex 921 as extractant in kerosene. The metal concentration in the aqueous phase before and after extraction was determined spectrophotometrically by Arsenazo Ⅲ method. The complete equilibration was achieved in 15 min. The effects of shaking time, nitric acid concentration, nitrate concentration, extractant concentration, and temperature on the extraction were studied. The extraction of Nd(Ⅲ) was found to increase very slowly with increase in concentration of HNO3 in the range of 0.001-0.008 mol/L and then decreased when 0.01 mol/L HNO3 was used. The percentage of extraction was increased with increase in nitrate concentration from 0.01-0.45 mol/L and then decreased when nitrate concentration increased to 0.5 mol/L. Quantitative extraction of Nd(Ⅲ) (98%) was obtained from the aqueous phase containing 0.001 mol/L HNO3 and 0.1 mol/L KNO3 using 0.5 mol/L Cyanex 921. On the basis of slope analysis, the extracted complex in the organic phase was proposed to be Nd(NO3)3.2Cyanex 921. The extraction of Nd(III) was found to increase with increase in concentration of metal ion in the range of 0.001-0.05 mol/L from 0.001 mol/L HNO3 and 0.1 mol/L KNO3 with 0.1 mol/L Cyanex 921. The percentage of extraction of neodymium was found to decrease with increase in temperature. From temperature variation studies, the negative value of △H indicated the extraction reaction to be exothermic and the negative value of △S indicated the formation of a stable complex. Almost 100% Nd(Ⅲ) was recovered from the fully loaded organic phase using 0.002 mol/L H2SO4 and 0.01 mol/L HCl.     

Electrochemical behavior of Y(Ⅲ) and preparation of Y-Ni intermetallic compounds in molten LiCl-KCl salts

The work concerned the electrochemical behaviors of Y(Ⅲ) on W and Ni electrodes in molten LiCl-KCl salts by a series of electrochemical techniques. The electrochemical reaction of Y(Ⅲ) to Y(0) proceeded in a one-step reduction process with the exchange of three electrons, Y(Ⅲ)+3e~–→Y(0). Compared with the cyclic voltammogram and square wave voltammogram obtained on W electrode, the reduction potential of Y(Ⅲ) on Ni electrode was observed at less negative potential than the one of Y(Ⅲ) to give pure Y metal on W electrode, which revealed the occurrence of underpotential deposition of Y(Ⅲ) on Ni electrode. Electromotive force(emf) measurements were performed to calculate the relative partial molar Gibbs energies and activities of Y in Y-Ni alloys. The standard Gibbs energies of formation for different Y-Ni intermetallic compounds were also estimated. The different Y-Ni alloys were formed by potentiostatic electrolysis at different potentials and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), and energy dispersive spectrometry(EDS). It was found that four intermetallic compounds, YNi_5, Y_2Ni_7, YNi_3 and YNi_2, were selectively produced by controlling applied potential.     

Voltammetric determination of venlafaxine as an antidepressant drug employing Gd2O3 nanoparticles graphite screen printed electrode

Graphite screen printed electrode modified with Gd_2 O_3 nanoparticles(Gd_2 O_3/SPE) was developed for the determination of venlafaxine(VF). The Gd_2 O_3 nanoparticles were thoroughly characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses. To study the electrochemical behaviour of venlafaxine cyclic voltammetry(CV), chronoamperometry(CHA)and differential pulse voltammetry(DPV) were employed. These studies reveal that the oxidation of venlafaxine is facilitated at Gd_2 O_3/SPE. After optimization of analytical conditions, analysis of venlafaxine using the modified electrode in 0.1 mol/L PBS(pH 7.0) demonstrates that the peak currents corresponding to venlafaxine vary linearly with its concentration in the range of 5.0 ×10~(-6)-9.0 × 10~(-4) mol/L. The detection limit(S/N = 3) of 2.1 × 10~(-7) mol/L is obtained for venlafaxine using DPV. The prepared modified electrode benefits from advantages such as simple preparation method, high sensitivity and low detection limit.Moreover, the evaluation of practical applicability of this proposed method is successful in the identification of venlafaxine in pharmaceutical formulations, urine and water samples.     

