铁闪锌矿晶体中类质同象铁离子对表面铜活化作用的位阻效应及机理

It has been widely demonstrated through experiments and industrial practices that the flotability of marmatite proves worse than that of sphalerite, even with low recovery and tremendous copper sulfate consumption, which is principally due to the hindering effect of the isomorphous iron ions in the crystals on the copper activation of marmatite. So as to investigate its mechanism, in the project, marmatite with different iron contents were adopted as the main research object, the essential influences of iron ions on the crystal surface properties, the copper adsorption and the surface wettability, were researched through the density functional theory, the reaction path, transient state and the change of adsorption energy were analyzed theoretically，thus the micro-mechanism of steric effect as well as the surface wettability evolution law reflected were explored. subsequently, the thermodynamic paths of adsorption between copper and marmatite with different iron contents were calculated, and the surface adsorption kinetics of copper ions were experimentally studied, and then the apparent activation energy and energy barrier of chemical reactions were determined, through which the thermodynamics and kinetics effect of iron ions on the copper adsorption was figured out; moreover, the situ surface hydrophobic parameters were characterized through employment of contact angle measurement, atomic force microscope (AFM) and ion mass-spectrometer (SIMS), and the relative index model of surface hydrophobicity/hydrophilicity was established, additional, through combination with the Halimond floatation test, the surface hydrophobicity evolution law associated with steric effect was finally made clear. Thus, the influencing essence of the isomorphous iron ions on the marmatite flotation was eventually revealed, providing a theoretical foundation for the efficient recovery of marmatite by flotation separation.

大量试验和工业实践表明，铁闪锌矿的可浮性差于闪锌矿，回收率低，且消耗大量硫酸铜。主要原因是晶体中的类质同象铁离子对铁闪锌矿的表面铜活化存在着阻碍作用。为探明其机理，本项目以不同铁含量的铁闪锌矿为主要研究对象，采用密度泛函理论计算研究铁离子对晶体表面性质、铜吸附作用及表面润湿性的影响，进行反应路径、过渡态和吸附能变化理论分析，探究位阻效应微观机制及所反映的表面润湿性演化过程；进行不同铁含量的铁闪锌矿与铜吸附反应的热力学计算和动力学试验研究，确定表观活化能和化学反应能垒，考察铁离子对铜吸附的热力学和动力学影响；应用接触角测量、原子力显微镜（AFM）和离子质谱仪（SIMS）进行表面疏水参数表征，建立表面疏水/亲水相对指数模型，结合Halimond浮选试验，弄清与位阻效应相关的表面疏水演变规律。从而揭示类质同象铁离子影响铁闪锌矿浮选的本质，为铁闪锌矿的浮选高效回收和分离提供理论依据。

大量试验和工业实践表明，铁闪锌矿的可浮性差于闪锌矿，回收率低，且消耗大量硫酸铜，主要原因是晶体中的类质同象铁离子对铁闪锌矿的表面铜活化存在着阻碍作用。同时，几十年来，关于铁杂质对闪锌矿晶胞参数、电子结构性质、铜吸附量及其涉及的微观机理一直存在正反两方面的矛盾结论和争议。本项目采集了不同地区的5种铁含量的天然铁闪锌矿，构建了6种不同铁掺杂和取代含量的铁闪锌矿晶体模型，采用TOF-SIMS、AFM、EPMA、SEM-EDS、XRF、接触角测量和DFT理论计算模拟等手段进行了铁含量对铁闪锌矿晶体弛豫重构和表面铜活化影响的位阻效应进行了系统研究。得到的主要成果包括：确认了铁含量对晶体几何结构影响的规律性，随着铁含量的增加，晶胞参数减小，晶体空间几何结构收缩。Fe、Zn赋存性质与成矿条件有关，Fe取代闪锌矿晶格中的Zn不是均匀取代的过程。确认了铁含量对晶体电子结构的影响规律，导电性不断增强，其导电性经历了半导体-半金属-金属的变化过程；空隙掺杂中Fe原子的加入不仅带入磁性还使得Fermi能级附近的能带增多；导电性的增强主要通过下自旋能带实现。确认了铁含量对天然闪锌矿的润湿性和可浮性的影响规律，铁的存在使铁闪锌矿表面疏水/亲水指数降低，原子力显微镜测得的粘附力下降，不利于闪锌矿的天然疏水性和可浮性。在铁对矿物表面铜活化影响的微观机制方面取得了重要进展，Cu不仅会取代表面的Zn，也会取代晶格内部的Zn；并且随着Fe含量增加，Cu2+在晶体内层扩散速率增加；晶格中的Fe不会被Cu取代，闪锌矿表面的Zn也不会被Cu完全取代；Cu2+会扩散至晶格的内部，但不是以Cu逐层取代Zn的方式发生；Fe杂质的存在不利于黄药吸附，并首次发现黄药能够与晶格中的Fe作用。本项目的研究结果解释了几十年来关于铁含量对闪锌矿晶体参数和铜活化影响的持续争议，揭示了类质同象铁离子影响铁闪锌矿浮选的内在机理，为铁闪锌矿的浮选高效回收和分离提供了重要依据。