Abstract

Metallic iron (Fe⁰) is a reactive material that is widely used for industrial water treatment. The course of the metal ion removal process using Fe⁰ (iron powder) was monitored electrochemically (differential pulse polarography). As probe species, Zn²⁺, Pb²⁺, and Cd²⁺ were selected for their different (1) adsorptive affinity to iron corrosion products (FeCPs), (2) redox properties, (3) precipitation ability at various pH. Batch experiments were carried out with binary (Zn²⁺/ Pb²⁺ and Zn²⁺/ Cd²⁺) and ternary (Zn²⁺/Cd²⁺/Pb²⁺) systems to reveal the mutual interference of these cations. Detailed time monitoring of iron aging for up to 14 days as well as concentration decay of individual removed cations represent important data for mechanistic discussions. The aqueous concentration of Fe²⁺ was also monitored. FeCPs were characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Results showed that the presence of Pb²⁺ delays the Zn²⁺ removal whereas the presence of Cd²⁺ in solution accelerates its removal. The removal of Pb²⁺ by FeCPs was not affected by the presence of Zn²⁺ and Cd²⁺, moreover, the Pb²⁺ inhibited the effect of Cd²⁺ on the removal of Zn²⁺. XPS has proven existence of Fe₂O₃ and hydrated Fe oxidic phase, whilst the SEM showed that the original Fe grains were partly dissolved into buffered ambient under formation of fine particles of FeCPs. Results confirm that reductive transformation of any contaminant in a Fe⁰/H₂O system is the consequence and not the cause of iron corrosion.

Graphic abstract

中文翻译：

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Fe 0 / H 2 O系统中金属离子去除的电化学监测：阳离子Zn 2+，Pb 2+和Cd 2+的竞争效应

摘要

金属铁（Fe ⁰）是一种反应性材料，广泛用于工业水处理。使用Fe ⁰（铁粉）去除金属离子的过程进行了电化学监测（微分脉冲极谱法）。选择Zn 2 ⁺，Pb ²⁺和Cd ²⁺作为探针种类，因为它们具有不同的（1）对铁腐蚀产物（FeCPs）的吸附亲和力，（2）氧化还原特性，（3）在各种pH下的沉淀能力。使用二元（Zn ²⁺ / Pb ²⁺和Zn ²⁺ / Cd ²⁺）和三元（Zn ²⁺ / Cd ²⁺ / Pb ²⁺）系统以揭示这些阳离子的相互干扰。铁老化长达14天的详细时间监控以及单个去除的阳离子的浓度衰减是进行机械讨论的重要数据。还监测Fe ²⁺的水溶液浓度。FeCPs使用X射线光电子能谱（XPS）和扫描电子显微镜（SEM）进行了表征。结果表明，Pb ²⁺的存在会延迟Zn ^2+的去除，而溶液中Cd ²⁺的存在会加速其去除。FeCPs对Pb ²⁺的去除不受Zn ²⁺和Cd ²⁺的存在的影响，此外，Pb ²⁺抑制了Cd ²⁺去除Zn ^2+的作用。XPS已证明存在Fe ₂ O ₃和水合的Fe氧化相，而SEM显示，在形成FeCPs细颗粒的情况下，原始的Fe晶粒部分溶解在缓冲的环境中。结果证实，Fe ⁰ / H ₂ O系统中任何污染物的还原性转化是结果，而不是铁腐蚀的原因。

图形摘要