Pure CuCl Research Articles

Capacitive-faradaic fuel cells (CFFCs) for selective separation of copper(II) ions from water and wastewater

• The mechanism of Cu 2+ ions removal from water by the CFFCs was studied. • Cu 2+ are catalytically reduced to Cu 0 by H 2 on the Pt within the separation step. • The Cu 0 is oxidized by oxygen within the regeneration step. • The electrosorption mechanism is insignificant in Cu 2+ separation by the CFFCs. • Cu 2+ ions are selectively separated from Ni 2+ , Cd 2+ , Fe 3+ , Ca 2+ , Mg 2+ and Zn 2+ . The capacitive-faradaic fuel cells (CFFCs), previously proposed for separation of anions and cations from water and wastewater, were investigated for Cu 2+ ions removal. It is shown in this study that the electrosorption of copper ions plays an insignificant role in the process and the major mechanisms that govern the H 2 -induced Cu 2+ separation and the O 2 -induced regeneration of the CFFCs are ( i ) catalytic reduction of Cu 2+ ions into the elemental copper (Cu 0 ), and ( ii ) oxidation of Cu 0 into Cu 2+ ions, respectively. The process was investigated in pure CuCl 2 solutions at different pH values with an activated granular charcoal on which different loadings of Pt catalyst were embedded (0, 0.1, 0.25, 0.5, 1.0 and 2.5 %wt.). Higher adsorption density of Cu was obtained at higher Pt loading (i.e., 30 mgCu/gCFFCs in 0.1%Pt-CFFCs and 75 mgCu/gCFFCs in 2.5%Pt-CFFCs), but the Pt-utilization efficiency decreased from 30 mgCu/mgPt in 0.1%Pt-CFFCs to 3 mgCu/mgPt in 2.5%Pt-CFFCs. Better Cu 2+ removal was achieved at higher pH due to lower reversible potential of the hydrogen oxidation reaction. Excellent selectivity of the process for Cu 2+ ions removal was obtained in experiments conducted with aqueous solution that comprised Cu 2+ , Ni 2+ , Cd 2+ , Fe 3+ , Ca 2+ , Mg 2+ and Zn 2+ ions (100 mg/l each). Further studies are required to develop the CFFCs with ultralow Pt loading or/and to replace Pt with non-noble metal catalysts.

Ferromagnetism in partially oxidized CuCl

A search for superconductivity in systems of CuCl/Si and CuCl2/Si leads to the observation of ferromagnetism with a Tc of 18K in powder samples. The magnetism emerges when pure CuCl is exposed to humid air, while the observed magnetic moment depends on the exposure level. We used magnetic field modulated microwave spectroscopy, as well as SQUID magnetometry, to identify magnetic phase transitions as a function of temperature. Crystallographic phase information of partially oxidized CuCl specimens is obtained via x-ray diffraction and Rietveld refinement. Transition temperature and moment are found to be unmatched with transitions in CuCl based compounds reported to date.

Modified Markó’s aerobic oxidation of alcohols under atmospheric pressure with air or molecular oxygen at room temperature

A modified version of Markó’s aerobic oxidation procedure, using highly pure (99.995+%) CuCl with 4,7-diphenyl-1,10-phenanthroline (dpPhen), DBAD, and Cs2CO3 (98% purity) successfully oxidized primary and secondary alcohols to the corresponding aldehydes and ketones in excellent yield at room temperature with either air or molecular oxygen under atmospheric pressure.

CuCl/phen/NMI in Homogeneous Carbonylation for Synthesis of Diethyl Carbonate: Highly Active Catalyst and Corrosion Inhibitor

The effects of N-donor ligands on CuCl-catalyzed oxidative carbonylation of ethanol were investigated. It was found that 1,10-phenanthroline (phen) and N-methyl imidazole (NMI) exhibited a synergic effect on the catalytic activity. Catalytic efficiency of the CuCl system was enhanced dramatically, and corrosion of the reaction system was effectively inhibited when phen and NMI were simultaneously used as the ligands. Under the reaction conditions of cCuCl = 0.2 mol/L, nCu:nphen:nNMI = 2:1:1, T = 393 K, P = 2.4 MPa with PCO/PO2 = 2:1, and time = 3 h, conversion of ethanol and selectivity to diethyl carbonate (DEC) were 15.2% and 99.0%, respectively. As compared to pure CuCl, the catalytic activity of CuCl/phen/NMI is much higher (3.6-fold). Furthermore, the high catalytic activity could be kept for a long time of service during the reaction. Corrosion of CuCl was also inhibited by using phen and NMI as ligands. For example, the inhibition efficiencies of CuCl/phen/NMI catalyst system on stainless steel 304...

