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 Ca^(2+),Mg^(2+) and HCO_3^- on the reduction of para-chloronitrobenzene by zero-valent iron

通过间歇式实验,考察了地下水中常见硬度离子Ca2+、Mg2+及HCO3-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。HCO3-浓度为0～100mg/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HCO3-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。

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 zero-valent 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-3had 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.