钙镁离子及重碳酸盐对零价铁还原对氯硝基苯的影响
Effect of Ca2+, Mg2+ and HCO-3 on the reduction of para-chloronitrobenzene by zero-valent iron
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摘要: 通过间歇式实验,考察了地下水中常见硬度离子Ca2+、Mg2+及HCO-3的独立作用和联合作用对零价铁还原对氯硝基苯的影响。实验结果表明,Ca2+、Mg2+对零价铁还原对氯硝基苯反应的促进作用不明显。HCO-3浓度为0~100 mg/L时可显著提高零价铁还原对氯硝基苯的速率,反应2 h后对氯硝基苯转化率由44.1%升至84.8%;当HCO-3浓度大于100 mg/L时,促进作用会由于碳酸铁盐类物质的产生而下降。当Ca2+或Mg2+与HCO-3共存时,会产生碳酸钙或碳酸镁之类的沉淀物,占据还原位点,不利于反应的进行。当采用零价铁修复地下水氯硝基苯化合物污染时,应考虑地下水硬度的影响。Abstract: Batch tests were conducted to investigate individual and cooperative effects of Ca2+, Mg2+ and HCO-3 in groundwater on the reduction of para-chloronitrobenzene (p-CNB) by zerovalent iron (ZVI). The results showed that Ca2+ and Mg2+ did not improve p-CNB reduction. HCO-3 significantly enhanced p-CNB conversion rate when its concentration was 0~100 mg/L; p-CNB removal increased from 44.1% to 84.8% in 2 h. But p-CNB removal efficiency decreased owing to the formation of ferric carbonates when HCO-3 concentration exceeded 100 mg/L. Due to the formation of CaCO3 (or MgCO3) blocking the active sites where electron transfer took place, the coexistence of Ca2+ (or Mg2+) and HCO-3 had an inhibitory effect on p-CNB removal. It indicated that the effects of hardness and bicarbonate in groundwater should be taken into account when zero-valent iron is applied for the remediation of chloronitrobenzenes contaminated groundwater.
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Key words:
- groundwater /
- hardness /
- zero-valent iron /
- para-chloronitrobenzene
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