Khizar Hussain Shah

Chromium (III) removal by weak acid exchanger Amberlite IRC-50 (Na)

Chromium (III) sorption on a weakly macroporous cation exchanger Amberlite IRC-50 (Na) is studied as a function of time and temperature. The rate constant values for chromium (III) sorption are calculated both for film and particle diffusion processes. The temperature is found to have a positive effect on both the diffusional processes. The high values of energy of activation confirm the particle diffusional nature of the process. The pH changes in the system show a competition between the Cr(OH)(2+) and H(+) ions for the exchange sites of the adsorbent. Equilibrium data are explained with the help of Langmuir equation. Various thermodynamic parameters (DeltaH degrees , DeltaS degrees and DeltaG degrees) from chromium (III) exchange on the resin are calculated.

Removal of Co2+ ions from aqueous solution by cation exchange sorption onto NiO

Batch adsorption technique was used to study the adsorption of cobalt on NiO. The aim of this work was to examine the effect of pH, concentration and temperature on the ion exchange removal of Co2+ from aqueous solution by the NiO surface. We used Langmuir model to interpret the adsorption data. The Kurbatov-type plots were tested to determine the adsorption mechanism. The kinetics of Co2+ adsorption on NiO was best described by film diffusion model. A well-known thermodynamic equation was used to assess the enthalpy and entropy of the system. The thermodynamic data were indicative of the spontaneous nature of the endothermic sorption process of Co2+ onto the NiO.

Adsorption of heavy metal ions in ternary systems onto Fe(OH)3

The adsorption behavior of amorphous Fe(OH)3 has been studied in multicomponent metal system. The metal ions uptake in the ternary system is lower than in the single system, suggesting that certain sites on the surface of the solid are blocked due to competition. The selectivity trend in the ternary system is observed to be Ni2+>Zn2+>Cd2+ which is, however, lost with increase in the temperature of the aqueous solution. Further, the observed selectivity trend is neither related to electronegativity of the metal ions nor to the pH of the hydrolysis, but has been found dependent on charge to radius ratio. The metal ions adsorption is found to increase with pH, while the converse is true with the rise in temperature. The uptake of metal ions data has been interpreted in terms of stoichiometry, binding constants and adsorption capacities. The negative values of ΔG show that uptake of metal ions is favored at lower temperatures, indicating that the adsorption mechanism essentially remains ion exchange in nature.

Adsorption of Cd2+ ions on plant mediated SnO2 nanoparticles

Plant mediated SnO2 nanoparticles were synthesized by using SnCl4.5H2O as a precursor material. The nanoparticles were then characterized for BET surface area measurements, energy dispersive x-rays (EDX), scanning electron microscopy (SEM), UV–vis diffuse reflectance (DRS) spectra and x-rays diffraction (XRD) analysis. The successful synthesis of SnO2 nanoparticles was confirmed by EDX analysis. The particle sizes were in the range 19–27 nm whereas the crystallite size computed from XRD measurement was found to be 19.9 nm. Batch adsorption technique was employed for the removal of Cd2+ ions from aqueous solution. The sorption studies of Cd2+ ions were performed at pHs 4 and 6. The equilibrium concentration of Cd2+ ions was determined by atomic absorption spectrometer (flame mode). The uptake of Cd2+ ions was affected by initial concentration, pH and temperature of the electrolytic solution. It was observed that the adsorption of Cd2+ ions enhanced with increase in the initial concentration of Cd2+ ions whereas a decrease in the percent adsorption was detected. From the thermodynamic parameters, the adsorption process was found spontaneous and endothermic in nature. The n values confirmed 2:1 exchange mechanism between surface protons and Cd2+ ions.

Synthesis, physical characteristics, and Cd2+ sorption studies of amorphous Fe(OH)3

AbstractThis work investigates the physical characteristics of amorphous Fe(OH)3 synthesized by precipitation method for the sorption studies of Cd2+ ions. The exchange of surface protons was determined by potentiometric titration method. The particle size distribution shows the agglomeration of smaller particles and also the presence of nanoparticles. Batch sorption studies are performed with respect to concentration, pH, and temperature of the solution. The adsorption of Cd2+ ions is found to increase with increasing concentration and temperature of the solution. To interpret the sorption data, Langmuir and Freundlich models are used. The values of both the adsorption enthalpy ΔH and entropy ΔS are found to be positive, suggesting that sorption process is endothermic and spontaneous in nature. The Fe dissolved from the solid is found to be less than 1 mg/L, which proves the integrity of the adsorbent. Further, the mechanism of the sorption reaction is also explored.

Chromium (III) removal by microporous ion exchanger Amberlite.120 (Na + ): kinetic, equilibrium and thermodynamic studies

Cr (III) sorption on microporous strong cation exchanger Amberlite.120 (Na+) is studied as a function of time and temperature. The pH changes show the co-sorption of H+ ions along with the chromium. The rate constant values for Cr (III) sorption are calculated for both film and particle diffusion processes. However, the particle diffusion is found to be more dominant than the film diffusion. The temperature is found to have a positive effect on both the diffusional processes. The low values of energy of activation also confirm the diffusional nature of the process. Equilibrium data are explained with the help of Langmuir equation. Various thermodynamic parameters (ΔH, ΔS and ΔG) for Cr (III) exchange on the resin are calculated. The ΔG values are found to be negative, while both the ΔH and ΔS values obtained are positive.

Counter-Ion Effect on the Thermodynamics of Cr(III) Exchange by Macroporous Amberlyst-15

Abstract In the present study, we have investigated the counter-ion effect on the thermodynamics of Cr(III) sorption by macroporous resin Amberlyst-15. The exchange reaction was studied as a function of concentration of Cr(III) and nature of counter-ions at different temperatures. It was observed that nature of counter-ions have a profound effect on the exchange of Cr(III) ions. The selectivity of Amberlyst-15 towards metal ion sorption follows the order univalent>divalent> trivalent forms. This trend can be associated to the electrostatic interaction of ions with the functional sites of the resin. The equilibrium pH values (pHeq) were observed to decrease with Cr3+/H+ exchange whereas an increase in pHeq was detected during the exchange of Cr3+/Li+, Cr3+/Na+, Cr3+/Ca2+ and Cr3+/Al3+. Different adsorption models such as Dubinin–Radushkevich (D–R) and Langmuir were employed to analyze the sorption data. The maximum exchange capacities (Xm ) and binding energy constants (Kb ) values were determined by using the Langmuir model. The values of both ΔHo and ΔSo were found positive inferring that the exchange process is endothermic accompanied by the dehydration of Cr(III) ions. The thermodynamic parameters revealed that the mechanism of Cr(III) sorption for all the counter ions is entropy driven ion exchange.