Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
Chemosphere. 2021 Apr;269:129413. doi: 10.1016/j.chemosphere.2020.129413. Epub 2020 Dec 22.
Mineral processing, pyro- and hydrometallurgical processes of auriferous sulfide ores and porphyry copper deposits (PCDs) generate arsenopyrite-rich wastes. These wastes are disposed of into the tailings storage facilities (TSF) in which toxic arsenic (As) is leached out and acid mine drainage (AMD) is generated due to the oxidation of arsenopyrite (FeAsS). To suppress arsenopyrite oxidation, this study investigated the passivation of arsenopyrite by forming ferric phosphate (FePO) coating on its surface using ferric-catecholate complexes and phosphate simultaneously. Ferric iron (Fe) and catechol form three types of complexes (mono-, bis-, and triscatecholate complexes) depending on the pH, but mono-catecholate complex (i.e.,[Fe(cat)]) became unstable in the presence of phosphate because the chemical affinity of Fe-PO is most probably stronger than that of Fe-catechol in [Fe(cat)]. When two or more catechol molecules were coordinated with Fe (i.e., [Fe(cat)] and [Fe(cat)]), however, these complexes were stable irrespective of the presence of phosphate. The treatment of arsenopyrite with [Fe(cat)] and phosphate could suppress its oxidation due to the formation of FePO coating, evidenced by SEM-EDX and XPS analyses. The mechanism of FePO coating formation by [Fe(cat)] and phosphate was confirmed by linear sweep voltammetry (LSV): (1) [Fe(cat)] was oxidatively decomposed and (2) the resultant product (i.e., [Fe(cat)]) reacts with phosphate, resulting in the formation of FePO.
金矿石和斑岩铜矿（PCD）的选矿、火法和湿法冶金过程会产生富含毒砂（FeAsS）的废物。这些废物被处置到尾矿储存设施（TSF）中，由于毒砂的氧化，有毒的砷（As）被浸出，产生了酸性矿山排水（AMD）。为了抑制毒砂的氧化，本研究通过同时使用铁儿茶酚酸盐复合物和磷酸盐在其表面形成磷酸铁（FePO）涂层来研究毒砂的钝化。铁（Fe）和儿茶酚根据 pH 值形成三种类型的配合物（单、双和三儿茶酚配合物），但单儿茶酚配合物（即[Fe（cat）]）在磷酸盐存在下变得不稳定，因为 Fe-PO 的化学亲和力很可能比[Fe（cat）]中 Fe-儿茶酚的化学亲和力强。然而，当两个或更多儿茶酚分子与 Fe 配位（即[Fe（cat）]和[Fe（cat）]）时，这些配合物是稳定的，无论是否存在磷酸盐。用[Fe（cat）]和磷酸盐处理毒砂可以抑制其氧化，这可以通过 SEM-EDX 和 XPS 分析得到证明。通过线性扫描伏安法（LSV）证实了[Fe（cat）]和磷酸盐形成 FePO 涂层的机理：（1）[Fe（cat）]被氧化分解，（2）生成的产物（即[Fe（cat）]）与磷酸盐反应，形成 FePO。
