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At least 289 records · Page 16

Influence of fuel ash on the recoverability of copper from the spent material of chemical looping combustion

Chemical looping combustion (CLC) is an advanced energy production technology that inherently separates the CO 2 generated. The oxygen needed for fuel conversion is supplied by the oxygen carrier. When using copper-based oxygen carriers, oxygen carrier attrition is a challenge to the process economics, unless the attrited copper that is mixed with fuel ash in the spent material can be recovered by, for instance, acid leaching. However, fuel ash may transform the attrited copper into certain complexes of low leachability (e.g., CuAl 2 O 4 ), hindering the copper recovery. In this study, the copper content in the spent material was first evaluated. The effects of ash composition and copper content on the occurrence mode of copper in spent material were predicted by thermodynamic modeling. Redox cycles of simulated spent materials based on various coal ashes were performed to reveal the characteristics of CuAl 2 O 4 /CuFe 2 O 4 formation. The CuO-Al 2 O 3 reaction was investigated under the temperatures and solid residence times experienced in CLC. The materials were analyzed by X-ray diffraction. The results suggest that the fuel ash with a high Al/Ca ratio may lower the recoverability of copper when the temperature is above 925 °C. The slow formation of CuFe 2 O 4 is not expected to affect the copper recovery.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Rapid assessment of human amylin aggregation and its inhibition by copper(II) ions by laser ablation electrospray ionization mass spectrometry with ion mobility separation

Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreas that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. In this paper, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin–copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the —HSSNN– residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin–copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of amylin oligomerization and fibril formation. Finally and more generally, this rapid technique opens the door for high-throughput screening of potential inhibitors of amyloid protein aggregation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Evaluating Effects of Shear Processing on 2D Crystalline Materials in 3D Metal Matrices: Atomistic Understanding of High Shear Deformation of Copper Graphene Composites

Composites made of copper and graphene demonstrate high strength, lubricity and enhanced electrical and thermal conductivity compared pure copper. However, manufacturing these composites at bulk volumes for industrial applications has been a big challenge. Shear deformation assisted processing is an effective method for manufacturing materials such as copper-graphene composites demonstrating ultra-fine grain structures and compositional homogeneity. Nevertheless, microstructural evolution of the composites and their property development under such conditions is not clearly understood currently. To rectify this gap in literature, high strain shear deformation of copper coated graphene foils was performed using a tribometer pin in this study. Changes in microstructure of the composite as well as the constituent components under shear deformation was correlated to process conditions. A sharp increase in the coefficient of friction attributed to rupture and smearing of graphene layer into copper substrate was observed during the shear processing. The coefficient of friction of the sheared copper/graphene composite was lower than that of pure copper, suggesting that partially worn graphene is effectively lubricious at the macroscale. A multimodal characterization of the processed region further revealed a shear deformation-induced ultrafine two-phase grain-structure consisting of copper and graphitic domains. Shear deformation reduced the copper grain size from around 50 – 100 µm to ~200 nm on an average and ~2 – 5 nm in some locations. The semicrystalline graphene films were observed to fracture into 10 – 50 µm size flakes. Oxygen enrichment was observed in the processed region. Finally, graphitic domain were identified for the first time in the copper matrix and not just at the grain boundaries providing evidence for a metastable composite microstructure as a result of solid phase processing at room temperature.

36 MATERIALS SCIENCE↗

Kinetics of copper ion absorption by cross-linked calcium polyacrylate membranes

The absorption of copper ions from aqueous copper acetate solutions by cross-linked calcium acrylate membranes was found to obey parabolic kinetics similar to that found for oxidation of metals that form protective oxide layers. For pure calcium polyacrylate membranes the rate constant was essentially independent of copper acetate concentration and film thickness. For a cross-linked copolymer film of polyvinyl alcohol and calcium polyacrylate, the rate constant was much greater and dependent on the concentration of copper acetate. The proposed mechanism in each case involves the formation of a copper polyacrylate phase on the surface of the membrane. The diffusion of the copper ion through this phase appears to be the rate controlling step for the copolymer film. The diffusion of the calcium ion is apparently the rate controlling step for the calcium polyacrylate. At low pH, the copper polyacrylate phase consists of the normal copper salt; at higher pH, the phase appears to be the basic copper salt.

