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Selective CO2 Reduction Electrocatalysis Using AgCu Nanoalloys Prepared by a "Host-Guest" Method.

Multimetallic nanoalloy catalysts have attracted considerable interest for enhancing the efficiency and selectivity of many electrochemically driven chemical processes. However, the preparation of homogeneous bimetallic alloy nanoparticles remains a challenge. Here, we present a room-temperature and scalable, host-guest approach for synthesis of dilute Cu in Ag alloy nanoparticles. In this approach, an ionic silver bromide precursor harboring exogenous Cu cations is reduced to yield ∼20 nm diameter AgCu alloy nanoparticles wherein the % Cu loading can be tuned precisely. AgCu nanoparticles with a 5% nominal loading of Cu exhibit peak activity (-0.23 mA/cm2 normalized partial current density) and selectivity (83.2% faradaic efficiency) for CO product formation from electrocatalytic reduction of CO2 at mild overpotentials. These AgCu nanoalloys exhibit a higher mass activity compared to Ag- and Cu-containing nanomaterials used for similar electrocatalytic transformations. Our host-guest synthesis platform holds promise for production of other nanoalloys with relevance in electrocatalysis and optics.

50 years of mining-induced environmental changes: topography, hydrology, and vegetation health in Kazreti, Georgia

Globally, prioritizing short-term economic gains from mineral extraction has led to a critical dilemma: a planet rich in resources struggles with environmental degradation and a diminishing ability to sustain future generations. Open-pit mining exemplifies this paradox, causing significant environmental damage. In Georgia, this extractive industry presents environmental problems. Despite these known consequences, the long-term impacts of mining activities remain understudied. This study addressed this gap by analyzing the effects of open-pit mining on terrain morphology, and water dynamics in the Kazreti region over a 50-year period (1970–2020) and vegetation health over 35-year period (1987–2022). By integrating water quality assessment, spatial analysis and remote sensing, we revealed the significant human-induced changes to the region’s ecosystem. Spatial analysis results suggested that over 156.7 million cubic meters of bedrock have been fragmented by mining in southern East Georgia, with 125.5 million cubic meters deposited in valleys. Consequently, discernible shifts in the trajectories of water flow were observed based on the hydrological model. Additionally, a comparative analysis of NDVI and EVI values revealed a decline in vegetation health near mining zones, while remote forest areas remained stable. June typically showed healthier vegetation due to cooler temperatures and optimal growing conditions, while August presented lower vegetation health due to increased heat stress. Water quality revealed significant loadings of Cu (58–1855 μg l−1), Zn (54–2582 μg l−1), Mn (1–2167 μg l−1), and Cd (0.1–4.5 μg l−1), in local river systems, which are higher than the Georgian official guideline values (Cu - 1000, Zn - 1000, Mn—100, Cd—1 μg l−1). This study highlighted the need for a broader long-term monitoring strategy to assess the migration of these contaminants within the food web and the consequent socio-economic impact.

Investigating Permselectivity in PVDF Mixed Matrix Membranes Using Experimental Optimization, Machine Learning Segmentation, and Statistical Forecasting.

This research examines the correlation between interfacial characteristics and membrane distillation (MD) performance of copper oxide (Cu) nanoparticle-decorated electrospun carbon nanofibers (CNFs) polyvinylidene fluoride (PVDF) mixed matrix membranes. The membranes were fabricated by a bottom-up phase inversion method to incorporate a range of concentrations of CNF and Cu + CNF particles in the polymer matrix to tune the porosity, crystallinity, and wettability of the membranes. The resultant membranes were tested for their application in desalination by comparing the water vapor transport and salt rejection rates in the presence of Cu and CNF. Our results demonstrated a 64% increase in water vapor flux and a salt rejection rate of over 99.8% with just 1 wt % loading of Cu + CNF in the PVDF matrix. This was attributed to enhanced chemical heterogeneity, porosity, hydrophobicity, and crystallinity that was confirmed by electron microscopy, tensiometry, and scattering techniques. A machine learning segmentation model was trained on electron microscopy images to obtain the spatial distribution of pores in the membrane. An Autoregressive Integrated Moving Average with Explanatory Variable (ARIMAX) statistical time series model was trained on MD experimental data obtained for various membranes to forecast the membrane performance over an extended duration.

