Location Of Cu Research Articles

Smart and responsive zeolite catalysts for toluene “storage-oxidation” cycling removal

“Storage - oxidation” cycling provides a novel and efficient route for VOCs’ removal. Herein, Cu and Ag modified β zeolite with different SiO2/Al2O3 ratio were prepared as smart and responsive materials for toluene removal. The storage strength for toluene on the metal sites (ion-exchange sites, metallic clusters and nanoparticles) and zeolite substrate (acid sites and channels) were discriminated, and the corresponding regeneration either by in-situ thermal oxidation or plasma assisted oxidation was coupled to fulfill the “storage-oxidation” cycle. By virtue of the collaboration of identified Cu2+ and Ag+ for toluene storage, a Cu2.0Ag3.0/β-25 catalyst was designed with high storage capacity (0.41 mmol/g) and adequate strength for trapping toluene, being available for in-situ thermal regeneration. In this study, the location of Cu and Ag species in β zeolite has been modulated to enable such smart and responsive materials available for toluene “storage and in-situ oxidation” cycling, which provides a general guidance for BTEX elimination.

Insight into the relationship between effective active sites and ultra-deep adsorption desulfurization performance of CuCeY with different Cu precursors

Adsorption desulfurization processes employing zeolites as sorbents are considered to be prospective desulfurization methods owing to their cost-effectiveness.Y zeolites modified with Cu and Ce have excellent adsorption capacity and selectivity for adsorption desulfurization. However, the effect of using different metal precursors on the active sites of these sorbents and their adsorption desulfurization performance still remains ambiguous, which impedes the development of improved desulfurization adsorbents. Herein, Cu(NO3)2, Cu(Ac)2, and CuSO4 were selected as Cu precursors to prepare a series of CuCeY from CeY zeolite. Desulfurization experimental results indicate that outstanding breakthrough adsorption capacities for thiophene (ca. 6.25 mg·g−1) with benzene as the solvent were achieved by the CuCeYA. The interaction between the CuCe metals was beneficial for enhancing the electron transfer between Cu2++Ce3+/Ce4++Cu+. Moreover, using different copper precursors significantly changed the redox ability of the adsorbent surface. Changing the copper precursor also had a significant effect on the locations of Cu and Ce ions, and using Cu(Ac)2 as a metal precursor facilitated the migration of Cu+ (53.6%) and cerium species (35.9%) to the supercage. In situ infrared characterization showed that the oligomerization of thiophene on CuCeYA was significantly restricted due to the lowest B acid content (11.85%) in the CuCeYA.

Bioimaging tools reveal copper processing in fish cells by mitophagy

As an essential trace metal, copper (Cu) regulation, distribution and detoxification among different cellular organelles remain much unknown. In the current study, bioimaging tool was used in visualizing the locations of Cu among different organelles in fish fin cells isolated from rabbitfish Siganus fuscescens. Exposure concentration of Cu directly affected the Cu bioaccumulation and toxicity. When the exposure dosage of Cu reached 100 µM, it began to damage the cells and affect the cell viability after 10 min of exposure. Remarkably, while various Cu concentrations (50∼150 µM) initially reduced the cell viability, they did not lead to a further loss in viability over extended exposure period. Upon entry to the cells, Cu was mainly targeted to the mitochondria whose number, size and network responded immediately to the incoming Cu. However, Cu toxicity did not increase time-dependently, strongly indicating that these mitochondria damaged by Cu could be removed and its cytotoxicity could be relieved. Bioimaging results showed that lysosomes interacted with the mitochondria, which were subsequently digested within a few minutes. Meanwhile the lysosomal number increased, and the size and pH of lysosomes decreased. These reactions were in line with the observed mitophagy, suggesting that mitochondrial Cu could be detoxified, and the damaged mitochondria were removed by lysosome via mitophagy. By further purifying the cellular organelles, the mitochondrial and lysosomal Cu amounts were quantified and found to be in line with the imaging results. The present study suggested that excessive mitochondrial Cu could be removed via mitophagy to relieve the Cu toxicity.

