Volume 67, Issue 12

In recent times, environmental production methods and organic products are increasingly sought after in food, perfume, and cosmetic industries, where the products are consumed or come into direct contact with humans. One such additive is 2-phenylethanol, an alcoholic aromatic rose like smell compound, mainly used as a flavor and aroma. 2-Phenylethanol can be produced by bioconversion from l-phenylalanine using Saccharomyces cerevisiae. This type of biotransformation is strongly limited by product inhibition which allows reaching the maximum concentration of 2-phenylethanol, 4 g L−1, in an ordinary batch, fed-batch, or chemostat bioreactor. The main aim of the presented work was to study the possible yield increase of 2-phenylethanol in a hybrid system consisting of membrane extraction performed by a hollow fiber membrane module immersed in the downcomer of an airlift reactor. Such hybrid system can be used to remove 2-phenylethanol from the fermentation medium and thus to overcome the product inhibition of biotransformation. In this paper, the influence of biomass on membrane extraction of 2-phenylethanol from aqueous solution in an airlift reactor to alkanes at different operational conditions was studied. The measured extraction kinetics was compared with the predictions obtained by a mathematical model. Hydrodynamics of the hybrid system was also studied.

The process of CFD model application for atmospheric dispersion modeling is presented. Increasing the CPU power opens new possibilities of the CFD approach application for consequence analysis in real complex urban environments. As successful CFD simulation is directly dependent on the quality and complexity of the computational mesh, a new methodology of transferring the Geographic Information System (GIS) data to the computational mesh can be utilized. A user software for importing and manipulation with the GIS data and their subsequent transfer to an instructional file for the generation of the computational mesh was prepared and tested. The introduced methodology is relatively simple and it requires only a small amount of input data. The process of creating a computational mesh is very straightforward and fast, which enables the application of CFD modeling in urban environments in all fields of engineering applications in safety analysis. Several recommendations concerning proper definition of boundary conditions for atmospheric dispersion modeling were summarized. The presented approach was tested on a realistic case study of liquefied chlorine release in a real town. Results obtained by the CFD approach were compared with those obtained by a simpler but standard integral model.

The present work deals with thermo-catalytic decomposition of pyrolytic oil from the scrap tire pyrolysis process. Such oil can be used as a model tar in an experimental study of tar removal from pyrolysis or gasification process gas. Several experiments under different conditions were carried out in order to determine conditions of the gasification and pyrolysis processes. Influence of the oil to steam ratio, temperature, and of the presence of dolomite catalyst was studied. Addition of water steam has positive effect on the hydrogen content in the outgoing process gas as well as on the conversion of the injected oil. The catalytic gasification experiment in a quasi steady state produced process gas with the composition: 61 mole % of H2, 6.4 mole % of CO, and 11.7 mole % of CH4. At temperatures lower than 800°C, the amount of process gas decreased resulting also in a decrease of the oil conversion. A comparison of gasification experiments using fresh calcined dolomite with experiments proceeding with regenerated dolomite was done under the same conditions. There was a decrease in the process gas volumetric flow when regenerated catalyst was used.

Kinetics of thermal decomposition of aseptic packages (e.g. Tetrapak cartons) and pyrolysis of this waste in a laboratory flow reactor was studied. Three different models for the calculation of the reaction rate and the determination of apparent kinetic parameters of thermal decomposition were used. The first method assumes a two stage thermal decomposition and the kinetic parameters were determined by fitting a derivative thermogravimetric (DTG) curve to experimentally determined thermogravimetric data of whole aseptic cartons. The second method uses kinetic parameters determined by fitting DTG curves to thermogravimetric data of individual components of aseptic packages. The last method was a multi-curve isoconversion method assuming a change of kinetic parameters with the increasing conversion. All types of the determined kinetic parameters were used in a mathematical model for thermal decomposition of mini briquettes made from aseptic packages at the temperature of 650°C. The model calculated also the heat conduction in the particles and it was verified by an independent set of experiments conducted in a laboratory screw type flow reactor.

