Tracer diffusion of Co2+ ions in agar gel containing multi-electrolyte systems

Tracer diffusion coefficients of cobalt ions have been measured in the supporting medium containing multi-electrolyte systems of alkali bromides. The electrolyte concentration was varied between 10^–6-0.1M at 25°C and the diffusion coefficients were determined by zone-diffusion technique using agar gel medium. The trend in the theoretical values of diffusion coefficients is accounted for by considering the relative contribution of mobility function, ionic strength as well as ion size parameter to the theoretical value in different systems. While the deviations between theoretical and experimental values of diffusion coefficients are explained on the basis of various co-occurring effects in ion-gel-water system.     

Tracer diffusion of Co2+ ions in some transition metal sulphates in agar gel

Tracer diffusion of Co²⁺ ions is studied in agar gel medium in the presence of some transition metal sulphates using the zone diffusion technique. A comparison between the experimental and theoretical values of diffusion coefficients computed on the basis of Onsager's theory shows a divergence between them. These deviations are explained on the basis of various effects in the iongel-water system.     

Tracer and self-diffusion of rosebengal sodium131I in 1% agar gel medium

Tracer and self-diffusion coefficients for Rosebengal labelled with¹³¹I are determined in agar gel medium at different temperatures and the activation energies for the two processes are determined by zone diffusion technique. The slight difference in tracer and self-diffusion values observed is small enough to be consistent with Hertz's recent theory of linear response of tracer diffusion coefficients in electrolyte and non-electrolyte systems.     

Tracer-diffusion of Mn2+ ions in agar gel containing alkali metal chlorides

Prompt gamma-neutron activation analysis, PGNAA, has been used to determine major and minor elements of bituminous coals. Calibration curves for H, C, N, Cl, Si, Ti, Al, Fe, Ca, Na, K, and S were obtained using six coals of different origin. The correlation coefficients are, in general, greater than 0.9 with the exception of C, N, and K. The -peak intensities were corrected for volume hydrogen content and normalised to the source intensity by using the 2615 keV -line from the (n, n) reaction induced in the lead container of the Cf source. Elemental compositions of new coal samples were determined. In spite of the weak neutron source intensity, the comparison between the elemental concentrations measured by PGNAA and by conventional analysis show good agreement except for N, K, S and Ca.     

Self-diffusion of Co2+ ions in CoSO4 in agar gel medium: Concentration dependence of obstruction effect and activation energy

The obstruction effect and activation enerqy for the self-diffusion of Co²⁺ ions in CoSO₄ have been computed using the zone-diffusion technique in agar gel medium at five different concentrations of the electrolyte. Both parameters are found to decrease with an increase in electrolyte concentration. The decrease in obstruction effect expressed in terms of is attributed to the competitive hydration between ions and agar molecules in a diffusion system while the decrease in activation energy is explained by considering the changes in the physical properties of the solution with concentration at microscopic level.     

Tracer diffusion of131I− ions in a few 1–2 electrolytes in agar gel

Tracer diffusion of¹³¹I^– ions is studied at different temperatures /20°C–50°C/ in 2.5% agar gel containing sodium and potassium sulphate solutions over a wide range of concentrations. The results are in qualitative agreement with the theoretical values in the concentration range 10^–6–10^–1M. Agar gel shows an obstruction effect to diffusional flow. The activation energy for tracer diffusion was found to be of the order of 16.3 kJ mol^–1.     

Determination of activation energy and the obstruction effect for tracer-diffusion of Co2+ ions in agar gel medium containing transition metal nitrates

Variation of activation energy for tracer-diffusion of Co²⁺ ions in Ni(NO₃)₂, Co(NO₃)₂ and Mn(NO₃)₂ is investigated using 1% agar gel over the temperature range of 25 to 45 °C. The activation energies are obtained by the least square fitting of the diffusion coefficient data obtained at various temperatures through the Arrhenius plots. Further, the extent of obstruction effect by gel macromolecules for Co²⁺ ions in Ni(NO₃)₂, Co(NO₃)₂ and Mn(NO₃)₂ systems at various concentrations of the electrolyte have been determined. The decrease in activation energy is explained by considering the changes in the physical properties of the solution with concentration at microscopic level, while the decrease in obstruction effect expressed in terms of a is accounted for on the basis of competitive hydration between ions and agar molecule.     

