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Due to the remarkable properties achieved under ambient conditions and with quite limited components, mollusk shells are very appealing natural bio-composites used as inspiration for new advanced materials. Calcium carbonate which is among the most widespread biominerals is used by mollusks as a building material that constitutes 95-99% of their shells. Within the investigation of calcium carbonate polymorphs present in the shells, diverse theoretical and experimental studies were performed, however, further research of these crystalline forms is required. There are very little researches on the energy landscapes of biogenic calcium carbonate which can provide us information about the free energies of already known as well as newly discovered plausible structures. To investigate the structural, mechanical, elastic, or vibrational properties and to predict new possible structures of biogenic calcium carbonate, different calculation methods could be employed. Some of these studies are presented and discussed in this paper.

In this contribution, the preparation of hierarchically structured ETS-10-based catalysts exhibiting notably higher activity in the conversion of triolein with methanol compared to microporous titanosilicate is presented. Triolein, together with its unsaturated analog trilinolein, represent the most prevalent triglycerides in oils. The introduction of mesopores by post-synthetic treatment with hydrogen peroxide and a subsequent calcination step results in the generation of an additional active surface with Brønsted basic sites becoming accessible for triolein and enhancing the rate of transesterification. The resulting catalyst exhibits a comparable triolein conversion (≈73%) after 4 h of reaction to CaO (≈76%), which is reportedly known to be highly active in the transesterification of triglycerides. In addition, while CaO showed a maximum conversion of 83% after 24 h, the ETS-10-based catalyst reached 100% after 8 h, revealing its higher stability compared to CaO. The following characteristics of the catalysts were experimentally addressed – crystal structure (X-ray diffraction, transmission electron microscopy), crystal shape and size (scanning electron microscopy, laser diffraction), textural properties (N2 sorption, Hg porosimetry), presence of hydroxyl groups and active sites (temperature-programmed desorption of NH3 and CO2, 29Si magic angle spinning nuclear magnetic resonance (NMR)), mesopore accessibility and diffusion coefficient of adsorbed triolein (pulsed field gradient NMR), pore interconnectivity (variable temperature and exchange spectroscopy experiments using hyperpolarized 129Xe NMR) and oxidation state of Ti atoms (electron paramagnetic resonance). The obtained results enabled the detailed understanding of the impact of the post-synthetic treatment applied to the ETS-10 titanosilicate with respect to the catalytic activity in the heterogeneously catalyzed transesterification of triglycerides.

The TiO2 /carbonized materials in composites provide a synergistic effect of adsorption and photocatalysis. The activated carbon or carbonized material can be prepared using various raw materials that present agricultural waste. The most commonly used process for the preparation of the activated carbon (AC)/carbonized material is chemical activation. Chemical activation produces the activated carbon with a good surface area and pore system, which contributes to better adsorption of organic pollutants. The TiO2 /AC composite materials can be prepared by sol-gel, hydrothermal and metal organic chemical vapor deposition (MOCVD) techniques. The most commonly used techniques for characterization of the TiO2 /AC materials are XRD, BET, TG Analysis and UV-Vis DRS, and will therefore be discussed in this paper. The TiO2 /AC composite materials have shown significant efficiency in removal of organic pollutants from aqueous solutions. The adsorption process of organic pollutants can be affected by various process parameters that will be observed in this paper.

The synthesis route by solution combustion, a glycine nitrate procedure (GNP) of CoMoO 4 nanopowders by a glycine as a fuel and as a complexant was examined concerning the photocatalytic aspects and powder characteristics. The synthesized samples were investigated by differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Ultraviolet-Visible (UV/Vis) spectroscopy and nitrogen adsorption method. In this work, we presented a simple and effective method for controlling the composition and morphology of CoMoO 4 . A single-phase α and β crystalline form of CoMoO 4 compound was confirmed by X-ray diffraction (XRD). The photocatalytic activity of CoMoO 4 nanopowders was estimated by the photocatalytic degradation of crystal violet in aqueous solution. In addition, the obtained specific CoMoO 4 nanopowder demonstrated acceptable specific surface area, which can be of particular importance for the photocatalytic processes.

