2,3,7,8-Tetrachlorodibenzodioxin Formation On Fe(III)-Montmorillonite Clay.

2,3,7,8-tetrachlorodibenzodioxin (TCDD) is the most toxic congener in dioxin family. People have great concern over this compound due to its extreme toxicity on human health. It is generally believed that the emission of dioxin was closely related to human activities, for example, waste incineration, metal smelting, and manufacture of certain herbicides, as well as natural contribution processes such as forest fires. However, our previous study found that octachlorodibenzo-p-dioxin (OCDD) can be formed from precursor pentachlorophenol on naturally occurring montmorillonite clay under environmentally relevant conditions. Similar experiments have been conducted using 2,4,5-trichlorophenol (TrCP) as the precursor molecule. Our results show that the major products are the dimer of TrCP, and both TCDD and pentachlorodibenzodioxin are formed on the clay surface. This study provides strong evidence that clay can be a potential source to account for the elevated level of dioxins in the environment.