Diffusion studies of cobalt ions and their salts in agar gel medium: Obstruction effect and gel hydration

The obstruction effect in the electrolyte diffusion of cobalt halides and in tracer diffusion of Co²⁺ ions in the presence of different supporting electrolytes at various concentrations has been studied at 25 °C using the zone diffusion technique. It has been observed that obstruction effect expressed in terms of increases with concentration and is higher for electrolyte diffusion than in tracer diffusion. Further, for a given concentration it is found to decrease with increasing charge density of an anion. These observations are explained on the basis of competitive hydration between ions and agar molecules.     

Sorption of Cd2+ ions by silicate materials of different origins

The sorption capacity of silicate materials with respect to Cd²⁺ ions was studied, and the kinetics and mechanism of the sorption process were determined.     

Electrolyte-diffusion of cobalt sulphate in agar gel medium at 25 °C

The diffusion of cobalt sulphate is studied in 1% agar gel over a concentration range of 10^–5 to 0.2M at 25 °C. The experimental values of the diffusion coefficient at various concentrations determined by the zone-diffusion technique are compared with the theoretical values of diffusion coefficinets computed on the basis of Onsager-Fuoss theory. The observed deviations are interpreted in terms of relative contributions of diffusion-enhancing and diffusion-retarding interactions occurring in the water-gel-electrolyte system.     

Diffusion of zinc sulphate in agar gel medium

The activation energy for the diffusion of ZnSO₄ as a function of electrolyte concentration is computed by least squares fitting of the diffusion coefficient data obtained at various temperatures in the Arrhenius equation. It is observed that the activation energy decreases with increasing concentration of the electrolyte. This observation is accounted for on the basis of Wang's model. Further, the obstruction effect caused by the agar macromolecules in the diffusion path of ZnSO₄ uis also determined at these concentrations by varying the gel concentration at 25°C., The obstruction effect expressed in terms of a found to decrease with ZnSO₄ concentration and explained on the basis of competitive hydration of diffusing ions and agar molecules.     

Cd2+和Ni2+在粉煤灰上的吸附特性

考察了粉煤灰对Cd2+和Ni2+的单组分吸附和双组分吸附性能。结果表明,粉煤灰可有效吸附水溶液中的Cd2+和Ni2+,去除率随pH升高而增加。吸附约60min后趋于平衡。粉煤灰对Ni2+的吸附容量高于Cd2+。单组分吸附平衡符合Freundlich模型和Redlich Peterson (R P)模型。双组分吸附时,Ni2+和Cd2+之间存在明显的竞争吸附效应;随干扰离子浓度升高,竞争吸附效应增强。不同模型拟合结果表明,双组分吸附平衡符合Freundlich竞争吸附模型。脱附实验表明,Cd2+比Ni2+易于脱附;0.1mol/L HCl、0.1mol/L HNO3 和0.05mol/L H2SO4的脱附效果接近,对Cd2+脱附率>60%,对Ni2+脱附率>35%。     

Tracer-diffusion of cobalt ions in sodium and potassium nitrates in agar gel

Tracer-diffusion of Co²⁺ ions is studied in agar gel in the presence of sodium and potassium nitrates at 25°C. The diffusion coefficient values at various electrolyte concentrations are compared with the corresponding theoretical values computed on the basis of Onsager's theory. The deviations from the theory are attributed to the various co-occurring effects in the diffusion medium. The activation energy for the process of diffusion of Co²⁺ ions in presence of above electrolytes is also reported.     

Effect of supporting electrolyte on obstruction effect and activation energy for the tracer diffusion of cobalt ions in agar gel

The effect of some alkali metal chlorides on obstruction effect // and activation energy /E/ for the tracer-diffusion of cobalt ions is studied in agar gel medium using the zone-diffusion technique. It is observed that both the parameters, and E, decrease with increasing charge density of cation of the supporting electrolyte. This trend is explained on the basis of competitive hydration between ions and agar molecules and the relative distortion in the water structure brought about by these different ions and agar molecules, respectively.     

