177 research outputs found

    Low temperature wet oxidation and catalytic wet oxidation of specific organic compounds in highly alkaline solution (synthetic Bayer liquor)

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    Low temperature (165°C) Wet Oxidation (WO) and Catalytic Wet Oxidation (CWO) of 12 organic compounds has been studied in highly alkaline, high ionic strength solution (simulating that encountered in the Bayer process used to refine alumina) for the first time. Most (11 out of 12) of the 12 organic compounds studied (formic, acetic, propionic, butyric, oxalic, malonic, succinic, glutaric, citric, lactic, malic and tartaric acids) have been identified in various worldwide Bayer liquors. The various aspects of WO and CWO studied for each of the above-mentioned compounds were as follows; -Extent of complete oxidation to carbonate (i.e. extent of removal of organic compound) -Extent of overall oxidation (i.e. extent of complete oxidation and partial oxidation to stable products) -The product(s) formed from partial (incomplete) oxidation -The reaction mechanism occurring -Why certain compounds undergo low temperature WO and/or CWO in highly alkaline, high ionic strength solution -The ability of various transition metal oxides to catalyse the WO of the selected organic compounds Of the 12 organic compounds studied only six (formic, malonic, citric, lactic, malic and tartaric acids) underwent appreciable (>2% overall oxidation) WO in isolation under the reaction conditions used (4.4 -7.0 M NaOH, 165°C, 500 kPa Po‚āā, 2 hours). Each of these six compounds underwent some complete oxidation and therefore can be partly removed from highly alkaline, high ionic strength solution using low temperature WO. The order of extent of complete oxidation determined was as follows tartaric> citric> malonic> formic> lactic> malic. All of these compounds also underwent some partial oxidation under the reaction conditions used, excluding formic acid, which only underwent complete oxidation. Oxalic acid was a major product of partial oxidation of all of the above-mentioned compounds (excluding formic acid), while acetic acid was a major product of partial oxidation of citric, lactic, malic and tartaric acids. The WO of formic, malonic, citric, lactic, malic and tartaric acids varied considerably with NaOH concentration over the NaOH concentration range studied (4.4 - 7.0 M). The extent of overall oxidation undergone by each of these compounds increased significantly with increasing NaOH concentration. All of the compounds that underwent appreciable WO under the reaction conditions studied contained hydrogen(s) significantly more acidic then the compounds that did not undergo appreciable WO, thus indicating that only organic compounds that contain acidic (albeit weakly acidic) hydrogens undergo low temperature (165°C) WO in highly alkaline, high ionic strength solution. Two different reaction mechanisms were identified to occur during low temperature WO in highly alkaline, high ionic strength solution. Malonic and formic acids underwent WO predominantly via a free radical based reaction mechanism, while citric, lactic, malic and tartaric acids underwent WO predominantly via an ionic based reaction mechanism. The six organic compounds that did not undergo appreciable WO in isolation (acetic, propionic, butyric, oxalic, succinic and glutaric acids) all underwent appreciable WO when in the presence of malonic acid undergoing low temperature WO. Hence, low temperature WO of all of the above-mentioned compounds can be initiated by free radical intermediates produced by malonic acid undergoing WO in highly alkaline, high ionic strength solution. The ability of several transition metal oxides to catalyse the WO of the chosen 12 organic compounds was investigated. Of the transition metal oxides studied CuO was clearly the most active. Five of the organic compounds studied (malonic, citric, lactic, malic and tartaric acids) were catalytically wet oxidised by CuO in highly alkaline, high ionic strength solution in isolation. The order of catalytic activity observed was malonic > tartaric> lactic> malic> citric. Two different catalytic reaction mechanisms were identified for CuO catalysed WO in highly alkaline solution for the organic compounds studied. CuO catalysed the WO of malonic acid predominantly by catalysing the formation of free radical intermediates. CuO catalysed the WO of citric, lactic, malic and tartaric acids predominantly via a complexation-based reaction mechanism

    An investigation on the role of ytterbium in ytterbium promoted y-alumina-supported nickel catalysts for dry reforming of methane

