Showing papers by "Ray L. Frost published in 2012"

The thermal behavior of kaolinite intercalation complexes : a review

Abstract: The kaolinite intercalation and its application in polymer-based functional composites have attracted great interest, both in industry and in academia fields, since they frequently exhibit remarkable improvements in materials properties compared with the virgin polymer or conventional micro and macro-composites. Also of significant interest regarding the kaolinite intercalation complex is its thermal behavior and decomposition. This is because heating treatment of intercalated kaolinite is necessary for its further application, especially in the field of plastic and rubber industry. Although intercalation of kaolinite is an old and ongoing research topic, there is a limited knowledge available on kaolinite intercalation with different reagents, the mechanism of intercalation complex formation as well as on thermal behavior and phase transition. This review attempts to summarize the most recent achievements in the thermal behavior study of kaolinite intercalation complexes obtained with the most common reagents including potassium acetate, formamide, dimethyl sulfoxide, hydrazine and urea. At the end of this paper, the further work on kaolinite intercalation complex was also proposed.

Mechanism of interaction of hydrocalumites (Ca/Al-LDH) with methyl orange and acidic scarlet GR.

Abstract: The development of new materials for water purification is of universal importance. Among these types of materials are layered double hydroxides (LDHs). Non-ionic materials pose a significant problem as pollutants. The interaction of methyl orange (MO) and acidic scarlet GR (GR) adsorption on hydrocalumite (Ca/Al-LDH-Cl) was studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), scanning electron microscope (SEM), and near-infrared spectroscopy (NIR). The XRD results revealed that the basal spacing of Ca/Al-LDH-MO was expanded to 2.45 nm, and the MO molecules were intercalated with a interpenetrating bilayer model in the gallery of LDH, with 49° tilting angle. Yet, Ca/Al-LDH-GR was kept the same d-value as Ca/Al-LDH-Cl. The NIR spectrum for Ca/Al-LDH-MO showed a prominent band around 5994 cm(-1), assigned to the combination result of the NH stretching vibrations, which was considered as a mark to assess MO(-) ion intercalation into Ca/Al-LDH-Cl interlayers. From SEM images, the particle morphology of Ca/Al-LDH-MO mainly changed to irregular platelets, with a "honey-comb" like structure. Yet, the Ca/Al-LDH-GR maintained regular hexagon platelets, which was similar to that of Ca/Al-LDH-Cl. All results indicated that MO(-) ion was intercalated into Ca/Al-LDH-Cl interlayers, and acidic scarlet GR was only adsorbed upon Ca/Al-LDH-Cl surfaces.

Red Mud from Brazil: Thermal Behavior and Physical Properties

Abstract: The main constituents of red mud produced in Aluminio city (S.P., Brazil) are iron, aluminum, and silicon oxides. It has been determined that the average particle diameter for this red mud is between 0.05 and 0.002 mm. It is observed that a decrease in the percentage of smaller particles occurs at temperatures greater than 400 °C. This observation corresponds with the thermal analysis and X-ray diffraction (XRD) data, which illustrate the phase transition of goethite to hematite. A 10% mass loss is observed in the thermal analysis patterns due to the hydroxide–oxide phase transitions of iron (primary phase transition) and aluminum (to a lesser extent). The disappearance and appearance of the different phases of iron and aluminum confirms the decomposition reactions proposed by the thermal analysis data. This Brazilian red mud has been classified as mesoporous at all temperatures except between 400 and 500 °C where the classification changes to micro/mesoporous.

Nitrate reduction over nanoscale zero-valent iron prepared by hydrogen reduction of goethite

