Co-precipitation of radionuclides by water-soluble melanin from the chitin—melanin glucan complex “Mikoton” in solutions

Eu, etc. present a potential hazard for hundreds of years.Measures to limit the spread of hazardous substances include not only improvement of waste treatment technology andvolume reduction of industrial wastes and releases but also post-radiative and toxicological rehabilitation of people andenvironmental sites.A trend toward the expanded use of compounds of natural origin focused special attention on melanin polymers,which can act as active binding agents for heavy metals [1, 2]. Melanins are high-molecular-weight compounds of irregularphenolic and (or) indolic structure [3]. They are subdivided according to chemical structure into three classes: eu-, pheo-,and allomelanins [4]. Eumelanins include black N-containing compounds that occur in animals and more rarely in plants.Pheomelanins are also characterized by their distinctive color (r ed, yellow, brown) and the presence in them of not only Nbut also S. This class of melanins is encountered only in animals. Allomelanins are blackish-brown compounds of higherplants and fungi that typically have a low N content. Highly stable paramagnetic centers, various reactive functionalgroups, and systems of conjugated double bonds are characteristic of melanin polymers. A lack of systematic informationon the structure and physicochemical proper ties of melanin polymers is currently hinder ing their broad use. Nevertheless,low toxicity, a broad spectrum of biological activity, and the ability to bind heavy metals portends with great promise theiruse in medicine, the food industry, agriculture, and biotechnology, including environmental protection.A comparison of the sorption capabilities of the chitin—melanin glucan complex Mikoton from higherbasidiomycetes, chitin— and chitosan—melanin complexes from dead bee bodies, and chitosan isolated from crab shellsshowed [5, 6] that polymeric sorbents containing melanin were most effective for radionuclides. The distribution coefficients(