Stanisław Ledakowicz

Hydrocarbon selectivity model for the slurry phase Fischer–Tropsch synthesis on precipitated iron catalysts

Abstract A new hydrocarbon product distribution model for Fischer–Tropsch-synthesis (FTS) reaction has been developed. The model is based on the assumption that there are two types of active sites on the catalyst surface: type-1, where growth of hydrocarbon intermediates occurs, and type-2, where reversible readsorption of 1-olefins occurs. The readsorbed 1-olefins form alkyl intermediates, C n H 2 n +1 , on the surface, which in turn can participate in several reactions: chain growth propagation, hydrogenation to n -paraffins, and dehydrogenation to 2-olefins. Chain growth is considered on the basis of methylene monomer (CH 2 ) insertion mechanism. Steady-state mass balances for adsorbed intermediates C 1 –C 50 and equations for the product formation rates were derived. The model has been tested using results from experiments conducted over long periods of time under industrially relevant conditions in a slurry reactor. The model predictions provide information on hydrocarbon product distribution, 2-olefin content and total olefin content as a function of carbon number. The curved line for the distribution of paraffins and olefins can be fitted well with the proposed hydrocarbon selectivity model, over the entire range (C 1 –C 50 ) of carbon numbers. The kinetic model proposed in this paper can be used for interpretation of experimental data, comparison of performance of different catalysts, and reactor modelling and simulation studies.

Advanced Oxidation of Textile Wastewaters

Abstract Model dyeing and laundering wastewaters produced during two basic technological operations of the textile industry were subjected to treatment by advanced oxidation processes (AOPs). The following agents were used: ozone (O3), hydrogen peroxide (H2O2) and UV radiation. They were applied separately and in all possible combinations: O3 + UV, O3 + H2O2, UV + H2O2, as well as all three at the same time: O3 + UV + H2O2. Effluents before and after the treatment were analyzed according to requirements of the Polish Standards that included pH, color threshold, COD and concentration of anionic and non-ionic surfactants. Ozonation was carried out in a lab-scale bubble column reactor with a centrally located UV burner. The most effective version of AOPs proved to be the simultaneous use of all three agents. In the case of such treatment of dyeing wastewaters nearly complete discoloration and full decomposition of surface-active substances were obtained at 80% reduction of COD. A similar tendency was observed in the case of laundering wastewater, though in that case the results were slightly worse, which may be explained by much higher initial concentrations of the pollutants. Good treatment effects have also been obtained in combined treatment by simultaneous use of hydrogen peroxide and ozone.

Oxidation of PAHs in water solutions by ultraviolet radiation combined with hydrogen peroxide

The destruction of three polycyclic aromatic hydrocarbons (PAHs): benzo(a)pyrene, chrysene and uorene in aqueous solution using advanced oxidation process H2O2/UV was investigated. The inuence of pH, initial hydrogen peroxide and radical scavenger concentrations on the reaction rate was studied. The oxidation reactions most rapidly run in neutral and acidic solution at optimal hydrogen peroxide concentra- tion (ca. 0.01M). The degradation of benzo(a)pyrene and chrysene follows radical reaction, for uorene the mechanism is not clear. The rate constants of the hydroxyl radicals and selected PAHs reaction were found to be 2:531010 ,9 :82109 and 2:77109 M 1s 1 for benzo(a)pyrene, chrysene and uorene, respectively.

Germicidal Properties of Ozonated Sunflower Oil

The aim of this work was to establish the minimal inhibition concentration (MIC) of ozonated sunflower oil for various microorganisms. To determine the influence of the ozonated medium on the growth of bacteria Bacillus subtilis, Escherichia coli and yeast Candida albicans the Petri dish method was used. Chemical and physical properties of ozonated sunflower oil were additionally studied. Microbiological studies proved that these microbes have various sensibility against ozonated oil. The most resistant are gram-negative bacteria E. coli and the yeast C. albicans. Gram-positive bacteria, B. subtilis turned out to be less resistant, because no growth was observed for preparation with an ozone dose of 200 mgO3/g oil.

Simultaneous absorption of two gases reacting between themselves in a liquid—I exact solutions

Abstract Simultaneous absorption and irreversible second order chemical reaction of two gases in an inert liquid have been considered. The nonlinear differential equations describing the absorption process have been solved analytically for particular cases by the use of the Weierstrass elliptic function and Airy functions. It is impossible to obtain a general analytical solution and therefore the accurate numerical solution for the diffusion-reaction process based on the film theory has been developed. The approximate formula for the enhancement factor E A , in the range of large values of the dimensionless parameter M is given.

Influence of dissolved organic matter in natural and simulated water on the photochemical decomposition of butylparaben.

