Abstract:

Hydrophobic ionic liquid (IL)-molecular solvent composite extractant was developed for the removal of phenols from aqueous solution. The results showed that tetradecyltrihexylphosphonium bromide ([P₆₆₆₁₄]Br)-ethyl acetate mixtures could not only decrease the viscosity of extractant notably, but also have good affinity to phenols. The distribution coefficient of phenol in [P₆₆₆₁₄]Br-ethyl acetate-water biphasic system ([P₆₆₆₁₄]Br/ethyl acetate molar ratio 1:4) was 5.3 times higher than that using pure ethyl acetate as extractant, 9—60 times higher than those using several common hydrophobic ILs and only 25.3% smaller than that using pure [P₆₆₆₁₄]Br. The viscosity of 20% (mol) [P₆₆₆₁₄]Br mixture was only 1% of pure [P₆₆₆₁₄]Br. The solvation interactions calculated by COSMO-RS indicated that there were strong hydrogen-bonding interaction between the phenol and [P₆₆₆₁₄]Br, which drove phenol into the [P₆₆₆₁₄]Br-rich phase. This mixture also showed good extraction abilities for phloroglucinol, 4-chlorophenol and 2,5-dinitrophenol with distribution coefficients of 91, 490 and 1492, respectively. These results provided a new opportunity for designing phenol-removing solvent with both good thermodynamic and kinetic properties.

Key words: ionic liquids, extraction, hydrogen bonding, phenols, water treatment

摘要：

构建了疏水性离子液体-分子溶剂复合萃取剂，并研究了其对酚类化合物的萃取性能。结果表明，与纯离子液体萃取剂相比，三己基十四烷基溴化（[P₆₆₆₁₄]Br）-乙酸乙酯复合萃取剂在显著降低萃取剂黏度的同时，获得了较高的酚类溶质分配系数。当萃取剂中[P₆₆₆₁₄]Br摩尔分数为20%时，苯酚的分配系数为345，是纯乙酸乙酯为萃取剂时的5.3倍，是[omim]BF₄、[C₁₂mim]NTf₂等常规疏水离子液体的9~60倍；比纯[P₆₆₆₁₄]Br为萃取剂时的分配系数下降25.3%，黏度却比纯[P₆₆₆₁₄]Br降低99%以上。COSMO-RS研究表明[P₆₆₆₁₄]Br与苯酚之间较强的氢键作用是获得较高苯酚分配系数的关键因素。该复合萃取剂对间苯三酚、4-氯苯酚和2,5-二硝基苯酚等物质也有良好的萃取能力。上述结果为开发兼具良好热力学性能和动力学性能的脱酚萃取剂提供了新的思路。

关键词: 离子液体, 萃取, 氢键, 酚类, 水处理