The tubular and layered structure of titanate nanotubes facilitate ion movement and provide a hig... more The tubular and layered structure of titanate nanotubes facilitate ion movement and provide a high rate capability. Moreover, expansion of the material can enhance its performance. In this study, regular titanate nanotubes and expanded titanate nanotubes were synthesized. To expand the nanotubes, dodecylamine were used under hydrothermal conditions. SEM, TEM, BET, and XRD were utilized to characterize these materials. In addition to that, electrochemical characterizations like cyclic voltammetry, rate capability, and cycle stability tests were made to understand the effect of titanate expansion on Li-ion electrode performance. After the expansion, the d-spacing increased from 8.1 Å to 9.5 Å and parallel to that, the specific surface area reached to 297 m 2 g À1 from 204 m 2 g À1. Cyclic voltammograms had broad peaks and suggested a pseudocapacitive character; which is common for titanate nanotubes. Sloping potential-capacity profiles also supported this character. The first discharge capacity of regular nanotubes was 823 mAh g À1. However, after the expansion, it increased to 1017 mAh g À1. Above all, both of the nanotubes had superior rate capabilities and stabilities due to their high aspect ratios. Moreover, dodecylamine created a protective layer on the titanate surface and enhanced the stability. Finally, it was realized that the expansion of the structure is crucial and enhances the electrode performance.
Functionalized Nanoscale Materials, Devices and Systems, 2008
In the present study, nanostructured titania particles were synthesized using hydrothermal proces... more In the present study, nanostructured titania particles were synthesized using hydrothermal processing and their photocatalytic antimicrobial activities were characterized. Sol-gel synthesized TiO2 samples were treated with a two step hydrothermal treatment. The first stage treatment was the alkaline treatment with 10 M of NaOH for 48 h at 130ºC, followed with the second step which applied with distilled water for 48 h at 200°C. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields lamellar structure particles from the sol-gel synthesized anatase. Further treatment of nanoplates with distilled water results in crystal growth and the formation of nano structured thorn like particles. The photocatalytic antimicrobial activities of samples were determined against Escherichia coli under solar irradiation for 4 h. It was observed that the samples treated under alkaline conditions have higher antimicrobial activity than the untreated samples.
Nanostructured titania particles were synthesized by using hydrothermal processing and the photoc... more Nanostructured titania particles were synthesized by using hydrothermal processing and the photocatalytic antimicrobial activities were characterized. Both sol–gel synthesized and commercial TiO2 (anatase) samples were processed with two step hydrothermal treatments,under alkaline and neutral conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol–gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coli under irradiation. It was observed that the samples treated under alkaline conditions have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However,a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic activity.
Expanded graphite oxide (GO) synthesized by graphite oxidation and thermal expansion was exposed ... more Expanded graphite oxide (GO) synthesized by graphite oxidation and thermal expansion was exposed to ultrasonic vibration to obtain graphite nanoplatelets (GNFs). Then, expanded GO as conductive filler was dispersed in polypyrrole matrix in order to be utilized as catalyst support. Electrical conductivities and polymer thickness of GNF-based composites were tailored at different feeding mass ratios. Thermal expansion led to the removal of oxygen functional groups on the surface, and the C/O ratio increased to 6. The highest C/O ratio had less hydrophilic carbon surface, and this decreased the interaction of Pt particles with support. When comparing Pt deposition behavior of GO, expanded GO, graphene nanosheets, and their composites, the results showed that Pt dispersion increased with increasing amount of oxygen functional groups on the surface of the samples. This work was the first comprehensive and quantitative investigation on the relationship between Pt dispersion and surface oxygen functional groups of graphene-based nanocomposites.