Hydrogel composites based on chitosan and CuAuTiO2 photocatalysts for hydrogen production under simulated sunlight irradiation

This study explored the photocatalytic hydrogen evolution reaction (HER) using novel biohydrogel composites comprising chitosan, and a photocatalyst consisting in TiO2 P25 decorated with Au and/or Cu mono- and bimetallic nanoparticles (NPs) to boost its optical and catalytic properties. Low loads of Cu and Au (1 mol%) were incorporated onto TiO2 via a green photodeposition methodology. Characterization techniques confirmed the incorporation of decoration metals as well as improvements in the light absorption properties in the visible light interval (λ > 390 nm) and electron transfer capability of the semiconductors. Thereafter, Au and/or Cu NP-supported TiO2 were incorporated into chitosan-based physically crosslinked hydrogels revealing significant interactions between chitosan functional groups (hydroxyls, amines and amides) with the NPs to ensure its encapsulation. These materials were evaluated as photocatalysts for the HER using water and methanol mixtures under simulated sunlight and visible light irradiation. Sample CuAuTiO2/ChTPP exhibited a maximum hydrogen generation of 1790 μmol g−1 h−1 under simulated sunlight irradiation, almost 12-folds higher compared with TiO2/ChTPP. Also, the nanocomposites revealed a similar tendency under visible light with a maximum hydrogen production of 590 μmol g−1 h−1. These results agree with the efficiency of photoinduced charge separation revealed by transient photocurrent and EIS.

Mechanistic Basis of the Cu(OAc)2 Catalyzed Azide-Ynamine (3 + 2) Cycloaddition Reaction.

The Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is used as a ligation tool throughout chemical and biological sciences. Despite the pervasiveness of CuAAC, there is a need to develop more efficient methods to form 1,4-triazole ligated products with low loadings of Cu. In this paper, we disclose a mechanistic model for the ynamine-azide (3 + 2) cycloadditions catalyzed by copper(II) acetate. Using multinuclear nuclear magnetic resonance spectroscopy, electron paramagnetic resonance spectroscopy, and high-performance liquid chromatography analyses, a dual catalytic cycle is identified. First, the formation of a diyne species via Glaser-Hay coupling of a terminal ynamine forms a Cu(I) species competent to catalyze an ynamine-azide (3 + 2) cycloaddition. Second, the benzimidazole unit of the ynamine structure has multiple roles: assisting C-H activation, Cu coordination, and the formation of a postreaction resting state Cu complex after completion of the (3 + 2) cycloaddition. Finally, reactivation of the Cu resting state complex is shown by the addition of isotopically labeled ynamine and azide substrates to form a labeled 1,4-triazole product. This work provides a mechanistic basis for the use of mixed valency binuclear catalytic Cu species in conjunction with Cu-coordinating alkynes to afford superior reactivity in CuAAC reactions. Additionally, these data show how the CuAAC reaction kinetics can be modulated by changes to the alkyne substrate, which then has a predictable effect on the reaction mechanism.

CO2 hydrogenation to methanol over the copper promoted In2O3 catalyst

The metal promoted In2O3 catalysts for CO2 hydrogenation to methanol have attracted wide attention because of their high activity with high methanol selectivity. However, there was still no experimental confirmation if copper could be a good promoter for In2O3. Herein, the Cu promoted In2O3 catalyst was prepared using a deposition-precipitation method. Such prepared Cu/In2O3 catalyst shows significantly higher CO2 conversion and space time yield (STY) of methanol, compared to the un-promoted In2O3 catalyst. The loading of Cu facilitates the activation of both H2 and CO2 with the interface between the Cu cluster and defective In2O3 as the active site. The Cu/In2O3 catalyst takes the CO hydrogenation pathway for methanol synthesis from CO2 hydrogenation. It exhibits a unique size effect on the CO adsorption. At temperatures below 250 °C, CO adsorption on Cu/In2O3 is stronger than that on In2O3, causing higher methanol selectivity. With increasing temperatures, the Cu catalyst aggregates, which leads to the formation of weak CO adsorption site and causes a decrease in the methanol selectivity. Compared with other metal promoted In2O3 catalysts, it can be concluded that the catalyst with stronger CO adsorption possesses higher methanol selectivity.

Chitosan Biocomposites with Variable Cross-Linking and Copper-Doping for Enhanced Phosphate Removal.

