金在碱性硫脲溶液中的阳极行为

Anodic Behavior of Gold in Alkaline Thiourea Solution

采用三电极体系研究了金及其伴生元素银、铜、镍和铁在硫脲中的阳极行为，详细考察了金在碱性硫脲溶液中阳极极化的各种影响因素，并对碱性介质中硫脲的稳定剂进行了选择。结果表明，只要硫脲在碱性介质中稳定存在，碱性硫脲可以实现金的选择性溶解；阳极电位是影响碱性硫脲溶金的关键因素，过高的阳极电位和温度易于导致硫脲的不可逆分解，而产生钝化金表面的元素硫；亚硫酸钠可以有效地抑制碱性硫脲的不可逆分解，大大提高金在碱性硫脲溶液中的阳极极化。

Anodic behaviours of gold and its associated elements, such as silver, copper, and nickel and iron in a thiourea solution were investigated by using a linear potential scanning method and a detailed study was made of all factors affecting anodic polarization of gold in alkaline thiourea solution. The authors made choice of stabilizers for thiourea. The results show that provided thiourea occurs stably in the alkaline medium, selective dissoulution of gold can be achieved. Anodic potential is a critical factor affecting dissolation of gold in the alkaline thiourea solution. Excessively high temperatures and potential can cause easily irreversible decomposition of thiourea, producing elemental sulfur which can passivate the surface of gold. However, Na 2SO 3 can depress effectively the irreversible decomposition of the alkaline thiourea solution, improving greatly the polarization of gold in the alkaline thiourea solution.