Tzou Y M, Wang M K, Loeppert R H
Department of Soil Environmental Science, National Chung-Hsing University, Taichung, Taiwan.
Chemosphere. 2003 Jun;51(9):993-1000. doi: 10.1016/S0045-6535(03)00002-X.
The complexation of Fe(II) with organic ligand results in the decrease of redox potential, and enhances the reduction ability of Fe(II). An important example is the use of Fe(II)-organic complexes to accelerate Cr(VI) reduction. Dissolved O(2) and light can potentially affect Cr(VI) reduction; however, these two factors have not been adequately evaluated. A batch technique was used to investigate the Cr(VI) reduction as influenced by the light and dissolved O(2) using N-hydroxyethyl-ethylenediamine-triacetic acid (HEDTA) and Fe(II) solutions. The oxidation of Fe(II) by dissolved O(2) was rapid in the presence of HEDTA at low pH; nonetheless, the oxidation proceeded slowly when HEDTA was absent. Although Cr(VI) could be reduced by free Fe(II) at low pH, the reaction was considerably slower than that of systems involving HEDTA. The enhancement of Cr(VI) reduction by Fe(II) in the presence of high concentrations of HEDTA was achieved as a result of two processes. First, HEDTA acted as a ligand for expediting electron transfer between Fe(II) and Cr(VI). Secondly, HEDTA served as a reductant for Cr(VI) under illumination.
Fe(II) 与有机配体的络合作用导致氧化还原电位降低，并增强了 Fe(II) 的还原能力。一个重要的例子是使用 Fe(II)-有机络合物来加速 Cr(VI) 的还原。溶解氧 (O₂) 和光照可能会影响 Cr(VI) 的还原；然而，这两个因素尚未得到充分评估。采用间歇式技术，使用 N-羟乙基乙二胺三乙酸 (HEDTA) 和 Fe(II) 溶液，研究光照和溶解氧 (O₂) 对 Cr(VI) 还原的影响。在低 pH 值下，在 HEDTA 存在的情况下，溶解氧 (O₂) 对 Fe(II) 的氧化反应迅速；然而，在没有 HEDTA 的情况下，氧化反应进行得很慢。尽管在低 pH 值下，游离的 Fe(II) 可以还原 Cr(VI)，但该反应比涉及 HEDTA 的体系要慢得多。在高浓度 HEDTA 存在的情况下，Fe(II) 对 Cr(VI) 还原的促进作用是由两个过程实现的。首先，HEDTA 作为配体，加速了 Fe(II) 和 Cr(VI) 之间的电子转移。其次，在光照条件下，HEDTA 作为 Cr(VI) 的还原剂。