The fabrication of chitosan (CH) biocomposite beads with variable copper (Cu2+) ion doping was achieved with a glutaraldehyde cross-linker (CL) through three distinct methods: (1) formation of CH beads was followed by imbibition of Cu(II) ions (CH-b-Cu) without CL; (2) cross-linking of the CH beads, followed by imbibition of Cu(II) ions (CH-b-CL-Cu); and (3) cross-linking of pristine CH, followed by bead formation with Cu(II) imbibing onto the beads (CH-CL-b-Cu). The biocomposites (CH-b-Cu, CH-b-CL-Cu, and CH-CL-b-Cu) were characterized via spectroscopy (FTIR, 13C solid NMR, XPS), SEM, TGA, equilibrium solvent swelling methods, and phosphate adsorption isotherms. The results reveal variable cross-linking and Cu(II) doping of the CH beads, in accordance with the step-wise design strategy. CH-CL-b-Cu exhibited the greatest pillaring of chitosan fibrils with greater cross-linking, along with low Cu(II) loading, reduced solvent swelling, and attenuated uptake of phosphate dianions. Equilibrium and kinetic uptake results at pH 8.5 and 295 K reveal that the non-CL Cu-imbibed beads (CH-b-Cu) display the highest affinity for phosphate (Qm = 133 ± 45 mg/g), in agreement with the highest loading of Cu(II) and enhanced water swelling. Regeneration studies demonstrated the sustainability and cost-effectiveness of Cu-imbibed chitosan beads for controlled phosphate removal, whilst maintaining over 80% regenerability across several adsorption-desorption cycles. This study offers a facile synthetic approach for controlled Cu2+ ion doping onto chitosan-based beads, enabling tailored phosphate oxyanion uptake from aqueous media by employing a sustainable polysaccharide biocomposite adsorbent for water remediation by mitigation of eutrophication.

Full utilization of Cu single atoms on carbon nitride nanofibers for enhanced Fenton-like degradation of methylene blue

The utilization efficiency of single atoms is limited by the active sites being buried in support. To maximize atom utilization, Cu single atoms are anchored on the external surface of g-C3N4 nanofibers (CNNFs), which are fabricated by partial thermal decomposition and subsequent self-assembly in H2O. The abundant N and O-containing functional groups of CNNFs are vital for the loading of Cu. Benefited from the full utilization of Cu sites, CNNF-Cu exhibits excellent Fenton-like catalytic activity for Methylene Blue degradation. The reaction kinetic constant is more than 10 times higher than that of the traditional single-atom catalyst with Cu sites evenly distributed throughout the entire support. CNNF-Cu maintains most of its catalytic activity after five cycle tests, suggesting good stability. This work provides a convenient method to maximize the utilization of single metal atoms for catalytic applications.

Microstructure and mechanical properties of ultrasonic welded copper to aluminum cables joints

The experiments of ultrasonic welding were carried out for BVR2.0 copper (Cu) cables and BLV6.0 aluminum (Al) cables with different welding parameters. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), temperature measurement, microhardness evaluation and tensile tests were conducted to investigate the microstructure and mechanical properties of Cu−Al cables joints. The results show that the tensile load of Cu−Al joints reaches 355.6 N, while the welding parameters are set as follows: welding pressure of 0.21 MPa, amplitude of 31%, and time of 860 ms. The diffusion thickness of well-welded Cu−Al joint is only about 3 μm and the peak temperature is 212 °C, which avoids the formation of intermetallic (IMC) effectively. The joint fractures on the copper side rather than the interface of the Cu−Al with a ductile−brittle hybrid fracture mode, indicating that the joint has excellent properties.