Highly enhanced thermal conductivity of TPU composites with segregated network constructed by the in-situ reduction of copper

Cu@TPU composite particles with a structure of TPU core and Cu particles shell were fabricated by in-suite reduction of Cu on the surface of TPU granules. The Cu@TPU composites were then prepared by the hot compression of the as-prepared core-shell particles. The Cu@TPU composite granules were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy, which verified that the outer layer of core-shell structure was Cu particles and the connection between Cu and TPU was chemical bonding. The cross-section of Cu@TPU composites showed typical pattern of segregated structure and the surface of those was covered by a layer of Cu particles. With the stacking effect of the special location of Cu and the chemical connection between Cu and TPU, the Cu@TPU composites exhibited a high thermal conductivity of 3.2146 W/m K at 23 vol% filler loading, which was 2.6 times to that of Cu/TPU composites fabricated through simple blending. The TC data of the composites were correlated with Foygel’s model. In addition, the dielectric properties and electrical conductivity of the composites were measured.

Structural and electrical properties of Mg–Cu- and Mg–Cu–Li-doped bismuth niobate semiconductors with the pyrochlore structure

This work studies a series of synthesized Bi1.6Mg0.8-xCuxNb1.6O7-δ (x = 0.2, 0.4) semiconductors and their Li-doped compositions. A detailed structure investigation combining high-resolution neutron-, synchrotron-, and X-ray diffraction methods, as well as DFT calculations, revealed the preferential location of Cu and Li atoms at the Bi sites and Mg atoms at the Nb ones. According to high-temperature X-ray diffraction data, a structural modification caused by the activation of oxygen transport occurs at 200 °C. The linear thermal expansion coefficient was found to be 3.6–4.6·10−6 K−1 (50–400 °C). Magnetic susceptibility measurements allowed us to determine weak antiferromagnetic exchange interactions. The direct band gap was predicted using the DFT-HSE03 hybrid functional calculation, and the optical direct band gap was estimated at 2.3–2.4 eV. Impedance spectroscopy and a dc four-probe technique were also employed to examine the samples' electrical properties. The high mixed electronic-ionic conductivity of the pyrochlores was detected, while the vacancies created by Li-doping in Bi1.5-yLiyMg0.375Cu0.375Nb1.5O7-δ have been found not to affect the conductivity. Besides, the pyrochlores are chemically compatible with the La0.7Sr0.3MnO3 perovskite (up to 800 °C). These make us believe that the studied Mg–Cu- and Mg–Cu–Li-doped bismuth niobate semiconductors can become the basis for composite electrodes to boost their oxygen conductivity.

Multiple incorporation of copper and iron ions into the channel of hydroxyapatite

As a way of tuning the composition of hydroxyapatite (Ca10(PO4)6(OH)2), metal ion incorporation into the hexagonal channel has been studied less than conventional isomorphous substitutions. In the present study, we successfully incorporated multiple metal ions into the hexagonal channel of hydroxyapatite by loading an aqueous solution containing Cu and Fe and subsequent heat treatment. The incorporation of multiple metal ions was confirmed by infrared spectroscopy, Raman spectroscopy and X-ray diffraction analysis combined with the Rietveld refinement. The composition of synthesized hydroxyapatite with the maximum content of multiple metal ions in the channel was Ca10(PO4)6Cu0.3Fe0.3OzHa. The location of Cu in the channel was revealed to be not affected by Fe in the channel and vice versa. In addition, deposition of the metal ions from the channel by heat treatment was examined for possible decoration of the hydroxyapatite by double-oxide nanoparticles.

