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Dr. Vesna Najdanovic
Aston University, Birmingham, B4 7ET, United Kingdom

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Research Keywords & Expertise

0 Biodiesel Production
0 Biomass Conversion
0 Downstream Processing
0 separation and purification
0 Green Chemistry and Engineering

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Biodiesel Production
separation and purification

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Journal article
Published: 14 July 2021 in Energies
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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.

ACS Style

Wanichaya Praikaew; Worapon Kiatkittipong; Farid Aiouache; Vesna Najdanovic-Visak; Kanokwan Ngaosuwan; Doonyapong Wongsawaeng; Jun Lim; Su Lam; Kunlanan Kiatkittipong; Navadol Laosiripojana; Sunya Boonyasuwat; Suttichai Assabumrungrat. Process and Energy Intensification of Glycerol Carbonate Production from Glycerol and Dimethyl Carbonate in the Presence of Eggshell-Derived CaO Heterogeneous Catalyst. Energies 2021, 14, 4249 .

AMA Style

Wanichaya Praikaew, Worapon Kiatkittipong, Farid Aiouache, Vesna Najdanovic-Visak, Kanokwan Ngaosuwan, Doonyapong Wongsawaeng, Jun Lim, Su Lam, Kunlanan Kiatkittipong, Navadol Laosiripojana, Sunya Boonyasuwat, Suttichai Assabumrungrat. Process and Energy Intensification of Glycerol Carbonate Production from Glycerol and Dimethyl Carbonate in the Presence of Eggshell-Derived CaO Heterogeneous Catalyst. Energies. 2021; 14 (14):4249.

Chicago/Turabian Style

Wanichaya Praikaew; Worapon Kiatkittipong; Farid Aiouache; Vesna Najdanovic-Visak; Kanokwan Ngaosuwan; Doonyapong Wongsawaeng; Jun Lim; Su Lam; Kunlanan Kiatkittipong; Navadol Laosiripojana; Sunya Boonyasuwat; Suttichai Assabumrungrat. 2021. "Process and Energy Intensification of Glycerol Carbonate Production from Glycerol and Dimethyl Carbonate in the Presence of Eggshell-Derived CaO Heterogeneous Catalyst." Energies 14, no. 14: 4249.

Journal article
Published: 19 March 2021 in Fluid Phase Equilibria
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Ethyl lactate is a hydrophilic solvent produced from bio-renewable sources (bioethanol and lactic acid produced from corn fermentation) that is considered as a “green” solvent due to its extremely low toxicity, biodegradability and negligible eco-toxicity. This work focuses on the utilization of ethyl lactate to form aqueous two-phase systems (ATPS) in the presence of inorganic salts for the extraction of antibiotics from aqueous solutions. The performance of three thiosulfate salts (Na2S2O3, K2S2O3 and (NH4)2S2O3) as salting-out media for the extraction of chloramphenicol and tetracycline 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 atmospheric pressure (0.1 MPa) and 298.2 K. Partition coefficients of chloramphenicol and tetracycline between the two phases were determined by chemical analysis of phases in equilibrium for different initial compositions at 298.2 K. This paper is the first report to demonstrate the ability of the ATPS based on ethyl lactate to efficiently separate antibiotics. Thus, ATPS based on ethyl lactate represents a new and green platform for the extraction of antibiotics from aqueous solutions which can facilitate their detection, identification and quantification in surface waters as well as their extraction from fermentation broths.

ACS Style

Małgorzata E. Zakrzewska; Ana V.M. Nunes; Aarti R. Barot; Alfred Fernández-Castané; Zoran P. Visak; Worapon Kiatkittipong; Vesna Najdanovic-Visak. Extraction of antibiotics using aqueous two-phase systems based on ethyl lactate and thiosulphate salts. Fluid Phase Equilibria 2021, 539, 113022 .

AMA Style

Małgorzata E. Zakrzewska, Ana V.M. Nunes, Aarti R. Barot, Alfred Fernández-Castané, Zoran P. Visak, Worapon Kiatkittipong, Vesna Najdanovic-Visak. Extraction of antibiotics using aqueous two-phase systems based on ethyl lactate and thiosulphate salts. Fluid Phase Equilibria. 2021; 539 ():113022.

