Research of thermal properties of nitro derivatives of polychlorobiphenyls

Polychlorinated biphenyls (PCBs), persistent organic pollutants, have become widespread during their production and use as dielectric fluids, due to transboundary transport via water, air, and the food chain. Nitro derivatives of PCBs — secondary pollutants — also pose a hazard to the environment and humans, but data on their thermal properties are insufficient. The aim of this study was to investigate the thermal properties of nitro derivatives of PCBs. Synthesized nitro derivatives of PCBs, which are components of technical mixtures of the brands «Trichlorbiphenyl» and «Sovol», were analyzed. Using simultaneous thermal analysis it was established that the studied mixtures of nitro derivatives are prone to sublimation rather than thermal decomposition. Onset temperatures of sublimation and enthalpies of sublimation were determined. It was found that as chlorine substituents accumulate in the biphenyl structure, the thermal stability of the nitro derivatives decreases. Furthermore, with increasing ambient temperature, polychlorinated nitroarenes can migrate into atmospheric boundary layers characterized by temperature inversion and increased pollution. The obtained results can be used to improve methods for monitoring nitro derivatives of polychlorinated biphenyls in environmental samples.

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