[Show abstract][Hide abstract] ABSTRACT: Investigation was conducted in order to elucidate the possibility of using perlite as support for preparation of nickel based precursor catalyst, potentially applicable in vegetable oil hydrogenation process. On three differently prepared expanded perlite, nickel catalyst precursors with identical Ni/SiO2 = 1.1 and Ni/Mg = 10/1 ratios were synthesized by precipitation-deposition method. Different techniques, SEM micrography, He-pycnometry, calcimetry, Hg-porosimetry, N2-physisorption, H2-chemisorption and temperature programmed reduction, were used for characterization of obtained samples. Determining the precursor texture, morphology and reducibility shows a successfully deposited nickel phase on perlite support with promising properties for vegetable oil hydrogenation. Chosen precursor was reduced and passivated in paraffin oil and the obtained catalyst showed significant catalytic activity in the test of sunflower oil hydrogenation.
[Show abstract][Hide abstract] ABSTRACT: Bentonite originated from Mečji Do, Serbia, was submitted to acid treatment at 70 °C for 30 min, while only the concentration of applied HCl varied. The obtained acid treated samples were used to modify glassy carbon (GC) electrode. The effect of applied acid treatment on the electrochemical behavior of GC electrodes modified with these materials was investigated. Furthermore, the effect of the introduction of nickel into acid treated samples was studied. The incorporation of nickel into acid treated bentonite was achieved by either ion exchange or impregnation/decomposition method. The obtained samples were characterized using the following methods: inductively coupled plasma (ICP), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and electron spin resonance (ESR) spectroscopy. The electrochemical behavior of these samples was tested by cyclic voltammetry in 0.1 mol dm-3 H2SO4 solution. The ICP, FTIR and ESR results exhibited a slight decrease of iron content in the acid treated samples. XRD and FTIR results confirmed that the conditions applied for the acid treatment were mild enough for the smectite structure to be preserved. The electrocatalytic test showed that the current response of Fe2+/Fe3+ oxidation/reduction process increased on the GC electrodes separately modified with each of the acid treated samples in comparison with current obtained on the GC electrode modified with untreated sample. These results indicated that applied acid treatment probably increased the accessibility of the electroactive iron within smectite. Cyclic voltammograms obtained for the GC electrodes modified with acid treated bentonite materials showed greater anodic charge (qa) than cathodic charge (qc). This difference might be due to iron detachment from smectite structure during the oxidation process. Further modification of the selected acid treated sample with nickel species resulted in decreased current response of the Fe2+/Fe3+ oxidation/reduction process and improved the reversibility of this process.
[Show abstract][Hide abstract] ABSTRACT: The influence of Ni on the electrochemical performance of Fe containing bentonite-based electrode materials was investigated in the electrochemical oxidation of phenol in acidic solution. Clay originated from Mečji Do, Serbia, was submitted to pillaring. Mixed pillaring solutions containing Al3+ and Fe3+ or Al3+, Fe3+ and Ni2+ were used for this purpose. The XRD, chemical and FTIR analysis and nitrogen physisorption at -196 °C were used for sample characterization. The electrochemical behavior of the pillared clay-based electrodes was tested by cyclic voltammetry. The results confirmed that the pillaring was successful. The presence of Ni in the electrode material enhanced the electrode stability. It is possible that the presence of Ni restricted the electrode fouling caused by the formation of polymeric products during the electrooxidation of phenol.
[Show abstract][Hide abstract] ABSTRACT: We report on ferromagnetic-like magnetic properties, at room temperature, of spherical nickel oxide core–shell nanoparticles synthesized by sol–gel combustion method. The sample is characterized by using transmission electron microscopy (TEM), selected electron area diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy (RS) and superconducting quantum interference device (SQUID) magnetometer. The SAED, EDX and RS show high quality and purity of the sample. The TEM images point to core–shell NiO nanostructure with a well crystallized NiO core and surface disorder shell. The size of the nanoparticles of about 5 nm and thickness of the surface shell below 1 nm are estimated from the TEM and HRTEM measurements. The measurements of the magnetization reveals ferromagnetic-like behavior of the sample at room temperature with remanent magnetization Mr = 0.0087 emu/g and coercive field HC = 115 Oe. These magnetic properties are quite different than in NiO bulk materials and uncommon for nanosized NiO materials. These results also indicate that the synthesized NiO core–shell nanostructure is suitable for spin-valve applications.
