Transition metal ions, cross-linking with

In Figure 4.11, the formula of a chelating resin is shown with the iminodiacetic acid group as the chelating ligand, which is bonded onto a cross-linked polystyrene matrix. This type of resin shows a large affinity for alkaline-earth and transition metal ions. 

The spectra of clathrochelate cobalt(III) tris-dioximates obtained by cross-linking with chromium, nickel, and zinc(II) complexes, alongside the bands assigned to the n-n transitions in dioximate fragments, contained the d-d transition bands from the capping metal ions that masks the corresponding transitions for the central Co3+ ion [46]. 

Binyamin, Chen and Heller reported that wired enzyme electrodes constituted of glassy carbon electrodes coated with poly(4-vinylpyridine) complexed with [Os(bpy)2Cl] and quarternized with 2-bromoethylamine or poly[(iV-vinylimidazole) complexed with [Os(4,4 -dimethyl-2,2 -bypyridine)2Cl] or poly(vinylpyridine) complexed with [Os(4,4 -dimethoxy-2,2 -bypyridine)2Cl] quaternized with methyl groups lost their electrocatalytic activity more rapidly in serum or saline phosphate buffer (pH 7.2) in the presence of urate and transitional metal ions such as Zn and Fe " " than in plain saline phosphate buffer (pH 7.2). It was reported that as much as two-thirds of the current is lost in 2 h in some anodes. However, when a composite membrane of cellulose acetate, Nafion, and the polyaziridine-cross-linked co-polymer of poly(4-vinyl pyridine) quaternized with bromoacetic acid was applied, the glucose sensor stability in serum was improved and maintained for at least 3 days [27,50]. 

The chelating ion-exchange resins Chelex-100 and Permutit S 1005 completely retain vanadium [Sc, Ni, Cu, Zn, Y, Mo, Ag, Cd, In, rare earths, W, Re (90%), Pb, Bi, and Th] from sea water. Manganese is retained quantitatively only by the Chelex resin. Vanadium (Mo, W, Re) is removed from the resins with 4N ammonia, the other metals with 2 N mineral acids 56). Both resins consist of a cross-linked polystyrene matrix with iminodiacetic acid [—CH2—N(CH2COOH)2] functional groups. Alkali and alkaline earth metals do not form chelates with iminodiacetic acid except at very high pH, whereas many transition metal ions form 1 1 complexes. 

Understanding the cross-linking of polysaccharides with transition metal ions requires understanding the competition between hydrolysis and cross-... 

Chitosan has potential applications in various wastewater treatments (44). Chitosan is a natural chelating polymer as a result of the amine group (C-2) and the adjacent hydroxyl group (C-3), and thus could be used to remove transition metal ions from wastewater streams. Some important factors that affect the level of ion removal are the degree of deacetylation, pH, and surface area of the chitosan substrate. Since protons compete for amine sites, the metal ions can be removed from the chitosan backbone by lowering the pH. Chitosan beads cross-linked with gluteraldehyde appear to be a more practical physical form because of its lack of solubility at low pH and its higher surface area. 

Sun, SL Ma, N Wang, AQ. Adsorption of the transition metal ions on cross-linked chitosan resin with Cu(II) templated. Ion Exchange and Adsorption, 2004, 20(3), 193-198. 

Other macrocyelic eompoimds sueh as cyelodextrins (CD) can be also polymerized and then used as ion carriers for transport of metal ions from aqueous solutions. The hydrophobie CD polymers have been used as ion earriers for separation of transition metal eations from dilute aqueous solutions by transport across polymer inelusion membranes. Recent developments of the CD polymers applieation in sorption processes of heavy metal ion from aqueous solution will be also presented in this ehapter. It is also shown that hydrophilic, water soluble CD polymers obtained by cross-linking of CD with anhydrides are useful in the removal of transition metal ions from diluted aqueous solutions by ion flotation process. 

Aiming at easier workup conditions, immobilization of several transition metal catalysts, which show activity for the epoxidation of allylic alcohols, on polymer support has been investigated. For example, Suzuki and coworkers incorporated an oxo-vanadium ion into cross-linked polystyrene resins functionalized with iminodiacetic acid or diethylenetri-amine derivatives (Scheme 57), which afforded a heterogeneous catalyst that can promote... 

Sfiica impregnated with saturated and unsaturated hydrocarbons (squalene, paraffin oil), silicone and plant oils, complexing agents (silver ions, boric add and borates, unsaturated and aromatic compounds), tigands (EDTA, digitonin), and transition metal salts silanized silica gel impregnated with anionic and cationic surfactants Cross-linked, polymeric dextran gels (Sephadex)... 

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