Biosorption potential of cerium ions using Spirulina biomass

Two types of cyanobacteria of the genus Arthrospira(commonly known as Spirulina) were tested for biosorption of cerium(III) ions from aqueous solutions. An endemic type(ES) found in the northern Negev desert, Israel, and a commercial powder(CS) were used in this study. Biosorption was evaluated as a function of p H, contact time, initial metal concentration, number of sorption-desorption cycles, and salt concentration. The optimum p H range for biosorption was found to be 5.0–5.5. The kinetic characteristics of both Spirulina types were found to be highly compatible with a pseudo-second order kinetic model. The adsorption isotherms of both types were found to be well-suited to Langmuir and Freundlich adsorption isotherms. Maximum biosorption uptakes, according to the Langmuir model, were 18.1 and 38.2 mg/g, for ES and CS, respectively. Sodium chloride concentrations of up to 5 g/L had a minor effect on cerium biosorption. Desorption efficiency was found to be greater than 97% with 0.1 mol/L HNO_3 after three sorption-desorption cycles, without significant loss in the biosorption capacity. The results indicated the feasibility of cerium recovery from industrial wastes using Spirulina biomass.     

THE MECHANISM OF ELECTROREDUCTION OF NEODYMIUM IN MOLTEN CHLORIDES

The cathodic reduction of neodymium ion has been studied using voltammetry and chronopotentiometrymethods in KCl-NaCl-NdCl_3 melt saturated by metallic neodymium.The electrode reaction of cathodic re-duction of Nd ion has been found to be Nd~2 2e→Nd in this molten salt system,and the reaction is a rever-sible and diffusion-controlled process.The electrochemical reduction potential of Nd is about-3.2V(versuschlorine reference electrode).     

Electrochemical Behavior of Dissolved Fe2O3 in Molten CaCl2KF

he electrochemical behavior of dissolved Fe2O3 in 825CaCl2175KF (mole percent, %) was studied using cyclic voltammetry, chronoamperometry, and galvanostatic electrolysis at 827 ℃, and the deposits were characterized by XRD and SEM. Pure iron was deposited on a rotating cylinder (210 r/min) with a cell voltage less than -10 V. Deposition rate was controlled by diffusion on a molybdenum electrode. The diffusion coefficient of iron species Fe(Ⅲ) in the melt at 827 ℃ was found to be 97×10-5 cm2/s.     

A novel Ce(Ⅳ) ion-selective polyvinyl chloride membrane electrode based on HDEHP and HEH/EHP

A novel Ce(Ⅳ) ion-selective polyvinyl chloride(PVC) membrane electrode based on HDEHP and HEH/EHP as ionophore was successfully prepared. The factors affecting the response of Ce(Ⅳ) ion were investigated, such as membrane composition, internal solution, concentration of SO_4~(2–), and acidity in test solution. The best performance was obtained using the membrane with PVC:DBP:HDEHP:HEH/EHP:OA mass ratio of 75:175:5:5:5. The proposed electrode exhibited a Nernstian slope of 30.44 mV/decade for Ce(Ⅳ) ion over a linear concentration range of 1×10~(–5)–1×10~(–1) mol/L with the detection limit of 9.0×10~(-6) mol/L. The electrode showed stable response within the SO_4~(2–) concentration range of 0.1–1 mol/L and the acidity range of 0.25–1.2 mol/L H+. The proposed electrode showed high selectivity for Ce(Ⅳ) over a wide variety of interfering ions and a fast response time. It was used as an indicator in the potentiometric titration of Ce(Ⅳ) solution with H_2O_2 solution, and could also be used for the determination of Ce(Ⅳ) in real Ce(Ⅳ)-containing aqueous samples.     

Electrochemical behavior of cerium（IV） in a RTIL and its mixture with ethanol

A systematic study was carried out to explore the electrochemical behavior of Ce in room temperature ionic liquid（CnmimBr, where n=6, 8, 10） and mixture of C6 mimBr and ethanol by cyclic voltammetry. With increase in the number of carbon atoms on the alkyl substituent on methyl imidazolium cation, the electrochemical window of the ionic liquids was found to extend towards more negative potential value, as a result there was a possibility of reduction of Ce to lower oxidation states. The diffusion coefficient and activation energy for the diffusion were calculated in all the ionic liquids and one of their mixtures with ethanol. With increase in n value, the diffusion coefficient of Ce decreased due to increase in viscosity of the medium while the activation energy for the diffusion followed a reverse trend for C6 mimBr, C8 mimBr and C10 mimBr, respectively. The observations indicated that the nature of species of Ce might be different in room temperature ionic liquids（RTILs） from that present in their mixtures with ethanol.     

Electrode process of La(Ⅲ) in molten LiCl-KCl

The electrode process of La(Ⅲ) at Mo electrode in the molten LiCl-KCl for temperatures ranging from 683 K to 773 K was studied by cyclic voltammetry and chronopotentiometry,respectively.The results showed that in the molten LiCl-KCl,reduction of La(Ⅲ) occurred in a step with a global exchange of three electrons.Cyclic voltammetry studies indicated that at a sweep rate lower than 0.2 V/s,the electroreduction of La(Ⅲ) to lanthanum metal was reversible and controlled by diffusion of La(Ⅲ).However,the process b...     

