Surface oxidation of polycrystalline α(75%Cu/25%Zn) and β(53%Cu/47%Zn) brass as studied by XPS: Influence of oxygen pressure

Removal performance and mechanism of phosphorus by different Fe-based layered double hydroxides

Phosphorus pollution has the potential to cause both aquatic eutrophication and global phosphorus scarcity. Fe-based layered double hydroxides (LDHs) have received much attention due to their high phosphorus adsorption and recovery. The composition of Fe-based LDHs is an important factor in determining their adsorption performance. However, the mechanism by which single component regulation of Fe-based LDHs affects phosphorus adsorption performance remains unknown. In this study, two typical types of Fe-based LDHs were prepared: Mg/Fe LDH and Zn/Fe LDH. Results showed that the equilibrium adsorption capacity of Zn/Fe LDH was much greater than that of Mg/Fe LDH, reaching 65.85 mg/g with a phosphorus concentration of 150 mg/L. Calcination facilitated a substantial increase of adsorption capacity for Mg/Fe LDH rather than Zn/Fe LDH. Meanwhile, the phosphorus removal efficiency of Fe-based LDHs both exceeded 90% with an initial pH of 3.0, but it decreased as pH increased, and pH inhibition was relatively weaker for Zn/Fe LDH than Mg/Fe LDH. The common coexisting anions caused a phosphorus adsorption loss, with SO₄^2- possessing the most competition with phosphorus. Combined with FTIR, XRD, XPS, and BET analyses, a superior adsorption performance of Zn/Fe-LDH over Mg/Fe-LDH was probably attributed to a higher surface complexation and larger specific surface area. It was also concluded that Fe-based LDHs are a promising method for removing phosphorus from recirculating aquaculture wastewater.

Sea-Island-Like Morphology of CuNi Bimetallic Nanoparticles Uniformly Anchored on Single Layer Graphene Oxide as a Highly Efficient and Noble-Metal-Free Catalyst for Cyanation of Aryl Halides

Aryl nitriles are versatile compounds that can be synthesized via transition-metal-mediated cyanation of aryl halides. Most of the supported-heterogeneous catalysts are noble-metals based and there are very limited numbers of efficient non-noble metal based catalysts demonstrated for the cyanation of aryl halides. Herein, bimetallic CuNi-oxide nanoparticles supported graphene oxide nanocatalyst (CuNi/GO-I and CuNi/GO-II) has been demonstrated as highly efficient system for the cyanation of aryl halides with K₄[Fe(CN)₆] as a cyanating agent. Metal-support interaction, defect ratio and synergistic effect with the bimetallic nanocatalyst were investigated. To our delight, the CuNi/GO-I system activity transformed a wide range of substrates such as aryl iodides, aryl bromides, aryl chlorides and heteroaryl compounds (Yields: 95-71%, TON/TOF: 50-38/2 h^-1). Moreover, enhanced catalytic performance of CuNi/GO-I and CuNi/GO-II in reduction of 4-nitropehnol with NaBH₄ was also confirmed (k_app = 18.2 × 10^-3 s^-1 with 0.1 mg of CuNi/GO-I). Possible mechanism has been proposed for the CuNi/GO-I catalyzed cyanation and reduction reactions. Reusability, heterogeneity and stability of the CuNi/GO-I are also found to be good.

Antibacterial Silicon Oxide Thin Films Doped with Zinc and Copper Grown by Atmospheric Pressure Plasma Chemical Vapor Deposition

Zn-doped and Cu-doped SiO_x films were synthesized by atmospheric pressure plasma chemical vapor deposition to study their antibacterial efficiency against Gram-negative Escherichia coli and their cytotoxic effect on the growth of mouse cells. Zn-rich and Cu-rich particles with diameters up to several microns were found to be homogeneously distributed within the SiO_x films. For both doping elements, bacteria are killed within the first three hours after exposure to the film surface. In contrast, mouse cells grow well on the surfaces of both film types, with a slight inhibition present only after the first day of exposure. The obtained results indicate that the films show a high potential for use as effective antibacterial surfaces for medical applications.

Supercapacitive performance of electrochemically doped TiO2 nanotube arrays decorated with Cu2O nanoparticles

Highly ordered TiO₂ nanotube arrays (TNAs) with enhanced electronic conductivity treated by introducing oxygen vacancies have been considered to be a promising electrode material for supercapacitors.

A photochromic nano-system via self-recovery for stable photocatalytic hydrogen evolution by optimizing TiO2 surface energy

AgBr photochromic self-recovery system was introduced into TiO₂ to repeatedly optimize its surface energy by the repeating Br₂ adsorption.

Initial oxidation of brass induced by humidified air

Complementary surface and near-surface analytical techniques have been used to explore a brass (Cu-20Zn) surface before, during, and after exposure in air at 90% relative humidity. Volta potential variations along the unexposed surface are attributed to variations in surface composition and resulted in an accelerated localized growth of ZnO and a retarded more uniform growth of an amorphous Cu₂O-like oxide. After 3 days the duplex oxide has a total mass of 1.3 μg/cm², with improved corrosion protective properties compared to the oxides grown on pure Cu or Zn. A schematic model for the duplex oxide growth on brass is presented.

Recovery of precious metals by an electrochemical deposition method

Conversion of soluble precious metals into a solid form for further reuse was studied by using an electrochemical deposition approach. It was found that the metal recovery followed a first-order reaction kinetics. The distance between the electrodes had no much impact on the recovery, while higher mixing led to faster kinetics. The presence of humic acid (HA) with lower concentration (<20mg l (-1)) did not have impact on the recovery. When its concentration was increased to 50 mg l (-1), it decreased the metal reduction. Presence of ethylene diamine tetraacetic acid (EDTA) and ionic strength slightly reduced the copper recovery rate. Around 50% removal of for HA and EDTA was achieved. In the competing environment, metal recovery was in the following order: silver>lead>copper. X-ray photoelectron spectroscopic and scanning electronic microscopic analysis of the reduced metals demonstrated that the depositions were composed of mainly elemental metals together with their oxides which were due to the oxidation.