Study on desulfurization performance of Cu modified red mud-fly ash sorbent

In this paper, fly ash, red mud and Cu(NO3)2·3H2O were used to prepare Cu modified red mud-fly ash sorbent (CuRMFA) by hydration impregnation method, and the sorbent was used to remove SO2 from coal-fired flue gas. The effects of Cu loading and removal conditions (temperature, O2 concentration and NO concentration) on the desulfurization ability of sorbent were studied. The desulfurization performance and mechanism of CuRMFA were analyzed by experimental results and characterizations. The experimental results show that the sorbent CuRMFA can meet the ultra-low emission standard of SO2, and the optimal load of Cu is 20 mg/g. The optimal removal conditions were 500 ℃, 5% O2, 50 mg/m3 NO and 500 mg/m3 SO2, and when the desulfurization efficiency was greater than 93%, the breakthrough time and sulfur capacity were 65.5 min and 230.88 mg/g, respectively. The CuRMFA mainly removes SO2 by chemical reaction, and the desulfurized product exists in the form of SO42-. The conversion of Cu+ to Cu2+ can enhance the electron transfer, enhance the adsorption oxygen conversion and catalytic oxidation performance, which plays an important role in improving the desulfurization performance of the CuRMFA. That Cu modified RMFA is beneficial to form active component 2MgO·SiO2 and decompose of (CaO)12·(Al2O3)7, and can promote the uniform dispersion of active component, which is conducive to reducing the activation energy of desulfurization reaction and speeding up the reaction process.

Preparation of EDTA-modified UiO-66 for the selective removal of Cu(II) from water

A novel metal-organic framework adsorbent, UiO-66-EDTA, was synthesized by chemically linking of UiO-66-NH2 with ethylenediaminetetraacetic acid (EDTA) to improve the sorption efficiency and selectivity for Cu(II) in water. The product UiO-66-EDTA was characterized by various instruments. The adsorption kinetic and isotherm data for Cu(II) were in line with the pseudo-second-order and Langmuir models, respectively, confirming monolayer chemisorption dominated the loading of Cu(II) on pore channel surface. For Cu(II) ion adsorption, UiO-66-EDTA showed a high maximum adsorption capacity of 154.8 mg/g at pH 6.0, which was much greater than the precursor UiO-66-NH2. Besides, thermodynamic analysis revealed that the loading of Cu(II) on UiO-66-EDTA was spontaneous and endothermic. Furthermore, the functionalization with EDTA significantly improved the adsorption selectivity of UiO-66 for Cu(II) compared to other coexisting cations in water. X-ray photoelectron spectroscopy depicted that Cu(II) ion binding occurred by complexation with oxygen/nitrogen atoms on the EDTA ligand. As a regenerable adsorbent, UiO-66-EDTA was considered to have an obvious application prospect for selectively absorbing Cu(II) ions in water.

Distribution of Copper, Iron, and Zinc in the Retina, Hippocampus, and Cortex of the Transgenic APP/PS1 Mouse Model of Alzheimer's Disease.

A mis-metabolism of transition metals (i.e., copper, iron, and zinc) in the brain has been recognised as a precursor event for aggregation of Amyloid-β plaques, a pathological hallmark of Alzheimer's disease (AD). However, imaging cerebral transition metals in vivo can be extremely challenging. As the retina is a known accessible extension of the central nervous system, we examined whether changes in the hippocampus and cortex metal load are also mirrored in the retina. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to visualise and quantify the anatomical distribution and load of Cu, Fe, and Zn in the hippocampus, cortex, and retina of 9-month-old Amyloid Precursor Protein/Presenilin 1 (APP/PS1, n = 10) and Wild Type (WT, n = 10) mice. Our results show a similar metal load trend between the retina and the brain, with the WT mice displaying significantly higher concentrations of Cu, Fe, and Zn in the hippocampus (p < 0.05, p < 0.0001, p < 0.01), cortex (p < 0.05, p = 0.18, p < 0.0001) and the retina (p < 0.001, p = 0.01, p < 0.01) compared with the APP/PS1 mice. Our findings demonstrate that dysfunction of the cerebral transition metals in AD is also extended to the retina. This could lay the groundwork for future studies on the assessment of transition metal load in the retina in the context of early AD.

Cu-loaded MOF-303 for iodine adsorption: The roles of Cu species and pyrazole ligands