Chicago/Turabian Style

Małgorzata E. Zakrzewska; Ana V.M. Nunes; Aarti R. Barot; Alfred Fernández-Castané; Zoran P. Visak; Worapon Kiatkittipong; Vesna Najdanovic-Visak. 2021. "Extraction of antibiotics using aqueous two-phase systems based on ethyl lactate and thiosulphate salts." Fluid Phase Equilibria 539, no. : 113022.

Journal article
Published: 05 January 2021 in Education for Chemical Engineers
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This paper demonstrates a novel approach for a computer-based course assessment. A test is introduced in which computers are deployed. This significantly contributes to the enhancement of the marking consistency, individual performance distinction and feedbacks, and widen the questions range for computer-based modules. The proposed test method, for the first time, uses the simulation files marking for individualised evaluation purposes. The methodology has successfully been implemented in practice for three modules including Process Simulation (CE2105), Advanced Process Simulation (CE4023), and Process Computation (CE3021) at Aston University (UK) over three academic years, from 2016 to 2019. The effectiveness of the proposed approach has been evaluated using several factors, including final marks, consistency multiple academic years, and mark distribution. In contrast to the common teamwork assessments, individualised feedback became possible. While ASPEN has been used for CE4023 and CE2105 tests, MATLAB has been applied as the computation platform for CE3021 module. This reveals the applicability of different software in proposed methodology. The number of students in the cohorts studied was from 52 to 204, demonstrating the applicability of the method for various cohort sizes. Even though the methodology has been demonstrated based on the chemical engineering discipline modules, it allows digitalising the delivery and assessment of a wide range of simulation techniques in many disciplines.

ACS Style

Amirpiran Amiri; Jiawei Wang; Nigel K.H. Slater; Vesna Najdanovic-Visak. Enhancement of process modelling and simulation evaluation by deploying a test for assessment and feedback individualisation. Education for Chemical Engineers 2021, 35, 29 -36.

AMA Style

Amirpiran Amiri, Jiawei Wang, Nigel K.H. Slater, Vesna Najdanovic-Visak. Enhancement of process modelling and simulation evaluation by deploying a test for assessment and feedback individualisation. Education for Chemical Engineers. 2021; 35 ():29-36.

Chicago/Turabian Style

Amirpiran Amiri; Jiawei Wang; Nigel K.H. Slater; Vesna Najdanovic-Visak. 2021. "Enhancement of process modelling and simulation evaluation by deploying a test for assessment and feedback individualisation." Education for Chemical Engineers 35, no. : 29-36.

Review
Published: 01 December 2020 in Sustainability
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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.

ACS Style

Kelum Gamage; Roshan Pradeep; Vesna Najdanovic-Visak; Nanda Gunawardhana. Academic Standards and Quality Assurance: The Impact of COVID-19 on University Degree Programs. Sustainability 2020, 12, 10032 .

AMA Style

Kelum Gamage, Roshan Pradeep, Vesna Najdanovic-Visak, Nanda Gunawardhana. Academic Standards and Quality Assurance: The Impact of COVID-19 on University Degree Programs. Sustainability. 2020; 12 (23):10032.

Chicago/Turabian Style

Kelum Gamage; Roshan Pradeep; Vesna Najdanovic-Visak; Nanda Gunawardhana. 2020. "Academic Standards and Quality Assurance: The Impact of COVID-19 on University Degree Programs." Sustainability 12, no. 23: 10032.

Journal article
Published: 11 May 2020 in Ceramics International
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Wire mesh packings have seen increasing applications to multiphase processes in recent years. Despite the high surface area, open structure and thermal and chemical resistance, wire mesh packings have a complex geometry which hinders some chemical applications, including changes of surface properties through application of a uniformly adhesive coating. In this work, the sol-gel deposition method of alumina coating ceramics was investigated for the first time on stainless steel wire mesh by using Dixon rings as example. The kinetics of deposition during the hydrolysis and polycondensation was followed for a range of initial composition of the coating such as the ratios of Al2O3 to water, acid content, polyethyleneimine binder content and the number of deposition cycles. Well-adhered alumina with a thickness up to 20 μm was successfully deposited. The molar ratios of acid to alumina and alumina to water of 0.25 and 0.01, respectively, 48 h of the aging time, 96 h of the mixing time and 2.1 g/L of polyethyleneimine binder formed a free of cracks coating of controlled thickness alumina on the Dixon rings.