Boron is an essential element for plant growth, but it may also result in toxicity when present i... more Boron is an essential element for plant growth, but it may also result in toxicity when present in excessive amounts. In this study, continuous polymer enhanced ultrafiltration (PEUF) was developed to selectively recover aqueous boron species (collectively termed "boron" hereafter) from solution. The PEUF process consisted of complexing boron to a water-soluble polymer, removing all non-complexed solutes by UF, restoring the unloaded polymer, and isolating the newly freed boron by UF. Three different polymers were synthesized to complex boron. One was derived from N-meth-yl-D-glucamine (P1). Two others were derived from iminodipropyleneglycol (P2 and P2G). Operating parameters such as the boron/polymer ratio (0.01-1), pH value (7-10), and polymer type (P1, P2, and P2G) were assessed. An increase of the pH value led to increased boron retention. As well, a decreased loading value enhanced retention. A maximum retention of 90.1% exceeded the highest values reported in the literature under similar conditions. The permeate flux remained constant at approximate to 20 L/m(2) h, and operation was unaffected by classic problems such as fouling. The results showed that continuous PEUF utilizing the above polymers could serve as an alternative method for the removal of environmental boron.
Iron oxide nanoparticles were deposited on activated carbon (AC) with the microwave hydrothermal ... more Iron oxide nanoparticles were deposited on activated carbon (AC) with the microwave hydrothermal (MH) treatment technique. The effect of heating duration and AC's oxidation on structural properties were studied. X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), focused ion beam (FIB) microscopy, Brunauer, Emmett and Teller (BET), and porous texture analyses were utilized to characterize iron oxide/AC system. XRD characterization revealed dependence of crystal structure to heating duration. BET and porous texture analyses showed some pore filling in AC, but pore volume increase in iron oxide particles. With the MH technique, porous iron oxide was obtained with a high loading value of 20.27% in just 9 min. Additionally, As(V) adsorption capacity of synthesized materials was studied. As(V) adsorption onto iron oxide deposited supports obeyed Langmuir and pseudo-second order models. Batch adsorption experiments revealed a high efficiency of As(V) removal with the MH synthesized materials. Maximum adsorption capacity was 27.78 mg/g, and for a loading of 0.75 g/L, 99.90% uptake was reached within just 5 min due to the porous nature of iron oxide. Moreover, more than 99.00% of uptake was obtained within the pH range of 6-8. The results suggest that MH synthesized iron oxide particles are promising materials for water treatment. (C) 2014 Elsevier B.V. All rights reserved.
The production of novel catalyst support materials could open up new ways to enhance the catalyti... more The production of novel catalyst support materials could open up new ways to enhance the catalytic activity by reduced catalyst loadings. Nanocomposites composed of conducting polymers reinforced with graphene nanosheets (GNS) or graphite oxide (GO) sheets can ...
Titanate nanotubes are promising materials for Li-ion battery anodes because of their special mor... more Titanate nanotubes are promising materials for Li-ion battery anodes because of their special morphology and high specific surface areas. These titanates provide high rate capability and low volume expansion upon lithiation. More importantly, their tubular structure helps the transport of ions through the crystal. In this study, we synthesized elongated titanate nanotubes and modified their interlayer distances by changing the pH (2-13). For the structural characterization XRD, BET, SEM and TEM techniques were used. In addition, the effect of interlayer distance on energy capacity and rate capability was investigated. The highest interlayer distance was obtained at pH 10 and with decreasing pH, the interlayer distance dropped until reaching a pH value of 4. Conversely, the specific surface area reached its maximum value of 204 m(2) g(-1) at a pH of 4. Different from anatase (TiO2), titanate nanotubes had broad peaks in cyclic voltammograms suggesting a pseudocapacitive behavior. The...
ABSTRACT Graphite oxide nanosheets (GO), graphene nanosheets (GNS), and nanocomposites comprising... more ABSTRACT Graphite oxide nanosheets (GO), graphene nanosheets (GNS), and nanocomposites comprising of GO or GNS coated with polypyrrole (PPy) were prepared and assessed for their ability to influence the surface deposition and growth of Pt nanoparticles. GO was obtained from graphite via oxidation and exfoliation, and GNS was obtained from GO in a subsequent reduction. Both GO and GNS were coated with PPy via in situ polymerization of pyrrole (Py), forming surface-enhanced materials. SEM, EDX, TEM, EELS, Raman, and AFM findings showed that the Pt nanoparticle loading, agglomeration size, aggregate morphology and surface dispersion varied according to the nanosheet surface, nanocomposite type, and Py/nanosheet feed ratio. Surface oxygen functionalization along GO, GNS and their nanocomposites influenced the loading, dispersivity and morphology of nanoparticle agglomerates. PPy/GO nanocomposites yielded an improved nanoagglomerate surface dispersion and loading compared to samples. The PPy-coated substrates offered a greater intrinsic propensity for redox processes, resulting in higher Pt loadings. Additionally, these nanocomposites provided more surface reduction sites compared to bare nanosheets, and the additional sites contributed towards forming smaller, more homogeneously dispersed Pt nanoparticle agglomerates. Bringing together the electrical properties of PPy and physico-mechanical traits of carbon nanosheets, it follows to reason that the nanocomposites produced, particularly GO-based nanocomposites, offer promise as a nanoparticle support material for use in catalysis, electrocatalysis, and hydrogen storage.
