Igor Plazl

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Papers by Igor Plazl

Microfluidics with redox-responsive hydrogels for on-demand BPA degradation

Chemical engineering journal, Apr 1, 2024

Hydrolysis of Micron Alkylketene Dimert Particles Under Alkaline Conditions

Chemical and Biochemical Engineering Quarterly, Dec 18, 2006

The hydrolysis of alkylketene dimer (AKD) in a diluted dispersion was studied under alkaline cond... more The hydrolysis of alkylketene dimer (AKD) in a diluted dispersion was studied under alkaline conditions. The dispersion consisted of particles with 1 mm in diameter with the reaction product forming a porous insoluble layer on the particle surface. The shrinking core model (SCM) for particles of unchanging size is proposed for describing the overall rate of hydrolysis reaction. The model assumes a process controlled by a surface reaction on the boundary between unreacted AKD core and outer ketone layer, with no significant transport phenomena due to the small particle dimensions and porous structure of the reaction product layer on the particle surface. Under conditions studied (at pH 10.3), where the concentration of OHions is in excess compared to the AKD concentration and in the temperature range between 40 and 60°C, the proposed model is in good agreement with experimental data. A temperature dependence of reaction rate was tested and the apparent activation energy was calculated as well. Compared to the activation energy for reaction between AKD and cellulose, AKD hydrolysis can represent an important competitive process that significantly influences the sizing efficiency.

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Microbioreactors

Elsevier eBooks, 2017

Microscale bioprocess design and optimisation

Journal of Biotechnology, Nov 1, 2019

Time scale analysis & characteristic times in microscale-based chemical and biochemical processes: Part I – Concepts and origins

Chemical Engineering Science, Jul 1, 2021

Abstract Time-Scale Analysis and Characteristic Times are suggested as a novel and useful tool in... more Abstract Time-Scale Analysis and Characteristic Times are suggested as a novel and useful tool in the analysis of the performance of microscale-based reactors, unit operations, and plant flow-sheet diagrams embodying microscale-based chemical processes. Transport phenomena, reaction kinetics, and phase contacting in microstructured architecture can be easily represented by unique time constants. These Characteristic Times are estimated from first principles and are controlled by a user to support a meaningful chemical process analysis and provide insight or suggestions for successful design choices. While the origin of Characteristic Times in microscale-based processes is rooted in fundamentals of molecular transport and reaction kinetics, the evolution of Characteristic Time definitions could be easily found in detailed mathematical models of microscale-based reaction processes and operations. The user-defined scaling parameters contribute to the flexibility of TSA implementation. This work uses a microscale-based solid catalyzed reaction process to demonstrate the concept of TSA and systematically define Characteristic Times and their origin. Lastly, varying forms of TSA have been implemented to evaluate specific phenomena or aspects of processes but have yet to encompass the full unit operation or process within the analysis. Part I and Part II of this work develop a comprehensive TSA for unit operations and a (bio)chemical process flow-sheet (Part II only).

Process Intensification and Miniaturization of Chemical and Biochemical Processes

Computer-aided chemical engineering, 2019

On a global scale, the quantity of biomass waste is steadily increasing, particularly in densely ... more On a global scale, the quantity of biomass waste is steadily increasing, particularly in densely populated urban areas. The electricity and heat energy generation from biomass gasification is viable sustainable process and substitutes fossil fuels, that can decrease greenhouse gas emissions in particular reduce carbon dioxide gas. In this work, sugar cane bagasse as a biomass fuel was considered for combustible gas generation by utilising an intensified downdraft-throated gasifier. The study showed that sugar cane bagasse has a calorific value of around 17.7MJ/kg and densified in the form of briquettes which is found to be an appropriate feedstock for gasification in a downdraft gasifier generating an average of 2.05 Nm 3 of produced gas per kilogram of bagasse with a calorific value between 3.30 to 4.56 MJ/Nm 3. Biomass feed rates for the gasifier varied between 2.87 to 7.44 kg/hr was utilised in the experiments. The produced combustible gas mixtures were determined as CO, H 2, CH 4 , C 2 H 2 , C 2 H 4 and C 2 H 6 which contained 25% to 27% V/V of the entire produced gas. The volume of produced synthetic gas (syngas) ranged from 2.05 to 2.16 Nm 3 /kg of bagasse gasified. Above 99% transformation of solid carbon in the bagasse to product gas was accomplished by utilising the intensive gasification system however, it is required to apply a gas clean-up process to mitigate against any possible harmful impacts.