ACS Style

Mohamed Abdelraouf; Josef Hegarty; Allan Rennie; Rémi Elizalde; Neil Burns; Louise Geekie; Vesna Najdanovic-Visak; Farid Aiouache. Sol-gel alumina coating of wire mesh packing. Ceramics International 2020, 46, 20777 -20787.

AMA Style

Mohamed Abdelraouf, Josef Hegarty, Allan Rennie, Rémi Elizalde, Neil Burns, Louise Geekie, Vesna Najdanovic-Visak, Farid Aiouache. Sol-gel alumina coating of wire mesh packing. Ceramics International. 2020; 46 (13):20777-20787.

Chicago/Turabian Style

Mohamed Abdelraouf; Josef Hegarty; Allan Rennie; Rémi Elizalde; Neil Burns; Louise Geekie; Vesna Najdanovic-Visak; Farid Aiouache. 2020. "Sol-gel alumina coating of wire mesh packing." Ceramics International 46, no. 13: 20777-20787.

Journal article
Published: 17 April 2020 in Nutrients
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Circulating uric acid concentrations have been linked to various metabolic diseases. Consumption of large boluses of nucleotides increases serum uric acid concentrations. We investigated the effect of a nucleotide-rich mixed meal on postprandial circulating uric acid, glucose, and insulin responses. Ten healthy adults participated in a randomised, controlled, double-blind, crossover trial in which they consumed a mixed-meal containing either nucleotide-depleted mycoprotein (L-NU) or high-nucleotide mycoprotein (H-NU) on two separate visits. Blood samples were collected in the postabsorptive state and throughout a 24 h postprandial period, and were used to determine circulating uric acid, glucose, and insulin concentrations. Mixed meal ingestion had divergent effects on serum uric acid concentrations across conditions (time x condition interaction; P < 0.001), with L-NU decreasing transiently (from 45 to 240 min postprandially) by ~7% (from 279 ± 16 to 257 ± 14 µmol·L−1) and H-NU resulting in a ~12% increase (from 284 ± 13 to 319 ± 12 µmol·L−1 after 210 min), remaining elevated for 12 h and returning to baseline concentrations after 24 h. There were no differences between conditions in blood glucose or serum insulin responses, nor in indices of insulin sensitivity. The ingestion of a nucleotide-rich mixed-meal increases serum uric acid concentrations for ~12 h, but does not influence postprandial blood glucose or serum insulin concentrations.

ACS Style

Mariana O. C. Coelho; Alistair J. Monteyne; Ishara D. Kamalanathan; Vesna Najdanovic-Visak; Tim J. A. Finnigan; Francis B. Stephens; Benjamin T. Wall. Short-Communication: Ingestion of a Nucleotide-Rich Mixed Meal Increases Serum Uric Acid Concentrations but Does Not Affect Postprandial Blood Glucose or Serum Insulin Responses in Young Adults. Nutrients 2020, 12, 1115 .

AMA Style

Mariana O. C. Coelho, Alistair J. Monteyne, Ishara D. Kamalanathan, Vesna Najdanovic-Visak, Tim J. A. Finnigan, Francis B. Stephens, Benjamin T. Wall. Short-Communication: Ingestion of a Nucleotide-Rich Mixed Meal Increases Serum Uric Acid Concentrations but Does Not Affect Postprandial Blood Glucose or Serum Insulin Responses in Young Adults. Nutrients. 2020; 12 (4):1115.

Chicago/Turabian Style

Mariana O. C. Coelho; Alistair J. Monteyne; Ishara D. Kamalanathan; Vesna Najdanovic-Visak; Tim J. A. Finnigan; Francis B. Stephens; Benjamin T. Wall. 2020. "Short-Communication: Ingestion of a Nucleotide-Rich Mixed Meal Increases Serum Uric Acid Concentrations but Does Not Affect Postprandial Blood Glucose or Serum Insulin Responses in Young Adults." Nutrients 12, no. 4: 1115.