ABSTRACT The aim of the present paper was to measure the apparent diffusivities, Knudsen diffusiv... more ABSTRACT The aim of the present paper was to measure the apparent diffusivities, Knudsen diffusivities, pore diffusivities and activation energies of diffusion at 26–32 °C and to determine the modes of transport of some alcohols (methanol, ethanol, propanol, n-butanol) and aromatics (benzene, ethylbenzene, propylbenzene, toluene, o-xylene, m-xylene, p-xylene) into the mesoporous structure of MCM-41 synthesized. As the molecular weight of the alcohols and aromatics increased, apparent diffusivities decreased and the activation energy for diffusion increased. Lower molecular weight alcohols and aromatics had higher diffusivities compared to those with higher molecular weight alcohols at the same temperatures. The diffusion of isomeric molecules within the mesoporous channels were affected by the position of branching. The deterministic behavior depended on the molecular weight, length of side chain and ortho, meta and para isomerism of the molecule. Increasing the temperature raised the kinetic energy of the molecules, which resulted in an increase in the diffusivities of the alcohols and aromatics in MCM-41. Diffusion rate constants of alcohols and aromatics increased with increasing temperature within the range of 26–32 °C, and the rate decreased as the molecular weight of the diffusing chemical increased. The diffusion of alcohols and aromatics in MCM-41 obeyed the anomalous transport mechanism. Diffusion exponents, n, being in the range of 0.99–1.07, indicated an anomalous diffusion (non-Fickian/super-Case II) mechanism for alcohol diffusion. However, for the case of aromatics, diffusion exponents, from 0.7 to 1.00, indicated that the diffusion mechanisms were either non-Fickian or non-Fickian/super-Case II depending on the substitution to the benzene ring. Activation energies of alcohols and aromatics were also in good agreement with the values of diffusivities of alcohols and aromatics such that larger activation energies resulted in smaller diffusivities. Alcohols and aromatics with greater solubility parameters were found to have greater diffusivities.
ABSTRACT Semicokes obtained from the pyrolysis of petroleum pitches are important materials that ... more ABSTRACT Semicokes obtained from the pyrolysis of petroleum pitches are important materials that are used in the manufacture of many carbonaceous products. Therefore, new structural information of the semicokes will extend their utilization. The structural analysis of anisotropic semicokes of the pyrolysis of petroleum pitches obtained under various experimental conditions of temperature and time was investigated. The overall objective is to provide further detailed information of factors which influence formation of anisotropy or turbostratic structures in resultant semicokes. Experiments were carried out under an argon atmosphere at the temperature range of 500–1000 °C for 30, 60 and 120 min in a tube furnace. FTIR, 1H-NMR, and 13C-NMR results showed that the aromatic structure of the semicokes was increasing with respect to increasing temperature as well as increasing time. Aromaticity of the semicokes was calculated as 0.54 and 0.64, for Pitch A at 500 °C after 120 min, and Pitch B at 600 °C after 120 min, respectively. The intensity ratio between Raman “D” and “G” peaks, ID/IG (commonly used to characterize disorder in graphene structures) was observed to increase approximately linearly from 0.65 to 0.92 when the pyrolysis temperature of Pitch A was increased from 500 °C to 900 °C. XRD patterns of the semicokes showed the formation of some crystalline material with time and temperature. The average number of layers, calculated by the Debye–Scherer technique using the XRD patterns of the semicokes, was between 5 and 10. SEM images of the semicokes indicated the presence of turbostratic structures. All the results of characterizations were consistent and indicated the formation of highly amorphous hydrocarbon materials that contain turbostratic structures. Treatments at higher temperatures increased formations of aromatic structure with increased crystallinity. Temperature seemed to be the dominating parameter of the pyrolysis reactions. As the pyrolysis temperature was increased, aromatic structure formation was favored with increased crystallinity in the semicokes. We expect that findings of the present work will open new uses for the anisotropic semicokes obtained from petroleum pitches. The pitches can be widely applied to the templating synthesis of carbon nanostructures and other carbon nanomaterials.
