Modeling the formation of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the historical manufacture of 2,4,5-trichlorophenol

ABSTRACT

A universal model for the simulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin concentrations in the historical manufacture of 2,4,5-trichlorophenol was developed. The model successfully simulates the conversion of 1,2,4,5-tetrachlorobenzene to 2,4,5-trichlorophenol, and modeled the concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin with an r² of .941 against measured data from 38 experimental runs. The high r² supports the proposed formation mechanism (second order with respect to 2,4,5-trichlorophenol). Simultaneous degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin by methoxylation/hydroxylation was hypothesized to play a role; however, modeling indicated this was insignificant in the industrial production of 2,4,5-trichlorophenol. This model can be a useful tool in environmental forensic investigations of sites where 2,4,5-trichlorophenol was produced.

KEYWORDS:

• 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD)
• 2,4,5-trichlorophenol (2,4,5-TCP)
• 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)
• dioxin formation
• modeling