Journal article
Published: 27 February 2020 in Resources, Conservation and Recycling
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Spent coffee grounds (SCGs) have a potential to be used as a feedstock for higher value-added products, such as biodiesel. However, the environmental implications of the valorisation of SCGs are largely unknown. This study evaluates the life cycle environmental impacts of utilising SCGs for biodiesel production in comparison with the widely used disposal of SCGs as a waste stream: incineration, landfilling, anaerobic digestion, composting and direct application to land. The scope is from cradle to grave and the functional unit is defined as ‘treatment of 1 tonne of SCGs’. The results show that the most environmentally sustainable option is incineration of SCGs, with net-negative impacts (savings) in 14 out of 16 categories, followed by direct application of SCGs to land with 11 net-negative impacts. Biodiesel production is the least sustainable option with the highest impacts in 11 categories, followed by composting. The paper also demonstrates that following various waste hierarchy and resource valorisation guidelines instead of a life cycle approach could lead to a choice of environmentally inferior SCG utilisation options. Therefore, these guidelines should be revised to ensure that they are consistent and underpinned by life cycle thinking, thus aiding sustainable resource management in a circular economy context.

ACS Style

Ximena C. Schmidt Rivera; Alejandro Gallego-Schmid; Vesna Najdanovic-Visak; Adisa Azapagic. Life cycle environmental sustainability of valorisation routes for spent coffee grounds: From waste to resources. Resources, Conservation and Recycling 2020, 157, 104751 .

AMA Style

Ximena C. Schmidt Rivera, Alejandro Gallego-Schmid, Vesna Najdanovic-Visak, Adisa Azapagic. Life cycle environmental sustainability of valorisation routes for spent coffee grounds: From waste to resources. Resources, Conservation and Recycling. 2020; 157 ():104751.

Chicago/Turabian Style

Ximena C. Schmidt Rivera; Alejandro Gallego-Schmid; Vesna Najdanovic-Visak; Adisa Azapagic. 2020. "Life cycle environmental sustainability of valorisation routes for spent coffee grounds: From waste to resources." Resources, Conservation and Recycling 157, no. : 104751.

Conference paper
Published: 20 January 2020 in EPJ Web of Conferences
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In this paper, the irradiation of glycerol and ethylene glycol by either mixed (neutron-γ) or γ-only (γ) fields at the TRIGA reactor of the Jožef Stefan Institute is described. This is highly relevant to future applications of fission reactor systems to produce useful feedstock derivatives from organic waste, beyond the production of heat and power. Samples of glycerol and ethyl glycol have been exposed to neutron-gamma radiation with fast neutron fluxes ranging from 7.7×1010 to 3×1012 cm−2s−1 and gamma-only irradiation at maximum dose-rates of 492 and 10 kGy hr−1, respectively. A study of the dependence of product yield versus absorbed dose has been conducted, for total dose ranges of 1 to 100 kGy. The products of these exposures have been identified through Gas Chromatography – Mass Spectrometry (GC-MS) techniques. Analysis comparing neutron-gamma irradiated samples of ethylene glycol and glycerol with gamma-irradiated samples shows no detectable qualitative difference between either irradiation type. Although, additional radiolysis products were detected when compared with available literature; ethyl acetate from ethylene glycol and solketal from glycerol. Quantitatively, neutron-gamma irradiation seems to be less effective at producing acetaldehyde from ethylene glycol, compared with gamma-only which can be explained through neutron moderation and consequent heating effects due to the borosilicate vials.

ACS Style

Arran George Plant; Vesna Najdanovic-Visak; Malcolm J. Joyce; Luka Snoj; Anže Jazbec. Producing Useful Chemicals Using a Nuclear Reactor. EPJ Web of Conferences 2020, 225, 09003 .

AMA Style

Arran George Plant, Vesna Najdanovic-Visak, Malcolm J. Joyce, Luka Snoj, Anže Jazbec. Producing Useful Chemicals Using a Nuclear Reactor. EPJ Web of Conferences. 2020; 225 ():09003.

Chicago/Turabian Style

Arran George Plant; Vesna Najdanovic-Visak; Malcolm J. Joyce; Luka Snoj; Anže Jazbec. 2020. "Producing Useful Chemicals Using a Nuclear Reactor." EPJ Web of Conferences 225, no. : 09003.

Research article
Published: 16 October 2019 in Journal of Chemical & Engineering Data
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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.

ACS Style

Wanichaya Praikaew; Worapon Kiatkittipong; Kunlanan Kiatkittipong; Suttichai Assabumrungrat; Farid Aiouache; Vesna Najdanovic-Visak. Liquid–Liquid Phase Equilibria of Aqueous Biphasic Systems Based on Glycerol Formal: Application on Tetracycline Recovery from Water. Journal of Chemical & Engineering Data 2019, 64, 4856 -4862.

