(中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用電化學(xué)方法研究了金及常見伴生金屬元素銀、 銅、 鎳、 鐵在高穩(wěn)定性堿性溶液中陽極溶解的電化學(xué)行為， 及堿性硫脲浸金的選擇性。結(jié)果表明： 在最佳溶金電勢0.42 V時， 金在堿性硫脲溶液的溶解電流密度分別是銀、 銅、 鎳和鐵的3.4， 5.2， 27.3和42.6倍； 而且堿性硫脲體系進(jìn)行礦物浸出時金的伴生元素浸出率均小于0.1%，浸金具有顯著的選擇性。 采用配合物的化學(xué)鍵理論、 配位理論等分析了堿性硫脲選擇性溶金的機理。 堿性硫脲溶液中金、 銀、 銅、 鎳和鐵分別以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中反饋σ—π配鍵的形成顯著增強了其穩(wěn)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， 各配位體間硫原子和氮原子上電子云互相排斥， 使其穩(wěn)定性有所降低。 而且堿性硫脲溶液中， Ag， Cu， Ni， Fe易于形成致密的硫化物鈍化膜，在一定程度上也阻礙了金屬的進(jìn)一步溶解。
關(guān)鍵字: 堿性硫脲； 選擇性溶金； 機理； 配位理論
alkaline thiourea solutions based
on complex theory
（ School of Metallurgical Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: Electrochemical behaviors of gold and the co-existing elements, such as silver, copper, nickel and iron dissolving in alkaline thiourea solution with high stability, and gold leaching selectively in alkaline thiourea solution were studied by the methods of electrochemistry. The results indicate that at the optimal potential of 0.42 V, the anodic current density of gold in alkaline thiourea solution is 2.4, 4.2, 26.3 and 41.6 times as big as that of silver, copper, nickel and iron, respectively. Additionally, the leaching rates of the coexisting metals are less than 0.1% when gold ore is leaching in alkaline thiourea system, which indicates that gold leaching in alkaline thiourea solution shows excellent selectivity. The mechanism of gold dissolution selectively in alkaline thiourea solution was anatomied based on chemical bond theory and complex theory. The results indicate that Au, Ag, Cu, Ni and Fe exist in alkaline thiourea solution in the form of Au(TU)+2, Ag(TU)+3, Cu(TU)2+4, Ni(TU)2+4 and Fe(TU)2+6, respectively. σ—π bond is formed in
Au(TU)+2, which strengthens its stability markedly. In Ni(TU)2+4 and Fe(TU)2+6, repulsion of electron clouds between S atom and N atom amongst complexes decreases their stabilities owning to the particularity of thiourea molecular. Moreover, the compact sulphides passivation layers of Ag+, Cu2+, Ni2+, Fe2+ with S2-, being prone to form in alkaline thiourea solution, prevent their further dissolution to some extend.
Key words: alkaline thiourea; gold dissolution selectively; mechanism; complex theory