Abstract: Nitrate reduction with nanoscale zero-valent iron (NZVI) was reported as a potential technology to remove nitrate from nitrate-contaminated water. In this paper, nitrate reduction with NZVI prepared by hydrogen reduction of natural goethite (NZVI-N, -N represents natural goethite) and hydrothermal goethite (NZVI-H, -H represents hydrothermal goethite) was conducted. Besides, the effects of reaction time, nitrate concentration, iron-to-nitrate ratio on nitrate removal rate over NZVI-H and NZVI-N were investigated. To prove their excellent nitrate reduction capacities, NZVI-N and NZVI-H were compared with ordinary zero-valent iron (OZVI-N) through the static experiments. Based on all above investigations, the mechanism of nitrate reduction with NZVI-N was proposed. The result showed that reaction time, nitrate concentration, iron-to-nitrate ratio played an important role in nitrate reduction by NZVI-N and NZVI-H. Compared with OZVI, NZVI-N and NZVI-H showed little relationship with pH. And NZVI-N for nitrate composition offers a higher stability than NZVI-H because of the existence of Al-substitution. Furthermore, NZVI-N, prepared by hydrogen reduction of goethite, has higher activity for nitrate reduction and the products contain hydrogen, nitrogen, NH 4 +, a little nitrite, but no NOx, meanwhile NZVI-N was oxidized to Fe 2+. It is a relatively easy and cost-effective method for nitrate removal, so NZVI-N reducing nitrate has a great potential application in nitrate removal of groundwater. © 2012 Elsevier B.V.

Sulfate intercalated layered double hydroxides prepared by the reformation effect

Abstract: The removal of the sulfate anion from water using synthetic hydrotalcite (Mg/Al LDH) was investigated using powder X-ray diffraction (XRD) and thermogravimetric analysis (TG). Synthetic hydrotalcite Mg6Al2(OH)16(CO3)·4H2O was prepared by the co-precipitation method from aluminum and magnesium chloride salts. The synthetic hydrotalcite was thermally activated to a maximum temperature of 380 °C. Samples of thermally activated hydrotalcite where then treated with aliquots of 1000 ppm sulfate solution. The resulting products where dried and characterized by XRD and TG. Powder XRD revealed that hydrotalcite had been successfully prepared and that the product obtained after treatment with sulfate solution also conformed well to the reference pattern of hydrotalcite. The d(003) spacing of all samples was found to be within the acceptable region for a LDH structure. TG revealed all products underwent a similar decomposition to that of hydrotalcite. It was possible to propose a reasonable mechanism for the thermal decomposition of a sulfate containing Mg/Al LDH. The similarities in the results may indicate that the reformed hydrotalcite may contain carbonate anion as well as sulfate. Further investigation is required to confirm this.

Catalytic cracking of tar derived from rice hull gasification over palygorskite-supported Fe and Ni

Abstract: The catalytic performance of Fe–Ni/PG (PG: palygorskite) catalysts pre-calcined and reduced at 500 °C for catalytic decomposition of tar derived through rice hull gasification was investigated. The materials were characterized by using X-ray diffraction, hydrogen temperature reduction, and transmission electron microscopy. The results showed that ferrites with spinel structure ((Fe, Ni)3O4) were formed during preparation of bimetallic systems during calcination and reduction of the precursors (Fe–Ni/PG catalysts) and NiO metal oxide particles were formed over Fe6–Ni9/PG catalyst. The obtained experimental data showed that Fe–Ni/PG catalysts had greater catalytic activity than natural PG. Tar removal using Fe6–Ni9/PG catalyst was as high as Fe10–Ni6/PG catalyst (99.5%). Fe6–Ni9/PG showed greater catalytic activity with greater H2 yield and showed stronger resistance to carbon deposition, attributed to the presence of NiO nanoparticles. Thus, the addition of nickel and iron oxides played an important role in catalytic cracking of rice hull biomass tar.

Catalytic cracking of tar derived from rice hull gasification over palygorskite-supported Fe and Ni

Abstract: The catalytic performance of Fe–Ni/PG (PG: palygorskite) catalysts pre-calcined and reduced at 500 ◦C for catalytic decomposition of tar derived through rice hull gasification was investigated. The materials were characterized by using X-ray diffraction, hydrogen temperature reduction, and transmission electron microscopy. The results showed that ferrites with spinel structure ((Fe, Ni)3O4) were formed during preparation of bimetallic systems during calcination and reduction of the precursors (Fe–Ni/PG catalysts) and NiO metal oxide particles were formed over Fe6–Ni9/PG catalyst. The obtained experimental data showed that Fe–Ni/PG catalysts had greater catalytic activity than natural PG. Tar removal using Fe6–Ni9/PG catalyst was as high as Fe10–Ni6/PG catalyst (99.5%). Fe6–Ni9/PG showed greater catalytic activity with greater H2 yield and showed stronger resistance to carbon deposition, attributed to the presence of NiO nanoparticles. Thus, the addition of nickel and iron oxides played an important role in catalytic cracking of rice hull biomass tar.