Journal of Alloys and Compounds 02/2014; 586:S322-S325. DOI:10.1016/j.jallcom.2012.10.166 · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Removal of two different dyes: Acid Orange 10 (AO10) and Reactive Black 5 (RB5) from their aqueous solutions using organobentonite as adsorbent was investigated. The experiments were carried out at different temperatures (298, 313, 323, and 333 K) in order to obtain thermodynamic parameters for adsorbate/adsorbent system i.e., activation energy, Gibbs free energy, enthalpy and entropy. The results of thermodynamic studies indicated that the adsorption of both dyes onto organobentonite is an endothermic process, while the values for activation energies (76 kJ mol−1 for AO10 and 51 kJ mol−1 for RB5) indicated that chemisorption occurred.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to obtain enhanced textural properties of macroporous crosslinked copolymer poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) by synthesizing nanocomposites with acid-modified bentonite. Nanocomposites were obtained by introducing various amounts of acid-modified bentonite (BA) into the reaction system. All samples were characterized by attenuated total reflectance infrared spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), mercury intrusion porosimetry, and low temperature physisorption of nitrogen. The FTIR and TEM analysis confirmed incorporation of BA into the copolymer structure and the successful formation of nanocomposites. TEM images confirmed formation of nanocomposites having both intercalated and exfoliated acid-modified bentonite in copolymer matrix. A significant increase of specific surface area, pore volume, and porosity of the nanocomposites in comparison to the copolymer were obtained. The difference between textural properties of nanocomposites with different amounts of incorporated acid-modified bentonite was less prominent.
[Show abstract][Hide abstract] ABSTRACT: A natural bentonite, modified with different quaternary ammonium cations, hexadecyl trimethylammonium, (HDTMA), dodecyl trimethylammonium (DTMA) and tetramethylammonium (TMA), was used as an electrode material in a p-nitrophenol (p-NP) electrooxidation. On the basis of electrochemical response, TMA-modified bentonite (TMA-B) electrode was chosen for further investigations. The influence of TMA loading on the electrochemical properties of the TMA-B electrodes toward p-NP electrooxidation was examined. Electrode sensitivity toward p-NP was performed. The detection limit for p-NP of 1 · 10− 6 mol dm− 3 was obtained.
[Show abstract][Hide abstract] ABSTRACT: Zeolite NaX (faujasite type) was used as a support for platinum-ruthenium catalyst. A procedure for thermal decomposition of noble metal acetylacetonates to deposit noble metal clusters on the surface of solid support was adapted by authors to introduce noble metal clusters in zeolite cavities. The effectiveness of this composite material for methanol electrooxidation from alkaline solution was investigated by cyclic voltammetry. The influence of the concentration of supporting electrolyte, scan rate and rotation rate on the reaction of methanol oxidation was investigated. The obtained activity was compared with literature data for similar catalysts.
Science of Sintering 01/2013; 45(1):89-96. DOI:10.2298/SOS1301089M · 0.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to find a low cost, easy to synthesize and efficient adsorbent for the simultaneous adsorption of both organic and inorganic pollutants (including textile dyes, toxic metals, etc.). The starting material, domestic bentonite clay from Bogovina, was modified with amounts of hexadecyltrimethylammonium cations corresponding to 0.5 and 1.0 times the value of the cation exchange capacity. The organobentonites were tested as adsorbents in a three-dye-containing solution, a three-component solution of Pb 2+, Cd2+ and Ni2+ and a hexa-component solution containing all the investigated dyes and toxic metal cations. The used adsorbents showed the highest affinity toward acid yellow 99 and Ni 2+. Dye adsorption was enhanced in the presence of toxic metal cations, while the adsorption of all toxic cations from the hexa-component solution was lower than from the three-component solution containing only toxic cations. The synthesized hexadecyltrimethylammonium bentonite could be regarded as an efficient multifunctional adsorbent for the investigated types of water pollutants.
