Removal and recovery of copper (II) ions by bacterial biosorption

Studies were conducted toinvestigate the removal and recovery of copper (II) ions from aqueous solutions by Micrococcus sp., which was isolated from a local activated sludge process. The equilibrium of copper biosorption followed the Langmuir isotherm model very well with a maximum biosorption capacity (q_max) of 36.5 mg of Cu²⁺/gofdry cell at pH 5.0 and 52.1 mg of Cu²⁺/g of dry cell at pH 6.0. Cells harvested at exponential growth phase and stationary phase showed similar biosorption characteristics for copper, Copper uptake by cells was negligible at pH 2.0 and then increased rapidly with increasing pH un til 6.0. In multim etal systems, Micrococcus sp. exhibited a preferential biosorption order: Cu−Pb>Ni−Zn. There is virtually no interference with copper uptake by Micrococcus sp. from solutions bearing high concentrations of Cl⁻, SO ₄ ²⁻ , and NO3/− (0–500 mg/L). Sulfuric acid (0.05 M) was the most efficient desorption medium, recovering >90% of the initial copper sorbed. The copper capacity of Micrococcus sp. remained unchanged after five successive sorption and desorption cycles. Immobilization of Micrococcus sp. in 2% calcium alginate and 10% polyacrylamide gel beads increased copper uptake by 61%. Biomass of Micrococcus sp. may be applicable to the development of potentially cost-effective biosorbent for removing and recovering copper from effluents.     

Mononuclear and Tetranuclear Copper(II) Complexes Bearing Amino Acid Schiff Base Ligands: Structural Characterization and Catalytic Applications

Two new glycine-Schiff base copper(II) complexes were synthesized. Single crystal X-ray diffraction (SCXRD) allowed us to establish the structure of both complexes in the solid state. The glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-nitroacetophenone showed a mononuclear hydrated structure, in which the Schiff base acted as a tridentate ligand, and the glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-methylacetophenone showed a less common tetranuclear anhydrous metallocyclic structure, in which the Schiff base acted as a tetradentate ligand. In both compounds, copper(II) had a tetracoordinated square planar geometry. The results of vibrational, electronic, and paramagnetic spectroscopies, as well as thermal analysis, were consistent with the crystal structures. Both complexes were evaluated as catalysts in the olefin cyclopropanation by carbene transference, and both led to very high diastereoselectivity (greater than 98%).     

Characterization and comparison of metal accumulation in two Escherichia coli strains expressing either CopA or MntA, heavy metal-transporting bacterial P-type adenosine triphosphatases

MntA from Lactobacillus plantarum and copA from Enterococcus hirae both encode membrane proteins that are members of the P-type family of adenosine triphosphatases (ATPases). Both transporters act as metal importers to take up nutritionally required substrates; MntA translocates Mn(II) and CopA translocates Cu(I). Both ATPases can also translocate secondary substrates, Cd(II) and Ag(I), respectively. Although functionally and sequentially similar, these ATPases differ in several key residues and in their membrane topologies. The bioaccumulation properties of these two proteins were examined by coexpressing the transporters with overexpressed metallothionein in Escherichia coli cells, a system that has previously shown high levels of substrate-specific uptake. Both strains exhibited rapid metal accumulation, both saturated at around 50 μM metal, and both displayed temperature-sensitive uptake. However, the transporters responded differently when external conditions were varied; MntA displayed increased sensitivity to ionic strength, while CopA was more pH sensitive and more inhibited by chelating agents. The differences in accumulation are likely owing to structural differences in the transmembrane region of these two ATPases.     

Synthesis of symmetrical diaryl ethers from arylboronic acids mediated by copper(II) acetate

Copper promoted generation of phenols in situ through arylation of water and their subsequent arylation with arylboronic acids affords a wide range of symmetrical diaryl ethers in good to high yield. The reaction is rapid, mild, convenient and tolerant of a wide range of functionalities on the arylboronic acid.     

Aktivierungsanalytische Bestimmung von Spurenelementen in Tomaten

Die Autoren machen mit aktivierungsanalytischen Untersuchungen am Reaktor der Technischen Universität Budapest bekannt. Der thermische Neutronenfluβ war 2·10¹¹ ncm^?28^?1, und es wurde ein Ge(Li)-Detektor mit 25 cm³ Volumen und einer Energieauflösung von 2 keV angewendet. Die untersuchten Tomatenproben enthielten durchschnittlich 85% Trockensubstanz. Es wurden folgende Konzentrationen an Spurenelementen ermittelt (in mg/kg): Br: 50,1; Mn: 10,2; Zn: 9,3; Cu: 6,6; As: 0,051; Sb:0,030; Au: 0,005.     

Surface modification of an epoxy resin with polyamines via cyanuric chloride coupling

The presence of polyamine groups on the surface of dielectric resins potentially improves the adhesion with electrochemically deposited metals. In this article, first cyanuric chloride is covalently bound to the surface hydroxyl groups of the epoxy resin. The remaining reactive sites on the coupled cyanuric chloride molecule are then used to anchor polyamines. New data on the triazine coupling is presented. The surface reactions are monitored and characterized by means of ATR-IR, SEM-EDS, XPS and ToF-S-SIMS.     

Ligand-assisted, copper-catalyzed enantioselective benzylic amination

Several classes of ligands, including α-amino acids, diamines, diphosphines, bis-oxazolines, and diimines, support efficient copper-catalyzed amination of benzylic hydrocarbons by anhydrous chloramine-T. Catalysts derived from homochiral ligands, particularly chiral diimines, effect aminosulfonation with low to moderate enantioselectivity.