Abstract: The third-phase behavior in extraction oxalic acid by trioctylamine (TOA) was investigated through measuring the solubility of oxalic acid in organic solvent.The result showed that n-octanol affected the dissolution of oxalic acid in the organic solvent apparently, and the solubility of oxalic acid, the complex of oxalic acid with TOA in the organic solvent and the extractability of oxalic acid with TOA increased with n-octanol concentration in the organic solvent. An obvious shift of the solubility of oxalic acid appeared when the oxalic acid concentration was larger than the saturated concentration of oxalic acid for TOA, which depended on the formation of complex dimer. Comparatively, the solubility of oxalic acid in organic phase for the experiment of extraction equilibrium was more than that of the organic solvent without water, and the water in the organic solvent was good for the dissolution of oxalic acid. Meanwhile, mathematical models were established to describe the solubility of oxalic acid and the complex, and the model parameters were obtained by fitting the experimental data.

Key words:

三辛胺, 草酸, 萃取, 第3相

摘要： 以三辛胺（TOA）萃取草酸时出现第3相的基本规律为研究对象，实验测定了无水溶剂及液液萃取平衡有机相中草酸的溶解度及其随TOA和正辛醇浓度的变化规律.结果显示，正辛醇对草酸及其与TOA形成的缔合物在溶剂中的溶解度影响显著；随正辛醇含量的增加，草酸及其缔合物在溶剂中的溶解度提高，因而溶剂对草酸的萃取能力随之增大；在TOA与草酸以1∶1的化学计量比饱和后，草酸溶解度出现阶跃现象，这与形成草酸二聚体的缔合物有关；相比之下，液液萃取平衡实验中有机相对草酸的溶解度大于无水溶剂的结果，溶剂中水的存在有助于缔合物溶解.同时建立了描述液液萃取平衡有机相中草酸及其缔合物溶解度的数学模型，并通过参数寻优求得了相应的模型参数.

关键词:

三辛胺, 草酸, 萃取, 第3相