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    Addition of low quantities of ytterbium to sol-gel prepared Ni/yAl2O3 catalysts has been shown to lead to significant increases in catalytic activity and long term stability in the catalytic conversion of CO2 and CH4 into syngas (H2 and CO). The role of ytterbium in these catalysts was investigated in this study through detailed investigations on the structure and composition of ytterbium promoted Ni/y-Al2O3 catalysts using the following techniques: synchrotron X-ray diffraction, X-ray Photoemission Spectroscopy, Transmission Electron Microscopy, Scanning Electron Microscopy/Energy Dispersive X-ray analysis, Temperature Programmed Reduction techniques and N2 adsorption-desorption isotherms. The results obtained indicated that ytterbium, at small quantities (up to 2 wt%), interacted strongly with the support which in turn altered the interaction between nickel and the support (most notably it was found to completely inhibit the formation of NiAl2O4). This decreased interaction between Ni and the support also led to a higher quantity of Ni being present in the catalyst in the form of Ni

    Electro-deposition of gold nano-structures on gold Quartz Crystal Microbalance (QCM) electrodes for enhanced mercury vapour sensitivity in the presence of interferent gasses

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    Gold electrode quartz crystal microbalances (QCMs) were used as transducing platform to detect and sense elemental mercury (Hg) in gas phase. The enhanced sensitivity, resulting form the electro-deposition of gold nano-structures on the surface is shown to increase the response magnitude (RM) of the sensors in the presence of ammonia and humidity interference. The concentration of NH3 and H2O was varied in the range 590 to 1770mg/m3 and 4.2 to 10.4mg/m3, respectively. A constant gas flow of 200sccm, balanced in nitrogen was used as the carrier gas. The RM for Hg was enhanced by creating nanostructures on the sensorpsilas gold electrodes via electro-deposition of gold in a lead acetate electrolyte. The results presented are a critical step in the development of a cheap regenerable and reliable sensor for measuring Hg in the presence of interferents gases commonly found in industrial applications

    Characterisation of a uranium ore using multiple X-ray diffraction based methods

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    Uranium bearing ores are often a complex mixture of minerals and compounds, a number of which are not of economic importance and are commonly referred to as gangue materials. In order to improve the efficiency of the dissolution stage of the overall uranium extraction process, a greater understanding of the minerals and compounds present in the ore is required. A greater knowledge of the gangue materials present is important as they can influence various aspects of the dissolution process such as providing potential adsorption sites for aqueous uranium species and through influencing the equilibrium of reactions involving aqueous uranium species. In this study the mineralogy of a uranium ore was investigated using a range of X-ray diffraction (XRD) based methods including in situ high temperature XRD and XRD using a synchrotron beam line. The results obtained from standard XRD (Cu Ka), high temperature XRD and synchrotron XRD (16.534 keV) were compared and a number of minerals were identified. The improved spatial resolution and intensity of the synchrotron data allowed for superior phase identification of a variety of minerals where standard X-ray techniques gave inconclusive results

    Ni/H-ZSM-5 as a stable and promising catalyst for COx free H2 production by CH4 decomposition

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    Catalytic decomposition of methane for COx free hydrogen production is carried out over Ni supported on H-ZSM-5 catalysts with different Si/Al ratios (i.e. 40, 150, 300 and 485) at 550 ¬įC and atmospheric pressure. Methane decomposition activity of Ni/H-ZSM-5 is decreased with time on stream and finally deactivated completely. The fresh and reduced catalysts are characterized by BET-SA, XRD, FT-IR, UV-DRS, TPR, pulse chemisorption of H2 and N2O and some of the used catalysts are characterised by CHNS, SEM, TEM and Raman spectroscopy. Raman spectra of the used catalysts showed both ordered and disordered carbon at 1580 cm-1 and 1320 cm-1. The 20 wt% Ni/H-ZSM-5 (Si/Al = 150) exhibited a higher H2 production rate over the other Ni loadings. The superior performance of 20 wt% Ni/H-ZSM-5 (Si/Al = 150) is rationalized by the physico-chemical properties of the various Ni loaded H-ZSM-5 catalysts

