[omim]BF4离子液体萃取酚类化合物的研究

采用水浴微波法合成离子液体萃取剂omim]BF4.研究omim]BF4对苯酚、邻甲酚等7种酚类化合物的萃取,考察了萃取时间、温度、相比及pH值对萃取效果的影响.实验结果表明:萃取10 min就可以达到平衡;随着温度升高或omim]BF4与含酚水溶液相比的降低,分配系数降低;酚溶液在pH< pKa时,即酚类化合物主要以分子状态存在时,萃取效率较高.与萃取剂bmim]PF6及传统有机溶剂相比,omim]BF4萃取酚类化合物的分配系数处在同一数量级.同时对omim]BF4萃取酚类化合物的机理进行了探讨,离子液体中的氟与酚类化合物的羟基形成了氢键.

Extraction of Phenolic Compounds with [omim]BF4 Ionic Liquid

omim]BF4 ionic liquid synthesized with water-bath microwave method was selected as extractant to extract separately seven kinds of phenolic compounds, such as phenol, o-cresol and others. The effects of extraction time and temperature, phase ratio and pH of the aqueous solution of phenolic compounds on the extraction equilibrium were discussed. Results show that extraction equilibrium can reach within 10 minutes, and with increasing extraction temperature or decreasing the volume ratio of omim]BF4 ionic liquid to aqueous phase, the distribution coefficient decreases gradually. The extraction efficiency is higher when phenolic compounds are in molecular form which happens when the pH value of the aqueous solution of phenolic compound is smaller than its pKa value. The distribution coefficients of phenolic compounds between water and omim]BF4 are in the same order of that between water and bmim]PF6 or other conventional organic solvents. Meanwhile, the extraction mechanism of phenolic compounds with omim]BF4 ionic liquid was investigated. It was found that during extraction, hydrogen bonds are formed between the fluorine of the omim]BF4 and the hydroxy of the phenolic compounds.