Electrochemical behavior of Ce（III） in LiF-BaF2 melts

The electrochemical behavior of Ce(III) was investigated in the molten LiF-BaF2 (81 mol.%-19 mol.%) on a molybdenum elec-trode in the temperature range of 1098-1188 K using cyclic voltammetry and chronopotentiometry. It was observed that CeF3 could be re-duced into cerium metal in a reversible one-step process exchanging three electrons (Ce(III)+3e-→Ce(0)) at the operating temperatures on a molybdenum cathode. The electrochemical reduction process was controlled by the diffusion of Ce(III) in the solution. The Ce(III) diffusion coefficients were calculated at different temperatures and the values obeyed the Arrhenius law with an activation energy of 87.5 kJ/mol.     

Electrochemical behavior of dysprosium(Ⅲ) in eutectic LiF-DyF_3 at tungsten and copper electrodes

Electrochemical behavior of dysprosium(Dy) ions in LiF-DyF_3(24 mol%) was investigated by cyclic voltammetry,chronoamperometry and chronopotentiometry.Dy-Cu alloy samples were prepared by constant-potential electrolysis in LiF-DyF_3(24 mol%) at the Cu electrode.The Cu_5 Dy and Cu phases were characterized by an X-ray diffractometer and a scanning electron microscope equipped with an energy dispersive spectrometer.The results show that the reduction of Dy(Ⅲ) ions in a LiF-DyF_3(24 mol%)molten salt system is found to be a quasi-reversible diffusion-controlled process which occurs via a onestep reaction involving the transfer of three electrons.The electro-crystallization processes of the Dy metal at the W electrode and the mode of nucleation confirm that progressive nucleation is dominant at high concentrations of Dy ions in the LiF-DyF_3 salt.At lower concentrations,the instantaneous nucleation of Dy with three-dimensional growth of the nuclei is dominant.     

Reduction Mechanism of Scandium Ion in Fluoride Salt Melt

The electrochemical behavior of Sc^3 in LiF - NaF system was investigated. The cyclic voltammetry and chronopotentiometry were used to investigate the reduction mechanism of the electrochemical deposition of Sc^3 to Sc on Ag electrode in LiF-NaF system at 1043 K. Experimental results indicate that the electroreduction of Sc^3 to Sc is a reversible process with simple 3-electron transfer in one step controlled by diffusion.     

Electrochemical studies on cerium(Ⅲ)in molten fluoride mixtures

This study aims to determine the principal electrochemical characteristics of the electrodeposition of cerium metal from molten fluoride systems.The cathodic process of Ce3+ ions in LiF-NaF and LiF-NaF-CaF2 molten salts was studied using electrochemical techniques as steady state and cyclic voltammetry methods.The decomposition potential(Ed) and the overvoltage(η) were determined for NaCeF4 using current-potential curves under galvanostatic conditions.The Ed was found to be 2.025 V in LiF-NaF and 2.045 V in...     

LSM particle size effect on the overall performance of IT-SOFC

In this paper, we reported the fuel cell performance with La0.8Sr0.2MnO3 (LSM)/Ce0.8Sm0.2O1.9 (SDC) composite cathode prepared from LSM powders of different particle sizes via the silk-printing technique. It was found that the change in particle size of LSM nanoparticle from 40 to 90 nm resulted in an increase in the maximum power density from 132 to 228 mW/cm2 at 650 ℃ with H2 as fuel and O2 as oxidant. And the polarization resistance of the electrode decreased from 2.547 to 1.034 Ω·cm2. Concerning the particle size of electrode materials, a higher activity was anticipated with smaller particles because a large number of TPB or electrode surface sites along with a higher porosity could be developed. However, this study showed that the electrode prepared with particles of larger diameter had fine and uniform micro-structure resulting in higher power density and lower overpotential, where homogeneous distribution of particles and pores was beneficial for increasing the electrochemical active area and the electronic conductivity of the electrodes as well as the gas diffusion for the reactants.     

Corrosion protection of magnesium alloys anode by cerium-based anodization coating in magnesium-ait battery

CeN₃O₉·6H₂O(0.5,1.0,1.5,and 2.0 g/L) was added into an 8.0% NaCl electrolyte solution to investigate this electrolyte for use in a Mg-air battery.The effects of the amount of CeN₃O₉-6H₂O on the corrosion resistance of an AZ31 Mg alloy anode and battery performance were investigated using microstructure,electrochemical(dynamic potential polarization method and electrochemical impedance spectroscopy),and battery measurements.The re ...     

