Influence of the conditioning in reducing medium on the hydrophobicity of samples of pyrite and hematite

ABSTRACT The pyrite surface oxidation is a serious problem in the mining industry, since it decreases its hydrophobicity turning it difficult to float or leading to a high collector consumption. In this study, the products of the reaction between the Fe2+ and HS-, formed on the surface of oxidized pyrite and hematite, were studied. The conditions for the formation of a hydrophobic layer on the surface of these minerals were also investigated. The pH influence of sodium hydrosulphide (NaHS) solutions was evaluated in order to achieve a suitable Eh-pH condition for the formation of hydrophobic sulfur compounds on mineral surfaces. Measurements of contact angle, X-ray diffraction (XRD), scanning electron microscopy/dispersive energy spectroscopy (SEM/EDS) and Raman spectroscopy were the analytical techniques used to verify the nature of the products formed on the surface of those minerals. The formation of elemental sulfur crystals on the hematite and oxidized pyrite surfaces was identified after the conditioning in a reducing medium, and the best result was obtained at pH 8.0 during 96 hours with a 0.3 M NaHS solution for the two samples analyzed.

摘要：黄铁矿（pyrite）表面氧化是矿业领域的突出问题，其会降低矿物疏水性，进而导致浮选困难或捕收剂消耗量大幅增加。本研究针对氧化黄铁矿与赤铁矿（hematite）表面生成的亚铁离子（Fe²+）和硫氢根离子（HS⁻）之间的反应产物展开探究，同时考察了两类矿物表面形成疏水层的适宜条件。为获得可在矿物表面生成疏水含硫化合物的合适氧化还原电位-pH（Eh-pH）条件，本研究评估了硫氢化钠（sodium hydrosulphide, NaHS）溶液的pH值影响。采用接触角（contact angle）、X射线衍射（X-ray diffraction, XRD）、扫描电子显微镜/能谱仪（scanning electron microscopy/dispersive energy spectroscopy, SEM/EDS）及拉曼光谱（Raman spectroscopy）等分析技术，对两类矿物表面生成产物的属性进行了表征。实验结果显示，经还原介质调理后，赤铁矿与氧化黄铁矿表面均检出元素硫晶体；针对本次分析的两种样品，最优处理条件为：采用0.3 M硫氢化钠溶液，pH值为8.0，反应时长96小时。