Investigation of the Scorodite Formation Mechanism in As(V) Solution Containing Fe(II) with Hematite Addition Using a Stable Iron Isotope
Investigation of the Scorodite Formation Mechanism in As(V) Solution Containing Fe(II) with Hematite Addition Using a Stable Iron Isotope
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DOI：
10.2320/matertrans.m-m2022801
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发表时间：
2022-01-01
影响因子：
1.2
通讯作者：
Shibata, Etsuro
中科院分区：
文献类型：
--
作者：
Iizuka, Atsushi;Adachi, Ken;Shibata, Etsuro
砷是一种有毒元素，开发有效的砷去除和稳定方法是必要的。五价砷的去除和稳定化是一种很有前途的处理工业副产物砷的方法。在适当的条件下，将赤铁矿(Fe(III)(2)O-3)粉末加入含Fe(II)的As(V)溶液中，形成凝胶状前驱体，生成蝎石晶体。当溶液中不含Fe(II)时，即使加入赤铁矿，生成反应也不会进行。因此，认为溶液中的Fe(II)在形成机理中起着重要作用。本文通过在反应溶液中添加稳定的铁同位素(Fe-54)的合成实验，研究了赤铁矿加入法中蝎石晶体的形成机理。据估计，构成蝎子石晶体的Fe(III)主要(约80%以上)来源于溶液中的Fe(II)。根据这一结果，可以认为从反应溶液与固体赤铁矿形成蝎子石的过程如下。凝胶前驱体由反应溶液中的Fe(II)和赤铁矿中的Fe(III)组成。在凝胶状前驱体转化为蝎石晶体的过程中，前驱体中的Fe(II)被Fe(III)氧化，然后与砷酸根离子结合形成蝎石。在转化为蝎石晶体的过程中，这种电子交换产生的Fe(II)(最初来自赤铁矿)溶解在反应溶液中。推测溶液来源的Fe(II)和赤铁矿来源的Fe(III)之间的电子交换在这种合成方法中对蝎石晶体的形成起着重要的作用。
Arsenic is a toxic element, and development of effective methods for As removal and stabilization are necessary. Removal and stabilization of pentavalent As as crystalline scorodite (FeAsO4 center dot 2H(2)O) is a promising method for As treatment of industrial byproducts. When hematite (Fe(III)(2)O-3) powder is added to As(V) solution containing Fe(II) under appropriate conditions, scorodite crystals form from the gel-like precursor. When Fe(II) is not contained in the solution, the formation reaction does not proceed, even if hematite is added. Therefore, it is considered that the Fe(II) in the solution is heavily involved in the formation mechanism. Here, to elucidate the scorodite crystal formation mechanism in the hematite addition method, the origin of the iron in scorodite was investigated through scorodite synthesis experiments with addition of a stable iron isotope (Fe-54) to the reaction solution. It was estimated that the Fe(III) constituting the scorodite crystals was mainly (more than about 80 atom%) derived from the Fe(II) in the solution. From this result, scorodite formation from the reaction solution with solid hematite can be considered to occur as follows. The gel-like precursor is composed of Fe(II) from the reaction solution together with Fe(III) from hematite. During conversion of the gel-like precursor to scorodite crystals, Fe(II) in the precursor is oxidized by Fe(III), and it then combines with the arsenate ion to form scorodite. With conversion to scorodite crystals, the Fe(II) generated by this electron exchange (originally from hematite) dissolves in the reaction solution. It is speculated that electron exchange between solution-derived Fe(II) and hematite-derived Fe(III) plays an important role in formation of scorodite crystals in this synthetic method.