The aim of the presented work was to investigate the distribution of sulphur in tire pyrolysis products as well as the influence of process parameters (temperature and residence time) on sulphur distribution due to environmental concerns. Among modern methods used for waste tire recycling, pyrolysis is one of the most reasonable alternatives meeting current environmental standards. However, waste tire sulphur content can be a potential drawback for pyrolysis products utilisation as fuels. Sulphur is present in tires in different concentrations, depending on the type and age of the tires. Typical sulphur content in tires is about 1.6 mass %. In this paper, the distribution of sulphur in tire pyrolysis products was investigated. Tire pyrolysis yields three different products: liquid, gaseous, and solid residue composed mostly of carbon black (chars). Temperature and residence time are the two most important parameters affecting the yield and composition of the volatile fraction and they are therefore expected to affect the sulphur content in residues. Pyrolysis experiments were carried out in a laboratory pyrolysis reaction unit in the temperature range of 650°C to 750°C at different residence times: 88.6 s, 80.2 s, and 73.9 s. Liquid and solid products were analysed by elemental analysis and the distribution of total sulphur in tire pyrolysis products was calculated.

The performance of weak and strong anion- and cation-exchange membrane adsorbents with a grafted gel layer (Sartobind Q, D, S, and C) was investigated using six proteins: bovine serum albumin, human serum albumin, α-lactalbumin, β-lactoglobulin, lysozyme, and myoglobin. Static binding experiments were used to assess the effect of pH and buffer concentration and to determine the adsorption isotherms for selected membrane/protein combinations. The equilibrium data were duly described either by the Langmuir or Freundlich isotherms. Dynamic binding experiments were carried out for the same membrane/protein combinations in a broad range of linear flow velocity. Both the dynamic binding capacity at 10 % breakthrough and the final binding capacity at complete breakthrough were independent of the flow velocity despite strong dispersion of the adsorption zone. A good match between the equilibrium data from static and dynamic experiments was obtained for the anion exchangers. The correlation between the dynamic binding capacity and protein molecule size was observed for the strong cation exchanger. This was due to the different accessibility of the gel layer for the protein molecules.

Adsorption of human immunoglobulin G (IgG) on a commercial cation exchanger with a grafted polymer layer was investigated at pH 4.5 and in the NaCl concentration range of 0–150 mM. Adsorption equilibrium was determined in static batch experiments and verified in batch uptake experiments. Parameters of the Langmuir isotherm were estimated for each salt concentration separately. The batch uptake experiments provided also the estimates of effective pore diffusion coefficients of IgG for individual protein and salt concentrations. The values of the effective pore diffusion coefficient depended strongly on both factors. They increased by about 5–15 times with the NaCl concentration and decreased about three times with the protein concentration. The quality of the estimated parameters was confirmed by frontal experiments described by the general rate model of chromatography.

The study concentrates on the separation of aromatic hydrocarbons from aliphatic hydrocarbon mixtures using ionic liquids as a new alternative of extraction solvents. Influence of the phase equilibrium description accuracy on the separation equipment design using different thermodynamic models was investigated. As a model system, a heptane-toluene binary mixture was chosen, employing 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES) ionic liquid as an extractive solvent. Liquid-liquid equilibrium (LLE) data of the ternary system were calculated using NRTL equations with different quality model parameters. Model 1 corresponds to the NRTL equation with the original binary parameters evaluated independently from the respective binary equilibrium data. Model 2 is represented by an NRTL equation extended by the ternary correction term (with the original binary parameters and ternary correction term parameters evaluated from the ternary tie-lines). Model 3, i.e. the NRTL equation with binary model parameters determined via ternary LLE data regression using ASPEN Plus, was taken from Meindersma et al. (2006). Continuous-flow liquidphase extraction was simulated considering a cascade of mixer-settler type extractors according to the Hunter-Nash scheme (Hunter & Nash, 1934). Based on the simulation results, for a preset separation efficiency criterium, different accuracies of the equilibrium description caused serious discrepancies in the separation equipment design, e.g. in the number of theoretical stages, solvent to feed ratio, and product purity.

Solvent formulation is important in the optimization of the mass-transfer through supported liquid membranes (SLM) in pertraction and membrane extraction. Oleyl alcohol (OA) is frequently used as the solvent or diluent in the extraction of carboxylic acids. A disadvantage of OA is its relatively high viscosity of 28.32 mPa s at 25°C. This can be decreased by the application of a less viscous OA diluent, e.g. dodecane. The relationship between the ratio of the distribution coefficient of butyric acid (BA), D F, and the viscosity of OA-dodecane solvents, µ, as extraction and transport characteristics, and the overall mass-transfer coefficient, K p, through SLMs was analyzed. Dependence of the D F/µ ratio on the OA concentration showed a maximum at the OA concentration of 15 mass % to 30 mass %. The OA concentration dependence of K p for SLMs exhibited also a maximum at about 30 mass % and 20 mass % of OA at the BA concentration driving force of 0.12 kmol m−3 and 0.3 kmol m−3, respectively. Shifting of the maximum in K p dependences towards lower OA concentrations by increasing the BA concentration driving force is in agreement with the D F/µ ratio dependence. Using pure OA as the solvent or diluent is not preferable and a mixture of a low viscosity diluent with the OA concentration below 40 mass % should be used. The presented results show the potential of the D F/µ ratio in the screening and formulation of solvents in extraction and SLM optimization.