Crystalline, high-surface-area, hexagonal mesoporous MCM-41 having uniform
pore sizes and good th... more Crystalline, high-surface-area, hexagonal mesoporous MCM-41 having uniform pore sizes and good thermal stability was successfully synthesized at 90–120C in 30 min using low-power microwave irradiation. This appears to be the first comprehensive and quantitative investigation of the comparatively rapid synthesis of mesoporous MCM-41 using low-power microwave heating of 80W (90C) and 120W (120C). The influence of reaction temperature and the duration of heating were carefully investigated, and the calcined MCM-41 materials were characterized by XRD, SEM, TEM, nitrogen adsorption, TGA, and FT-IR. The mesoporous MCM-41 product synthesized in 30 min at 120W and calcined at 550C had a very high surface area of 1438m2=g and was highly ordered, containing uniform pores with diameters in the range of 3.5–4.5 nm. The wall thickness of the materials highly depended on the power of the microwave energy used during synthesis. Synthesis of the mesoporous MCM-41 products at 120C resulted in a structure with thinner walls. The mesoporous MCM-41 materials synthesized in the present work had good thermal stability.
In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish ligni... more In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish lignites with crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH, and also lignite source on the desulphurization have been examined. The values for incubation period, pulp density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0, respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29% reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples. Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur, sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison tests and ANOVA were performed.
The tubular and layered structure of titanate nanotubes facilitate ion movement and provide a hig... more The tubular and layered structure of titanate nanotubes facilitate ion movement and provide a high rate capability. Moreover, expansion of the material can enhance its performance. In this study, regular titanate nanotubes and expanded titanate nanotubes were synthesized. To expand the nanotubes, dodecylamine were used under hydrothermal conditions. SEM, TEM, BET, and XRD were utilized to characterize these materials. In addition to that, electrochemical characterizations like cyclic voltammetry, rate capability, and cycle stability tests were made to understand the effect of titanate expansion on Li-ion electrode performance. After the expansion, the d-spacing increased from 8.1 Å to 9.5 Å and parallel to that, the specific surface area reached to 297 m 2 g À1 from 204 m 2 g À1. Cyclic voltammograms had broad peaks and suggested a pseudocapacitive character; which is common for titanate nanotubes. Sloping potential-capacity profiles also supported this character. The first discharge capacity of regular nanotubes was 823 mAh g À1. However, after the expansion, it increased to 1017 mAh g À1. Above all, both of the nanotubes had superior rate capabilities and stabilities due to their high aspect ratios. Moreover, dodecylamine created a protective layer on the titanate surface and enhanced the stability. Finally, it was realized that the expansion of the structure is crucial and enhances the electrode performance.
Functionalized Nanoscale Materials, Devices and Systems, 2008
In the present study, nanostructured titania particles were synthesized using hydrothermal proces... more In the present study, nanostructured titania particles were synthesized using hydrothermal processing and their photocatalytic antimicrobial activities were characterized. Sol-gel synthesized TiO2 samples were treated with a two step hydrothermal treatment. The first stage treatment was the alkaline treatment with 10 M of NaOH for 48 h at 130ºC, followed with the second step which applied with distilled water for 48 h at 200°C. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields lamellar structure particles from the sol-gel synthesized anatase. Further treatment of nanoplates with distilled water results in crystal growth and the formation of nano structured thorn like particles. The photocatalytic antimicrobial activities of samples were determined against Escherichia coli under solar irradiation for 4 h. It was observed that the samples treated under alkaline conditions have higher antimicrobial activity than the untreated samples.
Nanostructured titania particles were synthesized by using hydrothermal processing and the photoc... more Nanostructured titania particles were synthesized by using hydrothermal processing and the photocatalytic antimicrobial activities were characterized. Both sol–gel synthesized and commercial TiO2 (anatase) samples were processed with two step hydrothermal treatments,under alkaline and neutral conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol–gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coli under irradiation. It was observed that the samples treated under alkaline conditions have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However,a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic activity.