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Applying Oxygen Imaging for Validation of a Diffusion-and-Convection Model for Microfluidics

Laccase catalysed oxidation of L-DOPA in a microreactor

Laccases (EC 1.10.3.2 p-diphenol: dioxygen oxidoreductases) are multi-copper proteins that use mo... more Laccases (EC 1.10.3.2 p-diphenol: dioxygen oxidoreductases) are multi-copper proteins that use molecular oxygen to oxidize various aromatic and non-aromatic compounds by radical-catalyzed reaction[1]. Their applications are numerous: delignification or decolouration of paper pulp, detoxification of environmental pollutants, textile dye-bleaching or diagnostic assays[2]. The fields of application of enzymatic microreactors grow every day. Their current use is primarily in biochemical analysis as components of integrated systems (lab-on-a-chip) or in micro total analysis systems - m ; TAS. Secondly, microreactors are used for screening of substrates, enzymes and to examine their kinetic characteristics. However, their huge potential is not yet exploited in biotechnology as well as in combinatorial chemistry and enzyme-targeted drug search[3]. In this work, the use of microreactor for oxidation of phenolic compounds was investigated. L-DOPA was selected as a model substrate for laccase-catalysed oxidation, which was carried out in a microreactor (220 m ; m X 50 m ; m X 0.332 cm) at four different residence times. Process model, comprised of reaction diffusion dynamics combined with fluid flow was developed. The simulation of the process for different substrate and enzyme concentrations, as well as for different flow rates was performed. A very good correlation of experimental data with the proposed model was achieved. Literature: [1] Claus H.: Laccases: structure, reactions, distribution ; Micron 35 (2004), 93-96 [2] Pilz R., Hammer E., Schauer F., Kragl U.: Laccase – catalysed of coupling products of phenolic substrates in different reactors: Appl Microbiol 60 (2003), 708-712 [3] Urban, P. L., Goodall D. M., Bruce N. C.: Enzymatic microreactors in chemical analysis and kinetic studies, Biotechnol Adv 24 (2006), 42-57

Modelling Reaction-Diffusion Dynamics in Microsystems

Computer-aided chemical engineering, 2016

Abstract The commonly used macroscale techniques based on the continuum approximation cannot alwa... more Abstract The commonly used macroscale techniques based on the continuum approximation cannot always be readily adapted to describe chemical reactions and transport processes that take place at the microscale. By contrast, particle-based mesoscale methods possess the unique ability to model relatively large physical systems, and, at the same time, effectively capture the essential features of the micro- and nanoscale structures. The lattice Boltzmann method (LBM) is a powerful mesoscopic computational tool for simulating complex flows and has the ability to efficiently solve the reaction-diffusion-advection equation (RDA). Typically reaction is incorporated into LBM by a macroscopic reaction source term similar in structure to the kinetic equations that are used when solving RDA problems by conventional numerical methods. A more accurate approach is to include reaction into LBM simulations at a meso or microscopic level and mimic collisions of reactive particles. In this study we present a novel algorithm based on an effective reaction cross section that is able to capture the underlying dynamics of reaction mechanism.

Inertial focusing of neutrally buoyant particles in heterogenous suspensions

Journal of Molecular Liquids, Apr 1, 2021

The modelling-based design of microfluidic devices leads to highly efficient process intensificat... more The modelling-based design of microfluidic devices leads to highly efficient process intensification, which provides insights into different temporal and spatial scales at which processes in various fields of application could be performed. This requires not only an understanding of the underlying mechanisms of different processes at the micro scale, but also the development of relevant computational tools. The macroscopic models are often unable to produce conclusive evidence for a given mechanism in systems with the complexity characterizing almost all chemical and biochemical processes. By contrast, mesoscale methods possess the unique ability to model relatively large physical systems, and, at the same time, effectively capture the essential features of the micro-and nanoscale structure, architecture, and relevant interactions. We demonstrate the feasibility and usefulness of this novel tool by considering a movement of neutrally buoyant particles in straight microchannels. The two-dimensional lattice Boltzmann method with immersed boundary conditions was used to study the influence of Reynolds number and particle diameter ratio on formation of particle trains. It was shown that an increase in particle diameter ratio leads to a less stable final particle configuration. An increase in Reynolds number was not found to significantly influence the train stability in the tested range.

