Volume 63, Issue 2

Methanol has recently attracted significant interest in the energetic field. Current technology for the conversion of methane to methanol is based on energy intensive endothermic steam reforming followed by catalytic conversion into methanol. The one-step method performed at very low temperatures (35°C) is methane oxidation to methanol via bacteria. The aim of this work was to examine the role of copper in the one-step methane oxidation to methanol by utilizing whole cells of Methylosinus trichosporium OB3b bacteria. From the results obtained it was found that copper concentration in the medium influences the rate of bacterial biomass growth or methanol production during the process of methane oxidation to methanol. The presented results indicate that the process of methane oxidation to methanol by Methylosinus trichosporium OB3b bacteria is most efficient when the mineral medium contains 1.0 × 10−6 mol dm−3 of copper. Under these conditions, a satisfactory growth of biomass was also achieved.

The paper presents the results of investigations into the technological possibilities of controlling the transgalactosylation process of lactose in permeate after whey ultrafiltration in order to improve the efficiency of galactooligosaccharides or lactulose synthesis. The synthesis efficiency was influenced by the selection of a β-galactosidase preparation, substrate concentration and, in the synthesis of lactulose, also by the ratio of lactose and fructose added to the reaction mixture. The obtained synthesis efficiency of GOS and, most of all, of lactulose (65 g L−1), may be found satisfactory. The study also resulted in a proposed GOS or lactulose concentrates (concentrated or dried) production technology using permeate after ultrafiltration of milk or whey as lactose sources.

An approach to stable covalent immobilization of chemically modified penicillin G acylase from Escherichia coli on Sepabeads® carriers with high retention of hydrolytic activity and thermal stability is presented. The two amino-activated polymethacrylate particulate polymers with different spacer lengths used in the study were Sepabeads® EC EA and Sepabeads® EC HA. The enzyme was first modified by cross-linking with polyaldehyde derivatives of starch in order to provide it with new useful functions. Such modified enzyme was then covalently immobilized on amino supports. The method seems to provide a possibility to couple the enzyme without risking a reaction at the active site which might cause the loss of activity. Performances of these immobilized biocatalysts were compared with those obtained by the conventional method with respect to activity and thermal stability. The thermal stability study shows that starch-PGA immobilized on Sepabeads EC-EA was almost 4.5-fold more stable than the conventionally immobilized one and 7-fold more stable than free non-modified PGA. Similarly, starch-PGA immobilized on Sepabeads EC-HA was around 1.5- fold more stable than the conventionally immobilized one and almost 9.5-fold more stable than free non-modified enzyme.

The creation of anoxic granulated biomass has been monitored in a laboratory USB (Upflow Sludge Blanket) reactor with the volume of 3.6 L. The objective of this research was to verify the possibilities of post-denitrification of residual NO3-N concentrations in treated wastewater (denitrification of 10-20 mg L−1 NO3-N) and to determine the maximum hydraulic and mass loading of the granulated biomass reactor. G-phase from biodiesel production and methanol were both tested as external organic denitrification substrates. The ratio of the organic substrate COD to NO3-N was 6. Only methanol was proven as a suitable organic substrate for this kind of reactor. However, the biomass adaptation to the substrate took over a week. The cultivation of anoxic granulated biomass was reached at hydraulic loading of over 0.35 m h−1. The size of granules was smaller when compared with results found and described in literary reports (granules up to 1 mm); however, settling properties were excellent and denitrification was deemed suitable for the USB reactor. Sludge volume indexes of granules ranged from 35-50 mL g−1 and settling rates reached 11 m h−1. Maximum hydraulic and mass loadings in the USB reactor were 0.95 m3 m−2 h−1 and 6.6 kg m−3 d−1. At higher loading levels, a wash-out of the biomass occurred.

