Partitioning of amino acids in the novel biphasic systems based on environmentally friendly ethyl lactate

For the first time, we report on the performance of biphasic system composed of ethyl lactate, water and inorganic salt (K3PO4, K2HPO4 and K2CO3) for the separation of amino acids (L-phenylalanine, L-tryptophan and L-tyrosine) from their aqueous solutions. Cloud points (solubility curve) and tie-lines for three ternary (ethyl la ctate + water + inorganic salt) systems at 298.2 K and 313.2 K at atmospheric pressure were determined. For certain composition range, these mixture exhibit biphasic systems – top and bottom phases rich in ethyl lactate and salt, respectively. Partition coefficients of amino acids and their extraction efficiencies, as essential parameters for design of any separation process, were measured at two temperatures – 298.2 K and 313.2 K. The maximum values of partition coefficients were observed for the system containing K3PO4: 3.5, 3.7 and 11.9 for L-phenylalanine at 313.2 K, L-tyrosine at 298.2 K and L-tryptophan at 313.2 K, respectively. The obtained results clearly showed that the biphasic systems based on ethyl lactate are suitable for the efficient and sustainable recovery of amino acids from solutions with water

Novel aqueous biphasic system based on ethyl lactate for sustainable separations: Phase splitting mechanism

Ethyl lactate is a hydrophilic green solvent which is bio-renewable and biodegradable with low toxicity towards humans and animals. For the first time, we report that aqueous solutions of ethyl lactate separate into two aqueous phases upon addition of salts. The performance of trisodium citrate, disodium tartrate and disodium succinate as salting-out media for the separation of natural organic compounds, such as caffeine and catechin, from their aqueous solutions was examined. In this respect, cloud points for the ternary solutions composed of ethyl lactate, water and salt were determined at ambient pressure (0.1 MPa) at 298.2 K. Partition coefficients of caffeine and catechin between two phases were determined by chemical analysis of phases in equilibrium for different initial compositions at 298.2 K. The obtained results clearly demonstrate the ability of the ternary mixture to phase separate, providing good salting-out media for the efficient and sustainable separation from aqueous solution. 1H NMR spectroscopy was employed to elucidate the mechanisms of phase splitting in the ternary (ethyl lactate + water + salt) systems at molecular level. The discovery of aqueous biphasic system (ABS) containing ethyl lactate as hydrophilic solvent opens a new and green platform for extraction of various compounds from aqueous solutions

Aqueous biphasic systems based on ethyl lactate: Molecular interactions and modelling

Aqueous biphasic systems (ABS) based on ethyl lactate are novel green solvent systems that are biorenewable and biodegradable with the potential to replace currently used hazardous organic solvents. Models to correlate and predict binodal curves of these systems are crucial for the design of separation processes but are currently nonexistent. Here, we report the development of two empirical models based on Merchuk’s equation and the Effective Excluded Volume model for ABS composed of ethyl lactate, water and a salt (K3PO4, K2HPO4, K2CO3, Na3C6H5O7, Na2C4H4O6, Na2C4H4O4, K2S2O3, Na2S2O3 and (NH4)2S2O3). Additionally, the use of Artificial Neural Networks (ANN) as a tool to predict binodal curves was explored. An ANN composed of tansig transfer function and five neurons was built using three inputs: mole fraction of salt, molar Gibbs energy of hydration of the salt cation and anion. Furthermore, Fourier-transform infrared-attenuated total reflection spectroscopy was used to reveal the molecular interactions which were used to explain binodal data

Experimental Determination and Modeling of the Phase Behavior of the CO2 + Propionic Anhydride Binary System at High Pressure

The phase equilibrium of the binary system (CO2 + propionic anhydride) was determined experimentally at temperatures of 308, 313, and 323 K and pressures up to 10 MPa. Measurements were carried out in a high-pressure visual cell with variable volume. The experimental data were modeled using the Peng–Robinson equation of state and the Mathias–Klotz–Prausnitz mixing rule. A good correlation was achieved with this model, with a total average absolute deviation of 0.21%

Academic Standards and Quality Assurance: The Impact of COVID-19 on University Degree Programs

COVID-19, caused by a member of the coronavirus family of viruses, has spread to most countries around the world since it was first recorded in humans in China in late 2019. Closing universities and cancelling all face-to-face activities have become a COVID-19 inevitable reality in many parts of the world. Its impact on university programs, particularly to maintain academic standards and quality assurance procedures, has become significantly more challenging and complex. New ways of working digitally, to minimize disruption to daily operations, have also led to enormous anxiety and uncertainty within the student population, and meeting students’ expectations has also become significantly more difficult. This paper reviews actions taken by universities to safeguard high academic standards and quality assurance procedures during this time and appraise the challenges and impacts on students’ academic performance

