Tang Hong-ping, Yang Ming-de, He Pei-jiong, Hu Tian-dou, Zhang Jing, Xie Ya-ning
Institute of Nuclear Energy and Technology, Tsinghua University, Beijing 102201, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2004 Jun;24(6):752-5.
Quaternary ammonium salt has strong affinity with gold in cyanide solutions, but it is not readily stripped. Stripping with acidic thiourea solutions and air sparging shows promise. There are some reports on the process of thiourea stripping, but little about its mechanism. In this paper, the stripping mechanism of N263/sulphuric thiourea/alkaline cyanide gold solution is studied by EXAFS. According to the experiments, sulphuric acid, thiourea and gold-thiourea complex can be extracted by N263 as a neutral molecule, and the stripping process can be described as following: (1) Sulphuric acid and thiourea are extracted by N263; (2) In organic phase, gold-cyanide complex is converted to gold-thiourea complex, which exists as Au[SC(NH2)2]2HSO4, and CN- forms HCN with acid at the same time; (3) HCN is removed by air sparging, and Au[SC(NH2)2]2HSO4 is distributed between organic phase and liquor phase, most of which transfers to liquor phase and is stripped.
季铵盐在氰化物溶液中与金具有很强的亲和力，但不易被反萃。用酸性硫脲溶液并鼓入空气进行反萃显示出一定的前景。关于硫脲反萃过程有一些报道，但对其机理的报道较少。本文利用扩展X射线吸收精细结构（EXAFS）研究了N263/硫酸硫脲/碱性氰化金溶液的反萃机理。根据实验，硫酸、硫脲和金-硫脲络合物可被N263作为中性分子萃取，反萃过程可描述如下：（1）硫酸和硫脲被N263萃取；（2）在有机相中，金-氰络合物转化为金-硫脲络合物，以Au[SC(NH2)2]2HSO4形式存在，同时CN-与酸形成HCN；（3）通过鼓入空气除去HCN，Au[SC(NH2)2]2HSO4在有机相和液相之间分配，其中大部分转移到液相并被反萃。