Polarized electronic spectra of tetrahedral nickel(II) ions in a Cs2ZnCl4 host lattice at temperatures between 300 and 10 K

The polarized visible spectra of tetrahedral nickel(II) ions in a Cs₂ZnCl₄ lattice at temperatures between 300 and 10 K is reported. Cs₂ZnCl₄ is orthorhombic and the polarization results confirm that the electric dipole process is operative. The degree of distortion from tetrahedral symmetry of the NiCl₄²⁻ moiety along each principal axis of the crystal is a major factor in determining the intensity of the spectrum taken with the incident-beam polarization in that direction. The spectra are unusual in that the double peak characteristic of tetrahedral nickel at room temperature is retained at 10 K along the two crystallographic axes where the distortion from tetrahedral symmetry is most marked. In common with most previous studies of tetrahedral nickel spectra at low temperature, the spectrum taken at 10 K with the incident-beam polarization along the third axis produces a quite different spectrum than at room temperature. The change occurs gradually between 200 and 100 K. A qualitative model to explain these observations based on the concept that a dynamic Jahn-Teller effect is operative at room temperature is proposed.     

The diffusion of H+ and Ni2+ ions in an inorganic cation-exchange matrix

The kinetics of sorption on zirconium hydrophosphates with various water contents was studied. The self-diffusion coefficients of Ni²⁺ and H⁺ and the effective diffusion coefficients of Ni²⁺ ions corresponding to the exchange Ni²⁺ → H⁺ were determined. The self-diffusion coefficients of ions in samples with an 85% water content were as high as 4.17 × 10^?11 m²/s (Ni²⁺) and 5.06 × 10^?10 m²/s (H⁺). Water loss caused by drying the sorbents resulted in a decrease in the rate of ion exchange.     

Removal of Pb2+ and Cd2+ ions from aqueous solutions using guanidine modified hydrogels

In this study, experimental measurements have been made on the batch adsorption of cadmium and lead ions from aqueous solutions using poly(guanidine modified 2‐acrylamido‐2‐methylpropan sulfonic acid/acrylic acid/N‐vinylpyrrolidone/2‐Hydroxyethyl methacrylate), P(AMPSG/AAc/NVP/HEMA) hydrogels. The guanidyl end group bearing AMPSG monomer was synthesized from the reaction of AMPS and guanidine. The hydrogels were prepared by UV‐curing technique. The morphology of the dry H10‐hydrogel sample was examined by SEM. The influence of the uptake conditions, such as pH, functional monomer per cent, contact time, initial feed concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, was also tested. The selectivity of the hydrogel toward the different metal ions tested was Hg(II) > Pb(II) > Au(III) > Cd(II). The adsorption isotherm models were applied to the experimental data, and it was seen that the Langmuir isotherm model was the best fit for the adsorption of Cd(II) and Pb(II) ions on P(AMPSG/AAc/NVP/HEMA) hydrogel. It was found that adsorbed lead and cadmium ions on P(AMPSG/AAc/NVP/HEMA) hydrogel can be effectively desorbed by acid leaching and the regenerated P(AMPSG/AAc/NVP/HEMA) hydrogel can be reused almost five times less without any loss of adsorption capacity. Copyright © 2009 John Wiley & Sons, Ltd.     

Gamma irradiation-induced Cd2+ and Pb2+ removal from different kinds of water

Gamma irradiation-induced removal of cadmium ion (Cd²⁺) and lead ion (Pb²⁺) in different kinds of water was investigated. It is observed that solution pH, dissolved oxygen (DO) concentration, sodium carbonate and EDTA played an important effect on Cd²⁺ and Pb²⁺ removal. Low solution pH, low DO concentration and sodium carbonate were favorable for removal of Cd²⁺ and Pb²⁺ by reducing species, while the presence of EDTA in solution restrained Cd²⁺ and Pb²⁺ reduction. Pb²⁺ removal percentage was higher compared to that of Cd²⁺ at the same experimental conditions. Cd²⁺ and Pb²⁺ removal under different conditions was well described by the pseudo-first-order kinetics model. Cd²⁺ and Pb²⁺ removal in different water followed an increasing order: water inflow<surface water<effluent<ground water. In addition, gamma irradiation resulted in a slight decrease in pH and TOC values of water inflow of municipal sewage treatment plant.