A Simple Approach for the Determination and Characterization of Ternary Phase Diagrams of Aqueous Two-Phase Systems Composed of Water, Poly(Ethylene) Glycol and Sodium Carbonate

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Autor/inn/en	Capela, Emanuel V.; Santos, João H. P. M.; Boal-Palheiros, Isabel; Carvalho, Pedro J.; Coutinho, João A. P.; Ventura, Sónia P. M.; Freire, Mara G.
Titel	A Simple Approach for the Determination and Characterization of Ternary Phase Diagrams of Aqueous Two-Phase Systems Composed of Water, Poly(Ethylene) Glycol and Sodium Carbonate
Quelle	In: Chemical Engineering Education, 53 (2019) 2, S.112-120 (9 Seiten) PDF als Volltext Verfügbarkeit
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	0009-2479
Schlagwörter	Chemistry; Science Instruction; Science Experiments; Scientific Concepts; Visual Aids; Computation; Science Laboratories; Laboratory Experiments; Spreadsheets; Educational Technology; Technology Uses in Education; Student Attitudes; Concept Formation; College Science + Suchen Sie Ihr Suchwort? Chemie; Teaching of science; Science education; Natural sciences Lessons; Naturwissenschaftlicher Unterricht; Anschauungsmaterial; Laboratory work; Laborarbeit; Spread sheet; Spredsheets; Spreadsheet; Tabellenkalkulation; Unterrichtsmedien; Technology enhanced learning; Technology aided learning; Technologieunterstütztes Lernen; Schülerverhalten; Concept learning; Begriffsbildung
Abstract	Through the experiments described in this article, students become acquainted with the principles behind ternary liquid-liquid systems and/or Aqueous Two-Phase Systems (ATPS), and their characterization by the determination of the binodal curve, tie-lines, tie-line lengths and critical point, as well as in applying the non-random two-liquid model (NRTL) activity coefficient model to ternary liquid-liquid equilibrium data. They also have the opportunity to understand the influence of using different polymers as phase-forming components and to better address the salting-out effect displayed by inorganic salts. A relevant feature of this set of experiments is the employment of complementary computational tools to effectively characterize the ternary phase diagrams. The relatively intense use of computational resources, both for calculations and parameters estimation, is a distinct feature from previously proposed experiments and a most valuable one in today's laboratories, both in academic and in industrial environments. The students are encouraged to use commercial spreadsheets that have advanced numerical tools packages, which allow sophisticated calculations in multivariate statistics, as well as linear and nonlinear optimizations that are essential tools in laboratory techniques and scientific research. Non-linear curve fitting is a commonly used tool in chemistry, from deconvolutions of overlapping bands in vibrational or electronic spectra to the analysis of chemical kinetics, and thus it is important for students to become acquainted with these procedures. Overall, the results showed that this set of lab experiments is a very successful approach in enabling the students to characterize ternary liquid-liquid phase diagrams, as well as to perform the data acquisition and analysis needed. According to the students' preparation and needs, help with the use of software for data treatment may be provided before or along the class; the students' previous acquaintance with the required software is a significant advantage that should be considered. The students' global overview of the work was positive; they considered the lab class useful in helping them to better understand theoretical concepts related to ternary liquid-liquid phase diagrams. They recognized that putting into practice previously learnt concepts allowed them to fully understand the main parameters needed to establish and characterize a chemical engineering process. This work may be part of a chemical engineering course (e.g. 3rd year) or similarly oriented courses where liquid-liquid equilibrium data and separation processes are important. It was designed to be accomplished in two practical laboratory sessions and requires only common laboratory equipment along with modern computational methods to characterize and describe the phase diagrams. Students are encouraged to relate theoretical aspects of phase diagrams and experimental determination and characterization alongside using software to help solving chemical engineering challenges. This lab work was also meant to update the curriculum to reflect environmental issues for chemical engineering, biotechnology, chemistry and biochemistry students at an intermediate level. The ATPS presented here will familiarize students with water-rich liquid-liquid systems, which may be used in extraction and separation processes, while avoiding the use of volatile organic solvents. (ERIC).
Anmerkungen	Chemical Engineering Education, Chemical Engineering Division of ASEE. P.O. Box 142097, Gainesville, FL 32614. Tel: 352-392-0861; Fax: 352-392-0861; e-mail: cee@che.ufl.edu; Web site: http://journals.fcla.edu/cee/
Erfasst von	ERIC (Education Resources Information Center), Washington, DC
Update	2020/1/01