Spider silk fibers, collected from Pholcus Phalangioides spider were used as a template for obtaining magnesium oxide (MgO, periclase) as well as magnesium hydroxide (Mg(OH)2, brucite) fibers. Magnesium oxide fibers were obtained in a simple manner by heat induced decomposition of magnesium salt (MgCl2) in the presence of the spider silk fibers, while magnesium hydroxide fibers were synthesized by hydration of MgO fibers at 50, 70 and 90 C, for 48 and 96 h. According to Scanning electron microscopy (SEM), dimensions of spider silk fibers determined the dimension of synthesized MgO fibers, while for Mg(OH)2 fibers, the average diameter was increased with prolonging the hydration period. The surface of Mg(OH)2 fibers was noticed to be covered with brucite in a form of plates. X-Ray diffraction (XRD) analysis showed that MgO fibers were single-phased (the pure magnesium oxide fibers were obtained), while Mg(OH)2 fibers were two- or single-phased brucite depending on incubation period, and/or incubation temperature. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 45012]

AX 2-type compounds can be ionic, covalent or molecular types of structure, which depends on the size of atoms and the polarization properties. The materials of such type of the structure have different properties that can find the application in various areas of science and industry. Titanium dioxide, as a material of AX 2-type of the structure is a wide band gap semiconductor that has been widely investigated due to its photocatalytic properties and applicability for various purposes, such as the production of solar cells, decontamination of pollutants, elimination of microorganisms, suppression of cancer cells, etc. Experimental and theoretical studies of this metal oxide can give different data on the stability of individual crystalline modifications and their transitions. This study has presented an overview of theoretically examined TiO 2 modifications and current problems that can be encountered (such as various band gap values obtained by different methods and functionals; the difference between the stability of modifications examined on ab initio level and experimentally; the character of chemical bonds and transitions at the specific temperature and pressure conditions…) and overrun by optimal corrections added in calculations.

A visible-light-responsive hybrid material was prepared by surface-modification of γ-Al2O3, an insulator with a bandgap of about 8.7 eV, with 5-aminosalicylic acid (5-ASA), leading to the formation of an interfacial charge transfer (ICT) complex. The microstructural characterization of pristine γ-Al2O3 includes X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The pristine γ-Al2O3 powder consists of agglomerated rod-like nanoparticles ((2-3) × (15-20) nm, diameter × length) with the large specific surface area (~420 m2/g). An enormous absorption red-shift is observed upon the formation of the ICT complex. The absorption onset of the inorganic-organic hybrid was found to be at 730 nm by diffuse reflection spectroscopy. The photocatalytic performance of prepared samples was thoroughly tested using the decolorization of the organic dye crystal violet (CV) under illumination in different spectral regions and different light intensities. Excitation with UV light leads to complete decolorization of CV, while the degradation kinetics are impeded when a visible light source is used. Also, the increase of UV light intensity induced significantly faster degradation kinetics of CV, while the degradation rates of CV are quite insensitive to the increase of visible light intensity.

Biomaterials are characterized as any material of natural or synthetic origin that comes into contact with the tissue, blood or biological fluids of a patient and which are, due to their exceptional structural characteristics but also potential applications in many branches of industry and medicine (prosthetic, diagnostic, therapeutic, or storage applications, etc.) used to improve the patient's life. Biomaterials which can be found everywhere in nature, both on land and in water, are of particular importance. These are materials based on spider silk, silkworms, corals, shells, fish bones as well as eggshells. The structure of these materials is extremely interesting because of the features such as remarkable physicochemical and mechanical properties that further allow the application in various branches of medicine such as orthopedics, neurology, dentistry, tissue engineering. The application is based on the use of these materials in the form of various implants, biomolecule carriers, wound healing agents, antimicrobial agents, dental fillings because they have an extremely long duration time and there is a minimal need for replacement or repair.