Quasicrystal stability in complex aluminum alloys: Insights from first principles models on structural motifs in crystalline approximants

Al81Cu7Fe4Cr8 is an alloy that readily forms quasicrystalline phases but understanding the complex atomic arrangements in the structure of such quasicrystals is challenging. For the Al-Cu-Fe-Cr system, the structures of crystalline approximants have been identified. These exhibit atomic motifs similar to those for the quasicrystalline configurations. We employ here a comprehensive methodology to analyze statistically generated ground states of orthorhombic approximants using density functional theory to shed light on the role of elemental variations of such complex alloys. Our findings show that the stability of QC approximants has a strong dependence on the specific locations of Cu and Cr atoms. The geometry of the atomic motifs from structural optimization suggests that the icosahedral phase is more favorable than the decagonal phase. The formation energy difference between these is small which indicates that the two quasicrystalline phases may coexist.

Iranian regional l ament zones and the location of Cu, Pb, Zn and Fe deposits

Background. Large-scale geological structures, such as lineaments, are of great research interest due to their potential to mark the presence of ore fields.Aim. To determine the relationship between ore deposits, lineaments and large-scale faults in Iran using satellite imagery, digital relief modelling and structural mapping.Materials and methods. In this study, we compiled a map of lineaments in the Iran, which were determined both automatically and manually. A database of the distribution of ore deposits and lineaments was compiled from available maps, publications and reports on ore deposits in Iran. These maps were overlaid to study the relationship between the locations of the lineaments, faults and ore deposits.Results. An analysis of the lineaments revealed on geological maps indicates the presence of four dominant strike directions of large and small lineaments. The developed lineament map shows the main northwest trending longitudinal faults, which are parallel to the main strike of the Zagros orogenic belt; sublatitudinal and submeridional trending oblique faults; northeast trending transverse faults. A “Combined map of lineaments and deposits of copper, lead, zinc and iron in Iran” was compiled by the ArcGis software using maps of lineaments and mineral deposits. The ore deposits identified were analysed to determine the distribution of the distances between each deposit using the counting and cumulative methods the ArcGis software.Conclusions. About 90% and 50% of ore deposits are located at a distance of less than 15 km and 5 km, respectively, from the centre line of the associated lineament. A direct relationship between the density of lineaments and the presence of deposits was observed. The obtained results demonstrate the potential of this method for assessing the prospects of ore fields in hard-to-reach and poorly studied regions.

Novel synthesis of fly-ash-derived Cu-loaded SAPO-34 catalysts and their use in selective catalytic reduction of NO with NH3

A combined acid–alkali hydrothermal method was used to prepare fly ash –derived SAPO-34 molecular sieves from a thermal power plant in Inner Mongolia (China). The specific surface area of the prepared fly-ash-derived SAPO-34 molecular sieves was 579 m2 g−1, the total pore volume was about 0.27 cm3 g−1, and the pore size was 0.56 nm; the molar ratios of Al2O3:P2O5:SiO2 were 1:0.86:0.45. Cu/SAPO-34 catalysts were prepared by impregnation of low-cost fly-ash-derived SAPO-34 molecular sieves as a support and tested in selective catalytic reduction with NH3 (NH3-SCR). Powder X-ray diffraction (XRD), N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), X-ray fluorescence analysis (XRF) and scanning electron microscopy (SEM) were used for catalyst characterization and investigation of the relationships between the catalyst structure and the catalytic activity. The actual silica:alumina ratio of the molecular sieves did not increase with increasing Cu loading, indicating that increasing the Cu loading does not change the original structure of the SAPO-34 molecular sieves. The XRF and NMR results showed that replacement by Cu results in more Si islands. The molecular sieve acidity decreased because of the increased number of Si islands. The NH3-TPD results showed that for the Cu/SAPO-34 catalysts there was a low correlation between the low-temperature activity and the amount of acidic sites. SCR activity is closely related to the location of Cu. The 4.47Cu/SAPO-34 catalyst has the highest isolated Cu2+ showed the highest NH3-SCR activities (> 90%) at 250–350 °C. This work opens up new avenues for recycling fly ash formed in coal-fired power plants (reducing environmental pollution) and developing low-cost SCR catalysts for NOx pollution control.