The paper is concerned with the constant pressure cake filtration of suspensions in viscoelastic fluids. The filtration equations, based on the capillary hybrid model for power law fluid flow, were used for the description of this type of filtration. Filtration experiments with suspensions of nearly spherical polystyrene particles Krasten in viscoelastic aqueous solutions of polyacrylamide Praestol were carried out at constant pressure in a laboratory cylindrical filtration unit. The fluid rheological properties were measured on a rotational rheometer Haake RheoStress 150. Elastic effects manifested themselves predominantly at the early period of the filtration due to higher filtration velocity which resulted in an evidently increased filtration resistance. Analysing the experimental data, procedures for the evaluation of the effective specific filter cake resistance γ ef, filter screen resistance R fs, and the elongation flow coefficient E have been proposed. The filtration process predicted using the proposed filtration equation agrees very well with that determined experimentally.

Two membrane bioreactors (MBRs; volume = 300 L) equipped with different types of immersed membrane modules were operated simultaneously under the same laboratory conditions as a low-loaded activated sludge process without any membrane regeneration and excess sludge uptake (sludge retention time SRT up to 170 d; activated sludge concentration MLSS up to 11 g L−1). The aim was to verify the quality of treated water and to study the properties of "very old" activated sludge. Another aim was to compare different selected membrane types and choose the best one for further pilot-scale testing.

Formation of precipitates containing CaSO4 during membrane distillation, applied to the concentration of aqueous salt solutions, is discussed in this paper. It was found that the concentration of SO42− ions in such solutions should not exceed 600 mg L−1 when they are subjected to concentration. However, concentration of sulphates at the level of 800 mg L−1 in the feed is permissible provided that the excess of CaSO4 is removed in a crystallizer. Crystallisation of salts, mainly CaSO4 · 2H2O, on the surface and inside the membrane was observed at higher feed concentrations, causing damage of the module. Precipitation of calcium sulphate was also observed during the production of demineralised water when high values of the water recovery coefficient (above 90 %) were used. In this case, the formed precipitate also contained CaCO3, the co-precipitation of which significantly changed the properties of the scaling layer. The precipitate containing both CaSO4 and CaCO3 was formed mainly on the membrane surface and it could easily be removed by rinsing the module with a HCl solution.

One of the critical issues for membrane application in wastewater treatment is membrane fouling majorly caused by dissolved organic matters. The aim of the present study was to lower membrane fouling by adsorption of polyelectrolytes. In the paper, the feasibility of coating for diverse ultrafiltration membrane materials was investigated and their filtration performance was compared to that of the unmodified ones. Different ultrafiltration flat-sheet membranes, polyvinylidene fluoride, polyethersulfone, polysulfone and cellulose acetate were coated by branched poly(ethyleneimine) (PEI), poly(diallyldimethylammonium chloride) (PDADMAC) and poly(allylamine chloride) (PAH) and filtrated with sludge supernatant. Short term experiments showed a substantial drop of permeability: almost 40 % for PEI, 23 % for PDADMAC, and about 19 % for PAH coating. This deterioration resulted from the additional resistance of the deposited layers. On the other hand, coating led to lower fouling rates during filtration. In the stable state of filtration, coated membranes showed higher permeabilities compared to the uncoated ones. For the polyethersulfone membrane, the average permeability enhancement was 11 %. For polysulfone and cellulose acetate membranes, the permeability improved by 28 % and 15 % respectively. For polyvinylidene fluoride membranes only coating with PDADMAC enhanced the permeability, by 13 %. PEI and PAH modified membranes featured lower permeabilities than the uncoated ones.

A new concept of investigation on granular material grinding process using a multi-ribbon blender is demonstrated. A new approach of mathematical description of this process is presented using the Shannon’s entropy definition for random processes. The analysis of experiments was carried out employing the probability size distribution variation with the time of grinding process. The investigations reported in this work provide useful insight into the granular material grinding process. Moreover, the proposed informational description may be used to quantify the progress of this process whose importance in plant design and process optimisation, according to other experimental works, appears to be underestimated.

