Maximum Cd Uptake Research Articles

Adsorptive removal of Cd(II) and Pb(II) ions from aqueous solutions by using Turkish illitic clay

The ability of Turkish illitic clay (TIC) in removal of Cd(II) and Pb(II) ions from aqueous solutions has been examined in a batch adsorption process with respect to several experimental conditions including initial solution pH, contact time, initial metal ions concentration, temperature, ionic strength, and TIC concentration, etc. The characterization of TIC was performed by using FTIR, XRD and XRF techniques. The maximum uptake of Cd(II) (11.25mgg(-1)) and Pb(II) (238.98mgg(-1)) was observed when used 1.0gL(-1) of TIC suspension, 50mgL(-1) of initial Cd(II) and 250mgL(-1) of initial Pb(II) concentration at initial pH 4.0 and contact time of 240min at room temperature. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin Radushkevich (D-R) isotherm models. The monolayer adsorption capacity of TIC was found to be 13.09mgg(-1) and 53.76mgg(-1) for Cd(II) and Pb(II) ions, respectively. The kinetics of the adsorption was tested using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The results showed that the adsorption of Cd(II) and Pb(II) ions onto TIC proceeds according to the pseudo-second-order model. Thermodynamic parameters including the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 5-40°C.

Modeling the kinetics of Cd(II) adsorption on Syzygium cumini L leaf powder in a fixed bed mini column

Syzygium cumini L leaf powder was used as a biosorbent for generating adsorption data in a fixed bed mini column. Effect of flow rate, initial Cd(II) concentration and bed height were the experimental parameters chosen to obtain breakthrough curves. The maximum uptake of Cd(II) in a fixed bed adsorption column was 29.08 mg g −1 at pH 5.5, initial Cd(II) concentration 100 mg L −1, bed height 5 cm and flow rate 40 mL min −1. Bohart–Adams, BDST, Thomas and Yoon–Nelson models were applied to the data for predicting breakthrough curves and to determine the characteristic parameters. Prominent and unique characteristics features of the respective models like service time (Hutchins BDST model), adsorption capacity (Thomas model) and time required for 50% breakthrough (Yoon–Nelson model) were determined. The utilization of column data in designing of a commercial column has been discussed. It was possible to desorb ∼98% of Cd(II) using 0.05 N HCl solution in column.

UPTAKE OF Cd2+ FROM AQUEOUS SOLUTIONS USING PROTONATED DRY ALGINATE BEADS

The use of protonated dry alginate beads for the uptake of cadmium ions from aqueous solutions was studied at 25 °C. The uptake of Cd2+ produced a release of protons, for which a molar ratio d[H+]/d[Cd2+] of 2.0 was established. This ion exchange was the mechanism of cadmium uptake which followed a pseudo-second order kinetic model.The uptake was strongly dependent on the solution pH up to a value of 4.5 after which it remained constant. The maximum Cd-uptake was computed in 285.7 mg per gram of alginate beads (dry wt.) at pH 4.5 by the Langmuir adsorption model. A residual concentration of around 0.09 mg/L of Cd2+ which allowed safety discharge of some types of effluents having this heavy metal ion, was reached with a solution initially having 25 mg/L of Cd2+.EPMA-EDX of Cd-loaded beads showed a uniform distribution of the metal ions throughout the structure of the alginate bead, regardless the solution pH.On a étudié l’utilisation de billes à protons d’alginate sec pour la capture d’ions cadmium à partir de solutions aqueuses à 25°C. La capture de Cd2+ produisait un dégagement de protons, pour lesquels on a établi un rapport molaire d[H+/]/d[Cd2+] de 2.0. Cet échange d’ion constituait le mécanisme de capture du cadmium, lequel suivait un modèle cinétique de pseudo second ordre.La capture était fortement dépendante du pH de la solution jusqu’à une valeur de 4.5, au-delà duquel elle restait constante. On a calculé la capture maximale de Cd à 285.7 mg par gramme de billes d’alginate (poids sec) au pH de 4.5 au moyen du modèle d’adsorption de Langmuir. Une concentration résiduelle d’environ 0.09 mg/L de Cd2+, qui permettait la décharge sécuritaire de certains types d’effluents contenant cet ion métal lourd, était atteinte avec une solution ayant initialement 25 mg/L de Cd2+.L’analyse d’EPMA-EDX de billes chargées de Cd a montré une distribution uniforme des ions de métal dans toute la structure de la bille d’alginate, peu importe le pH de la solution.

Cadmium accumulation in eurasian watermilfoil plants

The aquatic vascular plant Eurasian watermilfoil (Myriophyllum spicatum L.) was investigated for its potential to take up Cd from nutrient-rich water in a short-term growth and harvest regime. Eurasian watermilfoil plants were grown in and harvested weekly from 0.10M Hoagland nutrient solutions containing concentrations of Cd from 0.04 to 7.63μg Cd mL−1. Dry weights of plants significantly decreas4ed when exposed to 7.63μg Cd mL−1. For both 0.04 and 1.03μg Cd mL−1 treatment the greatest concentration of Cd in plants occurred during the first two weeks. The greatest Cd concentration of Cd in plants for the 7.63μg Cd ML−1 treatment occurred during week one and decreased through week 2. Tissue P concentration in control plants increased over time but did not increase significantly over time when plants were exposed to 0.04 and 1.03μg Cd mL−1 levels. Tissue P concentration decreased over time when plants were exposed to 7.63μg Cd mL−1. Stem length, root dry weights, and root number significantly increased over time in control plants and in those exposed to the 0.04 and 1.03μg Cd mL−1 treatments. Plants treated with 7.63μg Cd mL−1 did not grow. These results suggest that Eurasian watermilfoil would be useful for absorbing Cd from nutrient-rich water when the solution concentration was in the range of 0.04 to 7.63μg Cd mL−1. However, in solutions having the highest concentration of Cd, the harvest regime would have to sustain plant vigor, avoid tissue Cd loss, and realize maximum uptake of Cd from solution.