Using solar and ultraviolet light to degrade PCBs in sand and transformer oils

• Published in: Chemosphere (Oxford) Vol. 57; no. 7; pp. 645 - 654
• Main Authors: Manzano, M.A., Perales, J.A., Sales, D., Quiroga, J.M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-11-2004; Elsevier
• Subjects: Acetone - chemistry; Applied sciences; Aroclor 1242; Decontamination. Miscellaneous; Degradation byproducts; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geologic Sediments - analysis; Industrial Oils - analysis; Kinetic; Kinetics; Photodechlorination; Photolysis - radiation effects; Pollution; Pollution, environment geology; Polychlorinated Biphenyls - chemistry; Soil and sediments pollution; Sunlight; Ultraviolet Rays; Photodechlorination; Aroclor 1242; Kinetic; Degradation byproducts; Sand; Sediments; Polychlorobiphenyl; Transformer oil; Free radical reaction; Persistent organic pollutant; Chemical reduction; Dechlorination; Pollution; Ultraviolet radiation; Decontamination; Chlorine Organic compounds; Reaction mechanism; Kinetics; Dielectric liquids; Solar radiation; Degradation product; Organic compounds; Photochemical degradation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2004.07.014

The present study describes the effect of the operating variables in the sensitized solar photolysis of sandy sediments contaminated by polychlorinated biphenyls (PCBs) in alkaline isopropanol. PCBs were almost completely removed in two weeks with stoichiometric release of chloride and biphenyl (BP) by a mechanism of reductive dechlorination. The concentration of the sensitizer (acetone) was the variable found to have most influence on the process. Under the same conditions, only partial dechlorination of the PCBs (34%) was observed in dielectric fluids without generating biphenyl to any appreciable extent.
Direct photolysis (ultraviolet light at 254
nm) of dielectric oils dissolved in alkaline isopropanol lead to 92% removal of PCBs in 60
min. The observed mechanism was again that of reductive dechlorination, with stoichiometric release of chloride, and the accumulation of biphenyl, quaterphenyl and condensation products of biphenyl with isopropanol.