EK/Fe0-PRB联合修复实际砷污染土壤的协同机制

以我国某矿区砷污染土壤为研究对象，采用EK/Fe⁰-PRB联合修复工艺去除土壤中的砷，考察了土壤含水率及增强试剂对砷去除的影响，分析了修复前后土壤中砷的迁移分布及砷价态分布变化，并借助X射线光电子能谱（XPS）对修复前后PRB填料Fe⁰进行了表征分析，探讨了EK/PRB修复砷污染的协同机制。结果表明，在EK/PRB联合修复过程中，EK去除作用所占比例为22%～43%，而PRB的去除作用所占比例为52%～71%，以PRB的去除作用为主；未添加增强试剂时，阳极液砷收集含量明显高于阴极液砷收集含量，电动去除机制主要为电迁移作用，添加增强试剂后，阴极液砷收集含量所占比例明显升高；EK/PRB修复后，As（Ⅴ）和As（Ⅲ）在土壤、电极液、PRB中的含量比例基本没有变化，As（Ⅴ）含量比例略微升高，即处理之后土壤中的五价砷并不会经氧化还原作用而转变成毒性较高的三价砷；反应后Fe⁰表面存在As（Ⅲ）和As（Ⅴ），未发现As（0）的存在，因此砷在PRB中仅通过铁表面氧化物的吸附作用而去除。

Synergistic effects of electrokinetics process coupled with zero-valent iron permeable reaction barrier in remediation of arsenic-contaminated soil

The remediation of arsenic polluted soil from a mining area in China using the electrokinetics process coupled with zero-valent iron permeable reaction barrier was researched. The influence of soil moisture content and enhancement reagents on arsenic removal was investigated. The changes of distribution and valence state of arsenic before and after the remediation were analyzed. In addition, surface features of the fresh and used zero-valent iron were characterized by X-ray photoelectron spectroscopy (XPS). Then synergistic effects of EK/PRB in the remediation of arsenic-contaminated soil was discussed. The results showed that in the EK/PRB remediation process, fraction of the EK removal mechanism was 22% to 43%, while fraction of the PRB removal mechanism was 52% to 71%, so the PRB process was dominate. When the enhancement reagents was absent, arsenic mainly tends to move toward the anolyte, which indicated the mainly removal mechanisms was electromigration. However, when the enhancement reagents was added, the proportion of arsenic collected from the cathode solution was significantly increased. After EK/PRB remediation, the percentage content of As(Ⅴ) and As (Ⅲ) in soil, electrode liquid and PRB had no substantial changes, only the content ratio of As(Ⅴ) raised slightly. Pentavalent arsenic will not be reduced into trivalent arsenic with higher toxicity. There were no As(0) but As(Ⅲ) and As(Ⅴ) on the surface of the used Fe⁰. Therefore, arsenic was removed in PRB only through adsorption of the iron surface oxides.