(中南大學(xué) 資源加工與生物工程學(xué)院，長沙 410083)
摘 要: 結(jié)合掃描電子顯微鏡(SEM)和原子力顯微鏡(AFM)測定金氰化溶解過程表面產(chǎn)物的形貌。結(jié)果表明，金片表面溶蝕程度輕，少量溶解主要發(fā)生在棱和角等邊界斷點上。利用X射線光電子能譜(XPS)研究了金氰化溶解過程表面產(chǎn)物的組成元素及鍵合特性，得出表面產(chǎn)物的主要成分為AuCN、Au(OH)x和Au2(OHCN)。金在NaCN溶液中的溶解是分步進行的：第一步，Au與配位劑CN-作用形成長鏈結(jié)構(gòu)的AuCN，AuCN進一步與CN-反應(yīng)才形成 實現(xiàn)溶解；第二步反應(yīng)只能在AuCN長鏈的斷點處發(fā)生，因而成為總反應(yīng)的控制步驟，從而使表面產(chǎn)物AuCN大量累積形成表面覆蓋層，即表面鈍化層；而棱角部位的表面產(chǎn)物因斷點多而較易發(fā)生溶解，從而呈疏松顆粒狀，未能形成緊密相連的面覆蓋，即表面活性區(qū)。
關(guān)鍵字: 金；氰化物；氰化浸金；表面產(chǎn)物；鈍化
（School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China）
Abstract:The micro-morphology of gold surface products in cyanide solutions was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). It is found that, little corrosion occurs on the gold surface except on the surface edges and horns. The element composition and binding feature of gold surface products in cyanide solutions were studied by X-ray photoelectron spectroscopy (XPS). It is indicated that the composition of surface product include AuCN, Au(OH)x and Au2(OHCN). Gold dissolution process takes place by two steps, in which, AuCN first forms into a long-chain structure AuCN that further reacts with CN- to form the soluble complex in the second step. The second step that can only take place on the end of AuCN chain essentially acts as the rate-controlling step. This mechanism inevitably causes surface covering of accumulated AuCN, i.e., the surface passivated layer. On the other side surface products on the edges and horns dissolve faster because of more breakpoints in the AuCN chain and remain in separate particles which doesn’t form compact spread covering, i.e., surface activated area.
Key words: gold; cyanide; gold cyanidation; surface product; passivation
