采用电化学方法研究了金及常见伴生金属元素银、铜、镍、铁在高稳定性碱性溶液中阳极溶解的电化学行为,及碱性硫脲浸金的选择性.结果表明:在最佳溶金电势0.42 V时,金在碱性硫脲溶液的溶解电流密度分别是银、铜、镍和铁的3.4,5.2,27.3和42.6倍;而且碱性硫脲体系进行矿物浸出时金的伴生元素浸出率均小于0.1%,浸金具有显著的选择性.采用配合物的化学键理论、配位理论等分析了碱性硫脲选择性溶金的机理.碱性硫脲溶液中金、银、铜、镍和铁分别以Au(TU)+2,Ag(TU)+3,Cu(TU)2+4,Ni(TU)2+4和Fe(TU)2+6的形式存在,Au(TU)+2中反馈σ-π配键的形成显著增强了其稳定性.配合物Ni(TU)2+4和Fe(TU)2+6中,由于硫脲分子的特殊性,各配位体间硫原子和氮原子上电子云互相排斥,使其稳定性有所降低.而且碱性硫脲溶液中,Ag,Cu,Ni,Fe易于形成致密的硫化物钝化膜,在一定程度上也阻碍了金属的进一步溶解.
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