Expanded graphite oxide (GO) synthesized by graphite oxidation and thermal expansion was exposed ... more Expanded graphite oxide (GO) synthesized by graphite oxidation and thermal expansion was exposed to ultrasonic vibration to obtain graphite nanoplatelets (GNFs). Then, expanded GO as conductive filler was dispersed in polypyrrole matrix in order to be utilized as catalyst support. Electrical conductivities and polymer thickness of GNF-based composites were tailored at different feeding mass ratios. Thermal expansion led to the removal of oxygen functional groups on the surface, and the C/O ratio increased to 6. The highest C/O ratio had less hydrophilic carbon surface, and this decreased the interaction of Pt particles with support. When comparing Pt deposition behavior of GO, expanded GO, graphene nanosheets, and their composites, the results showed that Pt dispersion increased with increasing amount of oxygen functional groups on the surface of the samples. This work was the first comprehensive and quantitative investigation on the relationship between Pt dispersion and surface oxygen functional groups of graphene-based nanocomposites.
Boron is an essential element for plant growth, but it may also result in toxicity when present i... more Boron is an essential element for plant growth, but it may also result in toxicity when present in excessive amounts. In this study, continuous polymer enhanced ultrafiltration (PEUF) was developed to selectively recover aqueous boron species (collectively termed "boron" hereafter) from solution. The PEUF process consisted of complexing boron to a water-soluble polymer, removing all non-complexed solutes by UF, restoring the unloaded polymer, and isolating the newly freed boron by UF. Three different polymers were synthesized to complex boron. One was derived from N-meth-yl-D-glucamine (P1). Two others were derived from iminodipropyleneglycol (P2 and P2G). Operating parameters such as the boron/polymer ratio (0.01-1), pH value (7-10), and polymer type (P1, P2, and P2G) were assessed. An increase of the pH value led to increased boron retention. As well, a decreased loading value enhanced retention. A maximum retention of 90.1% exceeded the highest values reported in the literature under similar conditions. The permeate flux remained constant at approximate to 20 L/m(2) h, and operation was unaffected by classic problems such as fouling. The results showed that continuous PEUF utilizing the above polymers could serve as an alternative method for the removal of environmental boron.
Iron oxide nanoparticles were deposited on activated carbon (AC) with the microwave hydrothermal ... more Iron oxide nanoparticles were deposited on activated carbon (AC) with the microwave hydrothermal (MH) treatment technique. The effect of heating duration and AC's oxidation on structural properties were studied. X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), focused ion beam (FIB) microscopy, Brunauer, Emmett and Teller (BET), and porous texture analyses were utilized to characterize iron oxide/AC system. XRD characterization revealed dependence of crystal structure to heating duration. BET and porous texture analyses showed some pore filling in AC, but pore volume increase in iron oxide particles. With the MH technique, porous iron oxide was obtained with a high loading value of 20.27% in just 9 min. Additionally, As(V) adsorption capacity of synthesized materials was studied. As(V) adsorption onto iron oxide deposited supports obeyed Langmuir and pseudo-second order models. Batch adsorption experiments revealed a high efficiency of As(V) removal with the MH synthesized materials. Maximum adsorption capacity was 27.78 mg/g, and for a loading of 0.75 g/L, 99.90% uptake was reached within just 5 min due to the porous nature of iron oxide. Moreover, more than 99.00% of uptake was obtained within the pH range of 6-8. The results suggest that MH synthesized iron oxide particles are promising materials for water treatment. (C) 2014 Elsevier B.V. All rights reserved.
The production of novel catalyst support materials could open up new ways to enhance the catalyti... more The production of novel catalyst support materials could open up new ways to enhance the catalytic activity by reduced catalyst loadings. Nanocomposites composed of conducting polymers reinforced with graphene nanosheets (GNS) or graphite oxide (GO) sheets can ...