The effects of baffling of an agitated vessel on the production of floating particles suspension are presented in this paper. Critical agitator speed, needed for particles dispersion in a liquid agitated in a vessel of the inner diameter of 0.295 m, was determined. The just drawdown agitator speeds were defined analogously to the Zwietering criterion. Specific agitation energy was calculated from the power consumption experimental data obtained by means of the strain gauge method. The experiments were carried out for twelve configurations of the baffles differing in number, length and their arrangement in the vessels. The following high-speed impellers were used: up- and downpumping six blade pitched blade turbines, Rushton turbine, and propeller. The impeller was located in the vessel in the height equal to two-thirds or one-third of the vessel diameter from the bottom of the vessel. The results were described in the form of a dimensionless equation.

The effect of pelleting pressure (0–10 MPa) during the preparation of Co-Mn-Al mixed oxide catalyst on its texture and activity for N2O catalytic decomposition was examined for small grain sizes used in laboratory experiments, and for model industry catalyst particles. Adsorption/desorption measurements of nitrogen, mercury porosimetry and helium pycnometry were used for detail characterization of porous structure. A volume of micropores of about 20 mm3 g−1 was evaluated using modified BET equation. This value did practically not change with the increasing pelletization pressure except that of the sample formed at the pressure of 10 MPa. Although an increase of pelleting pressure caused an increase in bulk density and a decrease in pore size and pore volume of the prepared catalyst (resulting in lower values of N2O effective diffusion coefficient), no direct correlation between pelleting pressure used and catalyst activity has been found. In contrary, estimation of the internal diffusion limitation according to the Weisz-Prater criterion indicated that even laboratory experimental data obtained for catalyst grains with particle size lower than 0.315 mm pelletized at higher pressures could be influenced by internal diffusion. Estimation of the internal mass transfer limitation in industrial catalyst particles described by the effectiveness factor showed that effectiveness factor of about 0.07 and 0.2 can be obtained for spheres with the radius of 1.5 mm and 0.5 mm, respectively, if pelleting pressure of about 6 MPa was used for the catalyst preparation.

A new strategy, to augment the pH process control is offered in this paper. The intelligent controller proposed herein is based on an inverse neural plant model. An integration term is introduced to improve the pure inverse neural controller performance. This element, adjusted by a fuzzy system with respect to the control error, operates in parallel with the neural controller to ensure offset-free performance, in case of system uncertainties or modelling mismatch. Four fuzzy rules were applied to generate the integrator parameters. Experimental results, carried out under pH control on a laboratory scale set-up, demonstrate the feasibility of the proposed control system.

The aim of the research work was to investigate the effect of the presence and concentration of solid particles on the gas-liquid volumetric mass transfer coefficient in a mechanically stirred gas-solid-liquid system. Experimental studies were conducted in a tall vessel of the diameter of 0.288 m, equipped with two designs of double stirrers. Three high-speed stirrers were used: A 315, Smith turbine, and Rushton turbine. The following operating parameters were changed: gas flow rate, stirrer speed, and solid concentration. The volumetric mass transfer coefficient was determined using the dynamic gassing-out method. In the range of the measurements conducted, this coefficient was strongly affected by both the presence and the concentration of particles in the system. Generally, a low concentration of particles in the system, equal to 0.5 mass %, caused an increase of the volumetric mass transfer coefficient values for both stirrer configurations compared to a system without solids whilst more particles (2.5 mass %) caused a decrease of this coefficient. It could be supposed that an increase of slurry viscosity affected the decrease of the volumetric mass transfer coefficient at higher solid concentration. An empirical correlation was proposed for volumetric mass transfer coefficient prediction. Its parameters were fitted using experimental data.