The capture of toxic radioiodine is an increasingly important priority for the safe development of nuclear energy. Copper is a promising alternative for expensive silver to capture iodine. To develop novel copper-based adsorbents and determine the effect of copper species on iodine adsorption, the metal–organic framework with dual-pyrazole ligands (MOF-303) is employed as the scaffold to bind Cu2+ species. Cu0 nanoparticles were formed after the reduction by NaBH4. The obtained Cu2+-MOF-303 and Cu0-MOF-303 show high iodine uptake capacities at 353 K, 747 mg·g−1 and 837 mg·g−1, respectively. They also show high iodine uptake capacities of more than 300 mg·g−1 at a high temperature (423 K), which are better than other Cu-based adsorbents. Besides, the loading of Cu can enhance the iodine selectivity under humid vapor, and iodine adsorption rate in iodine-cyclohexane solutions. The Cu0 on Cu0-MOF-303 can react with iodine directly via the redox mechanism. For Cu2+-MOF-303, the adjacent pyrazole ligands can chelate with Cu2+ ions strongly and transfer charges to trapped iodine to form polyiodide anions, and thus stable CuI species could also be generated. The strategy of anchoring Cu species using MOF-303 provides large channels for iodine diffusion, and highly-dispersed Cu and N sites for iodine capture.

Coupling effect of reaction conditions on the catalytic activity of Cu-Mn composite oxide catalysts for toluene.

Volatile organic compounds (VOCs) are one of the major components of air pollution. Catalytic combustion is a promising technology for the treatment of VOCs and at its center is the preparation of efficient and cheap catalysts. In this study, by loading copper (Cu) and manganese (Mn) on Santa Barbara Amorphous-15 (SBA-15) molecular sieve, the Cux-Mny/SBA-15 (x = 1, 2; y = 1, 2) composite metal oxide catalyst was prepared using the equal volume impregnation method. Their performance in the toluene catalytic combustion reaction was investigated by adjusting the molar ratio (x : y), and the loading of Cu and Mn. The results of the Brunner-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses show that the CuMnO spinel phase can be detected in the Cu-Mn composite metal oxide catalyst doped with a low concentration of Cu. The overall rod-like structure of the fibrous network structure provides a large specific surface area, and the particle crystallinity is low and the dispersion is good. Due to the synergistic effect of Cu and Mn, the greater the amount of Mn3+ and adsorbed oxygen species (Oads) that are available, and the higher the turnover frequency (TOF) value, the better and more superior catalytic performance and excellent stability is obtained, when compared with the single-component oxides used in toluene catalytic combustion. After a continuous catalytic reaction for 12 h, the toluene conversion rate remained above 95%. The coupling effect of the catalytic reaction temperature and concentration of oxygen on the catalytic combustion of toluene was also studied. At a low reaction temperature (<250 °C), the increase of the concentration of oxygen played a superior role in promoting the conversion of toluene. The kinetic analysis of the toluene catalytic combustion process showed that the catalytic combustion of toluene by Cu-Mn/SBA-15 followed both the Mars-Van Krevelen (MVK) and Langmuir-Hinshelwood (L-H) reaction mechanisms. With the increase of the Oads amount caused by the decrease of the Cu ratio, the proportion of the L-H reaction mechanism increases.

Molecular dynamics simulation of spallation of metallic glasses under ultra-high strain rates

Metallic glass (MG) is often used in extreme operating conditions such as high-speed shock because of its excellent physical and mechanical properties. Spallation is a typical form of dynamic failure of materials under shock load. However, the mechanism and law of spallation in metallic glass have not been fully revealed. In this paper, the impact loading of Cu 50 Zr 50 MG at different velocities was carried out by using molecular dynamics (MD) and the piston method. The simulation results of the spall process of metallic glass at an ultra-high strain rate of ~10 10 s -1 were obtained. We found that a higher loading velocity will lead to a higher material strain rate, and the material will reach a higher temperature in the process of wave transmission, thus reducing the spall strength. Through the analysis of the atomic model, we can directly observe the process of nucleation, growth and coalescence of the voids and the formation of the fracture surface. We found that icosahedral clusters are greatly reduced in spallation through Voronoi analysis. We also found that a higher strain rate leads to more voids and a larger spall region, and the characteristics of the fracture surface also change from classical spall to micro-spall. The insights gained in this study can contribute to a better understanding of the spall mechanism and characteristics of MGs under an ultra-high strain rate loading.

