A kinetic and mechanistic study of the degradation of 1,2-dichloroethane and methyl tert-butyl ether using alkaline-activated persulfate oxidation

Abstract

In this study, alkaline-activated persulfate is used to treat groundwater that is contaminated with 1,2-dichloroethane (1,2-DCA)- and methyl tert-butyl ether (MTBE). The results show that alkaline-activated persulfate accelerates the degradation of 1,2-DCA. Vinyl chloride is produced because there is dehydrochlorination of 1,2-DCA at high pH. Although the rate of degradation of MTBE in alkaline-activated persulfate systems is decreased, there is a significant reduction in the accumulation of MTBE-degrading byproducts, tert-butyl alcohol and tert-butyl formate. Alkaline-activated persulfate degrades 1,2-DCA via the mechanisms of oxidation and dehydrochlorination, but oxidation alone contributes to the removal of MTBE. The use of low-cost basic oxygen furnace (BOF) slag increases the pH of the solution (>12) and allows the alkaline-activated persulfate reaction to proceed. No detectable heavy metals are released from the BOF slag in the persulfate system that is activated by BOF slag. The degradation of 1,2-DCA and MTBE follows the pseudo-first-order kinetics for all persulfate systems. Alkaline-activated persulfate causes a decrease in ORP because there is a high pH, which adversely affects the removal of contaminants if the contaminants do not undergo base-mediated degradation. Therefore, the performance in terms of contaminant removal must be evaluated before alkaline-activated persulfate is used for different compounds. This novel, slag-activated persulfate system is an environmentally friendly and cost-effective alternative to the remediation of groundwater.