Fibrous electrocatalytic materials based on carbon/copper/copper phosphides for effective hydrogen evolution

The detailed structural analysis of fibrous carbon electrode materials modified by Cu or Cu3P particles is designed for hydrogen evolution reaction (HER). Two different calcination temperatures and reduction atmospheres were used in order to uncover the most effective catalytic electrode material. The novel families of carbon fibrous electrode materials were prepared by low-cost and versatile needle-less electrospinning process. The chemical structure of prepared modified fibers was analyzed by XRD, 13C and 31P NMR spectroscopy. The morphology of the final samples and the location of Cu or Cu3P micro and nanoparticles were observed by SEM and TEM tomography. TEM XEDS mapping revealed the exact position of Cu, P, C and O elements within the matrix of fiber. The electrocatalytic activity for HER was evaluated by the linear sweep voltammetry, impedance spectroscopy and Tafel slopes analysis. The highest performance for HER was observed in the carbon fibers incorporating copper or copper phosphide nanoparticles thermally treated in argon atmosphere at 1000 °C and successively in hydrogen reduction atmosphere.

Oxycarbonylation of methanol over modified CuY: Enhanced activity by improving accessibility of active sites

CuY zeolite is a promising catalyst in the field of manufacturing dimethyl carbonate (DMC) through oxidative carbonylation of methanol. Cu+ exchanged with Brønsted acid sites are supposed to be active for this reaction. However, the location of Cu+ in small cages can not interact with reactants because of steric hindrance, which lead to a waste of Cu species. In this work, NH4F solution was used to modify the pore structure of zeolite Y by etching the framework T atoms. Physical and chemical adsorption of probe molecules with different size are used to determine the changes of porosity as well as the accessibility of Cu+ sites. At an optimized etching time, the small cages were opened with maintained zeolitic framework. As a result, more Cu+ species located in small cages become accessible to reactants, which contributes to the enhanced activity in this reaction.

XAFS study on the location of Cu and Mn in a greenish blue elbaite from Alto dos Quntos mine, Brazil

XAFS study on the location of Cu and Mn in a greenish blue elbaite from Alto dos Quntos mine, Brazil

Location of Cu(2+) in CHA zeolite investigated by X-ray diffraction using the Rietveld/maximum entropy method.

Accurate structural models of reaction centres in zeolite catalysts are a prerequisite for mechanistic studies and further improvements to the catalytic performance. The Rietveld/maximum entropy method is applied to synchrotron powder X-ray diffraction data on fully dehydrated CHA-type zeolites with and without loading of catalytically active Cu(2+) for the selective catalytic reduction of NO x with NH3. The method identifies the known Cu(2+) sites in the six-membered ring and a not previously observed site in the eight-membered ring. The sum of the refined Cu occupancies for these two sites matches the chemical analysis and thus all the Cu is accounted for. It is furthermore shown that approximately 80% of the Cu(2+) is located in the new 8-ring site for an industrially relevant CHA zeolite with Si/Al = 15.5 and Cu/Al = 0.45. Density functional theory calculations are used to corroborate the positions and identity of the two Cu sites, leading to the most complete structural description of dehydrated silicoaluminate CHA loaded with catalytically active Cu(2+) cations.

Possible sites of copper located on hydroxyapatite structure and the identification of active sites for formaldehyde oxidation

Different methods including ion exchange, co-precipitation and impregnation were used for the preparation of copper doped hydroxyapatite catalysts (CuHAP) to adjust the location of Cu on HAP and resulted in the difference of catalytic performance. Adjustments of synthesis conditions (ion exchange) were adopted for the further identification of active Cu sites for formaldehyde oxidation over CuHAP catalysts. Methods of characterization including XRD, H2-TPR, EPR and XPS were used for the identification of Cu species and its environment on the HAP. A hypothesis of five possible sites for Cu location was proposed based on the features of HAP structure and the experimental results. It has also been concluded that the highly-dispersed Cu(II) clusters was mainly responsible for HCHO oxidation. The best activity was achieved over CuHAP (1.4wt.%) prepared by the ion exchange method with the complete conversion temperature of 180°C.

