Publikační činnost Katedry analytické chemie a zkoušení materiálu / Publications of Department of Analytic Chemistry Processes (615)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64753

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry analytické chemie a zkoušení materiálu (615) v časopisech registrovaných ve Web of Science od roku 2003 do roku 2013. Katedra byla zrušena.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 70 results

Stanovení majoritních minerálů v jílovcích a jílových břidlicích chemometrickou analýzou infračervených spekter
(Česká společnost chemická, 2013) Josieková, Jana; Ritz, Michal
Model of synthesis of ZnS nanoparticles stabilized by cetyltrimethylammonium bromide
(Virtual Institute of Physics, 2013) Dvorský, Richard; Praus, Petr; Trojková, Jana
A mathematical model of synthesis and stabilization of ZnS nanoparticles in aqueous solutions of cetyltrimethylammonium bromide (CTAB) is presented. ZnS nanoparticles precipitated by the reaction of sodium sulphide and zinc acetate are significantly influenced by CTAB both in a stage of nucleation and in a stage of growth and stabilization. The suggested model assumes a dominating influence of the nucleation stage on future properties of emerging ZnS nanoparticles. On the basis of a calculated nucleation rate depending on a degree of the ZnS supersaturation, the model adopts an approximate assumption that ZnS nuclei are formed all at one moment.Mathematical formulation of the nucleation model attempts to explain a recently observed relationship between ZnS nanoparticles radii and the CTAB concentration. The dependence of a surface tension of zinc acetate and CTAB aqueous solutions on the CTAB concentration was measured and further applied to obtain the relation between the CTAB monomer concentration and the CTAB total concentration. The nucleation model assumed a key role of CTAB monomers, which were considered as nucleation centres. The predicted radii
Nanocomposite of montmorillonite and silver nanoparticles: Characterization and application in catalytic reduction of 4-nitrophenol
(Elsevier, 2013) Praus, Petr; Turicová, Martina; Karlíková, Martina; Kvítek, Libor; Dvorský, Richard
Silver ions previously intercalated into a montmorillonite (MMT) interlayer were reduced by sodium borohydride forming a nanocomposite of MMT and silver nanoparticles (Ag–MMT) with no other stabilizing additives. Within 360 min no coagulation of an aqueous Ag–MMT dispersion was observed. However, after 24 h the coagulation was indicated by a red shift of absorption maximum from 408 nm to 434 nm and by broadening of the absorbance band. The nanocomposite was characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and measurements of specific surface area (SSA). It contained 4.94 wt. % of silver. Ag nanoparticles with an average size of 6.9 nm were located on the external MMT surface, mostly in its pores. Ag–MMT was used as a catalyst for reduction of 4-nitrophenol with sodium borohydride forming 4-aminophenol. After 30 s the reaction kinetics changed from zero order to first order, which was explained by means of the Langmuir–Hinshelwood model. The whole reduction was completed after 290 s. During this time min. 95 wt. % of Ag nanoparticles stayed fixed on the MMT support.
A low-cost photoactive composite quartz sand/TiO2
(Elsevier, 2013) Tokarský, Jonáš; Matějka, Vlastimil; Neuwirthová, Lucie; Vontorová, Jiřina; Mamulová Kutláková, Kateřina; Kukutschová, Jana; Čapková, Pavla
The photoactive quartz sand/TiO2 composites were prepared by thermal hydrolysis of the suspension obtained by addition of quartz sand to a titanyl sulfate solution. The required amount of TiO2 in the prepared composites (i.e. 9, 22 and 45 wt.%, respectively) was achieved using a variable titanyl sulfate/quartz ratio. As reference materials, pure TiO2 was prepared using the thermal hydrolysis of the titanyl sulfate solution under the same condition as used during the preparation of composite quartz/TiO2. The composite samples, dried at 105 °C and calcined at temperatures of 500–900 °C, were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy. Structural ordering of TiO2 particles on the quartz surface was studied using atomistic simulations in a Material Studio modeling environment. Photodegradation activity of the composites was evaluated by the discoloration of Acid Orange 7 aqueous solution. The composite containing 22 wt.% of TiO2 and calcined at 800 °C exhibits the highest photoactivity. Higher and lower amounts of TiO2 led to worse results. The quartz/TiO2 composite is a promising material able to replace pure TiO2 in a wide range of building materials.