AMA Style

Wanichaya Praikaew, Worapon Kiatkittipong, Kunlanan Kiatkittipong, Suttichai Assabumrungrat, Farid Aiouache, Vesna Najdanovic-Visak. Liquid–Liquid Phase Equilibria of Aqueous Biphasic Systems Based on Glycerol Formal: Application on Tetracycline Recovery from Water. Journal of Chemical & Engineering Data. 2019; 64 (11):4856-4862.

Chicago/Turabian Style

Wanichaya Praikaew; Worapon Kiatkittipong; Kunlanan Kiatkittipong; Suttichai Assabumrungrat; Farid Aiouache; Vesna Najdanovic-Visak. 2019. "Liquid–Liquid Phase Equilibria of Aqueous Biphasic Systems Based on Glycerol Formal: Application on Tetracycline Recovery from Water." Journal of Chemical & Engineering Data 64, no. 11: 4856-4862.

Journals
Published: 27 March 2019 in Sustainable Energy & Fuels
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To fulfill the conditions required for a nuclear renewable energy concept, one has to explore a combination of processes going from the front end of the nuclear fuel cycle to the fuel production and the energy conversion using specific fluid fuels and reactors.

ACS Style

Claude A. Degueldre; Richard Dawson; Vesna Najdanovic-Visak. Nuclear fuel cycle, with a liquid ore and fuel: toward renewable energy. Sustainable Energy & Fuels 2019, 3, 1693 -1700.

AMA Style

Claude A. Degueldre, Richard Dawson, Vesna Najdanovic-Visak. Nuclear fuel cycle, with a liquid ore and fuel: toward renewable energy. Sustainable Energy & Fuels. 2019; 3 (7):1693-1700.

Chicago/Turabian Style

Claude A. Degueldre; Richard Dawson; Vesna Najdanovic-Visak. 2019. "Nuclear fuel cycle, with a liquid ore and fuel: toward renewable energy." Sustainable Energy & Fuels 3, no. 7: 1693-1700.

Journal article
Published: 05 April 2018 in Journal of Molecular Liquids
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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.

ACS Style

Ishara Kamalanathan; Zeljko Petrovski; Luis Branco; Vesna Najdanovic-Visak. Novel aqueous biphasic system based on ethyl lactate for sustainable separations: Phase splitting mechanism. Journal of Molecular Liquids 2018, 262, 37 -45.

AMA Style

Ishara Kamalanathan, Zeljko Petrovski, Luis Branco, Vesna Najdanovic-Visak. Novel aqueous biphasic system based on ethyl lactate for sustainable separations: Phase splitting mechanism. Journal of Molecular Liquids. 2018; 262 ():37-45.

Chicago/Turabian Style

Ishara Kamalanathan; Zeljko Petrovski; Luis Branco; Vesna Najdanovic-Visak. 2018. "Novel aqueous biphasic system based on ethyl lactate for sustainable separations: Phase splitting mechanism." Journal of Molecular Liquids 262, no. : 37-45.

Journal article
Published: 01 April 2018 in Fluid Phase Equilibria
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ACS Style

Ishara Kamalanathan; Luca Canal; Joe Hegarty; Vesna Najdanovic-Visak. Partitioning of amino acids in the novel biphasic systems based on environmentally friendly ethyl lactate. Fluid Phase Equilibria 2018, 462, 6 -13.

AMA Style

Ishara Kamalanathan, Luca Canal, Joe Hegarty, Vesna Najdanovic-Visak. Partitioning of amino acids in the novel biphasic systems based on environmentally friendly ethyl lactate. Fluid Phase Equilibria. 2018; 462 ():6-13.

Chicago/Turabian Style

Ishara Kamalanathan; Luca Canal; Joe Hegarty; Vesna Najdanovic-Visak. 2018. "Partitioning of amino acids in the novel biphasic systems based on environmentally friendly ethyl lactate." Fluid Phase Equilibria 462, no. : 6-13.

