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. Applying supercritical fluids for particle formation may produce powders and composites with special characteristics. Several processes for formation and design of solid particles using dense gases have been studied intensively. The unique thermodynamic and fluid-dynamic properties of supercritical fluids can be used also for impregnation of solid particles or for the formation of solid powderous emulsions and particle coating, e.g., for formation of solids with unique properties for use in different applications. We give an overview of the application of sub- and supercritical fluids as green processing media for particle formation processes and present recent advances and trends in development.
In this study, we developed a novel high methoxyl pectin – xanthan aerogel coating on medical-grade stainless steel, prepared by ethanolinduced gelation and subsequent supercritical drying. Two non-steroidal anti-inflammatory drugs, i.e. diclofenac sodium and indomethacin, were incorporated into the aerogel coating. Electrochemical analyses were performed on the coated samples using electrochemical impedance spectroscopy and cyclic polarisation techniques. The results showed that all passivated samples were highly resistant to general corrosion. The release of both non-steroidal anti-inflammatory drugs was complete after 24 h, as confirmed by the plateau in the drug release profiles as well as by IR spectroscopy after the final release point. The potential of samples for use in orthopedic applications was evaluated on a human bonederived osteoblast cell and all samples were shown to be biocompatible. The increased viability of some samples indicates the high potential of the developed approach for future evaluation of possible clinical use.
Aerogels are outstanding materials, obtained by the sol-gel process. The production of polysaccharide aerogels is however time-consuming and their use for life-science applications is limited. To accelerate the production time, ethanol was used to induce the gelation of pectin, alginate, xanthan and guar gum. Polysaccharide aerogels were produced by dissolution in water, gelation in ethanol and supercritical drying. Only ethanol was used for the gelation without the use of any other cross-linking agent. In addition there was no solvent-exchange step prior to supercritical drying since the gelation occurred directly in ethanol. Differential scanning calorimetry was used to analyze the decompositions of the samples and also to measure their thermal conductivities. SEM and rheological analyses were performed in order to characterize the new materials.
In the present work, the preparation of magnetic maghemite nanoparticles (MNPs), functionalized with amino-organosilanes and chitosan was investigated for a successful immobilization of enzyme ß-galactosidase from Aspergillus oryzae. MNPs were synthesized by co-precipitation of Fe2+ and Fe3+ ions in the presence of ammonium. Immobilization techniques on both carriers were optimized by differing concentration of cross-linking reagent glutaraldehyde (GA) and pentaethylenehexamine (PEHA), where their influence on immobilization efficiency and residual activity of ß-galactosidase was studied. Compared to the free enzyme, hyper-activation of enzyme was achieved in both immobilization methods. When functionalizing with amino-organosilanes, residual activity of 154%, 138% and 125% was achieved, using PEHA (20% (v/v)), GA (2.5% (v/v)) and combination of PEHA and GA (30% and 2% (v/v)), respectively. When functionalizing with chitosan, 129% of residual activity was achieved, with combination of PEHA and GA (30% and 0.5% (v/v)), respectively. Such immobilized ß-galactosidase opens up a wide range of possibilities for implementation in various cleaner technologies, mostly benefiting in diary industries.
A quantitative analysis of zinc endopeptidases matrix metalloproteinase 9 (MMP9) and matrix metalloproteinase 3 (MMP3) from human blood serum are presented. Both matrix metalloproteinases (MMP) are present in human blood serum and can be used as biomarkers for different diseases. The analysis was performed using LC-MS/MS with a triple quadrupole mass spectrometer, based on two specific peptides of each MMP in comparison with an enzyme-linked immunosorbent assay (ELISA). While the conditions for the LC-MS/MS analysis of MMP9 peptides were previously reported for bronchoalveolar lavage fluid, the analysis of MMP3 peptides was newly quantified for human blood serum herein for the first time. For MMP3, the linear behaviour was determined in the concentration range from 1.0-200.0ng/mL (R2=0.997) with an LLOD of 0.5ng/mL. For MMP9, linearity was determined in the concentration range from 6.5-65.0ng/mL (R2=0.995) with an LLOD of 2.0ng/mL.
