Elimination of PCBs from contaminated natural freshwaters: comparison of the fixation efficiency on chitosan and bioconcentration by Daphnia magna
Thys, I.; Weltrowski, M.; Thomé, J.-P. (1993). Elimination of PCBs from contaminated natural freshwaters: comparison of the fixation efficiency on chitosan and bioconcentration by Daphnia magna. Belg. J. Zool. 123(Suppl. 1): 72-73
In: Belgian Journal of Zoology. Koninklijke Belgische Vereniging voor Dierkunde = Société royale zoologique de Belgique: Gent. ISSN 0777-6276; e-ISSN 2295-0451, more
Chitosan, the deacetylated derivative of chitin, is well known as a chelating agent for binding heavy metals as well as a sorption polymer for pesticides and PCBs. This work deals with the study of the PC B adsorption ability of various lots of chemically modified chitosan in order to develop filter cartridges useful for the purification of contaminated stream waters. The PC B adsorption efficiency of pure chitosan (CHT 200) and of 2 derivatives synthesized by means of a cross-linking procedure with glutaric aldehyde (CHT 201) and terephtaldehyde (CHT 206) have been tested. The adsorption properties of these derivatives have been compared with the elimination of PCBs from contaminated water by two zooplanktonic species (Daphnia magna and Cyclops sp.), with chitinous cuticles, according to the bioaccumulation processes. The experiments were performed with six PC B congeners (tri- to heptachlorobiphenyls; 1 µg/l for each PCB). The efficiency of these different chitosan derivatives has been tested by means of a "batch" (closed system) and a "flow- through" chitosan filter cartridge system (opened system). The different chitosan derivatives appeared as very good purifiers, both in “batch” system and in flow-through system. However, the substitution of chitosan by aliphatic or aromatic carbons (CHT 201 and CHT 206 respectively) improves their adsorption properties. It appears that the fixation of PCBs on the different derivatives of chitosan is the result of a combination of two kinds of binding processes: a strong ionic bond, especially for non-modified chitosan (CHT 200) and a weak bond of hydrophobic type which is predominanting in PCBs adsorption on cross-linked chitosan (CHT 201 and CHT 206). The substitution of chitosan by a non-ionised molecule results in an increase of the hydrophobic interaction. The fixation of the PCBs on crustaceans is rather important but more complex than on chitosan powder and can not be explain by simple chemical interactions with chitinous cuticle. Although the PCB bioconcentration processes in microcrustaceans appear not as efficient as pure or chemically modified chitosan to remove high amounts of PCBs from contaminated water, the PCB accumulation by these organisms contributes to a large extent to the water purification in natural ecosystems. Chitosan, and its cross-linked derivatives, appear as powerful PCB adsorbents and, as a consequence, constitute promising materials for the purification of PCB polluted stream waters. However, there is still a need to develop a physical form of chitosan filters to perform the epuration of large volume of PCB polluted water.
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