Journal article
Published: 01 March 2018 in Bioresource Technology Reports
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Enormous amounts of brewers' spent grains (BSGs) per year are generated to produce bear worldwide. BSGs can be used as a carbon source, biofuel to generate energy and as a source of biogas. Typically, BSGs contain >60 mass% of water and, therefore, drying kinetics is a paramount for the development of any of these valorisation processes. In this work, we reveal the main parameters and mechanism of drying kinetics of BSGs at isothermal conditions (60 °C–90 °C), measured by thermogravimetric analysis. Diffusion coefficients ranged from 1.42 × 10−9 m2 s−1 to 2.67 × 10−9 m2 s−1 while the activation energy was 26.6 kJ mol−1. Furthermore, for the first time, biodiesel production from BSGs is reported. We employed acid catalysed in situ transesterification process, at different catalyst concentrations, methanol to BSGs ratios, reaction time and temperature. The outcomes of our study show promise for alternative valorisation of brewers' spent grains, an abundant waste spread around the world.

ACS Style

Elliot Mallen; Vesna Najdanovic-Visak. Brewers' spent grains: Drying kinetics and biodiesel production. Bioresource Technology Reports 2018, 1, 16 -23.

AMA Style

Elliot Mallen, Vesna Najdanovic-Visak. Brewers' spent grains: Drying kinetics and biodiesel production. Bioresource Technology Reports. 2018; 1 ():16-23.

Chicago/Turabian Style

Elliot Mallen; Vesna Najdanovic-Visak. 2018. "Brewers' spent grains: Drying kinetics and biodiesel production." Bioresource Technology Reports 1, no. : 16-23.

Journal article
Published: 01 June 2017 in Journal of Environmental Chemical Engineering
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Resource limits, environmental concerns and unstable petroleum costs have led to an increased effort to develop alternative liquid fuels. Purpose grown feedstocks are expensive and demand additional resources such as land and water. Spent coffee grounds (SCGs) are a good potential low-cost feedstock, however, processing times and costs must be lowered in order to be cost competitive with fossil fuels. In this work, we investigated the kinetics of oil extraction from SCGs to explore if current methods of oil extraction could be hastened and an integrated process which couples oil extraction and conversion to biodiesel stages in one single step (in situ transesterification) which could significantly cut down biodiesel production costs. Kinetics of oil extraction from SCGs using n-hexane as solvent was studied as a function of temperature, solvent to solid ratio and water content. We have found that oil extraction times could be significantly reduced to 10 minutes due to high diffusion coefficients. Further, we demonstrate, for the first time, the successful in situ transesterification of SCGs using different concentration of sodium hydroxide as catalyst and methanol to oil mole ratio, promising lower biodiesel production costs from a ubiquitous waste product around the world

ACS Style

Vesna Najdanovic-Visak; Florence Yee-Lam Lee; Márcia Tavares; Alona Armstrong. Kinetics of extraction and in situ transesterification of oils from spent coffee grounds. Journal of Environmental Chemical Engineering 2017, 5, 2611 -2616.

AMA Style

Vesna Najdanovic-Visak, Florence Yee-Lam Lee, Márcia Tavares, Alona Armstrong. Kinetics of extraction and in situ transesterification of oils from spent coffee grounds. Journal of Environmental Chemical Engineering. 2017; 5 (3):2611-2616.

Chicago/Turabian Style

Vesna Najdanovic-Visak; Florence Yee-Lam Lee; Márcia Tavares; Alona Armstrong. 2017. "Kinetics of extraction and in situ transesterification of oils from spent coffee grounds." Journal of Environmental Chemical Engineering 5, no. 3: 2611-2616.

Journal article
Published: 01 January 2017 in Education for Chemical Engineers
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Although it was originally developed for a business school environment to promote the benefits of small-group teaching in a large group setting, the method of the Team-based Learning (TBL) has recently been increasingly used within medical education. On the other hand, the reports on its implementation in engineering and science education are much scarcer. The aim of this work is to discuss the experience, evaluation and lessons learned from the implementation of the TBL within a Year 1 engineering module − Process Engineering Fundamentals, enrolling 115 students, and the TBL method was introduced for the first time. To evaluate the acquired knowledge and perception of TBL, a students’ performance analysis and questionnaire were completed on two occasions. It was observed that the TBL approach improved student learning, enhanced their integration and sharing of knowledge in class, supporting the implementation of this method in engineering disciplines

ACS Style

Vesna Najdanovic-Visak. Team-based learning for first year engineering students. Education for Chemical Engineers 2017, 18, 26 -34.