Water-scale precipitation was observed on electrical heaters within boilers for hot water preparation within households. Different permanent magnetic devices and electromagnetic device were installed on the inlet pipe in the boiler. The system was supplied with tap water of known chemical composition. The magnetic water treatment took place over several days under constant conditions (temperature in the boiler, water composition, etc.) along two parallel lines. The first one was the treated line and the second was for comparison. This paper presents the experimentally confirmed results using different permanent magnets and electromagnets for reducing the amount of precipitated water-scale on heaters for hot water. The impacts of different operational conditions are presented regarding the devices' effectiveness. Scale samples were analysed by X-ray diffraction, where it was discovered that all the samples were in the shapes of aragonite.
The main aim of this study was to evaluate pressurized hot water as a green and environmentally friendly extraction medium for the isolation of phenolic compounds from larch waste wood. Such isolates could find applications in the food, feed, pharmaceutical and cosmetics industries or as natural ingredients for adhesives or biocidal coatings in the wood industry. In the first step different larch wood fractions were extracted using batch system aiming to determine the most suitable fraction for isolation. The content of extractives, total phenolic and tannin content of obtained extracts and their antioxidant activity were evaluated. Secondly, semi-continuous operation was applied, where effects of temperature, addition of ethanol and flow rate were studied. Extraction yield was monitored and extracts were again analyzed for their total phenolic content and antioxidant activity. HPLC analysis was performed, in order to study the effect of temperature and addition of ethanol on the hydrothermal degradation of phenolics during semi-continuous operation. Finally, the economics of pilot-scale and industrial-scale processes with different extractor capacities, ranging from approximately 12 to 1200 kg of woody material per day and operating at optimal conditions for isolation of larch wood extractives was evaluated, in order to determine the cost of manufacturing of such a product.
Supercritical fluid extraction was used for obtaining Saw Palmetto extract and influence of parameters on extraction overall yield and extract composition were studied and compared with results from the literature. Catchpole et al.  developed supercritical fluid extraction at three different pressures (25, 28 and 30 MPa) and at two different temperatures (313 K and 323 K), in order to study extraction yield and the composition of the extract. In present work different operating conditions, i.e. pressure (30 MPa and 45 MPa), temperature (313 K and 333 K) and ethanol as co-solvent (10% w/w) were chosen as operating parameters. Extraction kinetic curves were modelled using Brunner’s equation showing perfect fitting. Compositions were analysed by Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) which confirmed the presence of fatty acids and beta-sitosterol. Solubility of the extract in CO2 was determined and studied by using different models. These models proved to fit quite accurate to experimental results.
The interfacial tension at the CO2 + PEG interface for polyethylene glycols (PEGs) of molar masses Mw = 200 g/mol, Mw = 400 g/mol and Mw = 600 g/mol has been measured in the present work for the pressure range from 0.1 MPa up to 18.0 MPa at two different temperatures of 313 K and 333 K. An experimental technique was developed to study the interfacial interactions of the liquids in equilibrium with gas in a glass-windowed equilibrium cell by the means of the capillary rise method. The new technique allows determining interfacial tension and visualization of the interfacial interactions phenomenon in the two component system of polymer and compressed CO2. In the first step, the experiments were conducted for the measurement of the interfacial tension between CO2 and pure water in order to validate the experimental technique. The obtained results are in good agreement with the ones found in the literature.
Supercritical fluids possess properties that make them attractive as media for chemical and biochemical reactions. Conducting reactions at supercritical conditions affords opportunities to manipulate the solvent properties by manipulating pressure and/or temperature, to enhance the solubilities of reactants and products, to reduce interphase transport limitations in terms to enhance the reaction rates, to improve the selectivity and to integrate reaction and separation steps. This perspective presents the developments of the past three decades on enzyme catalysed processes in the field of research and highlights the gaps and challenges for commercialization.