Capela Emanuel V, Santos João H P M, Boal-Palheiros Isabel, Coutinho João A P, Ventura Sónia P M, Freire Mara G
CICECO - Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
Chem Eng Educ. 2019 Spring;53(2):112-120.
In this work, a simple experimental protocol to determine liquid-liquid phase diagrams of aqueous two-phase systems (ATPS) on a Chemical Engineering course is described. Throughout this laboratory set of experiments, the liquid-liquid ternary phase diagrams, tie-lines, tie-line lengths and critical points of ATPS will be determined. Ternary liquid-liquid phase diagrams composed of water, polyethylene glycol (PEG 200, 400 and 600 g·mol) and sodium carbonate (NaCO) were obtained by cloud-point titration method at room temperature. The respective tie-lines, tie-line lengths and critical points were also determined. Phase diagrams were represented both as conventional ternary phase diagrams and orthogonal phase diagrams. Through the analysis of the results obtained it was identified a higher ability to form ATPS with the increase of the polymer molecular weight. The interpretation of phase diagrams, particularly the most complex, the orthogonal ones, is not always easy to grasp by students, so this novel 3-hour-class educational approach could be potentially used to teach and help understanding 3-component liquid-liquid equilibrium and the formation of biphasic systems to undergraduate students, without requiring the use of volatile organic solvents.
在这项工作中，描述了一种在化学工程课程中确定双水相体系（ATPS）液-液相图的简单实验方案。在这组实验室实验中，将确定ATPS的液-液三元相图、系线、系线长度和临界点。通过室温下的浊点滴定法获得了由水、聚乙二醇（PEG 200、400和600 g·mol）和碳酸钠（NaCO）组成的三元液-液相图。还确定了各自的系线、系线长度和临界点。相图既表示为传统的三元相图，也表示为正交相图。通过对所得结果的分析，发现随着聚合物分子量的增加，形成ATPS的能力更强。相图的解释，尤其是最复杂的正交相图，学生并不总是容易理解，因此这种新颖的3小时课程教学方法有可能用于向本科生教授和帮助他们理解三元液-液平衡以及双相体系的形成，而无需使用挥发性有机溶剂。