Nuclear-driven production of renewable fuel additives from waste organics

Non-intermittent, low-carbon energy from nuclear or biofuels is integral to many strategies to achieve Carbon Budget Reduction targets. However, nuclear plants have high, upfront costs and biodiesel manufacture produces waste glycerol with few secondary uses. Combining these technologies, to precipitate valuable feedstocks from waste glycerol using ionizing radiation, could diversify nuclear energy use whilst valorizing biodiesel waste. Here, we demonstrate solketal (2,2-dimethyl-1,3-dioxolane-4-yl) and acetol (1-hydroxypropan-2-one) production is enhanced in selected aqueous glycerol-acetone mixtures with γ radiation with yields of 1.5 ± 0.2 µmol J−1 and 1.8 ± 0.2 µmol J−1, respectively. This is consistent with the generation of either the stabilized, protonated glycerol cation (CH2OH-CHOH-CH2OH2+ ) from the direct action of glycerol, or the hydronium species, H3O+, via water radiolysis, and their role in the subsequent acid-catalyzed mechanisms for acetol and solketal production. Scaled to a hypothetically compatible range of nuclear facilities in Europe (i.e., contemporary Pressurised Water Reactor designs or spent nuclear fuel stores), we estimate annual solketal production at approximately (1.0 ± 0.1) × 104 t year−1. Given a forecast increase of 5% to 20% v/v% in the renewable proportion of commercial petroleum blends by 2030, nuclear-driven, biomass-derived solketal could contribute towards net-zero emissions targets, combining low-carbon co-generation and co-production

Liquid-liquid phase equilibria of aqueous biphasic systems based on glycerol formal:Application on tetracycline recovery from water

Biopharmaceuticals are commonly present in relatively low concentrations in aqueous solutions, making their detection and purification detrimental. In this work, we used novel aqueous biphasic systems based on glycerol formal (GF) to extract an important antibiotic - tetracycline. We report cloud points (solubility curve) and tie-lines for three ternary systems, containing GF, water, and inorganic salt (either K3PO4, K2HPO4, or K2CO3) at constant temperature of 298 K and at 0.1 MPa. The tie-line data of these ternary systems were correlated using the nonrandom two-liquid model, and binary interaction parameters of activity coefficients were estimated. The experimental and correlated tie-line data were compared in terms of average root-mean-square deviation and showed satisfactory agreements. The partition coefficients of tetracycline between two phases were measured, and corresponding extraction efficiencies were calculated. The maximum value of partition coefficient was 1551 for the system containing K3PO4, followed by values of 1145 and 927 for systems containing K2CO3 and K2HPO4, respectively. The calculated extraction efficiencies were very high - greater than 98.8%, demonstrating high potential for using aqueous biphasic systems based on GF for separation and purification processes

Influence of ionic liquid on polar organic compounds solubility in dense CO2 phase

Accurate measurement and prediction of the phase behaviour of mixtures involved in a chemical process are crucial for its optimisation. Given the importance of CO2 conversion technologies and considering possible benefits of CO2-ionic liquid biphasic systems, i.e., facilitating a product separation, we investigated the high-pressure behaviour of components of interest in a recently developed process of cyclic carbonate synthesis directly from CO2 and potentially bio-based alcohols. The solubility of 1,2-butanediol and 1,2-butylene carbonate in a dense carbon dioxide phase was determined experimentally at the temperature of 313.2 K and pressures between 6 and 18 MPa. The influence of 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ionic liquid, [hmim][FAP], as a solvent, on the solubility of these compounds in CO2-rich phase, in ternary (CO2 + 1,2-butanediol + [hmim][FAP]), CO2 + butylene carbonate + [hmim][FAP]) and quaternary (CO2 + 1,2-butanediol + butylene carbonate + [hmim][FAP]) mixtures was investigated. The experimental results of the two binary systems were correlated using the density-based Chrastil equation. The knowledge of phase equilibria behaviours reported in this work will be useful for designing chemical conversions of carbon dioxide using [hmim][FAP] ionic liquid as reaction solvents

Process and Energy Intensification of Glycerol Carbonate Production from Glycerol and Dimethyl Carbonate in the Presence of Eggshell-Derived CaO Heterogeneous Catalyst

The process and energy intensifications for the synthesis of glycerol carbonate (GC) from glycerol and dimethyl carbonate (DMC) using an eggshell-derived CaO heterogeneous catalyst were investigated. The transesterification reaction between glycerol and DMC was typically limited by mass transfer because of the immiscible nature of the reactants. By varying the stirring speed, it was observed that the mass transfer limitation could be neglected at 800 rpm. The presence of the CaO solid catalyst made the mass transport-limited reaction process more prominent. Mass transfer intensification using a simple kitchen countertop blender as an alternative to overcome the external mass transfer limitation of a typical magnetic stirrer was demonstrated. A lower amount of the catalyst and a shorter reaction time were required to achieve 93% glycerol conversion or 91% GC yield, and the turnover frequency (TOF) increased almost 5 times from 1.5 to 7.2 min−1 when using a conventional magnetic stirrer and countertop blender, respectively. In addition, using a simple kitchen countertop blender with 7200 rpm, the reaction temperature of 60 °C could be reached within approximately 3 min without the need of a heating unit. This was the result of the self-frictional heat generated by the high-shear blender. This was considered to be heat transfer intensification, as heat was generated locally (in situ), offering a higher homogeneity distribution. Meanwhile, the trend toward energy intensification was promising as the yield efficiency increased from 0.064 to 2.391 g/kJ. A comparison among other process intensification techniques, e.g., microwave reactor, ultrasonic reactor, and reactive distillation was also rationalized