A COMPARATIVE-STUDY OF THE PHOTOLYTIC DEGRADATION OF OCTACHLORODIBENZOFURAN (OCDF) AND OCTACHLORODIBENZO-P-DIOXIN (OCDD)

Photolysis at 290 nm and higher wavelengths of octachlorodibenzofuran (OCDF) and octachlorodibenzo-p-dioxin (OCDD) was studied in three organic solvents hexane, 1,4-dioxane and methanol. It appeared that the degradation kinetics strongly depended on the type of solvent. OCDD degraded fastest in hexane, whereas OCDF degraded fastest in methanol. Less than 5% of the total loss of OCDD degraded by reductive dechlorination, with preferential loss of chlorine atoms at the 1 or 9 positions. 35 to 50% of the total loss of OCDF degraded via reductive dechlorination, with preferential loss of lateral chlorine. OCDF degraded faster than OCDD in all studied solvents. Photolysis at 290 nn and higher wavelengths of OCDD and OCDF adsorbed onto alumina impregnated with copper (alumina/Cu) in the presence of natural and distilled water was also investigated. Under these more relevant environmental aquatic conditions, photolysis of OCDD and OCDF was much slower than photolysis in the studied organic solvents. Significant loss was only found for OCDF. A part of the loss of OCDF could be explained by reductive dechlorination; the results suggested that other mechanisms of degradation occurred in addition to reductive dechlorination. All photolysis experiments showed that OCDF was photochemically less stable than OCDD.