Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Department of Mining and Petroleum Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand.
Sci Total Environ. 2017 Mar 1;581-582:126-135. doi: 10.1016/j.scitotenv.2016.12.050. Epub 2017 Jan 3.
The oxidative dissolution of pyrite is an important process in the redox recycling of iron (Fe) and is well-known for its role in the formation of acid mine drainage (AMD), which is considered as the most serious and widespread problem after the closure of mines and mineral processing operations. Because this process requires the movement of electrons, common metal oxides in nature that have either semiconducting (e.g., hematite) or insulating (e.g., alumina) properties may have strong effects on it. In this study, changes in the electrochemical behavior of pyrite in the presence of hematite and alumina were investigated. Results showed that the formation of surface-bound species directly influenced the anodic and cathodic half-cell reactions as well as the transfer of electrons between these sites. Pyrite pretreated in the air became anodically more reactive than that pretreated in oxygenated water, but the type of oxidizing media had little effect on the cathodic half-cell reaction. The presence of hematite and alumina during pretreatment also had strong effects on the electrochemical properties of pyrite. Chronoamperometry measurements suggest that hematite and alumina enhanced the anodic half-cell reaction but suppressed the cathodic half-cell reaction of pyrite oxidation. Increased anodic half-cell reaction in the presence of hematite could be attributed to electron "bridging" and catalytic effects of this mineral. In contrast, the effects of alumina on the anodic half-cell reaction were indirect and could be explained by the formation of Fe-oxyhydroxide surface species during pretreatment. Suppression of the cathodic half-cell reaction by both minerals was attributed to their "protective" effect on cathodic sites. Our results also point to the cathodic half-cell reaction as the rate determining-step of the overall oxidative dissolution process.
黄铁矿的氧化溶解是铁（Fe）的氧化还原循环中的一个重要过程，其在酸性矿山排水（AMD）的形成中起着重要作用，AMD 被认为是矿山和矿物加工作业关闭后最严重和最广泛的问题。由于这个过程需要电子的移动，自然界中常见的具有半导体（例如赤铁矿）或绝缘（例如氧化铝）性质的金属氧化物可能对其有很强的影响。在这项研究中，研究了赤铁矿和氧化铝存在时黄铁矿电化学行为的变化。结果表明，表面结合物种的形成直接影响阳极和阴极半电池反应以及这些位点之间的电子转移。在空气中预处理的黄铁矿比在含氧水中预处理的黄铁矿更具有阳极反应性，但氧化介质的类型对阴极半电池反应几乎没有影响。预处理过程中存在赤铁矿和氧化铝也对黄铁矿的电化学性质有很强的影响。计时电流测量表明，赤铁矿和氧化铝增强了黄铁矿氧化的阳极半电池反应，但抑制了阴极半电池反应。在赤铁矿存在下阳极半电池反应的增加可以归因于该矿物的电子“桥接”和催化作用。相比之下，氧化铝对阳极半电池反应的影响是间接的，可以通过预处理过程中形成的 Fe-氢氧化物表面物种来解释。两种矿物对阴极半电池反应的抑制作用归因于它们对阴极位点的“保护”作用。我们的研究结果还表明，阴极半电池反应是整个氧化溶解过程的速率决定步骤。
