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Degradacja polichlorowanych difenyli (PCB)

Gryglewicz S.

Wiadomości Chemiczne

2000

[Z] 54, 5-6

499-516

Polychlorinated biphenyls ( PCBs ) do not bring about a sharp toxical effect in mammalian organisms. However, owing to the tendency of PCBs accumulation in the environment, low biodegradability and potential dangerous consequences for human health generating in long-term period, the efforts leading to PCBs elimination from environment are reasonable. In spite of the discontinuation of PCBs production, there are still their emission sources, i.e. mainly electrical facilities filled in insulating fluid, which contains polychlorinated biphenyls of high concentration. In this paper the bases of PCBs synthesis were discussed. The principle of nomenclature of working fluids produced on the base of PCBs and their main physicochemical properties were also given. In the second part of the paper the structure and chemical reactivity of polychlorinated biphenyls compounds were discussed, in particular, their inert behaviour in nucleophilic substitution reactions. Moreover, the theoretical bases of PCBs degradation methods including chemical, physicochemical and biological processes were described. It was emphasised that PCBs degradation methods and remediation of PCB contaminated materials are required to be environmentally safe. An efficient degradation method of liquid and solid materials showing high PCBs concentration is their incineration in a special furnace with precisely controlled technological regime as well as with the use of a plasma torch to avoid dioxine formation via recombination of uncompleted combustion products. It was indicated that PCB contaminated petroleum derived products are of the secondary potential source of PCBs propagation in the environment. For this kind of products, catalytic hydrogenation appears to be a particularly interesting means of dechlorination without destroing the initial material. Also the treatment of hydrocarbon mixture with colloidal suspension of metallic sodium offers an attractive dechlorination potential. The mechanism of this reaction is not well known. Probably, the reaction proceeds through aryne mechanism. Attempts to remediate PCB contaminated waters by means of electromagnetic radiation in the presence of suitable catalysts [52,53] were mentioned as well. Finally, biological degradation methods of PCBs removal particularly from contaminated water and sewage were described.