Intramolecular segregation in polymers and macromolecules studied by low-energy ion scattering

The intramolecular segregation in several generations of poly(propylene imine) dendrimers and oxygen plasma modified HDPE was studied with low-energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS). Although the different generations of poly(propylene imine) dendrimers contain almost the same atomic carbon to nitrogen (C/N) ratio, it is shown that this ratio at the outermost surface depends strongly on the generation of the dendrimer. The conformation of a dendrimer is probably related to the flexibility of the bis(3-aminopropyl)amine endgroups, which becomes lower for higher generations. Furthermore, the formation of a metallodendrimer, by complexation of CuCl 2 with the amine endgroups of a fourth generation dendrimer (D4), was followed with LEIS. Compared to pure CuCl 2, a relatively high copper concentration and a high atomic copper to chlorine ratio was found at the surface of the metallodendrimer. The high copper concentration and the reduced sterical hindrance by chlorine demonstrate the high potential of the metallodendrimers as catalytic material. The hydrophobic surface of HDPE can be made hydrophilic by treating it in an oxygen plasma. During such a treatment, oxygen containing functional groups are introduced at the surface, which improves wetting and thus adhesion. Unfortunately, the effect of an oxygen treatment is only temporary, an effect referred to as ageing or hydrophobic recovery. LEIS has been used to study this ageing process. We were able to follow the surface oxygen concentration as a function of the time between the plasma treatment and the LEIS analysis. Combined information obtained from LEIS and XPS measurements indicates that the ageing is mainly confined to the outermost atomic layers. Moreover, the ageing process depends strongly on the exact experimental conditions.

Synthesis and thermal properties of the inorganic–organic transition metal halogenides CuCl–pyrazine and Cu 2Cl 2–pyrazine

The coordination polymers CuCl–pyrazine and Cu 2Cl 2–pyrazine were synthesised by the reaction of CuCl with pyrazine in aqueous solution under hydrothermal conditions. Using an excess of pyrazine, phase pure CuCl–pyrazine can be prepared in high yield. On lowering the pyrazine excess only a small amount of Cu 2Cl 2–pyrazine can be obtained as a phase mixture with CuCl–pyrazine. Phase pure Cu 2Cl 2–pyrazine can only be synthesised via thermal decomposition of CuCl–pyrazine. This reaction was investigated using simultaneously difference thermal analysis and thermogravimetry measurements (DTA–TG), mass spectrometry, thermomicroscopy and temperature resolved X-ray powder diffraction.

Lattice phonon modes of the high-pressure phase CuCl-IV

Raman spectra of isotopically pure CuCl samples ${(}^{63}\mathrm{CuCl}$ and ${}^{65}\mathrm{CuCl})$ were measured under hydrostatic pressure up to 14 GPa at low temperature $(5 \mathrm{K}).$ Up to six Raman modes were resolved for the binary BC8-analog phase CuCl-IV in the range from 4.1 to 14 GPa. The phonon dispersion relations of this phase were calculated within a rigid ion model. Based on this calculation an assignment for the observed Raman-active modes is proposed. The calculated pressure dependences of mode frequencies reproduce the experimental results. Raman spectra support the existence of the phase CuCl-IIa in a narrow pressure range from 3.3 to 4.1 GPa.

Preparation of CuCl microcrystals-doped SiO2 glass by co-sputtering method

CuCl microcrystals-doped SiO2 glass is prepared by the co-sputtering method using extremely pure CuCl source materials as well as a pure SiO2 target. Low temperature optical absorption spectra (2 K) show the shift of the Z1,2 as well as the Z3 exciton peaks, indicating that the mean radius of the microcrystals is about 5.8 nm.

Investigations of exfoliating graphite intercalation compounds using time-resolved DEXAFS

The exfoliation processes (rapid thermal decomposition) of CuCl 2 graphite intercalation compounds (GICs) cointercalated with FeCl 3 or AlCl 3 were investigated using time resolved X-ray absorption spectroscopy in an energy dispersive mode. The experiments were carried out at the DEXAFS beam line at HASYLAB (Hamburg). The evolution of the absorption spectra of the Cu K-edge was compared with the reaction of pure CuCl 2 under the same conditions. From the exfoliation of the CuCl 2 /AlCl 3 -GIC a CuO graphite compound can be obtained. The formation resembles the reaction of pure CuCl 2 , whereas the exfoliation of the CuCl 2 /FeCl 3 -GIC results in a mixture of Cu 2 O, CuO and Cu clusters

Ultrasonic Velocity and Density Measurements of Molten CuCl–CuBr Mixtures

The ultrasonic velocity, sound attenuation and density measurements have been carried out for molten Cu(Cl 1- x Br x ) mixtures at temperatures from the melting points to about 800°C to investigate the thermodynamic and dynamical properties. The adiabatic compressibility of this system has obtained from the observed ultrasonic velocity and density. The observed compressibility has an interesting concentration dependence of positive deviation from linear one and has the maximum around Cu(Cl 0.2 Br 0.8 ), which suggests large fluctuations in the molten mixtures compared with pure molten CuCl and CuBr. The sound attenuation shows large temperature dependence around x =0.2 and 0.8. We discuss the thermodynamic and dynamical properties of the molten mixtures from a view point of chemical bond, taking the difference of ionicity between Cl and Br into account.