Journal of the Serbian Chemical Society 01/2013; 79(2). DOI:10.2298/JSC130125065J · 0.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pillared clays (PILCs) based on bentonite clay from “Bogovina” (Serbia) were obtained using Al3+ and Fe3+ pillaring cations in different ratios. Thorough characterization of the starting material and PILCs was performed for better understanding of the catalytic activity that they had exibited in the catalytic wet peroxide oxidation (CWPO) of organic pollutants in water. The characterization consisted of the following techniques: XRD, XRD of oriented samples (swelling test), Greene-Kelley test (smectite type determination), TGA/DTA followed by XRD analysis of samples heated at characteristic temperatures, elemental analysis using ICP-OES and microwave digestion, FTIR, DR UV–Vis, Mössbauer spectroscopy, nitrogen physisorption at −196 °C and SEM imaging.Smectite in admixture with quartz was identified, together with impurities like feldspar, illite, chlorite and X-ray amorphous matter. Smectite mineral was dominantly of the beidellite type. Pillaring led to changes in the d001 smectite basal spacing and stabilization of the smectite structure. Increasing Fe3+ content of the pillaring solutions resulted in the increased incorporation of iron into the PILCs as isolated octahedrally coordinated Fe3+ cations, smaller and bigger oligonuclear octahedrally coordinated Fe3+ species and octahedrally coordinated Fe3+ particles. The structure of incorporated pillars was similar to that of naturally occurring minerals akageneite and lepidocrocite. Micro- and mesoporosity were improved due to pillaring and the layered smectite structure was retained.
[Show abstract][Hide abstract] ABSTRACT: Phenol and its derivatives are regarded as 'priority pollutants' and p-nitrophenol (p-NP), in particular, is of great interest due to its toxicity and frequent presence in waste waters and fresh waters. Straightforward, inexpensive methods to identify p-NP in water, however, is lacking. In the present study, an electrochemical technique using clay-modified electrodes to measure p-NP was investigated as a potentially promising method to fill that gap. A glassy carbon electrode (GCE) was modified with a thin layer of Na-enriched bentonite and a series of benzyltrimethylammonium (BTMA+)-bentonites (BTMA+-B) in order to confirm these materials as p-NP electrosensitive. A series of organobentonites was synthesized using different BTMA+/bentonite ratios. The materials obtained were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and a low-temperature nitrogen adsorptiondesorption method. A monolayer arrangement of BTMA+ within the interlamellar region of beidellite-rich smectite was confirmed. Deterioration of the textural properties was observed with increase of BTMA+ loading. The electro-oxidation of p-NP in an acidic medium on BTMA+-B-modified GCE was investigated. The cyclic voltammetry method with a three-electrode cell was used. The reference electrode was Ag/AgCl in 3 M KCl and a Pt foil was the counter electrode. For each electrochemical measurement, a different BTMA+ loading in BTMA+-B was used as the material for GCE coating and applied as the working electrode. The electrochemical activity of BTMA+-B-based electrodes increased with BTMA+ loading. The results confirmed that the organophylic character of the BTMA+-B-modified surface was the main influence on the electrochemical activity of the BTMA+-B-based GCE; the influence of textural properties was almost negligible. The increased electrode activity toward p-NP was achieved by the adsorption of p-NP on the electrode surface, the process that commonly precedes the electro-oxidation. The present study showed that synthesized materials could potentially be used in an electrochemical test for the presence of p-NP in water solutions.
[Show abstract][Hide abstract] ABSTRACT: Ni/SiO2 materials with identical composition (SiO2/Ni = 1.0) have been synthesized by precipitation of Ni(NO3)2 · 6H2O solution with Na2CO3 solution on the silica gel, obtained at three different pH values. The present investigation was undertaken in an endeavor to study the effects of the silica gel support type and the reduction temperature on the formation and dispersion of the metallic nickel phase in the reduced Ni/SiO2 precursors of the vegetable oil hydrogenation catalyst. The physicochemical characterization of the unreduced and reduced precursors has been accomplished appropriately by powder X-ray diffraction, infrared spectroscopy, temperature programmed reduction and H2-chemisorption techniques. It can be stated that the texture peculiarities of the silica gels used as supports influence on the crystalline state and distribution of the deposited Ni-containing phases during the preparation of the precursors, on the reduction temperature of the investigated solids as well as on the bulk size and surface dispersion of the arising metallic nickel particles. It was shown that two types of Ni2+-species are formed during the synthesis procedure, namely basic nickel carbonate-like and Ni-phyllosilicate with different extent of presence, location and strength of interaction. The different location of these species is supposed to result in various strength of Ni-O and Ni-O-Si interaction, thus determining the overall reducibility of the precursors. It was specified that the Ni2+-species are strongly bonded to the surface of the silica gel obtained at neutral pH value and weakly bonded to the surface of those prepared in acidic and alkaline conditions. It was established that the precursor, derivates from the silica gel obtained at alkaline conditions, demonstrates both significant reduction of the Ni2+ ions at 430°C and finely dispersed metallic nickel particles on its surface. High dispersion of the metallic nickel might be the crucial reason for achieving of high activity in the vegetable oil hydrogenation.