A glassy carbon electrode was functionalized by MoO2 nanoparticle–decorated multiwalled carbon nanotubes (MWCNTs) and examined as a working electrode in oxyfluorfen (OXY) detection by differential pulse stripping voltammetry (DPSV). Measurement parameters were as follows: initial potential − 0.1 V, end potential + 0.5 V, accumulation potential − 0.15 V, accumulation time 80 s, and scan rate 50 mV s−1. A stripping potential of + 0.315 V vs. Ag/AgCl was employed. The pPesticide oxyfluorfen was determined in model samples by DPSV with good reproducibility (RSD

A new, simple, rapid, sensitive and selective kinetic spectrophotometric method for Pd(II) traces determination was elaborated in this paper. It is based on the catalytic effect of palladium ions upon the oxidation of methylene blue B (MBB) by (NH4)2S2O8 (APS) in citric buffer (BUF) solution. At the working temperature of 25 C and the wavelength of 662.4 nm, the optimal conditions for palladium determination were found. RSD value was found to be 2.6 to 4.9% for the investigated concentration range of Pd(II). Limit of detection (LD) was found to be 2.0 ng cm–3 Pd(II), and limit of quantification (LQ) is 6.9 ng cm–3 Pd(II). Only the presence of Pb2+, Hg2+ and Sn2+ in the reaction mixture interferes the determination of palladium by this method, while Au3+ and Ag+ have the catalytic effect upon the reaction rate. By this method, it is possible to determine the Pd(II) traces in the concentration range of 3.3x10–8 to 1.0x10–6 g cm–3. The method was confirmed by determination of Pd(II) traces in alloy PtRhG as well as in the powder of Pt. The obtained results were compared to those obtained by ICP-OES method and good agreement of results was found. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172051]

Titania based catalyst and TiO2 doped with zirconia were prepared by modified sol–gel method. The synthesized catalysts samples were characterized by BET, XRD, SEM and FTIR techniques. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolorization/decomposition under UV light irradiation. The effect of several operational parameters, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment and number of reaction cycles were also considered. The obtained results indicated faster dye decolorization with the increase of the catalyst amount and a decrease of initial CV concentrations. An influence of doping with zirconia on the physico-chemical properties of bare titania was studied. The doping procedure had affected photocatalytic properties of the final catalytic material, and had improved photocatalytic performances of doped catalyst on crystal violet decolorization/degradation in comparison to bare titania. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 1612008, Grant no. 45012 and Grant no. 172061]

Simple route was used for synthesis of nanostructured titania samples doped with 3 and 6 mol% of Cr3+ Titanium(IV)-isopropoxide and water were used as starting materials and as an agents for controlling hydrolysis and condensation reactions. The phase evolution of titania (TiO2) was followed by calcination at 400, 600 and 800 degrees C. The synthesized powders were examined by field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). Single-phase anatase was obtained at low temperature (400 degrees C) in all cases. The photocatalytic activity of TiO2 doped nanopowders was evaluated by the photocatalytic degradation of crystal violet in aqueous solution. The present study indicates that this simple synthesis method can be an effective route to produce efficient photoactive doped anatase nanopowders. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Heterogeneous catalysis is in recent focus of research for biodiesel production from vegetable oils because of advantages such as easy separation and reuse of catalysts, although homogeneous catalysis is most commonly used method. The aim of this study was preparation of γ-Al2O3 support by modified sol-gel procedure, synthesis of the KI/Al2O3 catalyst and testing its activity in the transesterification of sunflower oil with methanol. Influences of different process parameters on conversion of sunflower oil to methyl esters were examined. The gained results implicate that the potassium iodide incorporation into/onto the structure of γ-Al2O3 significantly influences textural and structural properties of the catalyst. Additionally, the catalyst basic strength is increased and all together those properties are positively affecting the activity of the catalyst in the reaction of transesterification of sunflower oil with methanol. The impregnation of alumina with potassium iodide resulted in the additional formation of basic catalytically active sites. The surface properties of the catalyst have an essential impact on its catalytic performance. Under relatively mild process conditions and relatively short reaction time, the usage of the KI/Al2O3 catalyst resulted in very high conversion to fatty acids methyl esters (i.e. 99.99 %). [Projekat Ministarstva nauke Republike Srbije, br. 172061 i br. TR 34008]

