Formation of volatile copper carbonyl during the preparation of copper nanoparticles in the copper acetate hydrate-polyacrylonitrile heterogeneous system under IR radiation

The products of reactions induced by IR heating in the copper acetate hydrate-polyacrylonitrile system and the intermediate Cu compounds formed during the preparation of Cu nanoparticles were studied by powder X-ray diffraction, atomic absorption spectroscopy, mass spectrometry, and IR spectroscopy. Mass spectra of the volatile products formed from the nanocomposite contain peaks typical of the CuCO molecular ion. After treatment of the nanocomposite at 500°C, the copper content in the composite decreased 10-fold as a result of evolution of volatile CuCO.     

Determination of copper in technical zinc electrolyte with the copper ion-selective electrode

Summary In technical zinc electrolyte of high ionic strength (10.4 M) a copper-sensitrode (type Cu₂Se/Ag₂Se) is able to measure direct-potentiometrically the copper content within a working range from 200 to 0.5 mg/l. The reproducibility of the potential readings is influenced by the quality of the electrode surface of the copper-sensitrode and by the composition of the reference cell. Zinc forms a surface layer on the sensor interfering with the emf-response. This effect may be avoided by a vibrating brush cleaning the electrode surface instantaneously. A special salt bridge developed for measuring in concentrated zinc solution diminished the liquid-junction potentials essentially. The determination of copper is not affected by cadmium (100–400 mg/l), manganese (1–4 mg/l), fluoride, chloride and arsenite. Iron(III) interfered considerably. The analyzing speed is lower than 10 min.

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Bestimmung von Kupfer in technischen Zinkelektrolyt-lösungen mit der Kupfer-selektiven Elektrode

Zusammenfassung In technischem Zinkelektrolyt hoher Ionenstärke (10,4 M) kann der Kupfergehalt im Arbeitsbereich von 200 bis 0,5 mg/l Cu direkt-potentiometrisch gemessen werden. Die Reproduzierbarkeit der Potentialwerte wird durch die Qualität der Elektrodenoberfläche der Kupfer-Sensitrode und die Zusammensetzung der Referenzzellen beeinflußt. Zink bildet eine Oberflächenschicht auf dem Sensor, die die Potentialanzeige stört. Dieser Effekt kann durch ständiges Bürsten der Elektrodenoberfläche mit einer vibrierenden Bürste verhindert werden. Eine speziell für die Messung in konzentrierter Zinkelektrolytlösung entwickelte Salzbrücke vermindert wesentlich die Diffusionspotentiale. Die Kupferbestimmung wird nicht beeinflußt durch Cadmium (100–400 mg/l), Mangan (1–4 mg/l), Fluorid, Chlorid und Arsenit, Eisen(III) stört erheblich. Die Analysenzeit beträgt weniger als 10 min.

     

Electrochemical processes on the copper electrode in water-ethanol solutions of copper sulfate

The system Cu/H₂O-C₂H₅OH-CuSO₄ was studied in a wide range of organic component concentrations by the impedance spectroscopy method. In the studied range of ethanol concentrations the diffusion of ions to an electrode is the limiting stage of the electrode process. An increase in the ethanol concentration results in a decrease in the double electrical layer capacity, which is caused by a change in the double electrical layer structure at the electrode-solution boundary.     

Stereochemistry of the copper perchlorate or copper bromide-catalyzed decomposition of aryldiazomethanes to stilbenes

Several phenyldiazomethanes easily decompose to $\text{cis}$- and $\text{trans}$-stilbenes when treated with catalytic amounts of copper perchlorate or copper bromide at 20°C. The preferential formation of $\text{cis}$ isomer is particularly noteworthy. The stereochemistry and the mechanism of these reactions will be discussed.     

A C-terminal domain of the membrane copper pump Ctr1 exchanges copper(I) with the copper chaperone Atx1

A cloned C-terminal domain of the yeast high-affinity copper uptake pump Ctr1 exchanges Cu(I) rapidly with the yeast copper chaperone Atx1: 10(-2) < Kex < 10(+2).     