Nonequilibrium model for steady state simulation of catalytic distillation is presented. Mathematical model takes into account both mass and heat transfers across the gas liquid interface and through the liquid-solid (catalyst) interface. Equations describing the mentioned phenomena are based on the effective diffusivity approach. The resulting system of nonlinear algebraic equations was implemented in the FORTRAN programming language and solved by the BUNLSI (Ferraris & Tronconi, 1986) solver. The described model was verified using the experimental data obtained from a continuous distillation column equipped with catalytic packing. As an experimental model system, synthesis of propyl propionate from propan-1-ol and propionic acid was chosen. Comparison of experimental and simulation data is presented, and appropriateness of the developed model for other types of catalytic distillation processes is discussed.

Metal wires are produced from different metals using drawing methods. The metal used influences both the technology applied and the composition of effluents generated during wires production. Ultrafiltration and nanofiltration are used for the separation of waste emulsions from cable factories. Membrane distillation was proposed for the treatment of acidic saline wastewater generated during steel wire manufacturing (etching). The possibility of the previously mentioned processes application for water reuse is presented. The application of poly(vinylidene fluoride) (PVDF) membranes (FP 100) with the molecular weight cut-off (MWCO) of 100 kDa in the ultrafiltration process resulted in the reduction of 99 % of oil and lubricants in the treated emulsions and allowed complete removal of suspended solids and colloidal substances. Such pre-treated emulsion was subsequently purified by nanofiltration (NF-90-2540) and a 98 % rejection of copper ions was achieved, resulting in a decrease of the permeate electrical conductivity from 3200 μS cm−1 to 260 μS cm−1. The obtained permeate was suitable for preparation of fresh oil emulsion utilized for lubrication in the wire drawing process. The spent etching baths (from steel wire production), which mainly contained FeSO4 and about 1 mass % of sulfuric acid, were separated by membrane distillation. The obtained permeates were: clean water with electrical conductivity at a level of 3–5 μS cm−1. Concentrates (190–200 g of Fe per L) from the MD process were cooled to 295 K, which enabled the FeSO4 crystallization. Application of the above-mentioned membrane processes allows producing high quality product water, over 90 % of water was recovered from the treated wastewaters.

A novel and efficient method of synthesis of 3-substituted derivatives of pentane-2,4-dione is proposed, wherein cheaper and easily accessible chloro derivatives are conversed into more reactive iodo derivatives. The method is based on the Finkelstein reaction for which the literature suggests highly polar organic solvents as ideal reaction media. In the presented work, the use of industrially used ketones, especially methyl isobutyl ketone, is proposed. The use of MIBK as a solvent additionally allows an azeotropic removal of water from the reaction mixture, enabling the application of moisture sensitive alkylating agents i.e. (3-chloropropyl)trimethoxysilane. The obtained products are isolated through distillation, which does however not allow the separation of C-alkylation products from O-alkylation ones. The products not containing water-sensitive substituents were isolated as copper complexes. The pure product of C-alkylation was obtained by decomposition of the copper complex with a hydrochloric acid solution and extraction of the formed ligand to an organic phase i.e. hexane. The obtained ligand can be further purified by distillation.

The paper analyses the influence of various kinds and amounts of titanium dioxide nuclei addition to a solution of titanyl sulphate on the conversion degree of TiOSO4 to hydrated titanium dioxide and sulphuric acid. An industrial solution of titanyl sulphate used to produce titanium white was used in the present investigations. It was found that the course of hydrolysis clearly depended on the investigated parameters. The anatase nuclei calcined at 373 K and 333 K and rutile nuclei increased the degree of titanyl sulphate hydrolysis as compared to non-nucleation hydrolysis. The final degree of hydrolysis was by 1–2 % higher than that achieved without any nuclei addition. The constant rates of both colloidal intermediate and final crystalline products formation were higher in the hydrolysis process with both anatase nuclei after heat treatment at lower temperature and rutile nuclei in comparison to the same processes conducted in the absence of these nuclei.

