Masa Knez Marevci

University of Maribor | UM · Faculty of Chemistry and Chemical Engineering

Carbon fiber-reinforced composites present an exciting combination of properties and offer clear advantages that make them a perfect replacement for a spread of materials. Consequently, in recent years, their production has dramatically increased as well as the quantity of waste materials. As future legislations are likely to prevent the use of lan...

Oregano (Origanum vulgare) is considered to be a good and cheap source of phenolic compounds with favorable biological activities, especially antimicrobial and antioxidant properties. Hypothesis/Purpose: The current work explored the optimization of the process conditions of solid–liquid extraction from Origanum vulgare to obtain extracts with high...

Cannabis sativa is one of the oldest medicinal plants used by humans, containing hundreds of bioactive compounds. The biological effects and interplay of these compounds are far from fully understood, although the plant’s therapeutic effects are beyond doubt. Extraction methods for these compounds are becoming an integral part of modern Cannabis-ba...

Hop cones (Humulus lupulus L.), or more specifically the lupulin glands, hold the reason for the specific, pleasant aroma of hops – its essential oil. The hops themselves, or the extracted oil, are used almost exclusively in beer production. The essential oil is an indispensable part of beer and is responsible for its characteristic aroma. However,...

Slovenia has one of the richest food traditions in Europe, encompassing a wide variety of foods maintained for centuries and still forming everyday and festive menus. The tastes of Slovenia are different in the Alps than they are on the Adriatic coast, and different in the Karst Region than in the Pannonian Plain. Each region has its own distinct g...

According to many reports, phenolic compounds isolated from olive leaves have very good biological activities, especially antimicrobial. Presently, the resistance of microorganisms to antibiotics is greater than ever. Therefore, there are numerous recent papers about alternative solutions for inhibiting their influence on human health. Olive leaf i...

This study presents an investigation of the anticancer and antimicrobial ability of a combination of ginger and cannabis extracts in different ratios (1:1, 7:3 and 3:7). Extracts were obtained using various methods (Soxhlet extractions, cold macerations, ultrasonic extractions and supercritical fluid extractions). The antioxidant activity and the p...

Phytochemical research based on ethnopharmacology is gaining interest in industries such as functional food, nutraceuticals, cosmetics and pharmaceutical industries. Plants and plant extracts are a rich source of bioactive secondary metabolites. These compounds are often involved in plant protection against biotic or abiotic stresses. The exploitat...

In this paper, we focus on the preparation of electrospun composite nanofibrous materials based on (poly)-phenol-polysaccharide formulation. The prepared composite nanofibres are ideally suited as a controlled drug delivery system, especially for local treatment of different wounds, owing to their high surface and volume porosity and small fibre di...

The importance of natural crops in medicine and pharmacy is growing. Beside bioactive compounds used directly as therapeutic agents, there are also raw materials used for drug synthesis or as a basic model for new biologically active compounds. In this paper, the optimum conditions for material extraction of Curcuma longa, Lycium barbarum, Equisetu...

Polypropylene (PP) and polyethylene (PE) foils, previously activated by ultraviolet (UV)/ozone, were functionalized using chitosan-extract nanoparticle dispersions. A solution of macromolecular chitosan was applied onto foils as a first layer, followed by the deposition of various extracts encapsulated into chitosan nanoparticles, which were attach...

Hydrothermal conversion of biomass is a promising technology for the conversion of biomass into biofuels and biobased chemicals. This chapter is focused on the waste biomass conversion for production of biofuels and chemicals by applying sub- and supercritical fluids. One of the biggest disadvantages in biomass conversion by SCF is the extremely hi...

Biodegradable polymers have been developed rapidly in the last years and are widely used today in the fields of pharmacy, clinical biomedicine, cosmetic, medical, packing industries, tissue engineering, agriculture and other areas. The interest in biodegradable polymers has been increasing, mainly due to rising oil prices, which is the basic feedst...