A thermoanalytical assessment of an organoclay

Abstract: High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications. In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition. There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important in the synthesis and processing of organoclays for environmental applications.

Effect of preparation method of palygorskite-supported Fe and Ni catalysts on catalytic cracking of biomass tar

Abstract: In this study, the effect of catalyst preparation and additive precursors on the catalytic decomposition of biomass using palygorskite-supported Fe and Ni catalysts was investigated. The catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is concluded that the most active additive precursor was Fe(NO3)3·9H2O. As for the catalyst preparation method, co-precipitation had superiority over incipient wetness impregnation at low Fe loadings.

Zinc aluminium layered double hydroxides for the removal of iodine and iodide from aqueous solutions

Abstract: 129I is a radioactive isotope of iodine that is readily absorbed by the body In this paper we investigated the potential of a 3:1 Zn/Al layered double hydroxide (LDH) as a sorbent for the removal of iodine and iodide from water Synthetic Zn6Al2(OH)16(CO3)·4H2O was prepared by the co-precipitation before thermal activation The LDH was treated with solutions containing iodide and iodine It was found that iodine could be more easily removed from solution than iodide Powder X-ray diffraction revealed the destruction of the LDH structure during thermal activation and the successful reformation of a similar LDH material after treatment with the iodide or iodine solution Thermal decomposition of all samples studied by thermogravimetry appeared to be similar A new decomposition mechanism similar to one previously described in the literature was proposed for the Zn/Al LDH The total mass loss of samples treated with iodide and iodine was signifi cantly lower than that of the original LDH indicating

Thermal stability of organoclays with mono- and di-alkyl cationic surfactants

Abstract: In this study, mono- and di-alkyl cationic surfactants were used to prepare organoclays through ion exchange and the prepared organoclays were characterised by X-ray diffraction (XRD) and thermogravimetric analysis (TG). Larger basal spacings were observed in the interlayer of the organoclays intercalated with DDDMA than organoclays intercalated with DDTMA. The DTG curves identify the thermal stability of organoclays intercalated with two different types of surfactants (DDTMA and DDDMA) and the different arrangements of the surfactant molecules intercalated in the montmorillonite. Both organoclays intercalated with organic surfactant molecules proved to be thermally stable at high temperature. This study provides an understanding of the structure and properties of organoclays, which will enhance the potential applications of organoclays in environmental remediation.

Effect of aging time and Al substitution on the morphology of aluminous goethite.

Abstract: Goethite and Al-substituted goethite were synthesized from the reaction between ferric nitrate and/or aluminum nitrate and potassium hydroxide. XRF, XRD, TEM with EDS were used to characterize the chemical composition, phase and lattice parameters, and morphology of the synthesized products. The results show that d(020) decreases from 4.953 to 4.949 A and the b dimension decreases from 9.951 A to 9.906 A when the aging time increases from 6 days to 42 days for 9.09 mol% Al-substituted goethite. A sample with 9.09 mol% Al substitution in Al-substituted goethite was prepared by a rapid co-precipitation method. In the sample, 13.45 mol%, 12.31 mol% and 5.85 mol% Al substitution with a crystal size of 163, 131, and 45 nm are observed as shown in the TEM images and EDS. The crystal size of goethite is positively related to the degree of Al substitution according to the TEM images and EDS results. Thus, this methodology is proved to be effective to distinguish the morphology of goethite and Al substituted goethite.

Raman spectroscopy of synthetic CaHPO4·2H2O– and in comparison with the cave mineral brushite

Abstract: The mineral brushite has been synthesised by mixing calcium ions and hydrogen phosphate anions to mimic the reactions in caves. The vibrational spectra of the synthesised brushite were compared with that of the natural cave mineral. Bands attributable to the PO43– and HPO42– anions are observed. Brushite, both synthetic and natural, is characterised by an intense sharp band at 985 cm−1 with a shoulder at 1000 cm−1. Characteristic bending modes are observed in the 300 to 600 cm−1 region. The spectra of the synthesised brushite matches very well the spectrum of brushite from the Moorba Cave, Western Australia. Copyright © 2011 John Wiley & Sons, Ltd.