Design and characterization of an urea-bridged PMO supporting Cu(II) nanoparticles as highly efficient heterogeneous catalyst for synthesis of tetrazole derivatives

In this work, a new periodic mesoporous organosilica with urea-bridges produced by the reaction of (3-aminopropyl)triethoxysilane and toluene-2,4-diisocyanate (APS-TDU-PMO) is introduced. The obtained APS-TDU-PMO was found to be an appropriate support for loading of Cu(II) nanoparticles to afford supramolecular Cu@APS-TDU-PMO nanocomposite. Uniformity and mesoporosity of both synthesized nanomaterials including APS-TDU-PMO and Cu@APS-TDU-PMO were proved by different spectroscopic, microscopic or analytical techniques including FTIR, EDX, XRD, FESEM, TEM, BET, TGA and DTA. Furthermore, the prepared Cu@APS-TDU-PMO nanomaterial was also used, as a heterogeneous and recyclable catalyst, for the synthesis of tetrazole derivatives through cascade condensation, concerted cycloaddition and tautomerization reactions. Indeed, the main advantages of this Cu@APS-TDU-PMO is its simple preparation and high catalytic activity as well as proper surface area which enable it to work under solvent-free conditions. Also, the introduced Cu@APS-TDU-PMO heterogeneous catalyst showed good stability and reusability for six consecutive runs to address more green chemistry principles.

Enhanced heavy metal adsorption on microplastics by incorporating flame retardant hexabromocyclododecanes: Mechanisms and potential migration risks.

Microplastics (MPs) are known to act as carriers of heavy metals; however, little is known about the intrinsic chemical additives of MPs, such as hexabromocyclododecane (HBCD), in terms of the adsorption behaviors and migration risks of heavy metals on MPs. Here, we reported the potential mechanisms and risks of HBCD inherent in polystyrene (PS) MPs with Cu(II), Ni(II), and Zn(II) adsorption/desorption. A comparison of the adsorption capacity of the metals onto HBCD/PS composites (HBCD/PS) MPs (10.31–20.76 μmol/g), pure MPs (0–3.60 μmol/g), and natural minerals (0.11–13.88 μmol/g) showed that the addition of HBCD significantly promoted the metals adsorption onto the HBCD/PS MPs, and even exceeded that of natural particles. Isotherms and thermodynamic data suggested that the adsorption process of the metals onto the HBCD/PS MPs was spontaneous and endothermic, and that the adsorption was a mainly multi-ion process with an inclined direction. Furthermore, the results of SEM-EDS, FTIR, and XPS analyses, as well as density functional theory well explained that the metals were mainly adsorbed on the –O and –Br groups of the HBCD/PS MPs via electrostatic interactions and surface complexation. More importantly, by comparing the desorption activity with natural river water and seawater, HBCD inherent in MPs can enhance the long-range transfer of metals carried by the HBCD/PS MPs from contamination sources to potential sink like oceans. Thus, the HBCD/PS MPs with high loading of Cu(II), Ni(II), and Zn(II) could be potential secondary sources of these metals in seawater. Overall, these findings revealed the potential risks of flame retardant in MPs associated with metal migration, and advocated that flame retardant-related waste MPs should be included in coastal sustainable development.

Pd/Cu bimetallic catalyst immobilized on PEI capped cellulose-polyamidoamine dendrimer: Synthesis, characterization, and application in Sonogashira reactions for the synthesis of alkynes and benzofurans

Polyamidoamine dendrimer (PAMAM) is an efficient material for immobilization of Pd(II) complex due to its unique tree-like structure and properties. To the purpose of enhancing of the loading of Cu(II) ions, a polyethyleneimine end-capped microcrystalline cellulose-polyamidoamine dendrimer (G2.5) (MCC-PAMAMG2.5-PEI) was designed and synthetized. The resultant MCC-PAMAMG2.5-PEI was furtherly treated by PdCl2 and CuSO4 solution to afford the corresponding dendrimer-supported Pd/Cu bimetallic catalyst (Pd/Cu@MCC-PAMAMG2.5-PEI). As a result, both Pd(II) and Cu(II) ions were well selectively immobilized within the interior architectures and exterior PEI layers of dendrimers, respectively. The as-prepared catalyst was fully characterized by elemental analysis (EA), inductively coupled plasma atomic emission spectrometry (ICP-AES), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), elemental mappings, energy-dispersive X-ray spectra (EDX), field emission transmission electron microscopy (FETEM), and thermogravimetry analysis (TGA) techniques. The presence of required Pd and Cu elements were confirmed from ICP-AES, XPS, EDX, and elemental mappings analysis, respectively. The synergetic effect between Pd and Cu can be observed by comparing it to the dendrimer supported monometallic Pd and Cu as well as the mixture of dendrimer supported Pd and Cu. The catalyst showed excellent performance in the synthesis of alkynes and benzofurans via Sonogashira reactions and could be reused for seven successive runs without any noteworthy loss of activity. Moreover, its efficiency was compared with other reported catalysts in the same transformations.