Chia (Salvia hispanica L.) is a small seed that comes from an annual herbaceous plant, Salvia hispanica L. In recent years, usage of Chia seeds has tremendously grown due to their high nutritional and medicinal values. Chia was cultivated by Mesopotamian cultures, but then disappeared for centuries until the middle of the 20th century, when it was...

The current work concerns solid liquid extraction from red and white grapes skin and the rosehip (Rosa canina) to obtain extracts with a high phenolic content. Extracts have been acquired using conventional extraction techniques and extraction with supercritical fluids (SCFs). The effect of extraction method and experimental parameters (time, press...

The present paper reports a novel method to improve the properties of polyethylene (PE) and polypropylene (PP) polymer foils suitable for applications in food packaging. It relates to the adsorption of chitosan-colloidal systems onto untreated and oxygen plasma-treated foil surfaces. It is hypothesized that the first coated layer of chitosan macrom...

High pressure technologies involving sub and supercritical fluids offer the possibility to obtain new products with special characteristics or to design new processes which are environmentally friendly and sustainable. Using high pressure as a processing tool, the legal limitations for solvent residues and restrictions on use of conventional solven...

Hop plants comprise a variety of natural compounds greatly differing in their structure and properties. A wide range of methods have been developed for their isolation and chemical analysis, as well as for determining their antioxidative, antimicrobial, and antigenotoxic potentials. This contribution provides an overview of extraction and fractiona...

The purpose of this work was to investigate phase equilibria, namely equilibrium solubility and melting point depression of fenofibrate in several dense gases (carbon dioxide, propane, trifluoromethane). The equilibrium solubility of fenofibrate in sub- and supercritical gases was measured using a static-analytical method at temperatures of 303.15...

This study covers a comprehensive investigation into the heat transfer performance of CO2, ethane and their azeotropic mixture under supercritical conditions. A double pipe heat exchanger was developed and set up to study the effects of different operating parameters on heat transfer performance over a wide range of temperatures (25 °C to 90 °C) an...

Subcritical fluid extraction from Chia seeds (Salvia hispanica L.) using n-propane as a solvent and classical extractions as Soxhlet and ultrasonic extraction in n-hexane were performed to obtain oil rich extract. Influence of elevated operating pressure (up to 300 bar) and temperature (40 °C and 60 °C) on the extraction yield and extract compositi...

In our study, a PEG 6000/CO2 system was used as a model in order to investigate basic thermodynamic and transport data such as density, viscosity and interfacial tension of a CO2 saturated PEG 6000 solution. Additionally, particle size and particle morphology were correlated for the first time with the interfacial tension and viscosity of a PEG 600...

Using high pressure as a processing tool can overcome the legal limitations for solvent residues and restrictions on the use of conventional solvents in chemical processes. Additionally, particulate products can also be achieved by means of supercritical fluid (SCF) processing. This contribution will give a limited overview of applications of subcr...

In this study, the effect of argon as a co-contaminant in a CO2 stream on interfacial tension, diffusion coefficients and storage capacity was experimentally determined under conditions relevant to carbon sequestration, using the pendant drop method. Interfacial properties affect primary capillary trapping mechanisms when CO2 is injected since they...

Ganoderma lucidum (Reishi) is a popular medicinal mushroom and has been used in oriental medicine because of its promoting effects on health and life expectancy.G. lucidumcontains various compounds with a high grade of biological activty, which increase the immunity and show antitumour, antimicrobial, anti-inflammatory, antioxidant and acetylcholin...

New optimized experimental setup based on pendant drop tensiometry was developed, and a mathematical model designed to fit the experimental data was used to determine the diffusion coefficients of binary systems at elevated pressures and temperatures. For the first time, the diffusion coefficients of propylene glycol in supercritical CO2 were deter...

PGSS™ process was applied to the carrier materials Brij S100 and polyethylene glycol PEG 4000 for the incorporation of the insoluble drugs nimodipine, fenofibrate, and o-vanillin with the purpose of improving their bioavailability and dissolution rate. Brij S100/CO2 system has been investigated in the first part. The system has an S-L-G (solid-liqu...

