Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: Implications for arsenic mobility
Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: Implications for arsenic mobility
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DOI：
10.1021/es030309t
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发表时间：
2003-09-15
影响因子：
11.4
通讯作者：
Hering, JG
中科院分区：
文献类型：
--
作者：
Dixit, S;Hering, JG
许多国家的地下水中含有天然来源的砷，影响到数百万人的健康。在这项研究中，通过比较As（V）和As（III）吸附到无定形氧化铁（HFO），针铁矿，磁铁矿在不同的溶液组合物的还原和成岩作用的氧化铁矿物砷的流动性的综合影响进行了研究。实验数据建模与扩散双层表面络合模型，提取的模型参数被用来检查我们的结果与以前报道的一致性。As（V）在HFO和针铁矿上的吸附在低于pH 5-6时比As（III）更有利，而在高于pH 7-8时，As（III）对固体具有更高的亲和力。As（V）和As（III）被同等吸附的pH值取决于固液比和矿物的类型和比表面积，并在磷酸盐存在下转移到较低的pH值，磷酸盐竞争吸附位点。吸附数据表明，在本研究中研究的大多数化学条件下，在HFO或针铁矿的存在下，As（V）的还原对其在近中性pH条件下在环境中的迁移率仅产生微小影响，甚至降低其迁移率。As（V）和As（III）吸附等温线表明三种氧化物的表面位密度相似。内在的表面络合常数为As（V）的针铁矿比HFO高，而As（III）的结合是类似的这两种氧化物，也为磁铁矿。然而，减少比表面积，因此吸附位点密度，伴随着无定形铁氧化物转化为更多的结晶相，可以增加砷的流动性。
Arsenic derived from natural sources occurs in groundwater in many countries, affecting the health of millions of people. The combined effects of As(V) reduction and diagenesis of iron oxide minerals on arsenic mobility are investigated in this study by comparing As(V) and As(III) sorption onto amorphous iron oxide (HFO), goethite, and magnetite at varying solution compositions. Experimental data are modeled with a diffuse double layer surface complexation model, and the extracted model parameters are used to examine the consistency of our results with those previously reported. Sorption of As(V) onto HFO and goethite is more favorable than that of As(III) below pH 5-6, whereas, above pH 7-8, As(III) has a higher affinity for the solids. The pH at which As(V) and As(III) are equally sorbed depends on the solid-to-solution ratio and type and specific surface area of the minerals and is shifted to lower pH values in the presence of phosphate, which competes for sorption sites. The sorption data indicate that, under most of the chemical conditions investigated in this study, reduction of As(V) in the presence of HFO or goethite would have only minor effects on or even decrease its mobility in the environment at near-neutral pH conditions. As(V) and As(III) sorption isotherms indicate similar surface site densities on the three oxides. Intrinsic surface complexation constants for As(V) are higher for goethite than HFO, whereas As(III) binding is similar for both of these oxides and also for magnetite. However, decrease in specific surface area and hence sorption site density that accompanies transformation of amorphous iron oxides to more crystalline phases could increase arsenic mobility.