AMA Style

Vesna Najdanovic-Visak. Team-based learning for first year engineering students. Education for Chemical Engineers. 2017; 18 ():26-34.

Chicago/Turabian Style

Vesna Najdanovic-Visak. 2017. "Team-based learning for first year engineering students." Education for Chemical Engineers 18, no. : 26-34.

Research article
Published: 30 November 2016 in Journal of Chemical & Engineering Data
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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%.

ACS Style

Sílvia Rebocho; Ana V. M. Nunes; Vesna Najdanovic-Visak; Susana Barreiros; Alexandre Paiva. Experimental Determination and Modeling of the Phase Behavior of the CO2 + Propionic Anhydride Binary System at High Pressure. Journal of Chemical & Engineering Data 2016, 62, 210 -213.

AMA Style

Sílvia Rebocho, Ana V. M. Nunes, Vesna Najdanovic-Visak, Susana Barreiros, Alexandre Paiva. Experimental Determination and Modeling of the Phase Behavior of the CO2 + Propionic Anhydride Binary System at High Pressure. Journal of Chemical & Engineering Data. 2016; 62 (1):210-213.

Chicago/Turabian Style

Sílvia Rebocho; Ana V. M. Nunes; Vesna Najdanovic-Visak; Susana Barreiros; Alexandre Paiva. 2016. "Experimental Determination and Modeling of the Phase Behavior of the CO2 + Propionic Anhydride Binary System at High Pressure." Journal of Chemical & Engineering Data 62, no. 1: 210-213.

Journal article
Published: 08 April 2016 in The Open Chemical Engineering Journal
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This paper presents data on mutual solubility of the binary (soybean oil + ionic liquid) and ternary (soybean oil + methanol + ionic liquid) systems, where ionic liquid stands for 1-butyl-3-methylimidazolium thiocyanate [C4MIM][SCN] or 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C4MIM][NTf2] or 1-butyl-3-methylimidazolium dicyanamide [C4MIM][DCA] or 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6] or 1-butyl-3-methyl imida zolium hydrogensulfate [C4MIM] [HSO4] or 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C10MIM][NTf2] or methyltrioctylammonium bis(trifluoromethylsulfonyl)imide [ALIQUAT][NTf2] or methyltrioctylammonium chloride [ALIQUAT][Cl]. Solubilities were determined by the cloud point titration method in the temperature range of 298 K to 343 K. Obtained results suggest that imidazolium based ionic liquids exhibit lower solubility in soybean oil than ionic liquids with the aliquat cation. Thus, aliquat based ionic liquids are good candidate to be used as co-solvents for biphasic (methanol + soybean oil) mixture.

ACS Style

Marina S. Manic; Vesna Najdanovic-Visak. Solubility of Mixtures Containing Soybean Oil, Ionic Liquid and Methanol. The Open Chemical Engineering Journal 2016, 10, 41 -49.

AMA Style

Marina S. Manic, Vesna Najdanovic-Visak. Solubility of Mixtures Containing Soybean Oil, Ionic Liquid and Methanol. The Open Chemical Engineering Journal. 2016; 10 (1):41-49.

Chicago/Turabian Style

Marina S. Manic; Vesna Najdanovic-Visak. 2016. "Solubility of Mixtures Containing Soybean Oil, Ionic Liquid and Methanol." The Open Chemical Engineering Journal 10, no. 1: 41-49.

Journal article
Published: 01 March 2016 in Journal of Catalysis
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Zinc(II) complexes of arylhydrazones of β-diketones (AHBD) were used for the first time as catalysts combined with tetrabutylammonium bromide (TBABr), in the coupling reaction between CO2 and epoxides. The influence of pressure and temperature on cyclic carbonate formation was investigated, as well as the catalytic activity toward different substrates (e.g. styrene oxide, propylene oxide and cyclohexene oxide). The molar ratio between metal complex and TBABr was determined for maximum catalytic activity.

ACS Style

Carmen Alicia Moreno Montoya; Clara F. Gómez; Ana Inês Paninho; Ana V.M.Nunes; Kamran Mahmudov; Vesna Najdanovic-Visak; Luisa Martins; M. Fátima C. Guedes da Silva; Armando Pombeiro; Manuel Nunes da Ponte. Cyclic carbonate synthesis from CO2 and epoxides using zinc(II) complexes of arylhydrazones of β-diketones. Journal of Catalysis 2016, 335, 135 -140.