A review of the solubility data for solids in sub- and supercritical fluids published in the literature between 2010 and 2017 is presented, including the pressure and temperature ranges and correlation methods. Compounds are categorized into the following groups: pharmaceutical, biological, aromatic, nonaromatic, organometallic, and polymer. The mo...

Review summarizes the research on the biomass conversion for production of chemicals and an overview on recent activities of our research group on isolation of substances from biomass using sub- and supercritical water. Herein, hydrothermal processing of biomass waste represents an alternative approach to upswing the productivity chemicals, basic c...

This study covers a comprehensive investigation on heat transfer characteristics of CO2 in the vicinity of the critical point. A double pipe heat exchanger set-up to study effects of different operating parameters on heat transfer performance over a wide range of temperatures (298.15 K to 363.15 K) and pressures (5 MPa to 30 MPa) has been developed...

This review summarises the research work published in the last two decades on the use of natural compounds as corrosion inhibitors for aluminium and aluminium alloys in different solutions. Herein, plant extracts, gums, drugs, and oils have been considered as green corrosion inhibitors. The advantages and disadvantages of the methods used to obtain...

Feasibility for removal of two commonly used antibiotics (amoxicillin and ciprofloxacin) from hospital wastewater was experimentally investigated using sub- and super-critical water oxidation. Effect of temperature and flow rate on the concentration of antibiotics was observed in the temperature range from 473 K to 773 K and at flow rates of 3 and...

Hydrothermal conversion of biomass is a promising technology for the conversion of biomass into biofuels and biobased chemicals. This chapter is focused on the waste biomass conversion for production of biofuels and chemicals by applying sub- and supercritical fluids. One of the biggest disadvantages in biomass conversion by SCF is the extremely hi...

The binary system of vitamin K3 and CO2 was investigated at temperatures of 40°C, 60°C and 80°C up to a pressure of 40 MPa. Solubility was measured by a static-analytic method. Partial molar volumes were determined by a method involving a vibrating tube densimeter. The solubility of vitamin K3 in CO2 is found as a function of pressure and temperatu...

Thermodynamic and transport properties of systems PEG 600/CO2 and Brij52/CO2 at different experimental conditions were determined with the aim of choosing optimal conditions for further polymer processing. Solubility and diffusivity of CO2 were measured by a magnetic suspension balance, density by the density meter with a U-tube, and interfacial te...

Being secondary plant metabolites, polyphenols represent a large and diverse group of substances abundantly present in a majority of fruits, herbs and vegetables. The current contribution is focused on their bioavailability, antioxidative and anticarcinogenic properties. An overview of extraction methods is also given, with supercritical fluid extr...

Hydrogen is expected to become an important fuel in the long-term since in combination with fuel cells it offers the opportunity of an intrinsically clean energy supply. By application of supercritical water gasification (SCWG) concept, sustainable hydrogen can be produced from biomass and waste. The paper offers an overview of some recently publis...

Thermodynamic data of polyethylene glycol in argon, based on a gravimetric method using a magnetic suspension balance are presented. Polyethylene glycol with an average molecular weight of 1500 (PEG 1500) and argon binary system was investigated at temperatures 343 K and from 373 to 433 K and pressures from 0 to 33 MPa with an increment of 2 MPa. S...

Traditional methods for solids processing involve either high temperatures, necessary for melting or viscosity reduction, or hazardous organic solvents. Owing to the negative impact of the solvents on the environment, especially on living organisms, intensive research has focused on new, sustainable methods for the processing of these substances. A...

Applying supercritical fluids may overcome the drawbacks of several conventional processes for formulation of products. For production of particles with micron and submicron size, several methods using supercritical fluids like rapid expansion of supercritical solution and gas antisolvent recrystallization, gas antisolvent precipitation, supercriti...

