Chitosans metal chelates

Polyvinylalcohol [10] Nylon [11-13] Polypyrrole [14] Sephadex LH 20 [15] Perfluoropolymer [16] Polypropylene [17] Metal-chelate [25] Carboxymethyl-dextran [31,32] Chitosan [33,34]... 

One advantage of chitosan in chelating transition and post-transition metals is the low activity shown for magnesium and other alkaline earths, which makes it very useful for the analysis of seawater copper and zinc have been preconcentrated from 10 liters of seawater into 5 ml prior to analysis (344). Another report indicates a more efficient extraction from pH 3-5 ammonium-sulfate solutions of Cr(III), Fe(III), Ni(II), Cu(II), Zn(II), and Hg(II) (350). Although a chitosan membrane has a lower capacity than the powdered material. 

Acylation of the amine groups of chitosan can be readily carried out using acyl anhydride as the reactant. During the acylation process of a chitosan solution, the chitosan slowly loses the solubility and a gel is formed. Muzzarelli et al. (Muzzarelli et al, 1986) modified chitosan with aldehyde-acids and keto-acids, from which they obtained a series of polymers possessing such groups as carboxylic acids, primary and secondary amines and primary and secondary hydroxyl groups. The product showed excellent metal chelating properties (Muzzarelli, 1973). 

CHITOSAN AND MODIFIED CHITOSAN AS CHELATING AGENTS FOR METAL IONS... 

Hall, L. D. and Yalpani, M. (1980). Enhancement of the metal-chelating properties of chitin and chitosan. Carbohydr. Res. 83, C5-C7. 

High-capacity chitosan-based chelating resin for on-line collection of transition and rare-earth metals prior to inductively coupled plasma-atomic emission spectrometry measurement. 7a-lanta. 79, 1252-1259. 

Katarina, R. K., Takayanagi, T., Oshita, K., Mit-suko Oshima, M., and Motomizu, S. (2008). Sample Pretreatment Using Chitosan-based Chelating Resin for the Determination of Trace Metals in Seawater Samples by Inductively Coupled Plasma-Mass Spectrometry. Analytic. Sci. 24, 1537-1544. 

Holme, K. R. and Hall, L. D. (1991). Novel metal chelating chitosan derivative attachment of iminodiacetate moieties via a hydrophilic spacer group. Canadian Journal of Chemistry, 69(2), 585-590. 

Xi F, Wu J. Macroporous chitosan layer coated on non-porous silica gel as a support for metal chelate affinity chromatographic adsorbent. J Chromatogr A 2004 1057 41 7. 

In addition, molecular imprinting technique is also used in anion recognition. Ozkutuk et al. reported the preparation and adsorption ability of the phosphate-imprinted chitosan-succinate beads [34]. Chitosan was modified with succinic anhydrides firstly. Second the mixture of chitosan-succinate and Fe (III) ions stirred continuously at room temperature. And Na3P04 was added to Fe (III)-chitosan-succinate mixture. This mixture was slowly dropped into NaOH solution to form beads. Afterwards, beads were crosslinked with epichlorohydrin and the template (phosphate ions) was removed using IM KOH solution. Selective cavity for the phosphate ion was obtained in the phosphate imprinted metal-chelate polymer. The phosphate-imprinted metal-chelate polymer was used in the adsorption-desorption process. The adsorption process was fast and equilibrium was reached around 30 min. The adsorption behaviour of this system was described approximately by the Langmuir equation. 

The subject of the separation and purification of metals with the aid of chitosan has been reviewed by Inoue (1998) who collected data relevant to chitosans modified with chelating functional groups as well [111]. 

Chitosan (> 75% deacelylation, 800-2000 cps) was mixed wilh stock so-lulions of Cu(II), Fe(ll), Cd(ll) and Zn(II), prepared in 0.1 M HNO3, and of Ca(ll) and Mn(II), in 0.1 MHCl. It was found that, in the chelation of most metal ions by chitosan, 1 1 binding of chitosan is more dominant than 2 1 cooperative binding, but vice versa for Zn(II) and Cd(II). The chelation of Cu(II) by chitosan showed much higher reactivity when compared to other divalent metal ions. Cu(II), Fe(II), Cd(II) andZn(II) showed strong reactivity and stability of their chelates. In contrast, the interactions between Ca(II) or Mn(II) and chitosan were almost negligible. These data confirm brilliantly previous data by Muzzarelli et al. [116]. 

Important characteristics of chitosan are its MW, viscosity, DD (Bodek, 1994 Ferreira et al., 1994a,b), crystallinity index, number of monomeric units, water retention value, pKa, and energy of hydration (Kas, 1997). Chitosan has a high charge density, adheres to negatively charged surfaces, and chelates metal ions. 

Major applications of chitosan were previously focused on sludge dewatering, food processing, and metal ion chelation until the mid-1980s. Further, it has received considerable attention for its commercial applications in agriculture, chemistry, biomedical, food, cosmetic, and biotechnology industries (Alasalvar et ah, 2002 Knorr, 1984 Kurita,... 

Metal ions. Chitosan is known to complex metal ions. The chelating ability of chitosan is superior compared to other known biopolymers [30]. This property is widely investigated for its use as sensors or filtration materials in heavy metal ion detection or separation [17, 20a, 31]. The binding of chitosan with metal ions is thought to provide donor atoms that may improve the antimicrobial activity of the material however, studies on this area are quite limited [32]. 

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