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Separation and purification of biomacromolecules based on microfluidics

Green Chemistry, 2020

Separation and purification of biomacromolecules either in biopharmaceuticals and fine chemicals ... more

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Enzymatic packed-bed microreactor: Transport phenomena and kinetics

Journal of Biotechnology, 2018

Personalized medicine (also called precision medicine) is a medical practice which uses methods a... more Personalized medicine (also called precision medicine) is a medical practice which uses methods and tailored products to the patient. Diagnostic tests based on variant genetic analysis are used for the appropriate selection of specific therapies. Combining together genomic and clinical data is possible to obtain more precise and faster diagnoses. An example of personalized medicine is the use of targeted practices for the treatment of cancer cells. The first goal of the precision medicine method is to set up a new prescription process for the identification of cancer drugs by means of an IT platform. For example, the Watson computer system (IBM) is based on artificial intelligence methods that allow to give correct answers to specific questions. The answers of Watson are based on the elaboration of millions of stored information. Watson's wisdom is based, not only on scientific information, but also on experimental protocols both diagnostic and with new drugs, and on patient data. The super computer is provided with symptoms, examinations, the patient's medical history and other useful information (for example the data obtained with Illumina's "Trusight Tumor 170 Panel"). The big advantage of the Watson system is that it is updated in real time.

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Feasibility of Carbon Nanofiber Catalyst Support for the Heterogeneous Fenton Process

Journal of Environmental Engineering, 2016

AbstractThe heterogeneous Fenton oxidation reaction was investigated at two different catalytic s... more AbstractThe heterogeneous Fenton oxidation reaction was investigated at two different catalytic supports including the blank alumina plates and alumina plates with thin carbon nanofiber (CNF) layer. Iron (III) oxide was used as a catalyst and propionic acid (PA) was studied as a model organic compound. A carbon nanofiber layer and a thin catalytic layer of iron (III) oxide were prepared using the chemical vapor deposition method with acetylene and ferrocene precursors. The reaction rate of heterogeneous Fenton oxidation was compared with the rate of homogeneous reaction. Obtained results indicate that the reaction rate is significantly higher at homogeneous Fenton oxidation at high temperature (70°C), however, the reaction rate for homogeneous and heterogeneous oxidation is comparable at room temperature (25°C) if carbon nanofiber support is used for the iron (III) oxide catalyst.

To the Memory of Prof. Dr. Valentin Koloini (1940 – 2008)

In October this year we bade farewell to Professor Valentin-Tine Zdravko Koloini. He left us much... more

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Effect of oxygen on laccase catalysed L-DOPA oxidation