Phase equilibrium data of caffeine, vanillin, o-ethyl vanillin and a natural rosemary extract (containing 73.9% carnosic acid and 14.7% carnosol) in argon have been determined in present work. Solubility data were determined at temperatures of 313.15 K, 333.15 K and 363.15 K and in the pressure range from 0.82 MPa up to 50.27 MPa using a static-ana...

Density of CO2 saturated solutions of polyethylene glycols (PEGs) of different molecular weight was measured in pressure range from 8.0 MPa up to 47.7 MPa at a temperature of 343 K by a volumetric method. To validate the method density of pure CO2 was measured at different pressures and a temperature of 293 K. The results were compared to the liter...

High pressure technologies involving sub and supercritical fluids offer the possibility to obtain new products with special characteristics or to design new processes, which are environmentally friendly and sustainable. By using high pressure as a processing tool one can also avoid the legal limitations for solvent residues and restrictions on use...

The conversion of different organic substances, including wastes, sludge, biomass to biofuels and biobased chemicals has attracted a lot of attention recently, largely due to the environmental and socio-economic problems associated with the use of fossil fuels. In recent time many novel technologies have been introduced for conversion of biomass to...

The solubility and diffusivity of CO2 in polyethylene glycols (PEGs) of different molecular weight measured by two different methods are discussed in the present work. Before solubility measurements, the melting temperatures of PEG with different molecular weights were determined by means of differential scanning calorimetry. For the purpose of the...

Phase equilibrium data for the system hydrogen/pyrolysis oil as well as hydrogenated pyrolysis oils, at temperatures from 353.15 K to 423.15 K and pressures from 3.0 MPa up to 17.2 MPa were measured. The procedure was verified by measuring the phase equilibrium data for systems CO2/water and H2/water in the pressure range from 8.0 MPa up to 35.0 MP...

Phase behavior was observed for the systems bio-oil + diesel + carbon dioxide and bio-oil + tail water + carbon dioxide at temperatures from 353.15 K to 423.15 K and within the pressure range from 0.1 MPa to 49.0 MPa. First, equilibria was observed at ambient pressure and temperatures of 353.15 K, 383.15 K, and 423.15 K in a glass flask, which was...

“Process intensification” as a part of necessary sustainable development and “green” revolution uses also high pressure as a processing tool. The main impetus for this is on one way driven by environmental concerns to reduce the usage of conventional solvents and energy. On the other hand high pressure is a tool to design and produce the products w...

The traditional methods for polymer processing involve either high temperatures, necessary for melting or viscosity reduction, or hazardous organic solvents and chlorofluorocarbons. Due to the undesirable environmental and biological impact of these solvents, intensive research is focused on seeking new and cleaner methods for the processing of pol...

A review of solubility data for solid compounds in sub- and supercritical fluids published in the literature between 2005 and 2010 is given in tabular form along with the temperature and pressure ranges and the correlation methods applied by the authors for modeling the experimentally determined data. Compounds are classified into groups on the bas...

A genetic algorithm with resizable population has been applied to the estimation of parameters for Sovova's mass transfer model. The comparison of results between a genetic algorithm and a global optimizer from the literature shows that a genetic algorithm performs as good as or better than a global optimizer on a given set of problems. Other benef...

In chemical engineering, reliable models are necessary to reduce the cost of process design. An evolutionary algorithm with resizable population was used to estimate coefficients of Sovova's mass transfer model and was compared with a global optimiser found in the literature and commonly used differential evolution algorithm. Comparison of the evol...

The capacity of European biodiesel production is increasing rapidly, from approx. 3 million tons per year in 2005 up to an expected amount of 7 million t in 2007. Biodiesel is generally made when fats and oils are chemically reacted with an alcohol, typically with methanol, to produce an ester, or biodiesel. This reaction is generally known as tran...

Phase equilibria of sunflower and soybean oils in propane and sulphur hexafluoride (SF6) have been investigated. The phase behavior of sunflower oil–propane and soybean oil–propane systems has been studied using high-pressure variable-volume cell. For both systems, the transition of the two-phase system to one-phase system was observed visually at...