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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.

Aqueous biphasic systems (ABS) composed of polypropylene glycol and carbohydrates, two benign substances are proposed to separate two food colorants (E122 and E133). ABS are promising extractive platforms, particularly for biomolecules, due to their aqueous and mild nature (pH and temperature), reduced environmental impact and processing costs. Another major aspect considered, particularly useful in downstream processing, is the "tuning" ability for the extraction and purification of these systems by a proper choice of the ABS components. In this work, our intention is to show the concept of ABS as an alternative and volatile organic solvent-free tool to separate two different biomolecules in a simple way, so simple that teachers can effectively adopt it in their classes to explain the concept of bioseparation processes. Informative documents and general information about the preparation of binodal curves and their use in the partition of biomolecules is available in this work to be used by teachers in their classes. In this sense, the students use different carbohydrates to build ABS, then study the partition of two food color dyes (synthetic origin), thus evaluating their ability on the separation of both food colorants. Through these experiments, the students get acquainted with ABS, learn how to determine solubility curves and perform extraction procedures using colorant food additives, that can also be applied in the extraction of various (bio)molecules.

The understanding of molecular interactions that control phase separation in polymer/polymer aqueous two-phase systems (ATPS) has been a subject of debate up to this day. In light of this, we set out to investigate the molecular interactions occurring in ternary mixtures composed of polyethylene glycol (PEG600), polypropylene glycol (PPG400) and water. The ternary phase diagram was plotted at two temperatures (298 K and 323 K), revealing a transition from a type 0 to a type I diagram. Molecular dynamics (MD) simulations were performed to elucidate the polymer–polymer and polymer–water interactions occurring at different temperatures and water concentrations. COnductor-like Screening Model for Realistic Solvents (COSMO-RS) was used to assess the thermodynamic properties of the polymer–water binary mixtures and their correlation with ATPS formation. The MD simulations clearly demonstrate the effect of segregation/separation with increasing water content and temperature, highlighting a significant reduction in PPG–water interactions compared to PEG–water counterparts. Polymer–water interactions were identified as those controlling the phase separation mechanism, and the thermodynamic properties determined with COSMO-RS for the polymer–water binary systems further support this view. [ABSTRACT FROM AUTHOR]