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Speciation of EDTA in Natural Waters: Exchange Kinetics of Fe-EDTA in River Water

机译：天然水中EDTA的形态：河水中Fe-EDTA的交换动力学

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摘要

In order to understand the speciation of EDTA, the exchange kinetics of Fe(Ⅲ)—EDTA with other cations (Zn, Ca) are studied under the conditions of natural river water. Measurements in sewage treatment plant effluents indicate that EDTA is partly present as Fe(lll)-EDTA. At equilibrium, Fe-EDTA introduced into river water is expected to exchange with Zn(Ⅱ) and Ca to form Zn-EDTA or Ca-EDTA. The exchange of Fe-EDTA with Zn(Ⅱ), which was followed by voltammetric measurement of labile Zn, as well as the disappearance of Fe—EDTA, which was measured as a photolabile species, occur on a time scale of days. The results are presented in terms of second-order rate laws, with the average observed rate constant, k= 10.3 M~(-1) s~(-1) for the exchange of Zn(Ⅱ) with Fe-EDTA in river water; the dissociation of Fe-EDTA appears to be the rate-limiting step forthis reaction, with a first-order rate constant of 4 x 10~(-7) s~(-1). The exchange of Zn(Ⅱ) with Ca-EDTA is much faster, with k = 1.1 x 10~3 M~(-1) s~(-1). From the first-order rates, a half-time of about 20 days is obtained for the exchange of Fe(Ⅲ)-EDTA in the river water. If a slowly dissociating complex, such as Fe-EDTA, is initially present, the initial speciation is determining the fate of EDTA in river water; equilibrium speciation of EDTA and trace metals may not be reached within the time scale of the river flow if the inputs occur as Fe-EDTA.
机译：为了了解EDTA的形态，研究了天然河水条件下Fe（Ⅲ）-EDTA与其他阳离子（Zn，Ca）的交换动力学。对污水处理厂废水的测量表明，EDTA部分以Fe（III）-EDTA的形式存在。在平衡状态下，引入河水中的Fe-EDTA有望与Zn（Ⅱ）和Ca交换形成Zn-EDTA或Ca-EDTA。 Fe-EDTA与Zn（Ⅱ）的交换，然后通过伏安法测量不稳定的Zn，以及Fe-EDTA的消失（以光不稳定物质的形式进行测量）发生在几天的时间范围内。结果以二阶速率定律表示，平均观测速率常数k = 10.3 M〜（-1）s〜（-1），用于河水中Zn（Ⅱ）与Fe-EDTA的交换; Fe-EDTA的解离似乎是该反应的限速步骤，其一级速率常数为4 x 10〜（-7）s〜（-1）。 Zn（Ⅱ）与Ca-EDTA的交换要快得多，k = 1.1 x 10〜3 M〜（-1）s〜（-1）。从一级速率，获得了约20天的半衰期，用于交换河水中的Fe（Ⅲ）-EDTA。如果最初存在缓慢解离的复合物，例如Fe-EDTA，则最初的物种决定了河水中EDTA的命运。如果输入物为Fe-EDTA，则在河流流量的时间范围内可能无法达到EDTA和痕量金属的平衡形态。

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  • 来源
    《Environmental Science & Technology》 |1995年第1期|p.59-68|共10页
  • 作者

    HANBIN XUE; LAURA SIGG; FRANZ GUENTER KARI;

  • 作者单位

    Research Center for Limnology, Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH-6047 Kastanienbaum, Switzerland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 环境化学;
  • 关键词

  • 入库时间 2022-08-17 14:09:37

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