ESCA studies of copper oxides and copper molybdates

Valence band, $\text{Cu}\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{,}\text{O}\text{1s,}\text{Mo}\text{3d}$, and Cu L₃M₄₅M₄₅ photoelectron and X-ray-induced Auger spectra were recorded for metallic copper, Cu₂O, CuO, Cu₂Mo₃O₁₀, Cu₆Mo₄O₁₅, CuMoO₄, Cu₃Mo₂O₉, and Cu_3.85Mo₃O₁₂. $\text{Cu}\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ binding energy is 0.9 eV lower for Cu⁺-containing molybdates than for Cu₂O and 0.7 eV higher for Cu²⁺-containing molybdates with respect to that of CuO. Calculation of net chemical shift demonstrates the influence of Madelung potential on the binding energy of core electrons. On the basis of differences in binding energy it was possible to distinguish between various Cu-containing phases and to follow the surface redox processes of copper molybdates which, as it was seen, follow the same reactions as in the bulk processes. Auger spectra suggest the presence of a very thin layer of “surface phase” common for all five studied molybdates and independent of bulk structure and composition.     

Systematic investigations of the multi-element preconcentration from copper by precipitation of the matrix as copper(I) oxide and copper(I) thiocyanate

Two methods for multi-element preconcentration from copper by reductive matrix precipitation are presented. In systematic investigations on the coprecipitation behaviour of Ag, Al, Au, Bi, Cd, Co, Cr, Fe, Ga, In, Mn, Mo, NJ, Pb, Sb, Se, Sn, Te and Zn during precipitation of the copper matrix as Cu₂O or CuSCN, the separation parameters were optimized. By combination with a hexamethyleneammonium hexamethylenedithiocarbamate collector precipitation, a concentration of 8 elements (Cu₂O precipitation) or 13 elements (CuSCN precipitation) in a small volume was achieved. The limits of detection of the procedures are, depending on the element, 0.1–5 μg g^?1 for flame atomic absorption spectrometry (AAS) and 0.01–0.1 μg g^?1 for graphite furnace AAS. The relative standard deviations are about 3%. The analytical performance of the procedures is compared with that of an electrolytic copper separation.     

碘量法测定废杂铜屑中的铜含量

采用硝酸-盐酸溶解样品,在硫酸体系下加入氢溴酸,使得氢溴酸与试样中的砷、锑、锡等元素反应生成易挥发的溴化物,从而消除其干扰,滴定前用氟化氢氨掩蔽铁,在pH=3.0～4.0的范围采用碘量法测定废杂铜屑中的铜含量。用于测定金属样废杂铜屑中铜的含量,测定结果的相对标准偏差(RSD,n=7)为0.20%～0.25%,加标回收率在98.8%～101%,方法简单准确,能够满足日常检测需求。     

Release of copper from commercial solid-state copper ion-selective electrodes

The release of copper from two commercial solid-state cupric ion-selective electrodes [Orion 94-29 Cupric Electrode (I) and Radiometer F1112 Selectrode (II)] was measured by immersion in the following media: 0.1M potassium nitrate (pH = 4.7), 0.5M sodium chloride (pH = 4.7) and 0.1M nitric acid. In the 0.1M potassium nitrate medium, the amount of copper released from both electrodes causes interference when they are used for the determination of cupric ion at the 10⁻⁷M level. In comparison with the 0.1M potassium nitrate medium, the copper release in the 0.5M sodium chloride and 0.1M nitric acid media was increased for electrode II but not for electrode I. The release of copper was not affected by removal of oxygen from the media but can be substantially lowered by coating the electrodes with a thin cation-exchange membrane (Nafion). The mechanism of copper dissolution is investigated.     

Effect of the fineness of copper slag on the early hydration properties of cement–copper slag binder

Journal of Thermal Analysis and Calorimetry - In this experimental work, a comparative study of convective heat transfer and drop in pressure characteristics of Alumina–Cu/water and...     