    Soil and water bioengineering: practice and research needs for reconciling natural hazard control and ecological restoration

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    Soil and water bioengineering is a technology that encourages scientists and practitioners to combine their knowledge and skills in the management of ecosystems with a common goal to maximize benefits to both man and the natural environment. It involves techniques that use plants as living building materials, for: (i) natural hazard control (e.g., soil erosion, torrential floods and landslides) and (ii) ecological restoration or nature-based re-introduction of species on degraded lands, river embankments, and disturbed environments. For a bioengineering project to be successful, engineers are required to highlight all the potential benefits and ecosystem services by documenting the technical, ecological, economic and social values. The novel approaches used by bioengineers raise questions for researchers and necessitate innovation from practitioners to design bioengineering concepts and techniques. Our objective in this paper, therefore, is to highlight the practice and research needs in soil and water bioengineering for reconciling natural hazard control and ecological restoration. Firstly, we review the definition and development of bioengineering technology, while stressing issues concerning the design, implementation, and monitoring of bioengineering actions. Secondly, we highlight the need to reconcile natural hazard control and ecological restoration by posing novel practice and research questions

    Process design for the manufacturing of soft X-ray gratings in single-crystal diamond by high-energy heavy-ion irradiation

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    This paper describes in detail a novel manufacturing process for optical gratings suitable for use in the UV and soft X-ray regimes in a single-crystal diamond substrate based on highly focused swift heavy-ion irradiation. This type of grating is extensively used in light source facilities such as synchrotrons or free electron lasers, with ever-increasing demands in terms of thermal loads, depending on beamline operational parameters and architecture. The process proposed in this paper may be a future alternative to current manufacturing techniques, providing the advantage of being applicable to single-crystal diamond substrates, with their unique properties in terms of heat conductivity and radiation hardness. The paper summarizes the physical principle used for the grating patterns produced by swift heavy-ion irradiation and provides full details for the manufacturing process for a specific grating configuration, inspired in one of the beamlines at the ALBA synchrotron light source, while stressing the most challenging points for a potential implementation. Preliminary proof-of-concept experimental results are presented, showing the practical implementation of the methodology proposed herein

    Comparison of some chemical parameters of a naturally debittered olive (Olea europaea L.) type with regular olive varieties

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    Some olives grown in Karaburun peninsula in the west part of Turkey and mostly coming from Erkence variety lose their bitterness while still on the tree and are called Hurma among locals. This olive type does not require further processing to remove the bitter compounds. In this study, sugar, organic acid and fatty acid profiles of Hurma, Erkence (not naturally debittered) and Gemlik (commonly consumed as table olive) olives were determined throughout 8 weeks of maturation period for two consecutive harvest seasons, and the results were analysed by principal component analysis (PCA). PCA of sugar and organic acid data revealed a differentiation in terms of harvest year but not on variety. Hurma olive is separated from others due to its fatty acid profile, and it has higher linoleic acid content compared to others. This might be an indication of increased desaturase enzyme activity for Hurma olives during natural debittering phase.TUBITAK (TOVAG-110O780

    Wild food plants of popular use in Sicily

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    In the present work the authors report the result of their food ethnobotanical researches, which have been carried out in Sicily during the last thirty years. Data concerning 188 wild species used in the traditional Sicilian cuisine are reported. The authors underline those species that are partially or completely unknown for their culinary use and they illustrate other species that local inhabitants suggested in the prevention or treatment of symptomatologies caused by a refined diet, poor in vegetables. These data want to contribute to avoid the loss of traditional knowledge on uses and recipes concerning wild food botanicals, and to encourage further studies for those species that have not yet been sufficiently researched in their food chemical and nutritional profile. These studies may also suggest new applications for a few botanicals in medico-nutritional fields. The work includes also a short review of the seaweeds and mushrooms traditionally gathered and consumed in Sicily
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