Lignin je trodimenzionalni, netopljivi aromatski polimer[1]. Sastavni je dio lignoceluloznog mate... more Lignin je trodimenzionalni, netopljivi aromatski polimer[1]. Sastavni je dio lignoceluloznog materijala koji se nalazi u drvenim dijelovima biljaka i travi[2]. U prirodi postoje gljive bijelog truljenja koje ekstracelularno izlucuju razlicite oksidaze: lignin-peroksidaze, mangan-peroksidaze i lakaze. Ovi enzimi sudjeluju u procesima delignifikacije[1]. Lakaze (EC 1.10.3.2) su oksidoreduktaze koje uz pomoc molekulskog kisika oksidiraju o-, p- difenole, aminofenole, polifenole, poliamine, lignin, neke anorganske ione i arildiamine[3]. Primjenjuju se u postupcima delignifikacije i obezbojenja papirne pulpe, detoksifikacije oneciscivaca okolisa, obezbojenja tekstilnih bojila, dijagnosticnim testovima itd. [4]. Obzirom na kompleksnu strukturu lignina i na njegovu slabu topljivost u vodi, u svrhu bolje razgradnje lignina i razumijevanja mehanizma djelovanja enzima, rade se brojna istraživanja na modelnim supstratima nalik ligninu[5]. Kao modelni supstrat u ovom radu je izabran 3, 4-dihidroksifenil-L-alanin (L-DOPA), kao jeftin, komercijalno dostupni fenolni spoj, slabe topljivosti u vodi.Proucavana je oksidacija L-DOPE s lakazom porijeklom iz gljive bijelog truljenja Trametes versicolor. Kinetika reakcije je opisana Michaelis-Mentenicinim izrazom. Parametri kinetickog modela su procijenjeni na osnovi rezultata mjerenja dobivenih metodom pocetnih brzina i iznose Vm=1, 529p ; 0, 101 U mg-1 i KmL-DOPA = 0, 469p ; 0, 099 mmol dm-3. Razvijen je matematicki model procesa, te je provedena ocjena valjanosti modela usporedbom sa rezultatima pokusa dobivenih u saržnom reaktoru. Pokazalo se da ovakav model ne može opisati dinamiku procesa. Stoga je analiziran utjecaj razlicitih koncentracija kisika, kao drugog potencijalnog supstrata, na kinetiku oksidacije L-DOPE. Pretpostavljen je dvosupstratni Michaelis-Mentenicin kineticki model, a parametri modela Vm = 6, 897 p ; 0, 243 U mg-1 i KmO2 = 0, 099 p ; 0, 015 mmol dm-3 procijenjeni su iz rezultata saržnih pokusa, cime je pokazan znacajan utjecaj kisika na brzinu enzimatske reakcije. Ovakav model dobro opisuje kinetiku enzimatske razgradnje L-DOPE s lakazom. Literatura: [1] D'Acunzo F, Galli, C., Masci, B.: Oxidation of phenols by laccase and laccase-mediator systems, Solubility and steric issues. European Journal of Biochemistry 269 (2002), 5330-5335. [2] Howard R. L. et. al.: Lignocellulose biotechnology: issues of bioconversion and enzyme production. African Journal of Biotechnology 2 (2003), 602-619. [3] Rodakiewicz-Nowak et. al.: Phenols oxidazing enzymes in water-restricted media. Total in Catalysis 11/12 (2000), 419-431. [4] Pilz R., Hammer E., Schauer F., Kragl, U.: Laccase – catalysed of coupling products of phenolic substrates in different reactors: Applied Microbiology 60 (2003), 708-712 [5] Crestini CiA, D. S.: The Early Oxidative Biodegradation Steps of Residual Kraft Lignin Models with Laccase. Bioorganic and Medicinal Chemistry 6 (1998), 2161-2169.

A lattice Boltzmann study of 2D steady and unsteady flows around a confined cylinder

Journal of The Brazilian Society of Mechanical Sciences and Engineering, Jan 28, 2020

In this work, the lattice Boltzmann (LB) method was applied to simulate incompressible steady and... more In this work, the lattice Boltzmann (LB) method was applied to simulate incompressible steady and unsteady low Reynolds number (Re) flows around a confined cylinder. In the LB method, different collision models (Bhatnagar-Gross-Krook model, two-relaxation-time model, multi-relaxation-time model, and entropic lattice Boltzmann model) and a regularization model were used, and the results were compared. Numerical results pertaining to a two-dimensional flow around a cylinder are reported and compared with numerical and experimental data available in the literature. The results agree with the predictions made from the literature. A correlation for Strouhal number (St) for 55 ≤ Re ≤ 300 is suggested.

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Review for "Kinetic modelling: Regression and validation stages, a compulsory tandem for kinetic model assessment

Prospect of microfluidic devices for on-site electrochemical production of hydrogen peroxide

Current Opinion in Electrochemistry

Validation of a Diffusion-and-Convection Model for Microfluidics by Oxygen Imaging

Implementation of Microreactor Technology in Biotechnology - IMTB 2013, 2013

Rheological aspects of polysaccharides

Materials Today: Proceedings, 2022

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