Three types of functional ceramic composites were designed, synthesized and probed for effective sulfide removal from aqueous solutions. The main goal was to examine complex influence of graphite, surpluses of Fe (similar to 4%) and micro-additions of Cu (similar to 0.2%) on the functional features of the composites. The structural, textural, morphological and surface characteristics of the composites were examined in detail by XRD, nitrogen sorption, SEM and FTIR. It has been shown that all composites are solid heterogeneous systems containing amorphous and crystalline phases (graphite, hematite, montmorillonite, quartz, etc.) with pronounced redox activity in contact with sulfide aqueous solutions. Great enhancment of sulfide consumption was detected for composites which contained graphite and it was established that reaction kinetics is fitted to irreversible second-order batch reaction with two reactants. After the treatment of 1 mM S2- solution, using composite dossage of 1 g/dm(3), concentration dropped down to 0.02 mM. In addition, cyclic voltammetry at 50 mV/s revealed the key role of dopants in electrochemical aspect of the process. Obvious boost of S2- uptake is ascribed to numerous electrochemical, chemical and sorption processes on the composite's developed surface.

Titanium dioxide, as environmental (decontamination) photocatalyst, is increasingly gaining importance in the removal of organic pollutants from water and air, as well. Different methods can be used for obtaining TiO2 catalyst, but sol-gel and hydrother­mal methods are most commonly used for the synthesis and modification of TiO2. The properties of nanostructured materials such as crystal phase, surface features and electronic structures can be changed with doping. In this paper, the influence of Fe and Zn as dopants on the physico-chemical properties of TiO2 catalyst will be presented based on the reported literature data. Usually applied instrumental tech­niques for the materials characterizations are X-ray diffraction (XRD), SEM, TEM, FTIR and UV-vis spectroscopy. The removal efficiency of various organic pollutants (organic dyes, antibiotics, pesticides, xenobiotics) is determined by the characteristics and dosage of the catalyst, nature and initial concentration of pollutants.

The influence of the physicochemical properties of a series of CaO catalysts activated at different temperatures on the biodiesel production was investigated. These catalysts show dissimilar yields in the transesterification of triglycerides with methanol. We have found significant relationships between structural properties (the type of the pore system, the typical CaO crystal phase and the sizes of crystallites (up to 25 nm), the minimal weight percentage of CaO phase, the total surface basicity and potential existence of two types of basic active sites) of CaO prepared and activated by means of thermal treatment at highest temperature and catalytic efficiency. Benefits of this catalyst are short contact time, standard operating temperature and atmospheric conditions, relatively low molar ratios and small catalyst loading. These all together resulted in a very high biodiesel yield of high purity. The properties of different biodiesel (obtained with the use of the prepared CaO catalyst) blends with different diesel and biodiesel ratios indicate that the higher the fraction of biodiesel fuel the better the achieved fuel properties according to the EU standards. A significant reduction of CO2 and CO emissions and only a negligible NOx increase occurred when blends with an increased biodiesel portion was used. The use of biodiesel derived blends, and the eventual complete replacement of fossil fuels with biodiesel as a renewable, alternative fuel for diesel engines, would greatly contribute to the reduction of greenhouse gases emissions. [Projekat Ministarstva nauke Republike Srbije, br. ON 172061 i TR 34008]

This paper presents a complete characterization of rapeseed oil, of Banaćanka variety, as well as the potential use of oil generated after filtering, in order to obtain biodiesel. Researches are based on the fact that Banaćanka is the oldest domestic rapeseed variety, the so-called double zero "00" (low in erucic acid, below 5%, and glucosinolates below than 30 mmol g-1), suitable for use in the region, since it is low temperatures tolerant, posseses high genetic potential for seed yield of about 5.2 t/ha, and high oil content of around 45%. Transesterification was carried out in batch reactor Parr 4520, with KOH as a catalyst. Cold pressed oil without prior treatment was used as feedstock for transesterificataion. The paper analyses the effects of temperature, reaction duration, catalyst amount and rate of agitation on the synthesis of biodiesel at constant pressure and molar methanol/oil ratio.[Projekat Ministarstva nauke Republike Srbije, br. TR-31046: Improvement of the quality of tractors and mobile systems with the aim of increasing competitiveness and preserving soil and environment]