Synthesis of hybrid biosorbent based on 1,2-cyclohexylenedinitrilotetraacetic acid modified crosslinked chitosan and organo-functionalized calcium alginate for adsorptive removal of Cu(II)

The present study is based on the synthesis of a novel hybrid biosorbent using 1,2-cyclohexylenedinitrilotetraacetic acid modified crosslinked chitosan and amino-thiocarbamate moiety functionalized sodium alginate (CDTA-CS/TSC-CA). The fabricated sorbent was employed to investigate the efficient recovery of Cu(II) from aqueous media. CDTA-CS/TSC-CA was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Analysis confirmed the successful modification of both biopolymers and subsequent loading of Cu(II) ions. CDTA-CS/TSC-CA was casted in the form of hydrogel beads having different CDTA-CS to TSC-CA mass ratios i.e., 10.0–40.0% by mass. The hydrogel beads 4CDTA-CS/TSC-CA with CDTA-CS/TSC-CA mass ratio of 40.0% was found most effective for copper sorption. Equilibrium sorption results showed that initial concentration of copper, medium pH, contact time, sorbent dosage and temperature influenced the sorption capacity (qe). Rate of sorption data was interpreted using different kinetic models and found best fitted with pseudo second order rate expression (R2 ≈ 0.99), illustrating that the rate determining step includes the electron density transfer from sorbent coordination sites to central copper ions. Crank's RIDE equation and Elovich chemisorption model (ECM) revealed the presence of two sorption phases, initially rapid sorption followed by comparatively a slow uptake. Equilibrium sorption data was well depicted by Langmuir model and maximum monolayer adsorption capacity (qm) was computed as 276.53 mg·g−1 at 298 K. Standard Gibbs free energy change, ∆G° (−19.99, −20.18 and −20.36 kJ/ mol), standard enthalpy change, ∆H° (−8.95 kJmol) and standard entropy change, ∆S° (0.04 kJ/mol K−1) values suggested that the adsorption process is spontaneous and exothermic. Hence, 4CDTA-CS/TSC-CA was found efficient biosorbent for copper removal from its dilute effluents.

Cu‐Fe/activated carbon catalyst for low‐temperature CO‐selective catalytic: Modification and denitration mechanism

AbstractTo study the Cu‐Fe modification and CO denitration mechanism of carbon‐based sorbent, coconut‐husk activated carbon (AC), which was activated via air thermo‐oxidation and modified using Cu(NO3)2 and Fe(NO3)2 was examined. In addition, the denitration activity was evaluated. The effects of air thermo‐oxidative activation, as well as Cu(NO3)2 and Fe(NO3)2 immersion on the pore texture and surface characteristics of the carbon materials, were examined by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, X‐ray powder diffraction (XRD) and Fourier‐transform infrared (FTIR) spectroscopy. The reduction performance and CO adsorptive property of xCu‐yFe/AC catalyst was measured using hydrogen temperature‐programmed reduction (H2‐TPR) and carbon monoxide temperature‐programmed desorption (CO‐TPD). The xCu‐yFe/AC's denitration activity showed that physical adsorption is a priority, then chemical adsorption recovers the denitration activity after physical adsorption saturation. The modification mechanism showed that higher loading of Cu and Fe resulted in enhanced dispersivity and more active sites but decreased specific surface area and pore volume. Then, the capability of physical adsorption decreased. Moreover, higher Fe loading was conducive to improved dispersivity of copper oxide species. The effects of Cu and Fe modification on the majority of functional groups were insignificant. The reduction peak at approximately 150°C indicated that the xCu‐yFe/AC catalyst has strong reduction characteristics. The number of CO active adsorption sites increased by high loading quantity at high‐temperature. The CO‐selective catalytic reduction (SCR) denitration conforms to Langmuir–Hinshelwood mechanism. The reciprocal transformation between Fe2+ and Fe3+, Cu+ and Cu2+, which is conducive to the rapid progress of the CO‐SCR reaction.