季铵盐萃取草酸的机理

季铵盐可以直接从氰化浸出液中萃取金，但反萃困难. 酸性硫脲通空气体系能有效反萃季铵盐中的氰化金，向反萃液中添加草酸可以显著提高金的反萃效率. 实验发现在反萃过程中，草酸会被萃取进入有机相. 本文通过3个萃取模型分别拟合草酸的萃取反应并用红外光谱法研究了萃取机理，结果表明，季铵盐萃取草酸的机理主要为中性缔合，草酸的COOH基团与季铵盐的极性端作用，形成1:1型氢键萃合物，表观平衡常数2.12，还有少部分草酸以失去一个氢离子的二聚体形式与Cl–发生阴离子交换，与季铵阳离子形成1:2型离子对萃合物，表观平衡常数0.0031.

Mechanism of Extraction of Oxalic Acid by Quaternary Ammonium Salt

Quaternary ammonium salt (N263) has strong affinity with Au(CN)2 in cyanide solutions, but Au is not readily stripped. Stripping by acidic thiourea solutions with air sparging shows good promise, and the stripping efficiency is improved significantly by addition of oxalic acid in the stripping solution. It is found that oxalic acid is extracted into the organic phase during stripping. In this paper, the mechanism of extraction of oxalic acid is studied by 3 models of extraction equilibrium and infrared spectrum. It is shown that oxalic acid is extracted mainly as neutral molecule (ratio to N263 is 1:1), which is associated with the anions of quaternary ammonium salts by hydrogen bond. There are still small quantities of oxalic acid anions H3C4O8 which exchange with Cl of N263 to form 1:2 ionic pairs with the cations of N263.