Degradation of 1,2-dichloroethane with advanced reduction processes (ARPs): Effects of process variables and mechanisms

• 1,2-DCA is rapidly degraded by various advanced reduction processes.
• Degradation is affected by pH, sulfite dose, light intensity, and target concentration.
• A kinetic model explains the dependence of rate constant on process variables.
• 1,2-DCA is degraded by the aqueous electron produced from the sulfite/UV ARP.
• Vinyl chloride is degraded by the sulfite radical produced from the sulfite/UV ARP.

1,2-Dichlroroethane (1,2-DCA) is a widely used chemical with potential to harm the environment and human health. In this study, successful degradation of 1,2-DCA was achieved with various advanced reduction processes (ARPs) that combine ultraviolet (UV) irradiation with various reagents (dithionite, sulfite, sulfide, ferrous iron). The degradation kinetics in the sulfite/UV ARP was found to follow a pseudo-first-order decay model and the effects on kinetics of several factors were studied. More than 90% of initial 1,2-DCA was removed within 20 min in alkaline conditions (pH 8.2, 9.0 and 11.0) while it took 130 min to reach same removal at pH 7.0. Increasing the sulfite dose and UV light intensity caused the rate constant to increase linearly, but higher initial 1,2-DCA concentrations resulted in lower rate constants. Scavenging experiments with nitrate and nitrous oxide demonstrated the aqueous electron is the major species causing 1,2-DCA degradation in the sulfite/UV ARP, while the sulfite radical appears to be more important in degradation of vinyl chloride. The dechlorination of 1,2-DCA to chloride ion was enhanced by raising the solution pH with more than 90% dechlorination obtained at pH 11. This work supports application of ARPs to degradation of other chlorinated organics.