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 orga nic solvents hexane, 1,4-dioxane and methanol. It appeared that the de gradation kinetics strongly depended on the type of solvent. OCDD degr aded fastest in hexane, whereas OCDF degraded fastest in methanol. Les s than 5% of the total loss of OCDD degraded by reductive dechlorinati on, with preferential loss of chlorine atoms at the 1 or 9 positions. 35 to 50% of the total loss of OCDF degraded via reductive dechlorinat ion, with preferential loss of lateral chlorine. OCDF degraded faster than OCDD in all studied solvents. Photolysis at 290 nn and higher wav elengths of OCDD and OCDF adsorbed onto alumina impregnated with coppe r (alumina/Cu) in the presence of natural and distilled water was also investigated. Under these more relevant environmental aquatic conditi ons, photolysis of OCDD and OCDF was much slower than photolysis in th e studied organic solvents. Significant loss was only found for OCDF. A part of the loss of OCDF could be explained by reductive dechlorinat ion; the results suggested that other mechanisms of degradation occurr ed in addition to reductive dechlorination. All photolysis experiments showed that OCDF was photochemically less stable than OCDD.