(Invited) How to Dope a Semiconductor Nanocrystal

The doping of colloidal semiconductor nanocrystals (NCs) presents an additional knob beyond size and shape for controlling the electronic properties. An important problem for impurity doping is associated with resolving the location and structural surrounding of the dopant within the small NCs, in light of tendency for driving of the impurity atom to the surface of the NC. A post-synthesis diffusion-based doping approach for introducing metal impurities into InAs NCs is described and characterized. This enables accurate correlation between the emerged electronic properties and the doping process. Optical absorption spectroscopy and scanning tunneling spectroscopy (STS) measurements revealed the n-type and p-type behavior of the doped NCs, depending on the identity of selected impurities. X-ray absorption fine structure (XAFS) spectroscopy measurements demonstrated the interstitial location of Cu within the InAs NCs, acting as an n-type dopant, which was found to occupy a single unique hexagonal interstitial site within the NC lattice for a wide range of doping levels.

Local Environment and Nature of Cu Active Sites in Zeolite-Based Catalysts for the Selective Catalytic Reduction of NOx

Cu-exchanged zeolites have demonstrated widespread use as catalyst materials in the abatement of NOx, especially from mobile sources. Recent studies focusing on Cu-exchanged zeolites with the CHA structure have demonstrated them to be excellent catalysts in the ammonia-assisted selective catalytic reduction (NH3-SCR) of NOx. Thorough characterization of these materials using state-of-the-art techniques has led to a significant improvement in the understanding of active sites present, which contributes toward a fundamental understanding of the catalytic processes and the rational design of new materials; however, the availability of multiple techniques at our disposal has led to various observations and conclusions on the nature of the active sites. This article begins with a brief introduction to exhaust emission control in the mobile sector, followed by an overview of hydrocarbon-SCR and NH3-SCR; the former technology having found common use in light duty passenger vehicles, whereas the latter are applied for medium (or heavy) duty vehicles, such as trucks and busses. This is followed by an overview of zeolite-based catalysts, especially for NH3-SCR reaction with a focus toward zeolites known to possess high activity. They include zeolites Y (FAU framework), ZSM-5 (MFI framework), SSZ-13 (CHA framework), and (briefly) zeolite Beta (BEA framework). A few common techniques used for the characterization of zeolites and the information that they bring to help determine the salient structural and mechanistic aspects of the NH3-SCR process are introduced. The combination and comparison of the information obtained from the approaches have resulted in an accurate elucidation of the local geometry and environment of Cu within zeolites, thus forming the active site. The article further focuses on three main aspects: (a) the crystallographic cation location of Cu within the structures as compared to results from techniques more sensitive to the local environment; (b) the interaction of Cu at these sites with reactant or probe molecules, which illustrates their (potential) mobility and accessibility; and (c) the proposed active sites within the zeolites ZSM-5, Y, and SSZ-13 as evident in literature. The discussion is focused toward the influence of the zeolite structure, from both a long-range perspective and that of the local structure around the active Cu species, on the thus formed active sites and their implications toward the NH3-SCR reaction.

QUANTITATIVE IMAGE ANALYSIS OF MICROSTRUCTURE EVOLUTION DURING SOLID STATE SINTERING OF W-Cu

The microstructure evolution of W-Cu composites during solid state sintering at 1050°C is studied on samples quenched after different sintering times. The microstructure is formed by 3 phases: tungsten (W), copper (Cu) and pores. During the process, the initial mixture of W- and Cu-powder is transformed by migration of Cu and rearrangement of W particles. These microstructural changes are studied to identify the underlying phenomena and to control the material properties. Based on experiments performed with two different W powders, this paper deals with various aspects of the quantitative analysis of the observed evolution. A careful preparation of the images is necessary. The porous samples are impregnated with a resin under vacuum before being cut and carefully polished. Low voltage (<10 kV) is used during image acquisition on a scanning electron microscope. Area fraction measurements are used to check the quality of the images and the segmentation process. Classical measurements are used to study the spreading of Cu onto the surface of W particles: surface area of each phase, area of contact between phases, chord length distributions. New measurements based on classical methods are also developed to distinguish between two mechanisms of Cu migration in the microstructure : Cu spreading on W surface (wetting of the surface), and capillary penetration in the inter-W channels. An analysis of the location of Cu and pores in the space between W particles (inter-W space) is performed using a granulometry based on 2D openings. It evidences the mechanism of capillary penetration of Cu in the inter-W space in the case of small W-particles.

