Characterization of ferric arsenate-sulfate compounds: Implications for arsenic control in refractory gold processing residues
Characterization of ferric arsenate-sulfate compounds: Implications for arsenic control in refractory gold processing residues
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DOI：
10.2138/am.2013.4342
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发表时间：
2013-04
影响因子：
3.1
通讯作者：
D. Paktunc;J. Majzlan;L. Palatinus;J. Dutrizac;M. Klementová;G. Poirier
中科院分区：
文献类型：
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作者：
D. Paktunc;J. Majzlan;L. Palatinus;J. Dutrizac;M. Klementová;G. Poirier
摘要采用粉末X射线衍射（XRD）、电子探针分析（EPMA）、透射电子显微镜（TEM）和X射线吸收光谱（XAFS）等技术，对难处理金矿石高温加压氧化过程中常见的铁-砷酸盐-硫酸盐化合物进行了表征。沉淀物有三种类型，即含砷酸盐的碱式硫酸铁[FeSO 4（OH），命名为BFS]、砷酸-硫酸铁[广泛固溶体Fe（AsO 4）0.2-0.7（SO 4）0.7 -0.2（OH）0.7-0.2，命名为FAS]和水合原砷酸铁（FeAsO 4·0.75H2O）。通过旋进电子衍射实验解决了FAS的晶体结构。BFS和FAS的结构是由八面体Fe 3+链构成的，这些八面体Fe 3+链由硫酸盐和砷酸盐四面体交联。砷酸盐对硫酸盐的广泛取代发生在两种类型的化合物中，通过（OH）含量的变化保持电中性。XAFS谱表明，BFS和FAS的局部结构均由角连接的FeO 6八面体单链组成，其中链由AsO 4或SO 4四面体连接，形成FeO 6八面体和AsO 4或SO 4四面体的交替层。初步毒性特征浸出程序（TCLP）测试的沉淀物表明，FAS的摩尔比As/（As+S）的比例≤0.5可以是一个可接受的材料，用于尾矿库处置，而更多的富As FAS和BFS可能需要进一步处理。实验室制备的沉淀物的结果进行了比较，从处理难处理金矿石的三个残留物上获得的。其中一个残留物中的主要As载体是FAS，而含As的针铁矿和赤铁矿是另外两个残留物中的主要As载体。因此，残留物的矿物学特征决定了在处理难处理金矿石时适当的砷管理和处置选择。
Abstract A combination of techniques, including powder X-ray diffraction (XRD), electron microprobe analysis (EPMA), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAFS), is used to characterize the common ferric-arsenate-sulfate compounds, which could result from the pressure oxidation of refractory gold ores at elevated temperatures. Three general types of precipitate are identified; namely, arsenate-bearing basic ferric sulfate [FeSO4(OH) and designated as BFS], ferric arsenate-sulfate [an extensive solid solution Fe(AsO4)0.2-0.7(SO4)0.7-0.2(OH)0.7-0.2 and designated as FAS], and hydrated ferric orthoarsenate (FeAsO4·0.75H2O). The crystal structure of FAS is solved by precession electron-diffraction experiments. The structures of BFS and FAS are constructed from octahedral Fe3+ chains, which are cross-linked by sulfate and arsenate tetrahedra. Extensive substitution of arsenate for sulfate occurs in both types of compounds with charge neutrality being maintained by variations in the (OH) content. The XAFS spectra indicate that the local structures of both BFS and FAS are made of corner-linked single chains of FeO6 octahedra where the chains are linked by AsO4 or SO4 tetrahedra forming alternating layers of FeO6 octahedra and AsO4 or SO4 tetrahedra. Preliminary toxicity characteristics leaching procedure (TCLP) testing of the precipitates indicates that FAS with a molar ratio As/(As+S) ratio of ≤0.5 could be an acceptable material for disposal in a tailings impoundment, whereas more As-rich FAS and BFS may require further treatment. The results for the laboratory-prepared precipitates are compared with those obtained on three residues from the processing of refractory gold ores. The major As-carrier in one of the residues is FAS, whereas As-bearing goethite and hematite are the dominant As-carriers in the other two residues. Thus, the mineralogical characteristics of the residues dictate the appropriate arsenic management and disposal options in the processing of refractory gold ores.