Dechlorination of PCDD/F by organic and inorganic electron transfer molecules in reduced environments

The dechlorination of octa- and pentachlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was investigated using organic and inorganic electron shuttles relevant to anaerobic sediments. OctaCDD was dechlorinated to hexaCDD in the presence of resorcinol, catechol, and 3,4-dichlorobenzoate, resulting in an increase of 2,3,7,8-substituted hepta- and hexaCDD. Vitamin B12 mediated the dechlorination of octaCDD to tetraCDD, octaCDF to hexaCDF, and 1,2,3,7,8-pentaCDD to at least two tetraCDD, including 2,3,7,8-TCDD. Zerovalent zinc stoichiometrically dechlorinated octaCDD to hexa- and pentaCDD under basic and neutral conditions, respectively. Thus, abiotically-mediated dechlorination reactions may contribute significantly to the fate of PCDD/F in reduced environments.