Titanate nanotubes are promising materials for Li-ion battery anodes because of their special mor... more Titanate nanotubes are promising materials for Li-ion battery anodes because of their special morphology and high specific surface areas. These titanates provide high rate capability and low volume expansion upon lithiation. More importantly, their tubular structure helps the transport of ions through the crystal. In this study, we synthesized elongated titanate nanotubes and modified their interlayer distances by changing the pH (2-13). For the structural characterization XRD, BET, SEM and TEM techniques were used. In addition, the effect of interlayer distance on energy capacity and rate capability was investigated. The highest interlayer distance was obtained at pH 10 and with decreasing pH, the interlayer distance dropped until reaching a pH value of 4. Conversely, the specific surface area reached its maximum value of 204 m(2) g(-1) at a pH of 4. Different from anatase (TiO2), titanate nanotubes had broad peaks in cyclic voltammograms suggesting a pseudocapacitive behavior. The...
ABSTRACT Graphite oxide nanosheets (GO), graphene nanosheets (GNS), and nanocomposites comprising... more ABSTRACT Graphite oxide nanosheets (GO), graphene nanosheets (GNS), and nanocomposites comprising of GO or GNS coated with polypyrrole (PPy) were prepared and assessed for their ability to influence the surface deposition and growth of Pt nanoparticles. GO was obtained from graphite via oxidation and exfoliation, and GNS was obtained from GO in a subsequent reduction. Both GO and GNS were coated with PPy via in situ polymerization of pyrrole (Py), forming surface-enhanced materials. SEM, EDX, TEM, EELS, Raman, and AFM findings showed that the Pt nanoparticle loading, agglomeration size, aggregate morphology and surface dispersion varied according to the nanosheet surface, nanocomposite type, and Py/nanosheet feed ratio. Surface oxygen functionalization along GO, GNS and their nanocomposites influenced the loading, dispersivity and morphology of nanoparticle agglomerates. PPy/GO nanocomposites yielded an improved nanoagglomerate surface dispersion and loading compared to samples. The PPy-coated substrates offered a greater intrinsic propensity for redox processes, resulting in higher Pt loadings. Additionally, these nanocomposites provided more surface reduction sites compared to bare nanosheets, and the additional sites contributed towards forming smaller, more homogeneously dispersed Pt nanoparticle agglomerates. Bringing together the electrical properties of PPy and physico-mechanical traits of carbon nanosheets, it follows to reason that the nanocomposites produced, particularly GO-based nanocomposites, offer promise as a nanoparticle support material for use in catalysis, electrocatalysis, and hydrogen storage.
ABSTRACT The aim of the present paper was to measure the apparent diffusivities, Knudsen diffusiv... more ABSTRACT The aim of the present paper was to measure the apparent diffusivities, Knudsen diffusivities, pore diffusivities and activation energies of diffusion at 26–32 °C and to determine the modes of transport of some alcohols (methanol, ethanol, propanol, n-butanol) and aromatics (benzene, ethylbenzene, propylbenzene, toluene, o-xylene, m-xylene, p-xylene) into the mesoporous structure of MCM-41 synthesized. As the molecular weight of the alcohols and aromatics increased, apparent diffusivities decreased and the activation energy for diffusion increased. Lower molecular weight alcohols and aromatics had higher diffusivities compared to those with higher molecular weight alcohols at the same temperatures. The diffusion of isomeric molecules within the mesoporous channels were affected by the position of branching. The deterministic behavior depended on the molecular weight, length of side chain and ortho, meta and para isomerism of the molecule. Increasing the temperature raised the kinetic energy of the molecules, which resulted in an increase in the diffusivities of the alcohols and aromatics in MCM-41. Diffusion rate constants of alcohols and aromatics increased with increasing temperature within the range of 26–32 °C, and the rate decreased as the molecular weight of the diffusing chemical increased. The diffusion of alcohols and aromatics in MCM-41 obeyed the anomalous transport mechanism. Diffusion exponents, n, being in the range of 0.99–1.07, indicated an anomalous diffusion (non-Fickian/super-Case II) mechanism for alcohol diffusion. However, for the case of aromatics, diffusion exponents, from 0.7 to 1.00, indicated that the diffusion mechanisms were either non-Fickian or non-Fickian/super-Case II depending on the substitution to the benzene ring. Activation energies of alcohols and aromatics were also in good agreement with the values of diffusivities of alcohols and aromatics such that larger activation energies resulted in smaller diffusivities. Alcohols and aromatics with greater solubility parameters were found to have greater diffusivities.