Philipp, W. H.↗

Antifouling Properties and Release of Dissolved Copper of Cold Spray Cu/Cu{sub 2}O Coatings for Ships and Steel Structures in Marine Environment

At the submarine screen doors of ships, the flow of water was fast and organic coatings were easy to peel off. To solve the problems of biofouling, the Cu/Cu{sub 2}O coatings were prepared by cold spray technology. In this paper, the release mechanism of effective antifouling components of the coatings was studied by micro-domain electrochemical potential scanning technique. Cuprous oxide in the coatings and the surrounding copper constituted micro-cells which accelerated the local electrochemical dissolution of copper. Cuprous oxide acted as the cathode, and the surrounding copper acted as the anode. Meanwhile, under the action of current, chloride ions were transferred from cathode to the anode and promoted local electrochemical dissolution of copper. Experiments show that the higher the Cu{sub 2}O content in the coatings, the greater the release rate of dissolved copper and inhibitory effect on diatoms. In the environments varied in dissolved oxygen, salinity, temperature and flow rate, the coatings maintained sufficient release rate of dissolved copper, unless the salinity was very low. Most of the dissolved copper was provided by the electrochemical dissolution process of copper. Whether in the indoor test or marine environment experiments, 30% Cu{sub 2}O coatings show the best performance. After insulating layer was sprayed, the effect of antifouling was improved evidently and the coatings were applied to the submarine screen doors of ships.

36 MATERIALS SCIENCE↗

Dynamic Copper Site Redispersion through Atom Trapping in Zeolite Defects

Single-site copper-based catalysts have shown remarkable activity and selectivity for a variety of reactions. However, deactivation by sintering in high-temperature reducing environments remains a challenge and often limits their use due to irreversible structural changes to the catalyst. Here, we report zeolite-based copper catalysts in which copper oxide agglomerates formed after reaction can be repeatedly redispersed back to single sites using an oxidative treatment in air at 550 °C. Under different environments, single-site copper in Cu–Zn–Y/deAlBeta undergoes dynamic changes in structure and oxidation state that can be tuned to promote the formation of key active sites while minimizing deactivation through Cu sintering. For example, single-site Cu 2+ reduces to Cu 1+ after catalyst pretreatment (270 °C, 101 kPa H 2 ) and further to Cu0 nanoparticles under reaction conditions (270–350 °C, 7 kPa EtOH, 94 kPa H 2 ) or accelerated aging (400–450 °C, 101 kPa H 2 ). After regeneration at 550 °C in air, agglomerated CuO was dispersed back to single sites in the presence and absence of Zn and Y, which was verified by imaging, in situ spectroscopy, and catalytic rate measurements. Ab initio molecular dynamics simulations show that solvation of CuO monomers by water facilitates their transport through the zeolite pore, and condensation of the CuO monomer with a fully protonated silanol nest entraps copper and reforms the single-site structure. Importantly, the capability of silanol nests to trap and stabilize copper single sites under oxidizing conditions could extend the use of single-site copper catalysts to a wider variety of reactions and allows for a simple regeneration strategy for copper single-site catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Vanadium (II) Sulfate for the Reductive Leaching of Chalcopyrite: Replacing Smelting with Electrolysis for Copper Production

The demand for copper is expected to outpace supply in the coming decades due in part to the emergence of wind and solar technologies, which require about five times as much copper as traditional energy sources. This work introduces a potentially transformative hydrometallurgical process to extract copper from chalcopyrite, and thereby sustain a high rate of copper production throughout the 21 st century. Chalcopyrite is reacted with vanadium (II) sulfate for the first time to enable the rapid, clean, and complete recovery of copper. Reactions between 39 g/L copper concentrate, 1 M vanadium (II) sulfate, and various concentrations of sulfuric acid yielded a final product of solid copper sulfate, which was characterized by X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis. The solid products were leached in a subsequent step to demonstrate copper yields ranging from 95–99%. The vanadium (II) ion may be regenerated by an electrolysis unit that leverages advances in vanadium flow battery technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Copper extraction from coarsely ground printed circuit boards using moderate thermophilic bacteria in a rotating-drum reactor

