Pd-catalyzed TCE dechlorination in water:: Effect of [H2](aq) and H2-utilizing competitive solutes on the TCE dechlorination rate and product distribution
Pd-catalyzed TCE dechlorination in water:: Effect of [H2](aq) and H2-utilizing competitive solutes on the TCE dechlorination rate and product distribution
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DOI：
10.1021/es001623f
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发表时间：
2001-02-15
影响因子：
11.4
通讯作者：
Reinhard, M
中科院分区：
文献类型：
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作者：
Lowry, GV;Reinhard, M
水相H-2浓度（[H-2]（aq））和利用H-2的竞争性溶质的存在影响Pd基井内处理反应器中TCE的脱氯效率。[H-2]（aq）和利用H-2的竞争溶质（顺-DCE、反-DCE、1，1-DCE、溶解氧（DO）、亚硝酸盐、硝酸盐）对TCE转化速率和产物分布的影响使用100 mg/L的粉末状Pd-/-Al 2 O3催化剂在间歇式反应器中或1.0 g的1.6 mm Pd-/-γ-Al 2 O3催化剂在塔式反应器中进行评价。当[H-2]（aq）从1000降至100 μ M时，TCE脱氯速率常数从0.034 +/- 0.006降至0.015 +/- 0.001 min（-1），下降了55%;当[H-2]（aq）从100降至10 μ M时，TCE脱氯速率常数急剧降至0.0007 +/- 0.0003 min（-1）。反应性氯化中间体和C4-C6自由基偶联产物的产生随着[H-2]（aq）的减少而增加。在[H-2]（aq）为10 μ M（P/P-o = 0.01）时，DCE异构体和氯乙烯占TCE转化的最大值的9.8%，但此后消失，C4-C6自由基偶联产物占TCE转化的18%。TCE转化率不受顺式-DCE（202 μ M）、反式-DCE（89 μ M）和1，1-DCE（91 μ M）的影响，表明这些化合物不与TCE竞争催化剂活性位点。DO的活性是TCE的两倍，但在低于370 μ M（11.8 mg/L）的浓度下，对TCE转化没有影响，表明在典型的地下水DO浓度下，DO和TCE不会竞争活性催化剂位点。在流入DO水平大于450 mM（14.3 mg/L）时，柱中的TCE转化率降低多达10倍，因为[H-2]（aq）由于DO转化中使用的H-2而降至100 μ M以下。亚硝酸盐的反应比TCE慢2-5倍，并且在6630 μ M（305 mg/L）的浓度下使TCE转化率降低小于4%。硝酸盐在1290 μ M（80 mg/L）浓度下不具有反应性，也不影响TCE转化。
The aqueous-phase H-2 concentration ([H-2](aq)) and the presence of H-2-utilizing competitive solutes affect TCE dechlorination efficiency in Pd-based in-well treatment reactors. The effect of [H-2](aq) and H-2-utilizing competing solutes (cis-DCE, trans-DCE, 1,1-DCE, dissolved oxygen (DO), nitrite, nitrate) on the TCE transformation rate and product distribution were evaluated using 100 mg/L of a powdered Pd-on-Al2O3 catalysts in batch reactors or 1.0 g of a 1.6-mm Pd-on-gamma -Al2O3 catalyst in column reactors. The TCE dechlorination rate constant decreased by 55% from 0.034 +/- 0.006 to 0.015 +/- 0.001 min(-1) when the [H-2](aq) decreased from 1000 to 100 muM and decreased sharply to 0.0007 +/- 0.0003 min(-1) when the [H-2](aq) decreased from 100 to 10 muM. Production of reactive chlorinated intermediates and C4-C6 radical coupling products increased with decreasing [H-2](aq). At an [H-2](aq) of 10 muM (P/P-o = 0.01), DCE isomers and vinyl chloride accounted for as much as 9.8% of the TCE transformed at their maximum but disappeared thereafter, and C4-C6 radical coupling products accounted for as much as 18% of TCE transformed. The TCE transformation rate was unaffected by the presence of cis-DCE (202 muM), trans-DCE (89 muM), and 1,1-DCE (91 muM), indicating that these compounds do not compete with TCE for catalyst active sites. DO is twice as reactive as TCE but had no effect on TCE conversion in the column below a concentration of 370 muM (11.8 mg/L), indicating that DO and TCE will not compete for active catalyst sites at typical groundwater DO concentrations. TCE conversion in the column was reduced by as much as a factor of 10 at influent DO levels greater than 450 mM (14.3 mg/L) because the [H-2](aq) fell below 100 muM due to H-2 utilized in DO conversion. Nitrite reacts 2-5 times slower than TCE and reduced TCE conversion by less than 4% at a concentration of 6630 muM (305 mg/L). Nitrate was not reactive and did not effect TCE conversion at a concentration of 1290 muM (80 mg/L).