Photocatalytic reactions of nanocomposite of ZnS nanoparticles and montmorillonite
(Elsevier, 2013) Praus, Petr; Reli, Martin; Kočí, Kamila; Obalová, Lucie
ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) forming a ZnS–CTA–MMT nanocomposite. The nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and UV diffuse reflectance spectra (DRS) spectrometry, X-ray powder diffraction (XRD) and specific surface area measurements. Thereafter, it was used for photocatalytic reactions under UV irradiation (Hg lamp) in three different reaction media with different pH: NaOH solution, HCl solution and water. Prior to the photocatalytic reactions the dispersions were saturated by carbon dioxide to buffer the systems. The main reaction products in gas phase determined by gas chromatography were hydrogen and methane. The reactions were monitored by measuring oxidation–reduction potentials. The highest yields of hydrogen were obtained in the dispersion acidified by HCl but the concentrations of methane were similar in all tested media. Hydrogen was supposed to be formed by the reaction of two hydrogen radicals. Methane was formed by the reduction of carbon dioxide and by the partial decomposition of CTAB.
Analysis of mechanisms of composite particles modification in liquid dispersions
(Elsevier, 2013) Dvorský, Richard; Trojková, Jana; Praus, Petr; Luňáček, Jiří
In this paper, we discuss two mechanisms of preparation of composite nanoparticles in liquid dispersions and their effects on size distributions of nanoparticles. In the first case of an adsorption process, the added particles form an external layer of approximately equal thickness on the surface of each of the supporting particles. The radii of all the particles then grow by the same amount irrespective of their original size. In the second case, analogous to bulking, secondary nanoparticles also settle over the dominant surfaces of internal micro-pores inside the primary particles, and sizes of the resulting composite particles then increase by the same factor. As each of these mechanisms affects the size distribution of nanoparticles in a different way, even a simple comparison of the initial and the final distribution functions can indicate the nature of the modification process.
Experimental study of Fe-C-O based system above 1,000 A degrees C
(Springer, 2013) Žaludová, Monika; Smetana, Bedřich; Zlá, Simona; Dobrovská, Jana; Watson, Andy; Vontorová, Jiřina; Rosypalová, Silvie; Kukutschová, Jana; Cagala, Michal
The paper deals with the study of phase transformation temperatures of the model Fe–C–O based metallic alloys in the high temperature region (above 1,000 °C). Six model alloys with graded carbon and oxygen content were prepared and studied. Temperatures of phase transitions were obtained using DTA method (differential thermal analysis). The Setaram SETSYS 18™ (TG/DTA/DSC/TMA) modular experimental system was used for measurements. Influence of composition change (carbon and oxygen content) on shift of phase transformation temperatures is investigated in this paper. New original data (phase transformation temperatures) were obtained in this study. Controlled heating of the alloys was conducted at the rates of 2, 4, 7, 10, 15 and 20 °C min−1. Comparison of the obtained experimental data with the data presented in the literature was also carried out. It follows from comparison of the obtained results with the data accessible in the literature that a lack of experimental data exists, and these available data significantly differ.
Determination of the predominant minerals in sedimentary rocks by chemometric analysis of infrared spectra
(The Clay Minerals Society, 2012) Ritz, Michal; Vaculíková, Lenka; Plevová, Eva; Matýsek, Dalibor; Mališ, Jiří
The objective of the present study was to determine the predominant minerals in sedimentary rocks using Fourier-transform infrared (FTIR) spectroscopy and chemometric analysis. The chemometric analysis was performed on three types of sedimentary rock samples (claystones, clay slates, and sandstones), each with different predominant mineral components. Chemometric models were created to determine the major minerals of the rock samples studied chlorite, muscovite, albite, and quartz. The FTIR spectra were obtained in transmission mode from pressed pellets of KBr-sample mixtures or by diffuse reflectance from hand-packed mixtures of samples with KBr. Spectral regions measured were 4000-3000 and 1300-400 cm-1, which contained important spectral information for the creation of the chemometric models. Principal component analysis was used in the chemometric method, with calibration models being created by a partial least-squares regression method. The mean relative error, standard error of prediction, and relative standard deviation were calculated for the assessment of accuracy, precision, and reproducibility. The value of the mean relative error was 15-20% for most of the calibration models; the value of the standard error of prediction was up to 6 w/w % for most of the calibration models. The values of the standard relative deviation ranged from ∼2 to 8% for calibration models based on diffuse reflectance spectra whereas calibration models based on transmission spectra had values of relative standard deviation of ∼15-20%.
