萃取剂相对酸(碱)度对极性有机物络合萃取平衡的影响

Dependence of Relative Acidity (Basicity) of Extractant on the Equilibrium of Complexation Extraction for Polar Organics

选择萃取剂的相对酸(碱)度为萃取剂的特征参数,以三种常用的络合萃取剂,TOA/正辛醇、TRPO/煤油、D2EHPA/煤油为研究对象,测定TOA和TRPO相对于HCl的pKa,BS,D2EHPA相对于NaOH的相对酸度(pKa,AS)物性参数,分别结合萃取有机羧酸、有机胺的平衡特性,进一步研究萃取剂的相对酸(碱)度与络合萃取平衡的关系。结果表明,萃取剂的相对酸(碱)度与萃取剂的浓度有关,并由此直接影响络合萃取平衡的结果,是影响络合萃取平衡的重要因素;提出了影响萃取平衡的三个重要因素:溶质的亲油性、溶质的电性参数、络合剂的相对碱(酸)度,并在不同体系下建立了表观络合萃取平衡常数与这三参数的关联式,关联精度是相当满意的,可以很好地预测络合萃取平衡的特性。

The extraction method based on reversible chemical complexation is highly effective and selective for separating polar organic solutes from dilute solutions. In this paper, three extractant systems, trioctylamine （TOA） in 1-octanoi, di-（2-ethyihexyi） phosphate（D2EHPA） and triaikyiphosphine oxide （TRPO） in kerosene were selected as the typical extractant systems respectively, and the relative basicity （acidity） of each extractant system to HCI was measured. The dependences of the extraction equilibrium behavior on the relative basicity （acidity） of the extractant were investigated, The results show that the relative basicity （acidity） of the extractant dependes on the concentration of the extractant, and it is one of the important parameters affecting the complexation extraction equilibrium directly. Three parameters of the system, such as the relative basicity （acidity） of the extractant, the dissociated constant and the hydrophobicity of the separated solute, were proposed as the most important parameters determining the extraction equilibrium behaviors, and the correlated equations of the apparent extraction equilibrium constant with these three parameters for different extractant systems were obtained respectively, and which can be used to predict the extraction equilibrium behaviors.