In the, at present, unstable fuel market, much attention is devoted to alternative technologies for fuel production and development of alternative products of the petrochemical industry. One of the prospective sources of fuel and alternative petrochemical products is biomass, and the use of oil plants is one of the possibilities. This paper reports on a possible conversion of rapeseed oil produced in Poland into intermediate hydrocarbon fractions by pyrolysis combined with parallel catalytic conversion. The products were analysed by gas chromatography coupled with a mass detector. The process was performed in a fixed-bed reactor and was monitored by FTIR and 1H NMR. Depending on the catalysts applied, the products contained: water, carbon oxides, hydrogen, aliphatic or aromatic hydrocarbons accompanied by some amount of C2-C5 hydrocarbons formed during the cracking process.

Commercial hopcalite calcined at different temperatures and hopcalite modified with noble metals (Pt, Pd, and Au) were studied in oxidation of thiophene. Surface and bulk properties of catalysts were studied using temperature-programmed reduction (TPRH2), X-ray diffraction method (XRD) and thermal analysis (TG-DTA-MS). It was shown that calcined samples displayed higher activity in comparison with commercial untreated hopcalite; however, a lower temperature of calcination was favourable. High temperature of thermal treatment induced an increase in the crystallinity and a decrease in the surface area of the samples, and, as a consequence, the loss of catalysts activity. Moreover, marked improvement in the catalytic performance of platinum and palladium modified catalysts in relation to base hopcalite was observed. The obtained results indicate that the higher activity of samples containing Pt and Pd was accompanied by better reducibility of the catalysts.

The modified four-step BCR sequential extraction procedure (exchangeable and weak acid available species, reducible, oxidisable and residual fractions) was used to examine the distribution of As, Cd, Cr, Cu, Pb, and Zn with soil depth in an area (Baia Mare — Bozanta, Romania) with both high natural level of elements considered as toxic and historical pollution resulting from nonferrous metallurgy. The BCR approach proved a high metal input of anthropogenic origin down to 40 cm, while at lower depths the naturally elevated metal content must be considered. Results of the partitioning study and XRD analysis of solid matrix showed the greatest potential for chemical remobilisation of Cd, Zn, and Cu in weak acidic medium as well as their affinity for the oxidisable fraction (organic matter/sulphide). The tendency of Cr, Pb, and As to be immobilised as residual or reducible species on Fe-Mn oxides was evident. Although the partitioning of As in chemically inactive forms such as scorodite (FeAsO4 · 2H2O) soluble under reducible conditions and beudantite (PbFe3(AsO4)(SO4)(OH)2)), a residual species soluble in acid media, chemical mobilisation from soil in groundwater was confirmed. Dynamic processes of metal retention in soil under different conditions, namely acidic, reducing or oxidisable, were predicted from the Pearsonșs correlation analysis of element species with soil characteristics and components such as Fe, Mn, organic matter content, pH, and total element content, respectively. At the moment of the study, soil and groundwater in the area were found to be polluted with As, Cd, Cu, Pb and Zn.

The use of photocatalysts supported on adsorbents is receiving substantial attention. Supporting TiO2 with zeolites is found to be one of the best solutions to increase the efficiency of TiO2-based photocatalysts. This work was focused on simple preparation of a TiO2/Na-ZSM-5 composite catalyst by the solid state dispersion (SSD) method and its modification with an organic photosensitizer — polythiophene (PT). Using the XRD diffractometry, structure of the new composite catalyst was proved. Beside this composite catalyst, mechanical mixtures of TiO2-based catalysts with Na-ZSM-5 zeolite were prepared. The efficiency of all five available photocatalysts (TiO2, TiO2-PT, mechanical mixture of TiO2 + Na-ZSM-5, mechanical mixture of TiO2-PT + Na-ZSM-5, and the modified SSD-PT composite) on photodegradation of 4-chlorophenol was compared. By measuring the formation of chloride ions and decreasing the 4-chlorophenol concentration at two different initial concentrations of 4-chlorophenol in the basic aqueous solution, the photoefficiency and adsorption properties of our photocatalysts were determined.