BackgroundIn the last few decades the quality of natural water has often deteriorated as a variety of novel pollutants have contaminated rivers and lakes. Trace amounts of some man-made chemicals can be hazardous to plants, animals as well as human health as carcinogens, mutagens or endocrine disruptors. Light radiation may help in its decomposition, aided by naturally occurring colored organic compounds (humic substances) in the water. The aim of these studies was to check the influence of presence of organic and inorganic matter on the removal of endocrine disrupting compound - butylparaben (BP) from water.MethodsPhotochemical decomposition of BP in aqueous solution using: photolysis by ultraviolet-C (UVC) and visible (VIS) irradiation, advanced oxidation in H2O2/UV system and photosensitized oxidation was examined. The degradation processes were carried out in different type of water matrix: natural water from Sulejow Reservoir, simulated natural water with humic acids and buffered solution.ResultsThe presence of dissolved organic matter in water did not influence much on UVC photolysis and increases only about 8% of BP depletion rate in H2O2/UV system. While during visible light photolysis and photosensitized oxidation the addition of natural water matrix causes the acceleration of reaction rate by 16% and 36%, respectively. Moreover BP degradation proceeds via singlet oxygen generated from humic substances.ConclusionsButylparaben undergoes both direct and indirect photodegradation in aqueous solution under UVC and visible radiation. The efficiency of the H2O2/UV process, photolysis as well as photosensitized oxidation processes is strongly dependent on composition of the water.

Modern morphological engineering techniques for improving productivity of filamentous fungi in submerged cultures

Morphological engineering techniques have recently gained popularity as they are used for increasing the productivity of a variety of metabolites and enzymes in fungi growing in submerged cultures. Their action is mainly associated with the changes they evoke in fungal morphology. Traditional morphological engineering approaches include manipulation of spore concentration, pH-shifting and mechanical stress exerted by stirring and aeration. As the traditional methods proved to be insufficient, modern techniques such as changes of medium osmolality or addition of mineral microparticles to the media (microparticle-enhanced cultivation, MPEC) were proposed. Despite the fact that this area of knowledge is still being developed, there are a fair amount of scientific articles concerning the cultivations of filamentous fungi with the use of these techniques. It was described that in Ascomycetes fungi both MPEC or change of osmolality successfully led to the change of mycelial morphology, which appeared to be favorable for increased productivity of secondary metabolites and enzymes. There are also limited but very promising reports involving the successful application of MPEC with Basidiomycetes species. Despite the fact that the mineral microparticles behave differently for various microorganisms, being strain and particle specific, the low cost of its application is a great benefit. This paper reviews the application of the modern morphology engineering techniques. The authors critically assess the advantages, shortcomings, and future prospects of their application in the cultivation of fungi.

Application of the TG-MS system in studying sewage sludge pyrolysis and gasification

Application of the TG-MS system in studying sewage sludge pyrolysis and gasification A method of monitoring sewage sludge pyrolysis and gasification was proposed. Samples of sludge were pyrolysed in Ar and gasified in CO2 in a thermobalance. The evolved gases were analysed on the calibrated MS, the samples of sludge and solid residues at different stages of the processes were subjected to elemental analysis. The identification and the quantitative characterisation of chemical reactions were performed, based on the DTG and MS profiles.

Application of Advanced Oxidation Technologies for Decolorization and Mineralization of Textile Wastewaters

Abstract Reactive dyes are the most abundantly used in textile industry due to their high color fastness, wide color spectrum as well as low energy consumption. The presence of these dyes in effluent released into receiving waters has become a serious environmental problem not only related to their color but mainly because of the hazardous byproducts. An environmentally sustainable development policy in textile industry requires development of new technologies to reduce water consumption as well as negative environmental impact of discharged wastewater. Advanced oxidation processes (AOPs) are the most promising technology for decolorization and mineralization of wastewater contamination. This paper presents the results of ozonation, Fenton’s oxidation and H2O2/UV treatment of simulated as well as industrial textile wastewater containing Reactive Black 5. The AOPs were carried out under varied process parameters such as: dye concentration, pH, oxidant and detergent doses and wide range concentration of NaCl. The decolorization was followed by absorbance while oxidation and mineralization progress by COD and TOC measurements respectively. The almost completely inhibition of decolorization in the presence of NaCl in concentration usually used in industry (60 - 80 g/L) was observed for Fenton reagent. The slight inhibition was observed for H2O2/UV system while for ozonation there was no influence of NaCl on the decolorization. The similar relationship of the influence of anionic detergent concentration was observed. The experiments indicated that ozonation is the best method from TOC and COD removal point of view. For the decolorization of real textile effluents two streams were used 1) containing C.I. Reactive Yellow 145, Red 195, Blue 221 and 2) Reactive Black 5. As a result of the treatment, almost complete decolorization of the wastewater was obtained. Considering both the experimental results and technological problems, it can be presumed that advanced oxidation with a application of ozone or hydrogen peroxide/UV are a very promising techniques for potential industrial implementation, however from economic point of view the more reasonable is the ozonation process.

Bioprocess Engineering Aspects of the Cultivation of a Lovastatin Producer Aspergillus terreus

The aim of this work is to review bioprocess engineering aspects of lovastatin (antihypercholesterolemia drug) production by Aspergillus terreus in the submerged culture in the bioreactors of various scale presented in the scientific literature since the nineties of the twentieth century. The key factor influencing the cultivation of any filamentous species is fungal morphology and that is why this aspect was treated as the starting point for further considerations. Fungal morphology is known to have an impact on the following issues connected with the cultivation of A. terreus reviewed in this article. These are broth viscosity in conjunction with non-Newtonian behaviour of the cultivation broths, and multistage oxygen transfer processes: from gas phase (air) to liquid phase (broth) and diffusion in the fungal agglomerates. The latest achievements concerning the controlling A. terreus morphology during lovastatin biosynthesis with the use of morphological engineering techniques were also reviewed. Last but not least, some attention was paid to the type of a bioreactor, its operational mode and kinetic modelling of lovastatin production by A. terreus.