Samples of natural peat (NP) were hydrothermally treated at different temperatures in oxidative and acidic aqueous medium to tailor their acid-base, adsorption, morphological and other properties. The obtained materials were thoroughly characterized by SEM, XRD and FTIR techniques, followed by determination of pH(pzc), examination of adsorption characteristics and the extent of organic matter leaching in water. Acid-base characteristics of these materials were examined by potentiometric and conductometric titration of corresponding aqueous suspensions. Experimental potentiometric data were interpreted using ProtoFit software (NEM, non-electrostatic model) which provided pKa values and concentrations of surface sites which are compared with corresponding values obtained by conductometric titration method. There are two main types of surface groups (carboxylic and phenolic) that are dominant in the materials and determine their acid-base behavior in the aqueous medium. Temperature during oxidative hydrothermal treatment has no significant effect on the total number of surface groups, but influences the ratio of carboxylic and phenol-type groups. Hence, acid-base properties of peat can be tailored, which is useful in designing and improving adsorptive characteristics of peat for the preferential removal of certain pollutants from water.

The procedure for obtaining a bentonite based composite involves the application of mixed Fe and Mg hydroxides coatings onto bentonite particles in aqueous suspension and subsequent thermal treatment of the solid phase at 498K. Structural and textural modifications of montmorillonite which occurred during the synthesis of composite were confirmed by XRD technique and N-2 adsorption at 77K. The composite structure was found to be less ordered, while its specific surface area was about two times higher than the specific surface area of the starting/native bentonite. The effectiveness of the composite in Pb(II) removal from aqueous solutions at different initial concentrations, pH and ionic strengths of the solutions was examined. The equilibrium adsorption data were analyzed using three widely applied isotherms: Langmuir, Freundlich and Dubinin-Radushkevich. The composite effectively removes both ionic and colloidal forms of Pb(II) from water and the maximum adsorption capacity obtained from the Langmuir equation was 95.88 mg/g. The main mechanisms of Pb(II) removal at low pH values were ion-exchange and outer-sphere surface complexation. (C) 2011 Elsevier B.V. All rights reserved.

Adsorption of a cationic phenothyazine dye methylene blueonto activated carbon prepared from pine cones was investigated with the variation in parameters of contact time, dye concentration and pH. The kinetic data were found to follow the pseudo-second-order kinetic modelclosely. The equilibrium data were best represented by the Langmuir isotherm with maximum adsorption capacity of 233.1 mg g-1. Adsorption was favored by using a higher solution pH. Textural analysis by nitrogen adsorption was used to determine specific surface area and pore structure of the obtained carbon. Boehm titrations revealed that carboxylic groups are present in the highest degree on the carbon surface. The results indicate that the presented method for activation of pine cones could yield activated carbon with significant porosity, developed surface reactivity and considerable adsorption affinity toward cationic dye methylene blue.

The heavy metals (Fe, Cu, Zn and Mn) contents of selected plant species, grown in Southeast region of Serbia, that are traditionally used in alternative medicine were determined. Among the considered metals, iron content was the highest one and varied from 137.53 up to 423.32 mg/kg, while the contents of Cu, Zn and Mn were remarkably lower, and ranged from 8.91 to 62.20 mg/kg. In addition, an analysis of plants extracts showed a significant transfer of heavy metals during extraction procedure; therefore, the corresponding extraction coefficients reached values up to 88.8%. Those were especially high in the ethanol based extracts. Moreover, it is established that such coefficients mostly depend on the solvent nature and also on the treated plant species. The obtained results impose that medicinal plants from Southeast region of Serbia due to rather low content of heavy metals are appropriate for preparation of teas and medicinal extracts.