Možnosti přípravy materiálů na bázi jíl-huminová látka
(Česká společnost chemická, 2012) Mucha, Martin; Pavlovský, Jiří; Herecová, Lenka; Míček, Dalibor; Věžníková, Hana
Determination of chlorite, muscovite, albite and quartz in claystones and clay shales by infrared spectroscopy and partial least-squares regression
(Akademie věd České republiky, Ústav struktury a mechaniky hornin, 2012) Ritz, Michal; Vaculíková, Lenka; Plevová, Eva; Matýsek, Dalibor; Mališ, Jiří
The objective of this work is the chemometric quantification of minerals in rocks. A chemometric method was developed for the determination of chlorite, muscovite, albite and quartz in claystones and clay shales using infrared spectroscopy. Bromide pellets and diffuse reflectance were used to measure the infrared spectra; principal component analysis and partial leastsquares regression were used as chemometric methods. Spectral regions (4000-3000 cm-1 and 1300-400 cm-1) containing important spectral information were chosen by principal component analysis. The calibration models were created by a partial least-squares regression. The mean relative error and relative standard deviation were calculated for the assessment of accuracy and reproducibility. The value of the mean relative error was about 10 % for most of the calibration models. The value of the relative standard deviation ranged from 1.1 to 3.0 % for most calibration models based on diffuse reflectance spectra and from 4.0 to 9.2 % for most calibration models based on spectra obtained with bromide pellets.
Distribution of selected elements during the co-combustion of lignite with wood and wood wastes
(Akademie věd České republiky, Ústav struktury a mechaniky hornin, 2012) Klika, Zdeněk; Bartoňová, Lucie; Serenčíšova, Jana
Combustion of lignite with limestone, co-combustion of lignite with limestone and wood, and combustion of wood were performed in a circulating fluidised bed in 7 different combustion regimes. The inorganic matter composition and properties of all input and output materials were characterized. For each combustion regime the material streams and the boiler outputs were calculated. The total inorganic mass and the mass of selected trace elements in fuels (Cl, Zn, As, Se, Hg, and Pb) were based on the output of a 1 GW circulating fluidised-bed boiler; additionally, the concentrations of volatile elements (As, Se, Hg) in fly ash (FA) were evaluated in relation to the mass of FA. Element (Cl, Zn, As, Se, Hg, and Pb) enrichment in FA compared with BA was related to the ratio R between the combusted mass of organic wood wastes and total combusted fuel. Additionally, the unburned carbon in bottom ash (BA) and fly ash (FA) was determined, and selected elements were studied in unburned materials separated from BA. The results show that combustion of wood and/or co-combustion of lignite with wood waste brings about significant environmental benefits.
Stabilization of ZnS nanoparticles in micellar dispersion of cetyltrimethylammonium bromide
(Slovenian Chemical Society, 2012) Praus, Petr; Dvorský, Richard; Kovář, Petr; Trojková, Jana
ZnS nanoparticles were precipitated in micellar dispersions of cetyltrimethylammonium bromide (CTAB). ZnS na no - particles and cetyltrimethylammonium (CTA+) ions for med po si ti vely char ged Zn S-CTA mi cel les with the mo de ze ta potential of 35 mV. The ZnS-CTA micelles were simulated by molecular modelling that confirmed the formation of po - sitive CTA+ bilayers on the ZnS surfa ce. The large agglomerates of the ZnS-CTA micelles were observed by the dynamic light scat te ring (DLS) met hod and electron transmission microscopy (TEM). The si ze of the Zn S na no par tic les of about 5 nm was es ti ma ted from their band-gap energy ob tai ned from UV spec tra and electron transmission mi cro - graphs. The relationship between zeta potentials (ξ) and hydrody na mic si zes (d) was found as ξ = 641/d – 5.9.