Highlights: • Copper bioleaching from PCB (20 mm) by moderate thermophiles was demonstrated. • Larger PCB sheets enable a cost reduction due to the elimination of fine grinding. • Crushing generated cracks in PCB increasing the copper extraction. • A pre-treatment step was necessary to remove the lacquer coating. • High copper extractions (85%) were possible with pulp density of up to 25.0 g/L. - Abstract: The current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake flasks to assess the effects of particle size (−208 μm + 147 μm), ferrous iron concentration (1.25–10.0 g/L) and pH (1.5–2.5) on copper leaching using mesophile and moderate thermophile microorganisms. Only at a relatively low solid content (10.0 g/L) complete copper extraction was achieved from the particle size investigated. Conversely, high copper extractions were possible from coarse-ground PCB (20 mm-long) working with increased solids concentration (up to 25.0 g/L). Because there was as the faster leaching kinetics at 50 °C Sulfobacillus thermosulfidooxidans was selected for experiments in a rotating-drum reactor with the coarser-sized PCB sheets. Under optimal conditions, copper extraction reached 85%, in 8 days and microscopic observations by SEM–EDS of the on non-leached and leached material suggested that metal dissolution from the internal layers was restricted by the fact that metal surface was not entirely available and accessible for the solution in the case of the 20 mm-size sheets.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Electron Paramagnetic Resonance Characteristics and Crystal Structure of a Tutton Salt Analogue: Copper-Doped Cadmium Creatininium Sulfate

Electron paramagnetic resonance and crystallographic studies on copper-doped cadmium creatininium sulfate (CdCrnS) were undertaken to study the characteristics of a copper-hexahydrate complex in an organic analogue of Tutton's salt. X-ray diffraction experiments determined the crystal structure of CdCrnS at both 100 and 298 K. CdCrnS, like Tutton salt, crystallizes in the monoclinic space group P2 1 /n. The unit cell contains two cadmium hexahydrate complexes, four creatininium ions, four sulfates, and four additional solvation waters. Both crystallography and EPR find that the doped copper replaces the cadmium in the structure. Single-crystal EPR measurements at room temperature determined the g and copper hyperfine (A Cu ) tensors (principal values: g = 2.437, 2.134, and 2.080 and A Cu = -327, -84.8, and 7.33 MHz). EPR spectra of the powder at room temperature gave g = 2.448, 2.125, and 2.085 and A Cu = -315, -75.0, and 35.0 MHz and at 110 K gave g = 2.462, 2.116, and 2.077 and A Cu = -340, -30.0, and 35.0 MHz. The room-temperature tensors are close to the "rigid lattice limit" values found in copper-doped Tutton salts but with a higher gmin and weaker A Cu x coupling than average. A small but measurable temperature dependency of the tensors indicated the presence of a dynamic Jahn-Teller (JT) effect. In addition, the EPR line width changed dramatically with temperature, which is like that found in all copper-doped Tutton crystals. Utilizing the model of Silver-Getz for the g-value variation gave an estimate for the energy difference (δ 12 = 640 cm -1 ) between the ground and next highest JT configurations. An empirical correlation appears to exist between δ 12 and g min and A Cu x for the copper hexahydrates studied in similar crystals. Finally, this suggests a relationship between the amount of unpaired spins in the copper d-orbital x lobe and the gap between wells of the adiabatic potential surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

A Copper-Binding Peptide with Therapeutic Potential against Alzheimer′s Disease: From the Blood–Brain Barrier to Metal Competition

Alzheimer’s disease (AD) is the most common form of dementia worldwide. AD brains are characterized by the accumulation of amyloid-β peptides (Aβ) that bind Cu 2+ and have been associated with several neurotoxic mechanisms. Although the use of copper chelators to prevent the formation of Cu 2+ -Aβ complexes has been proposed as a therapeutic strategy, recent studies show that copper is an important neuromodulator that is essential for a neuroprotective mechanism mediated by Cu 2+ binding to the cellular prion protein (PrPC). Therefore, in addition to metal selectivity and blood–brain barrier (BBB) permeability, an emerging challenge for copper chelators is to prevent the formation of neurotoxic Cu 2+ -Aβ species without perturbing the neuroprotective Cu 2+ -PrPC interaction. Previously, we reported the design of a tetrapeptide (TP) that withdraws Cu 2+ from Aβ(1–16) and impacts the Cu 2+ -induced aggregation of Aβ(1–40). In this study, we improved the drug-like properties of TP in a BBB model, evaluated the metal selectivity of the optimized peptide (TP*), and tested its effect on Cu 2+ coordination to PrPC and proteins involved in copper trafficking, such as copper transporter 1 and albumin. Our results show that changing the stereochemistry of the first residue prevents TP degradation in the BBB model and coadministration of TP with a peptide that increases BBB permeability allows its passage through the BBB model. TP* is highly selective toward Cu 2+ in the presence of Zn 2+ ions, transfers Cu 2+ to copper-trafficking proteins, and forms a ternary TP*-Cu 2+ -PrP species that does not perturb the physiological conformation of PrP and displays only a minor impact in the neuroprotective Cu 2+ -dependent interaction of PrPC with the N-methyl-d-aspartate receptor. Overall, these results show that TP* displays desirable features for a copper chelator with therapeutic potential against AD. Moreover, this is the first study that explores the effect of a Cu 2+ chelator with therapeutic potential for AD on Cu 2+ coordination to PrPC (an emerging key player in AD pathology), integrating recent knowledge about metalloproteins involved in AD with the design of copper chelators against AD.