Spider silk poses excellent mechanical properties, tenacity and elasticity and it has been used as a template for calcite mineralization to improve load bearing strength of osteoconductive calcite. The samples were obtained by mimicking biomineralization for five days in order to follow formation and growth of calcite on the surface of spider silk. Crystal phase was detected by XRD and FTIR spectroscopy. Microstructure, crystal size and its morphology were studied by means of FESEM. After two days of processing, pure calcite phase was obtained, and a size of the formed crystals increased with prolongation of biomineralization.

Magnesium-orthotitanate (Mg2TiO4) nano-powder was synthesized using a Pechini-type polymerized complex route. Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen adsorption-desorption isotherms indicated that well-crystallized Mg2TiO4 nanoparticles are small in size (about 10 nm) with large specific surface area (72 m(2) g(-1)). The surface modification of Mg2TiO4 nano-powders with 5-amino salicylic acid and catechol induced a significant shift of absorption to the visible spectral region due to charge transfer complex formation. It should be emphasized that tunable optical properties of Mg2TiO4 nano-powders have never been reported in the literature. Degradation reactions of an organic dye (crystal violet) were used to test the photocatalytic ability of pristine and surface-modified Mg2TiO4 nano-powders under illumination in different spectral regions. Excitation with UV light indicated, for the first time, photocatalytic ability of Mg2TiO4. Also, improved photocatalytic performance of surface-modified Mg2TiO4 nano-powders was found in comparison to unmodified ones.

Preparation, characterization and application of materials modified with TiO2 nanoparticle have been reviewed. Chitosan, bacterial biomass and dendrimers were the starting material for modification. Sorbents characterization was performed by scanning electron microscopy (SEM). In order to investigate the sorption capabilities of sorbents, we used them for removal of heavy metal ions from aqueous solution. The effect of contact time on heavy metal ions sorption and maximum sorption capacities of biosorbents are shown. As a very important parameter of the sorption process, the effect of initial pH values on heavy metal removal was examined. This paper indicates that sorption using the material modified with TiO2 is becoming a promising alternative to conventional adsorbents in removing heavy metal ions.

Due to its biocompatibility, biodegradability, hydrophility, technological properties and vast availability, polysaccharides are widely used as natural non-toxic polymers in different branches of industry (food, cosmetic, textile, construction industries). Exopolysaccharides (as dextran, pullulan) have recently taken up a significant position in pharmaceutical industry. Alginate has an irreplaceable role in biomedicine, since its hydrogel form is successfully applied for immobilization of a wide range of enzymes, therapeutics, biochemical agents and different kinds of microorganisms and cells (herbal, animal or human). Alginate microspheres and microcapsules are used for controlled release of biologically active molecules, as well as cell carriers in tissue engineering. Special benefits are brought by the simplicity of configuration of alginate hydrogel, including the possibility of the controlled production of micro- and nanoparticles. Taking into account a very important role of alginates in the form of hydrogel in biomedicine, in this paper a specific attention is paid on the preparation and application of alginate matrices, microspheres and microcapsules that may have essential and unexchangeable usage/application. This paper therefore displays various possibilities of use of polysaccharide matrices for biomolecules, polysaccharide as excipients of pharmaceutical products for oral or local application, and provides a review of the examples of innovative applications.

Nanocrystalline TiO2 films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO2 film modified with alanine that covalently binds to the surface of TiO2 and at the same time chelate silver ions induced formation of metallic silver film. Optical and morphological properties of thin silver films on nanocrystalline TiO2 support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO2 films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO2 support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact. (C) 2014 Elsevier Ltd. All rights reserved.