Optical properties of ZnS nanoparticles precipitated at various molar ratios of sulphide and zinc ions and stabilized by CTAB
(National Institute of Materials Physics, National Institute of Optoelectronics, 2012) Kozák, Ondřej; Praus, Petr; Dvorský, Richard
ZnS nanoparticles were precipitated by the reaction of zinc and sulphide ions in aqueous media and stabilized by cetyltrimethylammonium bromide (CTAB). The nanoparticles size (diameter) was calculated using the relationship between band-gap energy and radius as a result of the quantum size effect. Depending on the molar ratio of precursors S2-/Zn2+ = 0.25–2.0 and time elapsed from their preparation t = 0–5 h, nanoparticles with sizes of 3.5–4.8 nm were obtained. The absorption of UV radiation and photoluminescence (PL) of the nanoparticles dispersions were studied. The nanoparticles growth dependent on time and the S2-/Zn2+ ratio were indicated by changes in UV absorption and PL spectra. The stabilization effect of CTAB was observed for all S2-/Zn2+ ratios up to 5 hours. At longer time intervals (3 a 4 days) flocs of ZnS nanoparticles and CTAB were observed.
Photocatalytic decomposition of phenol by nanocomposite of ZnS nanoparticles and montmorillonite
(Sociedade Brasileira de Química, 2012) Praus, Petr; Matys, Jakub; Kozák, Ondřej
The nanocomposite of ZnS nanoparticles stabilized by cetyltrimethylammonium ions (ZnS-CTA) and montmorillonite (ZnS-CTA-MMT) was prepared and used as a catalyst for the photodecomposition of phenol under UV irradiation of a medium pressure Hg lamp. The content of ZnS in ZnS-CTA-MMT was about 7 wt.%. For comparison, the photodecomposition was also performed with ZnS-CTA, montmorillonite and with no catalyst, i.e., using only UV irradiation. The photodecomposition efficiency decreased in the order: UV + ZnS-CTA-MMT ≈ UV + ZnS-CTA > UV > UV + MMT. The photodecomposition in the presence of ZnS-CTA-MMT and ZnS-CTA proceeded according to the pseudo-first order reaction kinetics. In other cases, the photodecomposition corresponded to the pseudo-second order reaction of phenol and hydroxyl radicals. Hydroxyl radicals were produced by reactions of dissolved oxygen and electrons released from the ZnS nanoparticles and excited phenol molecules. MMT decreased the photodecomposition reaction rate and no MMT catalytic activity was observed.
Effect of unburned carbon content in fly ash on the retention of 12 elements out of coal-combustion flue gas
(Elsevier, 2012) Bartoňová, Lucie; Čech, Bohumír; Ruppenthalová, Lucie; Majvelderová, Vendula; Juchelková, Dagmar; Klika, Zdeněk
The aim of this study was to evaluate whether unburned carbon particles present in fly ash can help in the retention of S, Cl, Br, As, Se, Cu, Ni, Zn, Ga, Ge, Rb, and Pb out of flue gas during the coal combustion at fluidised-bed power station where the coal was combusted along with limestone. The competitive influence of 10%–25% CaO in fly ashes on the distribution of studied elements was studied as well to be clear which factor governs behaviour of studied elements. Except of S (with significant association with CaO) and Rb and Pb (with major affinity to Al2O3) the statistically significant and positive correlation coefficients were calculated for the relations between unburned carbon content and Br (0.959), Cl (0.957), Cu (0.916), Se (0.898), Ni (0.866), As (0.861), Zn (0.742), Ge (0.717), and Ga (0.588) content. The results suggest that the unburned carbon is promising material in terms of flue gas cleaning even if contained in highly calcareous fly ashes.
A comparative study of TiO2-supported and bulk Co-Mn-Al catalysts for N2O decomposition
(Elsevier, 2012) Karásková, Kateřina; Chromčáková, Žaneta; Študentová, Soňa; Matějka, Vlastimil; Jirátová, Květa; Obalová, Lucie
A series of Co–Mn–Al/TiO2 catalysts with different Co + Mn loading (5–24 wt.%) was prepared by impregnation of TiO2 support. Bulk Co–Mn–Al mixed oxides were prepared by different methods. The prepared catalysts were characterized by chemical analysis, surface area measurement, temperature programmed techniques (TPR, TPD) and tested for N2O catalytic decomposition. TiO2 acted only as a catalytic support and did not contribute to the catalytic activity. The N2O conversion over TiO2-supported Co–Mn–Al catalysts was increasing with Co + Mn loading, and was proportional to the amount of easily reducible components. Comparing the catalysts with identical amount of active components, the highest catalytic activity was achieved on the calcined precursors having carbonates in their molecules (layered double hydroxides Co–Mn–Al-HT-ex and Co–Mn–Al-carb), the lowest one on the calcined Co–Mn–Al nitrates due to the lower surface area, less advantageous porous structure and worse reducibility.
