Doong R A, Lee C C, Chen K T, Wu S F
Department of Atomic Science, National Tsing Hua University, Hsinchu, Chinese Taiwan.
Water Sci Technol. 2004;50(8):89-96.
The feasibility of using zerovalent silicon (Si0) as a novel reductant to remove chlorinated compounds and heavy metals in contaminated sites was investigated. The kinetics and degradation mechanism of carbon tetrachloride (CT) by Si0 were also examined. Results showed that zerovalent silicon could effectively dechlorinate the chlorinated compounds. A nearly complete dechlorination of CT by Si0 was obtained within 14 h. The produced concentrations of chloroform (CF) accounted for 71-88% loss of CT, showing that reductive dechlorination is the major degradation pathway for the degradation of chlorinated hydrocarbons by Si0. The degradation followed pseudo first-order kinetics and the normalized surface reaction rate constant (k(sa)) for CT dechlorination ranged between 0.0342 and 0.0454 L m(-2) h(-1) when CT concentrations were in the range of 3-20 microM. A linear relationship between the k(sa) and pH value was also established. In addition, zerovalent silicon has a high capability in the removal of heavy metals. 83% of Cr(VI) was removed by 0.5g Si0 within 5 h, which is higher than that by Fe0. The removal efficiency of divalent metal ions by Si0 followed the order of Cu(II) > Pb(II) > Ni(II). This indicates that zerovalent silicon is an alternative reductant and can undergo coupled reduction of heavy metals and chlorinated hydrocarbons in contaminated groundwater.
研究了使用零价硅（Si0）作为新型还原剂去除污染场地中氯代化合物和重金属的可行性。还考察了Si0对四氯化碳（CT）的动力学及降解机制。结果表明，零价硅能有效使氯代化合物脱氯。在14小时内Si0使CT几乎完全脱氯。生成的氯仿（CF）浓度占CT损失的71 - 88%，表明还原脱氯是Si0降解氯代烃的主要降解途径。降解遵循准一级动力学，当CT浓度在3 - 20 microM范围内时，CT脱氯的归一化表面反应速率常数（k(sa)）在0.0342至0.0454 L m(-2) h(-1)之间。还建立了k(sa)与pH值之间的线性关系。此外，零价硅对重金属有很高的去除能力。0.5 g Si0在5小时内去除了83%的Cr(VI)，这比Fe0的去除率高。Si0对二价金属离子的去除效率顺序为Cu(II) > Pb(II) > Ni(II)。这表明零价硅是一种替代还原剂，可在受污染地下水中实现重金属和氯代烃的耦合还原。