60 APPLIED LIFE SCIENCES↗

Grf10 regulates the response to copper, iron, and phosphate in Candida albicans

Abstract The pathogenic yeast, Candida albicans, and other microbes must be able to handle drastic changes in nutrient availability within the human host. Copper, iron, and phosphate are essential micronutrients for microbes that are sequestered by the human host as nutritional immunity; yet high copper levels are employed by macrophages to induce toxic oxidative stress. Grf10 is a transcription factor important for regulating genes involved in morphogenesis (filamentation, chlamydospore formation) and metabolism (adenylate biosynthesis, 1-carbon metabolism). The grf10Δ mutant exhibited resistance to excess copper in a gene dosage-dependent manner but grew the same as the wild type in response to other metals (calcium, cobalt, iron, manganese, and zinc). Point mutations in the conserved residues D302 and E305, within a protein interaction region, conferred resistance to high copper and induced hyphal formation similar to strains with the null allele. The grf10Δ mutant misregulated genes involved with copper, iron, and phosphate uptake in YPD medium and mounted a normal transcriptional response to high copper. The mutant accumulated lower levels of magnesium and phosphorus, suggesting that copper resistance is linked to phosphate metabolism. Our results highlight new roles for Grf10 in copper and phosphate homeostasis in C. albicans and underscore the fundamental role of Grf10 in connecting these with cell survival.

59 BASIC BIOLOGICAL SCIENCES↗

Two TonB-dependent transporters in Methylosinus trichosporium OB3b are responsible for uptake of different forms of methanobactin and are involved in the canonical ‘copper switch’

Copper is an important component of methanotrophic physiology as it controls the expression and activity of alternative forms of methane monooxygenase (MMO). To collect copper, some methanotrophs secrete a chalkophore or copper-binding compound called methanobactin (MB). MB is a ribosomally synthesized post-translationally modified polypeptide (RiPP) that, after binding copper, is collected by MbnT, a TonB-dependent transporter (TBDT). Structurally different forms of MB have been characterized, and here we show that different forms of MB are collected by specific TBDTs. Further, we report that in the model methanotroph, Methylosinus trichosporium OB3b, expression of the TBDT required for uptake of a different MB made by Methylocystis sp. strain SB2 (MB-SB2), is induced in the presence of MB-SB2, suggesting that methanotrophs have developed specific machinery and regulatory systems to actively take up MB from other methanotrophs for copper collection. Moreover, the canonical “copper-switch” in Ms. trichosporium OB3b that controls expression of alternative MMOs is apparent if one of the two TBDTs required for MB-OB3b and MB-SB2 uptake is knocked out, but is disrupted if both TBDTs are knocked out. Furthermore, these data indicate that MB uptake, including the uptake of exogenous MB, plays an important role in the copper switch in M. trichosporium OB3b and thus overall activity. Based on these data, we propose a revised model for the “copper-switch” in this methanotroph that involves MB uptake.

54 ENVIRONMENTAL SCIENCES↗

Thermotransport in liquid aluminum-copper alloys

A thermotransport study was made on a series of liquid aluminum-copper alloys which contained from trace amounts to 33 weight percent copper. The samples in the form of narrow capillaries were held in known temperature gradient of thermotransport apparatus until the stationary state was reached. The samples were analyzed for the concentration of copper along the length. Copper was observed to migrate to the colder regions in all the samples. The heat of transport, Q*, was determined for each composition from a plot of concentration of copper versus reciprocal absolute temperature. The value of Q* is the highest at trace amounts of copper (4850 cal/gm-atom), but decreases with increasing concentration of copper and levels off to 2550 cal/gm-atom at about 25 weight percent copper. The results are explained on the basis of electron-solute interaction and a gas model of diffusion.

