Polish Journal of Chemical Technology (v.10, #3)
Preparation and characterization of catalyst mix Fe-Co/MgO for carbon nanotubes growth
by Anna Steplewska; Roman Jedrzejewski; Ewa Borowiak-Palen; (pp. 1-3).
Fe-Co/MgO is one of the most common catalyst mix applied to carbon nanotubes (CNTs) growth in chemical vapor deposition process. Therefore, here we present detailed study on the preparation and characterization of Fe-Co/MgO. The precursors of Fe and Co are iron (II) acetate and cobalt acetates, correspondingly. The molar ratio of the catalyst mix is Fe:Co:MgO=1:1:100. Initially, thermogravimetric analysis (TGA) of the mixture was performed. TGA analysis of it indicated the stepwise mass losses which pointed out the crucial thermal conditions for the changes in the elemental composition, morphology, crystallographic structure and vibrational properties. In current state of the art the lowest growth temperature for singlewalled carbon nanotubes is 550°C in CVD technique and here the characterization of the catalyst mix strongly suggest that this temperature can be decreased what would enhance the compatibility of CNT growth with current complementary metal-oxide-silicon (CMOS) technology for CNTs-based nanoelectronics. The morphology, crystallographic structure, elemental composition of the samples and its spectroscopic properties were performed via high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and Infrared spectroscopy (IR), respectively.
Keywords: catalyst; thermogravimetric analysis TGA; chemical vapor deposition CVD; carbon nanotubes
The influence of admixtures on the course of hydrolysis of titanyl sulfate
by Barbara Grzmil; Daniel Grela; Bogumił Kic; Marcin Podsiadły; (pp. 4-12).
The study focused on the question how admixtures, such as iron(II), iron(III), magnesium and aluminium salts influence the degree of TiOSO4 conversion to hydrated titanium dioxide (HTD). Titanyl sulfate solution, an intermediate product in the industrial preparation of titanium dioxide pigments by sulfate route was used. The admixtures were added to the solution and their concentration was gradually changed. It was found that hydrolysis clearly depended on Fe(II) and Fe(III) concentrations. The higher the concentration of iron(II) (up to 5 wt %) in the solution was, the higher conversion degree was achieved. A reverse relationship was observed concerning the influence of iron(III) introduced up to 1.5 wt %. The constant rates of both phases of titanyl sulfate hydrolysis (including the formation of an intermediate colloidal TiO2 and final products) depended on iron(II) and iron(III) content in the solution. The concentration of other constituents did not influence hydrolysis in the investigated part of the process (up to 2.6 wt % of Mg and up to 0.3 wt % of Al). However, the size of primary particles of the obtained TiO2·nH2O did not depend on the content of the above-mentioned constituents in the solution.
Keywords: hydrate titanium dioxide; hydrolysis; titanyl sulfate; admixtures
Manufacturing of phosphoric acid from hydroxyapatite, contained in the ashes of the incinerated meat-bone wastes
by Kinga Krupa-Żuczek; Zygmunt Kowalski; Zbigniew Wzorek; (pp. 13-20).
The results of the investigations concerning phosphoric acid manufacturing, by the extraction method, from the ashes containing hydroxyapatite, obtained through the thermal treatment of bone sludge have been presented. The incinerated bone sludge with ~ 16% P content and the minimal amount of impurities can be an alternative source for phosphoric acid production. The process consists in two stages. In the 1st stage, reaction of hydroxyapatite with phosphoric acid resulting in monocalcium phosphate formation in the solution obtained is carried out. The tests revealed that overall hydroxyapatite dissolution in phosphoric acid takes place when the concentration is 37% H3PO4. In the 2nd stage monocalcium phosphate is converted into calcium sulphate using concentrated sulphuric acid at the recommended temperature of 95°C. The principles of the technological idea of the process of phosphoric acid manufacturing from HA-containing ashes, obtained by bone wastes incineration, as well as a preliminary economic analysis for the production of 10 000 t/year of food-grade phosphoric acid have been developed.
Keywords: meat waste; hydroxyapatite; phosphoric acid
Application of artificial neural nerworks in oxidation kinetic analysis of nanocomposites
by Jerzy Straszko; Anna Biedunkiewicz; Agnieszka Strzelczak; (pp. 21-28).
This study concerns the application of artificial neural networks in oxidation kinetic analysis of ceramic nanocomposites. The oxidation of the Ti-Si-C ceramic nanocomposite in dry air was studied. The size of the nanoparticles was determined by scanning electron microscopy (SEM). The gaseous oxidation products were analysed by mass spectroscopy (MS) while the solid oxidation products by X-ray diffraction (XRD). The kinetic analysis of the oxidation was based on the Coats-Redfern equation. The kinetic models were identified for the consecutive stages and then the A and E parameters of the Arrhenius equations were evaluated. Artificial neural networks were used at each step of the kinetic calculations.