ABSTRACT Semicokes obtained from the pyrolysis of petroleum pitches are important materials that ... more ABSTRACT Semicokes obtained from the pyrolysis of petroleum pitches are important materials that are used in the manufacture of many carbonaceous products. Therefore, new structural information of the semicokes will extend their utilization. The structural analysis of anisotropic semicokes of the pyrolysis of petroleum pitches obtained under various experimental conditions of temperature and time was investigated. The overall objective is to provide further detailed information of factors which influence formation of anisotropy or turbostratic structures in resultant semicokes. Experiments were carried out under an argon atmosphere at the temperature range of 500–1000 °C for 30, 60 and 120 min in a tube furnace. FTIR, 1H-NMR, and 13C-NMR results showed that the aromatic structure of the semicokes was increasing with respect to increasing temperature as well as increasing time. Aromaticity of the semicokes was calculated as 0.54 and 0.64, for Pitch A at 500 °C after 120 min, and Pitch B at 600 °C after 120 min, respectively. The intensity ratio between Raman “D” and “G” peaks, ID/IG (commonly used to characterize disorder in graphene structures) was observed to increase approximately linearly from 0.65 to 0.92 when the pyrolysis temperature of Pitch A was increased from 500 °C to 900 °C. XRD patterns of the semicokes showed the formation of some crystalline material with time and temperature. The average number of layers, calculated by the Debye–Scherer technique using the XRD patterns of the semicokes, was between 5 and 10. SEM images of the semicokes indicated the presence of turbostratic structures. All the results of characterizations were consistent and indicated the formation of highly amorphous hydrocarbon materials that contain turbostratic structures. Treatments at higher temperatures increased formations of aromatic structure with increased crystallinity. Temperature seemed to be the dominating parameter of the pyrolysis reactions. As the pyrolysis temperature was increased, aromatic structure formation was favored with increased crystallinity in the semicokes. We expect that findings of the present work will open new uses for the anisotropic semicokes obtained from petroleum pitches. The pitches can be widely applied to the templating synthesis of carbon nanostructures and other carbon nanomaterials.
Crystalline, high-surface-area, hexagonal mesoporous MCM-41 having uniform
pore sizes and good th... more Crystalline, high-surface-area, hexagonal mesoporous MCM-41 having uniform pore sizes and good thermal stability was successfully synthesized at 90–120C in 30 min using low-power microwave irradiation. This appears to be the first comprehensive and quantitative investigation of the comparatively rapid synthesis of mesoporous MCM-41 using low-power microwave heating of 80W (90C) and 120W (120C). The influence of reaction temperature and the duration of heating were carefully investigated, and the calcined MCM-41 materials were characterized by XRD, SEM, TEM, nitrogen adsorption, TGA, and FT-IR. The mesoporous MCM-41 product synthesized in 30 min at 120W and calcined at 550C had a very high surface area of 1438m2=g and was highly ordered, containing uniform pores with diameters in the range of 3.5–4.5 nm. The wall thickness of the materials highly depended on the power of the microwave energy used during synthesis. Synthesis of the mesoporous MCM-41 products at 120C resulted in a structure with thinner walls. The mesoporous MCM-41 materials synthesized in the present work had good thermal stability.
In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish ligni... more In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish lignites with crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH, and also lignite source on the desulphurization have been examined. The values for incubation period, pulp density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0, respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29% reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples. Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur, sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison tests and ANOVA were performed.
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Papers by Alp Yürüm
particles from the sol-gel synthesized anatase. Further treatment of nanoplates with distilled water results in crystal growth and the formation of nano structured thorn like particles. The photocatalytic antimicrobial activities of
samples were determined against Escherichia coli under solar irradiation for 4 h. It was observed that the samples treated under alkaline conditions have higher antimicrobial activity than the untreated samples.
conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol–gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with
distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coli under irradiation. It was observed that the samples treated under alkaline conditions
have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However,a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic
activity.