Dispersal of Contaminant Metals in the Mining-Affected Danube and Maritsa Drainage Basins, Bulgaria, Eastern Europe

Metal dispersal in the Danube and Maritsa drainage basins resulting from metal mining activities in Bulgaria has been assessed through the collection of 611 samples of river water, river channel and floodplain sediment, and mine waste from over 218 sites. Concentrations of Cd, Cu, Pb, and Zn in river water were found to be highest in close proximity to locations of Cu and Pb–Zn mining regions in the Maritsa catchment. Downstream dispersal of solute metals in these catchments, and into the River Danube, was found to be limited by physical dilution and a well-buffered pH environment. Dispersal of contaminant metals in channel and floodplain sediment was found to be extensive. Contamination was particularly severe in the Rivers Timok and Iskar (Danube catchment) and the Topolnitsa, Chepelarska, and Arda Rivers (Maritsa catchment) and creates the potential of transboundary dispersal of contaminant metals.

Testing differences in methods of preparing moss samples. Effect of washing on Pseudoscleropodium purum

When terrestrial mosses are used to study the risks associated with the accumulation of airborne pollutants, samples must be washed to remove deposits adhering to the surface. Here, we studied the effects of washing the samples as well as of freezing, drying, and acclimatization treatments. The differences between the concentrations of Al, As, Cd, Cr, Cu, Fe, Hg, K, Ni, Pb, Se, V, and Zn in washed and unwashed samples were significant, and therefore, it would not be valid to combine or compare the data corresponding to samples treated thus. We also investigated whether there were significant differences in the concentrations of various metals and metalloids yielded from samples subjected to different treatments prior to washing (freezing, drying, acclimatization after drying, and acclimatization only), while also considering possible effects of the level and type of contamination and the weather conditions. For many of the elements, we found significant differences that depended on both the levels of contamination at each sampling site and the weather. As these differences may be due to changes in the contents of the different cellular fractions, the sequential elution technique was applied to determine the locations of Cu, K, and Zn. The freezing and drying procedures were rejected because they alter the permeability of the membranes and lead to underestimation of the concentrations of elements. With the acclimatization procedure, particles of some elements adhere to the surface, making this option unsuitable when a description of bioconcentration is required. Taking into account these limitations and the lack of an optimal procedure, acclimatization after drying is proposed as the best option for harmonizing the method.

A theoretical study of the stability of Cu 2+ ion in IM-5 zeolite and the interaction of Cu-IM-5 with NO

Experimentally, Cu-exchanged IM-5 zeolite has been found to exhibit excellent catalytic activity in NO x reduction. Unfortunately, the origin of such property still remains obscure due to the rather complex structure of IM-5. In this paper, we made the first attempt to provide a theoretical rationalization. By calculating the (Al, Cu) location energies, the stability of both Cu 2+ and hydroxyl-Cu 2+ (i.e., [CuOH] +) was considered and compared to those in ZSM-5. It was shown that [CuOH] + located in IM-5 is comparable to that in ZSM-5. The most favorable location of Cu 2+ cation is in 6-membered ring in the wall of unusual two-dimensional medium-pore channel of IM-5. Moreover, through calculating the interaction of NO with copper-exchanged zeolite (Cu-IM-5), the most active center is Cu 2+ located in the 5-membered ring. The relatively high adsorption energies and numerous active centers in Cu-IM-5 might rationalize why Cu-IM-5 is more active than Cu-ZSM-5 in experiment of NO reduction. Thus, our theoretical results provide support that Cu-IM-5 is a more active and hydrothermically more stable catalyst than Cu-ZSM-5.