Precipitation, stabilization and molecular modeling of ZnS nanoparticles in the presence of cetyltrimethylammonium bromide
(Elsevier, 2012) Praus, Petr; Dvorský, Richard; Horínková, Petra; Pospíšil, Miroslav; Kovář, Petr
ZnS nanoparticles were precipitated in aqueous dispersions of cationic surfactant cetyltrimethylammonium bromide (CTAB). The sphere radii of ZnS nanoparticles calculated by using band-gap energies steeply decreased from 4.5 nm to 2.2 nm within CTAB concentrations of 0.4–1.5 mmol L−1. Above the concentration of 1.5 mmol L−1, the radii were stabilized at R = 2.0 nm and increased up to R = 2.5 nm after 24 h. The hydrodynamic diameters of CTAB–ZnS structures observed by the dynamic light scattering (DLS) method ranged from 130 nm to 23 nm depending on CTAB concentrations of 0.5–1.5 mmol L−1. The complex structures were observed by transmission electron microscopy (TEM). At the higher CTAB concentrations, ZnS nanoparticles were surrounded by CTA+ bilayers forming positively charged micelles with the diameter of 10 nm. The positive zeta-potentials of the micelles and their agglomerates were from 16 mV to 33 mV. Wurtzite and sphalerite nanoparticles with R = 2.0 nm and 2.5 nm covered by CTA+ were modeled with and without water. Calculated sublimation energies confirmed that a bilayer arrangement of CTA+ on the ZnS nanoparticles was preferred to a monolayer.
Montmorillonite ion exchanged by mercury (II)
(Akademie věd České republiky, Ústav struktury a mechaniky hornin, 2012) Praus, Petr; Motáková, Marcela; Ritz, Michal
Hg(II) ions dissolved in aqueous solutions were adsorbed by montmorillonite (MMT). The Hg(II) ion-exchange was strongly limited by the competition with H+ ions: the maximal amounts of adsorbed Hg(II) and H+ ions were 0.21 mmol g-1 and 1.10 mmol g-1, respectively. MMTs saturated with Hg(II) (Hg-MMTs) were examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermal analysis. Hg(II) ions, such as Hg2+ and [Hg(OH)+], along with H+ ones were mostly adsorbed on permanent sites (75 % of cation exchange capacity (CEC)) and also on pH dependent surface sites (25 % of CEC). While heating, Hg-MMTs was loosing their mass up to 700 °C as a result of the MMT dehydration and dehydroxylation accompanied by release of adsorbed Hg(II).
Influence of reactor geometry on the yield of CO(2) photocatalytic reduction
(Elsevier, 2011) Kočí, Kamila; Reli, Martin; Kozák, Ondřej; Lacný, Zdenek; Plachá, Daniela; Praus, Petr; Obalová, Lucie
The effect of reactor geometry on the photocatalytic reduction of CO2 employing ZnS-MMT (ZnS nanoparticles deposited on MMT) suspension was studied in two annular batch photoreactors. Reaction products in liquid phase (methanol) and in gas phase (methane, carbon monoxide, oxygen and hydrogen) were analyzed by GC/TCD/FID. The dependence of products yields on the reactor diameter and on the volume of the liquid phase confirmed the fact that the requirement of perfect mixing is difficult to fulfill in the annular configuration of the reactor. The highest yields of the photocatalytic reduction were achieved in a configuration where the lamp just touches the surface of the liquid in the reactor and the configuration of the reactor was not annular.
Antibacterial and antifungal activities of silver, copper and zinc montmorillonites
(Elsevier, 2011) Malachová, Kateřina; Praus, Petr; Rybková, Zuzana; Kozák, Ondřej
The antibacterial and antifungal activity of montmorillonite, Ag-MMT, Cu-MMT and Zn-MMT were investigated. The antibacterial effects on Escherichia coli decreased in the order: Ag-MMT > Cu-MMT ≈ Zn-MMT. Free metal ions were active in a similar manner. The growth inhibition of Pycnoporus cinnabarinus decreased as Zn-MMT ≥ Cu-MMT > Ag-MMT and of Pleurotus ostreatus as Cu-MMT > Zn-MMT > Ag-MMT. Free metal ions inhibited the growth of the fungi in the same order. The antibacterial and antifungal effects of the MMTs were explained by interactions of released metal ions with the bacteria and fungi. Montmorillonite could serve as a suitable carrier of metal ions with antibacterial and antifungal properties.

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