Formation of 3,3',4,4'-tetrachloroazobenzene from 3,4-dichloroaniline in Ontario soils.

Abstract

The formation of 3,3′,4,4′-tetrachloroazobenzene (TCAB) from 3,4-dichloroaniline (3,4-DCA) was studied using four Ontario soils. The disappearance of 3,4-DCA from Guelph loam was primarily due to chemical mechanisms under anaerobic and water-saturated conditions, while under aerobic and water-unsaturated conditions about 25% of the loss could be attributed to microbial activity. Only a small percentage of the disappearance of measurable 3,4-DCA was associated with TCAB formation. TCAB was formed in varying amounts in the limited number of soils examined. None was formed in a Peel clay. The optimum soil temperature for formation of TCAB was 25 °C, and the optimum concentration of 3,4-DCA required was found to be 500 μg/g of soil. Maximum conversion of 3,4-DCA to TCAB was 4.8% at optimal conditions. In soil shown to have an Eh of about −300 mV, TCAB formation was strikingly reduced. TCAB formed in low concentrations in Guelph loam disappeared with continued incubation, and evidence is presented for non-biological degradation of this condensed molecule.