Keywords: artificial neural networks; ceramic nanocomposites; oxidation; kinetics
Sedimentation of water dispersed systems of acrylate copolymers in xylene
by Edwin Makarewicz; Anna Zalewska; (pp. 29-34).
Methyl methacrylate - butyl acrylate - methacrylic acid copolymer and butyl methacrylate - methacrylic acid amide copolymer of a different segmental structure were stabilised with non-ionic and anionic surfactants. Gel chromatography, viscosimetry, tensiometry, conductometry and sedimentation methods were applied to define the properties of the synthesized copolymers, surfactants in water solutions and water dispersions. The types and the properties of the phases being in a state of sedimentation balance were also determined. The obtained experimental data were interpreted and justified by using the copolymer and surfactants properties. The existing correlations were pointed out. The obtained results show that the stability of a disperse system considerably depends on the structure of the copolymer. The MMA/BA/MAA copolymer has monomeric units of elastic butyl acrylate. Segments containing these monomeric units adsorb surfactants much better and form more stable water disperse systems. However, the MBA/AMAA copolymer with the polarity of amide group of methacrylamide makes disperse systems less stable.
Keywords: polymer; water colloid dispersions; sedimentations; stability
Fluctuations of the non-Newtonian fluid flow in a Kenics static mixer: An experimental study
by Sylwia Peryt-Stawiarska; Zdzisław Jaworski; (pp. 35-37).
The measurements for a Kenics static mixer were carried out using Laser Doppler Anemometer (LDA). The test fluid was non-Newtonian solution of CMC, Blanose type 9H4. The velocity data inside the 5th Kenics insert were collected for the axial components at five levels of Reynolds number, Re = 20 ÷ 120. Velocity fluctuations were also analyzed in the frequency domain, after processing them with the help of the Fast Fourier Transform (FFT) procedure. The spectra of fluctuations provided information about level of the fluctuations in the observed range of Reynolds number. The obtained data were then also used to plot the velocity profiles for the fifth insert of the Kenics mixer. It was concluded that in the investigated range of Reynolds numbers (Re = 20 ÷ 120) a strong dependence of the velocity profiles and the flow fluctuations on Reynolds number was observed.
Keywords: Flow instabilities; LDA measurements; non-Newtonian fluid; Kenics mixer
Atomization performance of effervescent atomizers with gas-liquid internal mixing
by Marek Ochowiak; Lubomira Broniarz-Press; (pp. 38-41).
The paper contains the results of experimental studies on water atomization process in effervescent nozzle in one-phase and two-phase systems. The gas phase flow rate causes the changes in characteristic parameters of atomization. The gas flow rate has certain effect on the Sauter Mean Diameter SMD values. SMD for airliquid systems investigated is decreasing with increase of gas volume rate. It is observed that SMD values are increasing with increase of liquid volume rate. The larger SMD values for one-phase flow in comparison with two-phase flow have also been observed. The increase of SMD value has been observed with a decrease of an outlet diameter of an effervescent nozzle.
Keywords: effervescent atomizer; atomization; spray formation; two-phase system
Effect of calcination temperature on photocatalytic activity of TiO2. Photodecomposition of mono- and polyazo dyes in water
by Sylwia Mozia; (pp. 42-49).
The presented studies have focused on the influence of TiO2 properties, such as crystalline phase, crystallite size and surface area, on the effectiveness of degradation of azo dyes in water under UV irradiation. Two monoazo dyes: Acid Red 18 (AR18, C20H11N2Na3O10S3) and Acid Yellow 36 (AY36, C18H14N3NaO3S), and one polyazo dye Direct Green 99 (DG99, C44H28N12Na4O14S4) were applied as model compounds. The photocatalysts were prepared from a crude titanium dioxide obtained directly from the production line (sulfate technology) at the Chemical Factory "Police" (Poland). The crude TiO2 was calcinated in air for 1-4h at the temperatures ranging from 600 to 800°C. The BET specific surface area of TiO2 decreased gradually with increasing the calcination temperature. The crude TiO2 exhibited specific surface area of 277 m2/g. In case of the catalysts heated at 600, 700 and 800°C the BET surface area amounted to 62.3-53.3, 33.4-26.8 and 8.9-8.3 m2/g, for the calcination time of 1-4h, respectively. The crystallite size of anatase increased with increasing heat treatment temperature and ranged from 19 to 53 nm, for the temperatures of 600-800°C, respectively. The catalysts annealed at 600 and 700°C contained primarily anatase phase (94-97%), whereas the photocatalysts heated at 800°C were composed mainly of rutile (97-99%). The highest effectiveness of azo dyes degradation was obtained in case of the photocatalyst calcinated for 1h at 700°C. The photocatalyst was composed mainly of anatase (97%) with crystallite size of 27 nm. The most effectively photodegraded was AR18, having the molecular weight of 640.4 g/mol. The most difficult to degrade was AY36 exhibiting the lowest molecular weight from all the dyes used (375.4 g/mol).
Keywords: photocatalysis; titanium dioxide; TiO2anatase; rutile; crystallite size; azo dye