AMA Style

Carmen Alicia Moreno Montoya, Clara F. Gómez, Ana Inês Paninho, Ana V.M.Nunes, Kamran Mahmudov, Vesna Najdanovic-Visak, Luisa Martins, M. Fátima C. Guedes da Silva, Armando Pombeiro, Manuel Nunes da Ponte. Cyclic carbonate synthesis from CO2 and epoxides using zinc(II) complexes of arylhydrazones of β-diketones. Journal of Catalysis. 2016; 335 ():135-140.

Chicago/Turabian Style

Carmen Alicia Moreno Montoya; Clara F. Gómez; Ana Inês Paninho; Ana V.M.Nunes; Kamran Mahmudov; Vesna Najdanovic-Visak; Luisa Martins; M. Fátima C. Guedes da Silva; Armando Pombeiro; Manuel Nunes da Ponte. 2016. "Cyclic carbonate synthesis from CO2 and epoxides using zinc(II) complexes of arylhydrazones of β-diketones." Journal of Catalysis 335, no. : 135-140.

Journal article
Published: 01 May 2015 in The Journal of Supercritical Fluids
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The production of cyclic styrene carbonate from CO2 cycloaddition to styrene oxide, using tetrabutylammonium bromide (TBABr) as catalyst, was investigated. Two different reaction systems, a CO2-rich and an epoxide-rich were studied. Reactions were performed in a visual high pressure cell, at different temperatures (313.2, 333.2, and 353.2 K) and pressures (0.5-18 MPa). High pressure phase behaviour manipulation of the reaction system was explored to shift catalysis from homogeneous to heterogeneous, by changing operation conditions. Styrene carbonate formation was monitored quantitatively by using 1H-NMR spectroscopy

ACS Style

C.A. Montoya; A.B. Paninho; P.M. Felix; M.E. Zakrzewska; J. Vital; V. Najdanovic-Visak; A.V.M. Nunes. Styrene carbonate synthesis from CO2 using tetrabutylammonium bromide as a non-supported heterogeneous catalyst phase. The Journal of Supercritical Fluids 2015, 100, 155 -159.

AMA Style

C.A. Montoya, A.B. Paninho, P.M. Felix, M.E. Zakrzewska, J. Vital, V. Najdanovic-Visak, A.V.M. Nunes. Styrene carbonate synthesis from CO2 using tetrabutylammonium bromide as a non-supported heterogeneous catalyst phase. The Journal of Supercritical Fluids. 2015; 100 ():155-159.

Chicago/Turabian Style

C.A. Montoya; A.B. Paninho; P.M. Felix; M.E. Zakrzewska; J. Vital; V. Najdanovic-Visak; A.V.M. Nunes. 2015. "Styrene carbonate synthesis from CO2 using tetrabutylammonium bromide as a non-supported heterogeneous catalyst phase." The Journal of Supercritical Fluids 100, no. : 155-159.

Journal article
Published: 01 August 2014 in The Journal of Supercritical Fluids
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ACS Style

Sílvia Rebocho; Ana V.M. Nunes; Vesna Najdanovic-Visak; Susana Barreiros; Pedro Simões; Alexandre Paiva. High pressure vapor–liquid equilibrium for the ternary system ethanol/(±)-menthol/carbon dioxide. The Journal of Supercritical Fluids 2014, 92, 282 -287.

AMA Style

Sílvia Rebocho, Ana V.M. Nunes, Vesna Najdanovic-Visak, Susana Barreiros, Pedro Simões, Alexandre Paiva. High pressure vapor–liquid equilibrium for the ternary system ethanol/(±)-menthol/carbon dioxide. The Journal of Supercritical Fluids. 2014; 92 ():282-287.

Chicago/Turabian Style

Sílvia Rebocho; Ana V.M. Nunes; Vesna Najdanovic-Visak; Susana Barreiros; Pedro Simões; Alexandre Paiva. 2014. "High pressure vapor–liquid equilibrium for the ternary system ethanol/(±)-menthol/carbon dioxide." The Journal of Supercritical Fluids 92, no. : 282-287.