Cadmium, adsorption

Gorman-Lewis D, Fein JB, Jensen MP (2006) Enthalpies and entropies of proton and cadmium adsorption onto Bacillus subtilis bacterial cells from calorimetric measurements. Geochim Cosmochim Acta 70 4862-4873... 

Temperature dependence of cadmium adsorption on oxides. 1. Experimental observations and model analysis. J. Coll. Int. Sd. 135 118-131... 

Yu, G., Saha, U. K., Kozak, L. M., and Huang, P. M. (2006). Kinetics of cadmium adsorption on aluminum precipitation products formed under the influence of tannate. Geochim. Cosmochim. Acta 70,5134-5145. 

Cavallaro, N., and McBride, M. B. (1978). Copper and cadmium adsorption characteristics of selected acid and calcerous soils. Soil Sci. Soc. Am. J. 42, 550-556. 

Figure 1 shows adsorption of Cd2+ for an initial cadmium concentration of 1 x 10 5 M as a function of pH on the metal oxide/0.001 M NaC104 solution interface. The adsorption of Cd(II) is pH dependent because the process of cadmium adsorption proceeds through exchange of hydrogen from surface hydroxyl groups. The plot of Cd(II) adsorption vs pH is characteristic for the adsorption of divalent cations on metal oxides and is called the edge of adsorption .10... 

Previous workers concluded that cadmium ions adsorb onto the goethite surface by the formation of bidentate surface complexes.11,12 However, the cadmium adsorption data and our calculations (see Figure 3) shows that cadmium adsorbs on goethite mainly on one surface hydroxyl group, forming monodentate complexes, according the following reaction ... 

Figure 7. A percentage of cadmium adsorption (0.001 M) at the anatase / electrolyte interface in a presence of oxalates ions (0.001 and 0.002 M).

Figure 12.27, Influence of pH and background electrolyte of cadmium adsorption by DowexZ 50W-X8 cation-exchange resin (background electrolyte included 20 mmol L l KC1 or NH4C1 plus 5 mmolc L-1 CaClz). The exchanger was first repeatedly washed with the background electrolyte (from Evangelou, 1997, unpublished data).

TABLE 12.12. Freundlich Cadmium Adsorption Constants (kr) for Various Exchangers... 

Pereira, M.G. and Arruda, M.A.Z. 2003. Vermicompost as a natural adsorbent material Characterization and potentialities for cadmium adsorption. Journal of Brazilian Chemical Society, 14 39 7. 

Fig. 15.5. Calculated metal sorption curves for Pb, Cu and Cd onto the bacterium Bacillus subtilis, shown as a function of pH versus the concentration of sorbed metal. Curves are calculated based on experimental metal sorption data of Fein et al. (1997), and were computed using the geochemical speciation programme JCHESS. The solution depicted contains 1 g 1 bacteria dry wt (155 m g surface area, 8.0 Cm electrical double layer capacitance), 1 mM dissolved CaC03 and 1 iM dissolved lead, copper and cadmium. Adsorption was calculated using a CCM treatment.

It is interesting in the in-situ investigation (Fig. 2b) that as the relative amount of the inactive stearyl alcohols to cadmium ion exceeds 20% the asymmetric carboxylate band suddenly decreases in its intensity and remains about the same afterwards. In Fig. 2c, it is clearly seen that the adsorbed amount of cadmium ions at 80% of stearic acid is reduced by more than half of those at larger compositions of the acid. By contrast, the ex-situ results showed a linear decrease in cadmium adsorption with the monolayer composition as well as a certain deviation from the theoretical calculation that is different to the case without adsorption of cadmium ions. 

Eehrmann, C., Pohl, P, 1993. Cadmium adsorption by the non-living biomass of microalgae grown in axenic mass culture. Journal of Applied Phycology, 5, 555-562. 

Figure 10.14 Influence of Cd-chloride complex ing on cadmium adsorption by montmo-rillonite. Molal values in the figure are the concentrations of NaCJ present for each isotherm curve. Modified after Garcia-Miragaya and Page (1976),Soil Sci Soc. Am. J., 40(5) 658-63.

Van Riemsdijk et al. [53] were the first to show that electrostatic effects could explain non-stoichiometric exchange ratios. Predictions with the one-pKn SCG model and the two-pKn SGC model were both in a good agreement with experimentally observed proton/M ratios and metal ion isotherms at a series of pH values for rutile, hematite and amorphous iron oxide. In contrast with Benjamin and Leckie [86], Van Riemsdijk et al. [53] concluded that incorporation of surface heterogeneity is not required to describe cadmium adsorption on amorphous iron oxide. 

Cowan, C. E., Zachara, J. M., and Resch, C. T. (1991). Cadmium adsorption on iron oxides in the presence of alkaline-earth elements. Environ. Sci. Technol. 25, 437-446. 

Neal, R. H., and Sposito. G. (1986). Effects of soluble organic matter and sewage sludge amendments on cadmium adsorption by soils at low cadmium concentrations. Soil Sci. 142, 164-172. 

Sakurai, K., and Huang, P. M. (1995). Cadmium adsorption on the hydroxyalu-minium-montmorillonite complex as influenced by oxalate. In Environmental Impact of Soil Componenet Interactions, Vol. Il, Metals, Other Inorganics and Microbial Activities, ed. Huang, P. M., Berthelin. J., Bollag, J.-M., McGill, W. B., and Page, A. L., Lewis Publishers, Boca Raton. FL, 39-46. 

Figure 6.8. Fit of the CD-MUSIC model to cadmium adsorption by goethite. Open symbols represent total dissolved Cd at le-6 mol L. Closed symbols represent total dissolved Cd at le-4 mol L. (From Venema et al., 1996a.)...

Weerasooriya. K,. Wijesekara, H.K.D.K, and Bandara, A., Surface complexation modeling of cadmium adsorption on gibbsite. Colloids Surf. A. 207, 13, 2002. 

Enhancement of copper and cadmium adsorption on kaolin by the presence of humic acids. Chemo-sphere 48 1081-1088. 

Lai CH, Chen CY, Wei BL and Yeh SH (2002) Cadmium adsorption on goethite-coated sand in the presence of humic acid. Water Res 36 4943 —4950. 

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