Effect of SO on 1,1,1-trichloroethane degradation by Fe(0) in aqueous solution

Abstract

Sulfate in groundwater has been previously shown to change the reactivity of Fe(0) in permeable reactive barriers for reducing chlorinated organics. To better understand the effect and mechanism of SO, the degradation of 1,1,1-trichloroethane (TCA) by Fe(0) in unbuffered aqueous solutions with and without SO was investigated. In a Fe(0) -TCA-H2 O system with initial pH of 2.0 to 10.0, the maximum removal rate of TCA was achieved at the initial pH 6.0 with pseudo-first-order constant Kobs 9.0 × 10(-3) /min. But in a Fe(0) -TCA-Na2 SO4 -H2 O system, the removal rate of TCA decreased remarkably with a reduction in Kobs to 1.0 × 10(-3) /min, and the pH varied from 6.0 to 9.6, indicating an inhibition of TCA dehydrochlorination by SO. Sulfate remarkably inhibited TCA degradation via changing the route of Fe(0) dissolution. It accelerated the dissolution of Fe(0) and transformed the intermediate form Fe(OH)ads to Fe2 (SO4 )ads , which weakened the affinity between Fe and TCA, and thus depressed the degradation of TCA by Fe(0) .