vibration to obtain graphite nanoplatelets (GNFs). Then, expanded GO as conductive filler was dispersed in polypyrrole matrix in
order to be utilized as catalyst support. Electrical conductivities and polymer thickness of GNF-based composites were tailored at different feeding mass ratios. Thermal expansion led to the removal of oxygen functional groups on the surface, and the C/O ratio
increased to 6. The highest C/O ratio had less hydrophilic carbon surface, and this decreased the interaction of Pt particles with support. When comparing Pt deposition behavior of GO, expanded GO, graphene nanosheets, and their composites, the results
showed that Pt dispersion increased with increasing amount of oxygen functional groups on the surface of the samples. This work was the first comprehensive and quantitative investigation on the relationship between Pt dispersion and surface oxygen functional groups of graphene-based nanocomposites.
pore sizes and good thermal stability was successfully synthesized at 90–120C
in 30 min using low-power microwave irradiation. This appears to be the first comprehensive
and quantitative investigation of the comparatively rapid synthesis of
mesoporous MCM-41 using low-power microwave heating of 80W (90C) and
120W (120C). The influence of reaction temperature and the duration of heating
were carefully investigated, and the calcined MCM-41 materials were characterized
by XRD, SEM, TEM, nitrogen adsorption, TGA, and FT-IR. The mesoporous
MCM-41 product synthesized in 30 min at 120W and calcined at 550C had a very
high surface area of 1438m2=g and was highly ordered, containing uniform pores
with diameters in the range of 3.5–4.5 nm. The wall thickness of the materials highly
depended on the power of the microwave energy used during synthesis. Synthesis of
the mesoporous MCM-41 products at 120C resulted in a structure with thinner
walls. The mesoporous MCM-41 materials synthesized in the present work had good
thermal stability.
crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize
desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH,
and also lignite source on the desulphurization have been examined. The values for incubation period, pulp
density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0,
respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29%
reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided
from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples.
Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change
in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur,
sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal
conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison
tests and ANOVA were performed.
particles from the sol-gel synthesized anatase. Further treatment of nanoplates with distilled water results in crystal growth and the formation of nano structured thorn like particles. The photocatalytic antimicrobial activities of
samples were determined against Escherichia coli under solar irradiation for 4 h. It was observed that the samples treated under alkaline conditions have higher antimicrobial activity than the untreated samples.
conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol–gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with
distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coli under irradiation. It was observed that the samples treated under alkaline conditions
have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However,a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic
activity.
vibration to obtain graphite nanoplatelets (GNFs). Then, expanded GO as conductive filler was dispersed in polypyrrole matrix in
order to be utilized as catalyst support. Electrical conductivities and polymer thickness of GNF-based composites were tailored at different feeding mass ratios. Thermal expansion led to the removal of oxygen functional groups on the surface, and the C/O ratio
increased to 6. The highest C/O ratio had less hydrophilic carbon surface, and this decreased the interaction of Pt particles with support. When comparing Pt deposition behavior of GO, expanded GO, graphene nanosheets, and their composites, the results
showed that Pt dispersion increased with increasing amount of oxygen functional groups on the surface of the samples. This work was the first comprehensive and quantitative investigation on the relationship between Pt dispersion and surface oxygen functional groups of graphene-based nanocomposites.
pore sizes and good thermal stability was successfully synthesized at 90–120C
in 30 min using low-power microwave irradiation. This appears to be the first comprehensive
and quantitative investigation of the comparatively rapid synthesis of
mesoporous MCM-41 using low-power microwave heating of 80W (90C) and
120W (120C). The influence of reaction temperature and the duration of heating
were carefully investigated, and the calcined MCM-41 materials were characterized
by XRD, SEM, TEM, nitrogen adsorption, TGA, and FT-IR. The mesoporous
MCM-41 product synthesized in 30 min at 120W and calcined at 550C had a very
high surface area of 1438m2=g and was highly ordered, containing uniform pores
with diameters in the range of 3.5–4.5 nm. The wall thickness of the materials highly
depended on the power of the microwave energy used during synthesis. Synthesis of
the mesoporous MCM-41 products at 120C resulted in a structure with thinner
walls. The mesoporous MCM-41 materials synthesized in the present work had good
thermal stability.
crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize
desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH,
and also lignite source on the desulphurization have been examined. The values for incubation period, pulp
density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0,
respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29%
reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided
from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples.
Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change
in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur,
sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal
conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison
tests and ANOVA were performed.