Removal of dissolved metals from waste water is a problem of import in environmental pollution control and in precious metal recovery. In this proposal, a series of new chelating agents will be prepared from chitosan. Chitosan is a modification of the biopolymer chitin, a polysaccharide found in the exoskeleton of crustaceans. In this proposed program, chitosan will be depolymerized, derivatized, and fractionated into various molecular weight ranges using membranes. These different molecular weight fractions will be evaluated for enhanced chelation properties and solubility of the complexes. The degree of substitution or chitosan derivatives will be optimized to achieve maximum chelation. The availability of different molecular weight derivatives will allow one to choose the desired solubility of the chelation complex. The soluble chelated metal complexes will be concentrated by ultrafiltration membranes. After using this ultrafiltration membrane technique, the aqueous filtrate will contain very low concentrations of metal ions, and can then be discharged or recycled. The retentate will contain concentrated metal ions within the chitosan chelate. The metal ions can then be recovered from the chitosan. This procedure can be applied to water effluent at industrial sites. The chitosan derivatives in the molecular weight range that produce insoluble chelation complexes can be used in precious metal recovery as a means of concentrating the metal. The metal can then be recovered from the complex. The enhanced chelating ability of these new polymers will allow them to compete economically with synthetic chelating agents, thereby expanding the utilization of wastes processed from shellfish.The potential commercial application as described by the awardee: Initial results will yield new chelation agents as part of the V-LABS specialty chemicals product line. Long range results would include scale-up of the manufacture of the most efficient chelation agents for use in the electroplating industry, electronics, manufacture, photography, jewelry production, and membrane water purification processes. This will expand the market for biopolymers isolated from processing waste from shellfish.