Effect of Lanthanum Ion on Peroxidase in Plant

The interaction of MP-11 as a model of antioxidatase enzymes with La^3 was investigated. It was found that La^3 can increase in the non-planarity of heme and the content of α helix and β turn conformations of the MP-11 molecule. The change in the secondary structure of the MP-11 molecule can increase in the exposure extent of heme to the solution. Therefore, the electrochemical reaction of MP-11 is promoted and the eleetrocatalytic activity to the reduction of H2O2 is increased. The results are consistent with that for the interaction of peroxidases(POD),one of the antioxidatase enzymes, obtained in the living plant experiments at low concentration of La^3 .     

Inhibition Performance of EnhancedMo Inhibitor for Carbon Steel in 55% LiBr Solution

The inhibition performance of enhancedMo inhibitor for carbon steel in 55% LiBr solution was measured by means of chemical immersion, electrochemical measurements, and physical detection technologies. Results indicated that enhancedMo inhibitor showed excellent inhibition performance of carbon steel in 55% LiBr solution, especially at high temperature. With increasing the temperature of solution from 160 ℃ to 240 ℃, the corrosion rates of carbon steel increased from 1767 μm/a to 3307 μm/a. EnhancedMo inhibitor might improve the anodic polarization performance of carbon steel and widen the passive potential region of carbon steel in 55% LiBr solution. EnhancedMo inhibitor belongs to anodic inhibitor. In 55% LiBr solution, the relationship between corrosion current density icorr and corrosion potential Ecorr of carbon steel accorded with the equation lgicorr=-266-354Ecorr, and the value of cathodic Tafel constant βc for the H2 reaction was 282 mVSCE. When 55% LiBr solution contained enhancedMo inhibitor, a passive film comprising Fe3O4 and MoO2 was formed on the carbon steel surface by electrochemical reactions. The corrosion of carbon steel might be retarded by this protective film, and the anticorrosion performance of carbon steel in 55% LiBr solution might be improved by enhancedMo inhibitor.     

Adsorption of arsenate and arsenite from aqueous solutions by cerium-loaded cation exchange resin

The removal of arsenic from water and wastewater is obligatory.Resin is one of the most effective adsorbents for the removal of arsenic.In order to improve the adsorption capacity of resin,a new cerium-loaded cation exchange resin arsenic adsorbent was prepared by impregnating cerium into the cation exchange resin.Batch adsorption experiments under various conditions,such as time,temperature,pH and with coexisting ions were carried out to evaluate the adsorption characteristics of cerium-loaded resin in the removal of As(Ⅴ)and As(Ⅲ) from aqueous solutions.The results showed that the adsorption kinetics of As(Ⅴ)and As(Ⅲ)obeyed a pseudo second-order kinetic model and the adsorption rate constants were 0.3159 and 0.5215 g·mg-1 ·min-1 ,respectively.The adsorption of As(Ⅴ)followed the Freundlich adsorption isotherm model and the adsorption isotherm data for As(Ⅲ)fitted well to the Langmuir equation model.The adsorption capacities were 1.0278 mg/g for As(Ⅴ)and 2.5297 mg/g for As(Ⅲ).Both the adsorption of As(Ⅴ)and As(Ⅲ)were found to be pH sensitive and the optimum pH was found to be 5-6.Except for the phosphate ion,the coexisting anionics,such as nitrate,chlorate,sulphate and carbonate,showed no remarkable effect on As(Ⅴ)and As(Ⅲ)adsorption.The desorption and regeneration study showed that the adsorption capacity of Ce-loaded resin for As(Ⅴ)and As(Ⅲ)could be restored to 97.80%and 69.61%,respectively,using 0.5 mol/L sodium hydroxide solution.     

Activity improvement of Pt/C catalysts by adding CeO2 nanoparticles

Carbon-supported platinum catalysts were prepared by NaBH4 reduction of metal precursors and the CeO2 nanoparticles were pre-pared by citric acid sol-gel method.The structure and morphology of two kinds of nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM),respectively.The Pt particles were uniformly dispersed on the carbon surface and showed the rod-like morphology.The CeO2 was spherical in shape.The appropriate amount of CeO2 nanoparticles was added into Pt/C sys-tems to improve activity of the catalysts.Several electrochemical techniques such as cyclic voltammogram (CV),chronoamperometry (I-t) and electrochemical impedance spectroscopy (EIS) were used to investigate the properties of CeO2-Pt/C catalysts for methanol electrooxidation in 1 mol/L CH3OH+0.5H2SO4 aqueous solutions.The results revealed that compared with Pt/C catalysts CeO2-Pt/C exhibited a higher activity and stability for methanol electro-oxidation.Moreover,the effect of CeO2 content on the activity of Pt/C catalysts was discussed in detail.