Bhat, B. N.↗

Effect of oxygen, methyl mercaptan, and methyl chloride on friction behavior of copper-iron contacts

Sliding friction experiments were conducted with an iron rider on a copper disk and a copper rider on an iron disk. The sputter cleaned iron and copper disk surfaces were saturated with oxygen, methyl mercaptan, and methyl chloride at atmospheric pressure. Auger emission spectroscopy was used to monitor the surfaces. Lower friction was obtained in all experiments with the copper rider sliding on the iron disk than when the couple was reversed. For both iron and copper disks, methyl mercaptan gave the best surface coverage and was most effective in reducing friction. For both iron and copper disks, methyl chloride was the least effective in reducing friction. With sliding, copper transferred to iron and iron to copper.

Buckley, D. H.↗

Effect of copper impurity on polycrystalline silicon solar cells

The presence of copper impurity, up to 10 to the 15th atoms/cc, in single crystal silicon has been shown to have no deleterious effect on the p-n junction solar cell performance. However, in polycrystalline silicon, copper atoms tend to migrate to the defect sites because of the structural sensitive properties of copper. This study was undertaken to investigate the influence of this behavior of copper impurity on the performance of p-n junction solar cells fabricated from structurally imperfect silicon. Two sets of polycrystalline silicon substrates containing copper were examined. In one set of samples, copper was incorporated during growth, whereas in the other, copper was diffused. Solar cells were fabricated on both the sets of substrates by a standard process. Dark and light I-V and spectral response characteristics of the cells were measured and compared with copper-free polycrystalline silicon solar cells. The results and the model are discussed.

Daud, T.↗

Textured carbon on copper: A novel surface with extremely low secondary electron emission characteristics

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for a range of primary electron beam energies and beam impingement angles are presented for a series of novel textured carbon surfaces on copper substrates. (All copper surfaces used in this study were oxygen-free, high-conductivity grade). The purpose of this investigation is to provide information necessary to develop high-efficiency multistage depressed collectors (MDC's) for microwave amplifier traveling-wave tubes (TWT's) for communications and aircraft applications. To attain the highest TWT signal quality and overall efficiency, the MDC electrode surface must have low secondary electron emission characteristics. While copper is the material most commonly used for MDC electrodes, it exhibits relatively high levels of secondary electron emission unless its surface is treated for emission control. The textured carbon surface on copper substrate described in this report is a particularly promising candidate for the MDC electrode application. Samples of textured carbon surfaces on copper substrates typical of three different levels of treatment are prepared and tested for this study. The materials are tested at primary electron beam energies of 200 to 2000 eV and at direct (0 deg) to near-grazing (85 deg) beam impingement angles. True secondary electron emission and relative reflected primary electron yield characteristics of the textured surfaces are compared with each other and with those of untreated copper. All the textured carbon surfaces on copper substrate tested exhibited sharply lower secondary electron emission characteristics than those of an untreated copper surface.

Curren, A. N.↗

Effect of Iron Phase Evolution on Copper Separation from Slag Via Coal-Based Reduction

Copper slag, a by-product of copper pyrometallurgy, inevitably contains a certain amount of copper. Oxygen-enriched smelting technologies increase the copper content in slag indirectly because of the production of higher-grade matte. The effect of iron phase evolution on the copper content in slag during the slag cleaning process in an electric furnace was investigated using the method of combining theory with experiments. Based on the analysis, the main factors that impede the separation of slag and copper/matte were determined. Subsequently, the properties of slag were analyzed after decreasing the magnetite content within the slag. The experimental results showed that decreases in magnetite content were beneficial for the separation of copper and slag because of the decrease of slag viscosity. Nevertheless, Cu-Fe alloys formed when magnetite was completely reduced to metallic iron, and the foaming slag was formed at 1250 °C. Furthermore, the distribution of copper in the reduced slags was studied in detail.

36 MATERIALS SCIENCE↗

Experimental evidence on removing copper and light-induced degradation from silicon by negative charge

In addition to boron and oxygen, copper is also known to cause light-induced degradation (LID) in silicon. We have demonstrated previously that LID can be prevented by depositing negative corona charge onto the wafer surfaces. Positively charged interstitial copper ions are proposed to diffuse to the negatively charged surface and consequently empty the bulk of copper. In this study, copper out-diffusion was confirmed by chemical analysis of the near surface region of negatively/positively charged silicon wafer. Furthermore, LID was permanently removed by etching the copper-rich surface layer after negative charge deposition. These results demonstrate that (i) copper can be effectively removed from the bulk by negative charge, (ii) under illumination copper forms a recombination active defect in the bulk of the wafer causing severe light induced degradation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