Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
Ground Water. 2013 Mar;51(2):286-92. doi: 10.1111/j.1745-6584.2012.00957.x. Epub 2012 Jun 20.
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) .
地下水硫酸盐先前已被证明可以改变可渗透反应性屏障中用于还原氯化有机物的零价铁的反应性。为了更好地理解 SO 的影响和机制，研究了在无缓冲水溶液中有无 SO 的情况下，零价铁对 1,1,1-三氯乙烷（TCA）的降解作用。在初始 pH 值为 2.0 到 10.0 的 Fe(0)-TCA-H2O 体系中，TCA 的最大去除率在初始 pH 值为 6.0 时达到，假一级常数 Kobs 为 9.0×10(-3)/min。但在 Fe(0)-TCA-Na2SO4-H2O 体系中，TCA 的去除率随 Kobs 降至 1.0×10(-3)/min 而显著降低，且 pH 值从 6.0 变化到 9.6，表明 SO 抑制了 TCA 的脱氯化氢作用。硫酸盐通过改变零价铁的溶解途径显著抑制了 TCA 的降解。它加速了零价铁的溶解，并将中间形式的 Fe(OH)ads 转化为 Fe2(SO4)ads，这削弱了 Fe 与 TCA 之间的亲和力，从而抑制了零价铁对 TCA 的降解。
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