TODGA/HNO_3萃取La^(3+)的界面性质

Extraction Interfacial Properties of La^(3+) from HNO_3 System with TODGA

利用滴体积法研究了La^(3+)/HNO_3/N,N,N',N'-四辛基-3-氧戊二酰胺(TODGA)/稀释剂体系的界面性质,考察了TODGA浓度、液滴形成时间、稀释剂种类、La^(3+)浓度、体系温度、离子强度和溶液酸度等因素对体系界面性质的影响.实验结果表明,体系达到界面饱和吸附时间约为120 s,可认为体系达到萃取平衡;TODGA浓度不同时,界面张力也不同,进而判定界面饱和吸附物种亦不相同;极性较小的稀释剂体系的界面张力降低较大,按照正辛烷>环己烷>苯>甲苯次序降低;HNO_3对TODGA的质子化作用使其表面活性显著增强,故硝酸浓度增大导致界面张力降低;Na NO_3的存在降低了界面上游离萃取剂分子的浓度,致使界面张力增大.

The interfacial properties of La3＋/HNO3/N,N,N＇,N＇-tetraoctyl diglycolamide（ TODGA）/dilute system were studied by the drop volume method,including the effect of TODGA concentration,equilibrium time,types of diluents,La3＋concentration system temperature,ionic strength and acidity on the interfacial properties. It was found that：（ 1） the interfacial saturated adsorption time is about 120 s in this system;（ 2） the interfacial tension are different with the different TODGA concentrations,so the interfacial saturated adsorption species may exist differences;（ 3） the decrease of the interfacial tension is bigger in small polarity dilute system,such as octane 〉 cyclohexane 〉 benzene 〉 toluene;（ 4） because of the protonation effect for TODGA,the interfacial activity enhanced with the increasing of HNO3 concentration,and reduced the interfacial tension; the presence of Na NO3 reduced the concentration of free TODGA molecules at the interface,and let the interface tension increased.