三烷基氧膦(TRPO)萃取有机羧酸的研究

Liquid-Liquid Extraction of Carboxylic Acid with TRPO

络合萃取法对极性有机物稀溶液的分离具有高效性和高选择性。选择甲酸、乙酸、一氯乙酸、二氯乙酸、三氯乙酸为分离对象，三烷基氧膦 (TRPO)为络合剂，煤油为稀释剂，进行了系统的萃取相平衡实验。结果表明，溶质的pKa对络合萃取平衡影响起主导作用。红外光谱定性分析表明，TRPO萃取有机羧酸为氢键溶剂化历程，负载有机酸的TRPO中的P=O吸收峰的位移与有机羧酸的酸性有关。采用质量作用定律分析方法，建立了相平衡分配系数的表达式，模型拟合精度是令人满意的。

Extraction of carboxylic acids from dilute solutions based on reversible chemical complexation is a highly effective and selective separation technique. Studies have been made for the extraction of formic, acetic, chloroacetic, dichloroacetic, and trichloroacetic acids by TRPO, a trialkyl phosphine oxide, dissolved in kerosene. The effects of complexing agent concentration and solutes to be extracted on distribution ratio D were discussed. According to mass action law, a general expression of experimentally accessible distribution ratio D in the molar concentration scale is developed. Extraction equilibrium constant K11 is then obtained by correlating experimental data using least square method. The calculated values are in good agreement with the experimental ones. The results show that the lower the pKa of carboxylic acid is, the higher the extraction equilibrium constant K11will be. By Fourier transform infrared spectroscopic (FTIR) analysis, it is found that the extraction process is mainly governed by hydrogen-bonding solvation.