[Show abstract][Hide abstract] ABSTRACT: Crosslinked macroporous copolymer of glycidyl methacrylate and ethylene glycol dimethacrylate (CP) and copolymer composite with acid modified clay (CP-SA) were prepared by radical suspension copolymerization and functionalized by ring-opening reaction of the pendant epoxy groups with diethylene triamine (CP-deta and CP-SA-deta). Both SAmples were characterized by mercury porosimetry. The influence of pH, sorption time and initial 4-nitrophenol (4-NP) concentration on sorption efficiency of CP-deta and CP-SA-deta was studied in order to evaluate this material as wastewater sorbent. The isotherm data were best fitted with Langmuir model, while the sorption dynamics obeyed the pseudo-second-order kinetic model.
[Show abstract][Hide abstract] ABSTRACT: The effect of the type of the silica gel pore structure on the surface properties of the Ni-silica gel catalyst precursors for the vegetable oil hydrogenation process has been examined applying N2 sorption and X-ray photoelectron spectroscopy techniques. The nickel catalyst precursors with identical composition (SiO2/Ni = 1.0) has been synthesized by precipitation of Ni(NO3)2 · 6H2O solution with Na2CO3 solution on the three types of silica gel with different pore structures. It is shown that the usage of the silica gel supports with different texture as source of SiO2 causes different location of Ni-species into the support pores and on the external surface area. The XPS data confirm the formation of surface species with different strength of interaction and different dispersion. These surface characteristics of the precursors will predetermine the formation of the active nickel metallic phase as well as the mass transfer of the reactants and products to and from the catalytic sites.
[Show abstract][Hide abstract] ABSTRACT: In order to enhance nickel effectiveness for methanol oxidation reaction, zeolite type 13X was used as a support for nickel nanodispersion. Nickel modified samples were characterized by XRD, SEM and nitrogen adsorption-desorption measurements. The incorporation of nickel into zeolite cavities led to the partial destruction of the zeolite framework. Modified zeolite was used as the electrode material for methanol oxidation in a deaerated 0.1 M NaOH aqueous solution. It showed similar electrochemical behavior to that of polycrystalline nickel. The destruction of zeolite structure probably enabled aluminum from the framework to stabilize α-Ni(OH)2. Mixture of β- and γ-NiOOH was obtained at the 13XNi100 electrode after cycling in alkaline solution. It was concluded from the electrochemical measurements that β-NiOOH was preferable oxide form for methanol oxidation.
Fuel and Energy Abstracts 10/2011; 36(21):13343-13351. DOI:10.1016/j.ijhydene.2011.07.097
[Show abstract][Hide abstract] ABSTRACT: The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.
[Show abstract][Hide abstract] ABSTRACT: Bentonite was modified by the exchange of inorganic cations with hexadecyl trimethylammonium, dodecyl trimethylammonium or tetramethylammonium cation. The obtained materials were characterized by physisorption of nitrogen and X-ray diffraction analysis. Multisweep cyclic voltammetry was applied to analyze phenol response on different organo bentonite-based electrodes. The aim of the investigation was to determine the influence of the type of modifying agent on the electrochemical performance of the investigated electrodes. All electrodes exhibited similar electrochemical behavior but with different intensities of the electrochemical response and Tafel slopes. The difference in Tafel slopes reflected different level of involvement of pores in the phenol electrooxidation.