Reductive transformation and sorption of cis- and trans-1,2- dichloroethene in a metallic iron-water system

Reductive transformation kinetic and sorption coefficients were determined for both cis- and trans-1,2-dichloroethene (DCE) in batch systems with zero-valent iron and water. Sorption quasi-equilibrium occurred rapidly (<1.1 h) for both compounds. Freundlich-type isotherms adequately described sorption over the measured concentration range. The magnitude of sorption was greater for trans-1,2-DCE than for the more soluble cis-1,2-DCE, indicating a possible influence of hydrophobicity. The trans-isomer was more reactive than the cis-isomer. The reaction order (95% confidence intervals) for trans-1,2- DCE was 1.22 (0.97-1.48), and for cis-1,2-DCE was 1.77 (0.92-2.63) and 1.64 (1.05-2.23) in relatively high and low initial concentration experiments, respectively. The fact that the reaction order for the cis-isomer could not be reduced to unity by assuming that the bulk of observed sorption was to nonreactive sorption sites suggests that either the assumption may not be valid or that a more complex process exists for this isomer. Chloride was produced by the transformation reaction and chlorine mass balances for the batch systems were 80 to 85%. Other products observed were acetylene, ethene, ethane, C₃-C₅ alkanes, and vinyl chloride.