Rapeseed meal is a solid by-product obtained from rapeseed after oil extraction. This contribution summarises experiences from batch experiments as well as the long-term processing of this substrate in a laboratory stirred anaerobic reactor (continuous stirred-tank reactor). On the basis of the batch tests of hydrolysis, acidogenesis, and methanogenic activity, it was concluded that the anaerobic degradation of rapeseed meal can be performed using a one-step system and it is not necessary to include a hydrolytic-acidogenic step prior to the methanogenic step. Although the methanogenic potential of rapeseed meal appears to be very promising, the long-term processing as a single substrate led to serious problems arising from the inhibitory effects. It was, therefore, co-fermented with crude glycerol from biodiesel production. From the long-term operation of the laboratory model, it may be stated that, due to the co-fermentation of by-products from biodiesel production, the individual inhibition effects can be suppressed to a large extent and biogas production can be stabilised. The maximum organic loading rate in the continuous stirred reactor achieved 2.42 kg m−3 d−1 of volatile solids (15 g of rapeseed meal and 20 mL of gas-phase), which was 3.13 kg m−3 d−1 of chemical oxygen demand.

Laboratory experiments involving shutdown and repeated start-up of a denitrification USB reactor with granulated anoxic biomass were conducted in order to find suitable conditions for a safe storage period of the biomass. Anoxic granulated biomass stored under anaerobic conditions for a half year period at 6°C and for a half month period at 18–20°C retained its activity and granular morphology. Storage of anoxic granules under anaerobic conditions for a half year period at 18–20°C led to the loss of the biomass original activity and a significant portion of the granules disintegrated. Anoxic granulated biomass stored for a one and a half month period under endogenous anoxic conditions at 18–20°C retained its activity and granular morphology. A two month storage under endogenous anoxic conditions at 18–20°C was too long and the shutdown of the reactor had to be followed by repeated anoxic granulation. Minimum loading of the USB reactor with N-NO3 to maintain endogenous anoxic conditions in the sludge bed was in the range of 0.06–0.1 kg of N-NO3 per m3 per day. Restart of the USB reactor can be accelerated by an addition of anaerobic granulated biomass.

Feasibility of ozone oxidation for the elimination of selected dissolved organic micropollutants from water and wastewaters was studied. Five organochlorine pesticides, i.e. hexachlorobutadiene, pentachlorobenzene, hexachlorobenzene, lindane, and heptachlor, were used as organic contaminants of model water. The first four of them are classified as priority hazardous substances. The oxidation treatment process was performed in a jet loop reactor. Ozone was prepared from pure oxygen. Quantification of the organochlorine pesticides in water was achieved by the gas chromatographic method after liquid-liquid extraction. Significant contribution of stripping to the removal of the investigated compounds during the ozonation treatment was also proven by the results. Effective ozonation time with regard to treatment efficiencies was 30 min, which corresponds to the ozone input of 317 mg per liter of active volume of the ozonation reactor. Single power law kinetic models were used to describe experimental data and kinetic parameters were estimated. The best fit of the experimental degradation data of all studied pollutants was obtained by the second order kinetic model. It can be concluded, based on the results obtained, that the applied ozonation process is a promising procedure for the removal of the investigated pesticides from aquatic environment.

Three priority pollutants, i.e. mono-, di-, and trichloroacetic acids, were degraded by the conventional Fenton AOP system (Fe2+ and H2O2). The results obtained suggest that the degradation decreased in the order: monochloroacetic, dichloroacetic, and trichloroacetic acid. The best of advanced oxidation processes (AOPs) for the degradation of trichloroacetic acid was reductive dechlorination with the use of zero-valent iron (Fe°). The results of Escherichia coli toxicity tests revealed that the reagents’ toxicity after the Fenton treatment process was decreased.