Sulfated fibrous ZrO2/Al2O3 core and shell nanocomposites: A novel strong acid catalyst with hierarchically macro–mesoporous nanostructure

Abstract: A series of solid strong acid catalysts were synthesized from fibrous ZrO 2 /Al 2 O 3 core and shell nanocomposites. In this series, the zirconium molar percentage was varied from 2% to 50%. The ZrO 2 /Al 2 O 3 nanocomposites and their solid strong acid counterparts were characterised by a variety of techniques including 27 Al magic angle spinning nuclear magnetic resonance (MAS-NMR), scanned electronic microscopy (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and infrared emission spectroscopy (IES). NMR results show that the interaction between zirconia species and alumina strongly correlates with pentacoordinated aluminium sites. This can also be detected by the change in binding energy of the 3d electrons of the zirconium. The acidity of the obtained solid acids was tested by using them as catalysts for the benzoylation of toluene. It was found that a sample with a 50% zirconium molar percentage possessed the highest surface acidity equalling that of pristine sulfated zirconia despite the reduced mass of zirconia.

Recent Advances in Catalytic/Biocatalytic Conversion of Greenhouse Methane and Carbon Dioxide to Methanol and Other Oxygenates

Abstract: Methane gas has been identified as the most destructive greenhouse gas (Liu et al., 2004). It was reported that the global warming potential of methane per molecule relative to CO2 is approximately 23 on a 100-year timescale or 62 over a 20-year period (IPCC, 2001). Methane has high C-H bond energy of about 439 kJ/mol and other higher alkanes (or saturated hydrocarbons) also have a very strong C-C and C-H bonds, thus making their molecules to have no empty orbitals of low energy or filled orbitals of high energy that could readily participate in chemical reactions as is the case with unsaturated hydrocarbons such as olefins and alkynes (Crabtree, 1994; Labinger & Bercaw, 2002)...

Thermal Stability of newberyite Mg(PO3OH)·3H2O

Abstract: The mineral newberyite Mg(PO3OH)·3H2O is a mineral that has been found in caves such as the Skipton Lava Tubes (SW of Ballarat, Victoria, Australia), Moorba Cave, (Jurien Bay, Western Australia) and in the Petrogale Cave (Madura, Eucla, Western Australia). Since these minerals contain water, the minerals lend themselves to thermal analysis. The mineral newberyite is found to decompose at 145 °C with a water loss of 31.96%, a result which is very close to the theoretical value. The result shows that the mineral is not stable in caves where the temperature exceeds this value. The implication of this result rests with the removal of kidney stones, which have the same composition as newberyite. Point heating focussing on the kidney stone results in the destruction of the kidney stone.

Raman spectroscopy of synthetic CaHPO4•2H2O– and in comparison with the cave mineral brushite

Abstract: The mineral brushite has been synthesised by mixing calcium ions and hydrogen phosphate anions to mimic the reactions in a Cave. The vibrational spectra of the synthesised brushite were compared with that of the natural Cave mineral. Bands attributable to the PO43- and HPO42- anions are observed. Brushite, both synthetic and natural, is characterised by an intense sharp band at 985 cm-1 with a shoulder at 1000 cm-1. Characteristic bending modes are observed in the 300 to 600 cm-1 region. The spectra of the synthesised brushite matches very well the spectrum of brushite from the Moorba Cave, Western Australia.

Catalytic cracking of tars derived from rice hull gasification over goethite and palygorskite

Abstract: Palygorskite (P), goethite (G), and hydrothermally synthesized goethite (HG) were used as supports for Fe and Ni. The catalytic activity of these materials was investigated involving in P, G and HG (supported Fe and Ni) for catalytic decomposition of biomass tar derived from rice hull gasification. The materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and transmission electron microscopy (TEM) with an energy dispersive X-ray (EDS). The catalytic activity of P for removal of tar was significantly better than that of G and HG. However, the activity of G with 6 mass% Ni labeled as Ni6/G (tar conversion 94.6%), which was equal to Fe6Ni6/P (94.4%), was better than Ni6/P (64.4%) and Ni6/HG (46.7%). When the loading of Ni (mass%) was 6 mass% on G, tar conversion had the best value (94.6%) and yield of gaseous products reached 486.9, 167.8 and 22.2 mL/(g·tar) for H2, CO, CH4, respectively. The catalytic activity of goethite supported Ni was better in improving tar conversion and improving increased yield of H2, CO, CH4, which was attributed to the existence of Al/Fe substitution of goethite