Metal adsorption ligand effects

Reed, B. and Nonavinakere, S., Metal adsorption by activated carbon—effect of complexing ligands, competing adsorbates, ionic strength, and background electrolyte, Sep Sci Technol, 27 (14), 1985-2000, 1992. 

Benjamin, M.M. Leckie, J.O. (1981) Multiple-site adsorption of Cd, Cu, Zn, and Pb on amorphous iron oxyhydroxide. J. Colloid Interface Sci. 79 209-221 Benjamin, M.M. Leckie, J.O. (1981a) Competitive adsorption of Cd, Zn, Cu and Pb on amorphous iron oxyhydroxide. J. Colloid Interface Sci. 83 410-419 Benjamin, M.M. Leckie, J.O. (1982) Effects of complexation by Cl, SO4, and S2O3 on the adsorption behavior of cadmium on oxide surfaces. Environ. Sci. Tech. 16 162-170 Benjamin, M.M. (1978) Effects of competing metals and complexing ligands on trace metal adsorption. Ph.D. Thesis Benjamin, M.M. Hayes, K.E. Leckie, K.O. 

Hoins, U. Charlet, L. Sticher, H. (1993) Ligand effect on the adsorption of heavy metals. The sulphate-cadmium goethite case. Water, Air, Soil Pollution 68 241-255 Holm, G. (1985) Substitution selectivity of some transition elements (Cr, Mn, Co, Ni, Cu, Zn) during formation of P-FeOOH. Geologiska Foreningsi Stockholm Forhandlingar 107 297-300... 

Pt-Sn surface. Even if hydrogen needs more than one transition metal atom in order to dissociate, this would only explain the large decrease in hydrogen adsorption if the possibility of spillover is largely reduced on the alloys. The ligand effect, to be discussed in Section IV, would have to be present for this assumption. 

On the other hand, by a ligand effect, the reactivity of sites located at varying distances from the sulfur-occupied site may be affected. As a proof of charge transfer, adsorbed sulfur is able to decrease the binding energy of adsorbed hydrogen when the free energy of adsorption ofolefinic compounds can be increased on partially sulfurized metallic catalysts. 

The cluster-size dependence has not yet been explained it may reflect an intrinsically low activity of the clusters, but it might also be a consequence of increasing removal of residual ligands such as C from the clusters with increasing severity of treatment in H2. Other possibilities include a steric effect of the support, limiting adsorption of the reactants on the metal— such an effect would be greatest for the smallest clusters. Electronic effects should not be ruled out. 

As elucidated from the adsorption experiment on BSA, adsorption of gallium ion by simple ion-exchange effect is negligible. The characteristics of metal ions such as ionic radius and hardness/softness, and the conformation of the metallothionein probably affect the selectivity of metal adsorption. The understanding of the mutual interactions among those factors would be a key dictor in designing the protein-based ligand suitable for a specific metal ion. 

Hoins, U., Chailet. L., and Sticher, H., Ligand effect on the adsorption of heavy metals The sulfate-cadmium-goethite case. Water Air Soil Poll., 68, 241, 1993. 

LiCAND EFFECTS. The effccts of metal-complexing ligands in a soil solution on the adsorption of metal cations by soil constituents can be classified into four general categories... 

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