Souvignet I, Olesik S V
Department of Chemistry, Ohio State University, Columbus 43210, USA.
Anal Chem. 1998 Jul 15;70(14):2783-8. doi: 10.1021/ac971263n.
Supercritical and liquid mixtures of ethanol/H2O/CO2 are increasingly used to extract solutes from solid or semi-solid matrixes when nontoxic solvents and fast extraction kinetics are desired. Accordingly, to better understand the mass transport capabilities of these mixtures, the diffusion coefficients of benzene, anthracene, m-cresol, and p-nitrophenol in enhanced-fluidity liquid mixtures of ethanol/H2O/CO2 were studied. The effect of mixture composition and temperature variation on the measured diffusion coefficients was studied. In a mixture containing 0.61/0.39 mole ratio ethanol/H2O, the diffusion coefficients of the four solutes increased comparably either by adding 30 mol % CO2 or by changing the temperature of the mixture from 25 to 60 degrees C. The experimental data were compared to that predicted by the Stokes-Einstein and the Wilke-Chang relations. Often, the experimental diffusion coefficients were greater than those predicted by these mass transport relations. However, the Eyring relationship was useful in describing the variation of diffusion coefficients as a function of temperature change for all of the ethanol/H2O/CO2 mixtures tested.
当需要无毒溶剂和快速萃取动力学时，乙醇/水/二氧化碳的超临界和液体混合物越来越多地用于从固体或半固体基质中萃取溶质。因此，为了更好地理解这些混合物的传质能力，研究了苯、蒽、间甲酚和对硝基苯酚在乙醇/水/二氧化碳的增强流动性液体混合物中的扩散系数。研究了混合物组成和温度变化对测得的扩散系数的影响。在乙醇/水摩尔比为0.61/0.39的混合物中，通过添加30 mol%的二氧化碳或通过将混合物温度从25℃改变到60℃，四种溶质的扩散系数以类似的方式增加。将实验数据与斯托克斯-爱因斯坦关系和威尔克-张关系预测的数据进行了比较。通常，实验扩散系数大于这些传质关系预测的值。然而，艾林关系对于描述所有测试的乙醇/水/二氧化碳混合物中扩散系数随温度变化的函数关系很有用。
