零价铁还原地下水硝酸盐过程中去除率降低原因探究

Reasons Discussion on Decreasing Removal Rate of Groundwater Nitrate in Zero-valent Iron Reduction Process

零价铁以其价格低廉、易操作等优点常被作为地下水硝酸盐污染原位修复材料,但随着工程运行时间增长,会出现修复介质透水能力减弱、去除率降低、产物中氨氮超标等问题,制约或限制了其在地下水污染原位修复中的推广和应用。为此,结合室内柱试验和PHREEQC数值模型,利用化学反应平衡模型模拟了Fe含量与水中各溶质组分变化的关系及其饱和相的分布规律,并探讨分析了成因机理。结果表明,反应过程中生成的Fe_3O_4和Fe_2O_3不仅造成了装置堵塞,还阻止了反应进一步进行,是去除率逐渐下降的重要原因。

Because of its low price and easy operation,zero-valent iron is commonly used in situ remediation of groundwater nitrate pollution.However,with the project operation time increasing,the hydraulic conductivity of the remediation medium decreases,the removal rate decreases,and the ammonia nitrogen is excessive in the reaction product.These problems restrict the popularization of zero-valent iron in situ remediation of groundwater nitrate pollution.Therefore,combined the column test and PHREEQC numerical model,the chemical reaction equilibrium model was used to simulate the solute components changes and equilibrium phases distribution with the increase of Fe.The reason was given detailed analysis.The results reveal that the formation of Fe3O4 and Fe2O3 caused the device clogging during the reaction.They also prevented the further progress of the reaction,which was an important reason for the gradual decrease of the removal rate.