Nanostructured compounds with general formula Ca1-xYxMnO3 (0 LT = x LT = 1) were synthesized by modified glycine nitrate procedure. In the next step, we have investigated crystal structure and microstructure of the synthesized samples using X-ray methods and Rietveld analysis. Focus of this research was the structural stability of the yttrium-doped CaMnO3 perovskite phases, which crystallize in orthorhombic space group Pnma. We observed that the unit cell volumes of the investigated compounds increase proportionally with yttrium amount. Furthermore, we investigated the influence of yttrium amount on Mn-O bond angles and distances, tilting of MnO6 octahedra and deformation due to the presence of Jahn-Teller distortion around Mn3+ cation. In order to estimate effective coordination of A and B sites, bond valence calculations (BVC) were performed for A and B site cations. Finally, the photoelectron spectroscopy (XPS) method was applied in order to follow yttrium concentration in the perovskite phases.

Resorcinol-formaldehyde carbon cryogel has been prepared, characterized and used for the removal of commonly used herbicide clopyralid from the aqueous solutions under varying experimental conditions. Carbon has shown a relatively high specific surface area, significant mesoporosity and an amorphous structure. A set of the following isotherm models has been used to interpret the equilibrium data: Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Jovanovic, Hurkins-Jura, and Helsey model. Several models have fitted well although the calculated values for qmax poorly correlate with the data obtained experimentally. The kinetic models of the pseudo-first and pseudo-second-order, the models of Elovich, Bangham and the intraparticle diffusion model have been used for fitting the kinetic data. The rate of the process is fast in the beginning while adsorption equilibrium is attained not until 24 hours. Adsorption was found to be pH dependent and favored in acidic solutions.

We have performed a crystal structure prediction study of CaMnO3focusing on structures generated by octahedral tilting according to group–subgroup relations from the ideal perovskite type (Pm\overline 3 m), which is the aristotype of the experimentally known CaMnO3compound in thePnmaspace group. Furthermore, additional structure candidates have been obtained using data mining. For each of the structure candidates, a local optimization on theab initiolevel using density-functional theory (LDA, hybrid B3LYP) and the Hartree-–Fock (HF) method was performed, and we find that several of the modifications may be experimentally accessible. In the high-pressure regime, we identify a post-perovskite phase in the CaIrO3type, not previously observed in CaMnO3. Similarly, calculations at effective negative pressure predict a phase transition from the orthorhombic perovskite to an ilmenite-type (FeTiO3) modification of CaMnO3.

The quality of a straight-run fuel oil can be improved if saturated n-hydrocarbons of low octane number are converted to their branched counterparts. Poor reactivity of traditional catalysts in isomerization reactions imposed the need for the development of new catalysts among which noble metal promoted acid catalysts, liquid and/or solid acid catalysts take a prominent place. Sulfated zirconia and metal promoted sulfated zirconia exhibit high activity for the isomerization of light alkanes at low temperatures. The present paper highlights the original results which indicate that the modification of sulfated zirconia by incorporation of metals (platinum and rhenium) significantly affects catalytic performances in n-hydrocarbon conversion reactions. Favourable activity/selectivity of the promoted sulfated zirconia depends on the crystal phase composition, critical crystallites sizes, platinum dispersion, total acidity and type of acidity. Attention is also paid to the recently developed solid acid catalysts used in other conversion reactions of hydrocarbons.

The ordered mesoporous silica SBA-15 was synthesized and used as a template for obtaining mesoporous carbon replicas. Adsorptive removal of pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions onto two carbon replicas was investigated. Batch adsorption experiments varied in initial adsorptive concentration, contacting times, solution pH, and adsorbent dosage. Pseudo-first order model, pseudo-second order model, and intraparticle diffusion model were selected to interpret the kinetics of adsorption. Kinetic parameters such as rate constants, equilibrium adsorption capacities and correlation coefficients were calculated and discussed for each model. Equilibrium data were linearly fitted to Langmuir, Freundlich, Tamkin, Dubinin-Radushkevich, Jovanovic, Hurkins-Jura and Halsey isotherm models. It was shown that adsorption of 2,4-D onto two carbon replicas well followed the pseudo-second order kinetic model. Langmuir isotherm represented experimental data in the best way since this model gave the best fit. Adsorption capacity strongly depends on the solution pH and increases at lower pH values. (C) 2012 Elsevier B.V. All rights reserved.