Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Sai Kung, Hong Kong, PR China.
Water Res. 2012 Sep 1;46(13):4071-80. doi: 10.1016/j.watres.2012.05.015. Epub 2012 May 15.
Nano zero-valent iron (NZVI) offers a promising approach for arsenic remediation, but the spent NZVI with elevated arsenic content could arouse safety concerns. This study investigated the fate of As(V)-treated NZVI (As-NZVI), by examining the desorption potential of As under varying conditions. The desorption kinetics of As from As-NZVI as induced by phosphate was well described by a biphasic rate model. The effects of As(V)/NZVI mass ratio, pH, and aging time on arsenic desorption from As-NZVI by phosphate were investigated. Less arsenic desorption was observed at lower pH or higher As(V)/NZVI mass ratio, where stronger complexes (bidentate) formed between As(V) and NZVI corrosion products as indicated by FTIR analysis. Compared with the fresh As-NZVI, the amount of phosphate-extractable As significantly decreased in As-NZVI aged for 30 or 60 days. The results of the sequential extraction experiments demonstrated that a larger fraction of As was sorbed in the crystalline phases after aging, making it less susceptible to phosphate displacement. However, at pH 9, a slightly higher proportion of phosphate-extractable As was observed in the 60-day sample than in the 30-day sample. XPS results revealed the transformation of As(V) to more easily desorbed As(III) during aging and a higher As(III)/As(V) ratio in the 60-day sample at pH 9, which might have resulted in the higher desorption.
纳米零价铁（NZVI）为砷修复提供了一种很有前途的方法，但高砷含量的废弃 NZVI 可能会引起安全问题。本研究通过考察不同条件下磷对 NZVI 中砷的解吸潜力，研究了处理过的 As(V)-NZVI（As-NZVI）的命运。磷诱导的 As-NZVI 中砷的解吸动力学很好地用双相速率模型描述。考察了 As(V)/NZVI 质量比、pH 值和老化时间对 As-NZVI 中砷由磷解吸的影响。在较低的 pH 值或较高的 As(V)/NZVI 质量比下，观察到较少的砷解吸，这表明 As(V)与 NZVI 腐蚀产物之间形成了更强的配合物（双齿），如 FTIR 分析所示。与新鲜的 As-NZVI 相比，在老化 30 或 60 天后，As-NZVI 中可被磷酸盐提取的砷量显著减少。顺序提取实验的结果表明，在老化后，更多的砷被吸附在晶相中，使其不易被磷酸盐置换。然而，在 pH 9 时，在 60 天的样品中观察到比 30 天的样品略高比例的磷酸盐可提取的砷。XPS 结果表明，在老化过程中 As(V)转化为更容易解吸的 As(III)，并且在 pH 9 时 60 天的样品中 As(III)/As(V)比值更高，这可能导致了更高的解吸。