Kinetic evidence for the copper peroxide intermediate with two copper ions in proximity

The decomposition of caroate (peroxomonosulfate, PMS) is catalyzed by Cu(II) ions even at 5 × 10^?5 M in aqueous alkaline solution. The rate is second order in copper(II) ions concentrations and first order in [PMS]. The rate constant values are found to decrease with increase in hydroxide ion concentrations. The turnover number for the reaction is estimated as >1000. The experimental results suggest that the formation of peroxide type intermediate with two copper(II) ions is the rate‐determining step. This peroxide intermediate reacts with another molecule of PMS to give the products oxygen, SO and copper ions. The overall entropy of activation is positive with a value of ～20 cals/mol/K. The very high turnover number suggests that Cu(II) ion is one of the best catalysts for the decomposition of caroate ions in alkaline medium. The reaction also represents a system in which metal ion catalyzed decomposition of caroate does not involve radical intermediates. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 439–443, 2006     

Modelling the precipitation of copper oxalate aggregates

The precipitation of copper oxalate has been studied in a batch reactor. Like many other systems, the morphology of these particles suggests that they were formed by an aggregation mechanism. A mathematical model has been developed to predict particle-size distributions grown in a batch reactor, which accounts for growth by two competing mechanisms, i.e., atomistic growth and particle aggregation. The results of this model are in good agreement with experimental observations for the precipitation of copper oxalate aggregates and other spherical aggregation systems cited in the literature.     

INAA for the validation of chromium and copper determination in copper chromite by infrared spectrometry

Summary Elérhetoség     

Analysis of growth dynamics of dendrite copper deposit in copper sulfate solutions under the galvanostatic conditions

It is shown that, under certain conditions, the dynamics of dendrite copper deposit formation in the galvanostatic electrolysis may be analyzed using the model of cylindrical electrode, which was developed for the systems with a single cathodic reaction. The model enables one to estimate the structural parameters of the deposit (the radii of dendrite tips at the growth front r _tip and their location density N). The deposit growth dynamics was studied experimentally in the laboratory conditions by combining the recording of electrical parameters with video recording of dendrite deposit growth. An analysis of spectral density of measured chronopotentiograms is proposed as an additional way of following the formation dynamics of dendrite deposit, which is meant for the production of powder with prescribed structure.     

Unravelling the chemical nature of copper cuprizone

During the last 50 years, formation of the highly chromogenic copper cuprizone complex has been exploited for spectrophotometric determinations of copper although the precise chemical nature of the resulting species has never been ascertained; we eventually show here, in contrast to current opinion, that copper cuprizone is a copper(III)complex.     

Exploring the possibility of high-valent copper in models of copper proteins with a three-histidine copper-binding motif

An important function of many copper-containing proteins is activation of O2 and subsequent substrate oxidation. The Cu (III) oxidation state is generally considered to be less accessible because of the highly positive Cu (III)/Cu (II) redox potentials with typical amino acid ligands. Here, we employ density functional (DFT) calculations to explore to what extent copper (III) may be accessed in a biologically-relevant coordination environment around a mononuclear copper center, by breaking the oxygen-oxygen bond in a copper-(hydro) peroxide complex. In agreement with previous findings by Solomon and co-workers on copper models with related coordination patterns, the formally high-valent copper complex produced by O-O bond cleavage appears to harbor both oxidizing equivalents on the ligands. The potential energy surface for such a reaction reveals that with the three-histidine binding motif at the copper, O-O bond cleavage is not impossible, but rather disfavored thermodynamically.      

Parameters of electrical double layer on the boundary copper electrode/water-organic solution of copper sulfate

By the method of impedance spectroscopy the properties of the phase boundary of Cu|H₂O + i-C₃H₇OH + CuSO₄ system were investigated. The impedance hodographs were obtained, in the form of circles with displaced centers. The capacity values of electrical double layer, exchange currents, and resistance of the electrolyte solution depending on the mole fraction of 2-propanol were determined. The role of organic component in the formation of the electrical double layer in the studied system is elucidated.