Solubilities, densities and electrical conductivities of aqueous copper(I) and copper(II) chlorides in solutions containing other chlorides such as iron, zinc, sodium and hydrogen chlorides

With a view to industrial applications, solubilities, densities and electrical conductivities of aqueous copper(I) and copper(II) chlorides were measured in solutions containing other chlorides like those of iron, zinc, sodium and hydrogen. In these solutions copper(I) chloride shows a behaviour similar to that observed in pure CuClNaClHCl solutions. Increasing the FeCl 2 concentration decreases the solubility of CuCl less than increasing the ZnCl 2 concentrations does. Moreover, increasing total Cl − concentration increases CuCl solubility if Cl − is added as FeCl 2 and decreases CuCl solubility if Cl − is added as ZnCl 2. NaCl solubility remains unchanged by FeCl 2 additions and is increased by ZnCl 2 additions. Copper(II) chloride also shows in these solutions a behaviour similar to that observed in pure CuCl 2NaClHCl solutions. FeCl 3 additions decrease CuCl 2 · 2 H 2O solubility in a more drastic manner than ZnCl 2 additions. However, NaCl additions have a much higher effect. These results can be qualitatively interpreted when taking into account the relative Cl − donor or acceptor character of the constituent chloride salts of the solution. FeCl 2 additions slightly decrease the electrical conductivity of Cu(I) solutions. However, this can easily be compensated by a slight increase in temperature or in acidity.

Molecular beam epitaxy of CuCl films on mica

Molecular beam epitaxy of pure CuCl films on mica was studied for various substrate temperatures (16–250 °C). Both the transmission Laue method and diffractometer methods were used to characterize the films. All films showed the [111] zinc blende texture but only those films prepared at about 150 °C showed excellent, though twinned, epitaxy.

Enhanced ionic conduction and disproportionation in pure CuCl at high pressure

The optical and electrical properties of pure cuprous chloride (CuCl) single crystals have been studied under pressure up to 12 GPa. The transition pressures for the three crystallographic phases have been determined as 5.1 ± 0.1 GPa (ZnS → tetragonal) and 8.8 ± 0.4 GPa (tetrag.-NaCl). During the transition at 5.1 GPa, where the coordination number changes, the formation of cupric ions is observed. This is interpreted as a result of a partial, transient, and reversible disproportionation. In the ZnS and NaCl phase, an enhanced ionic conductivity is found following the first transformation into the tetragonal structure. The concentration of the mobile ions is typically 10 18 cm −3 and their diffusivity is ∼ 4×10 −7 cm 2s −1. An applied voltage in excess of 0.7 V causes anodic oxidation of Cu + which mimics much higher conductivity.

Definite Experimental Evidence against Intrinsic Electron-Hole Superconductivity in Pure CuCl

Optical absorption measurements on very pure CuCl single crystals, prepared by a novel process, show the exponential drop of the direct optical absorption edge to continue below an absorption coefficient $K\ensuremath{\sim}{10}^{\ensuremath{-}2}$ ${\mathrm{cm}}^{\ensuremath{-}1}$. This rules out unambiguously the existence of an indirect-gap absorption below 3 eV, which is not only consistent with band-structure calculations but also excludes pure CuCl from being a suitable candidate for intrinsic high-${T}_{c}$ superconductivity (on the grounds of existing theories).

Absorption spectra of heavily Cu+-doped KCl, SrCl2 and KI crystals

Optical absorption and magnetic circular dichroism spectra have been investigated in heavily Cu+-doped KCl, SrCl2, and KI crystals (the concentration is more than 0.1 mole%). In KCl, CuCl microcrystal is formed in the annealed crystals and gives rise to two sharp bands in the 350–380 nm region, which are attributable to the Z1,2 and Z3 exciton bands in the microcrystal by analogy with the Z1,2 and Z3 exciton bands of pure CuCl crystal. The two bands of the microcrystal shift toward lower energy and approach to the pure CuCl exciton band spectrum with increasing microcrystal size. Similar microcrystal has been suggested to be formed in CuCl-doped SrCl2, and CuI microcrystal in CuI-doped KI.

Cuprous hydrometallurgy: Part VIII. Solvent extraction and recovery of copper(I) chloride with organic nitriles from an iron(III), copper(II) chloride, two-step oxidative leach of chalcopyrite concentrate

Water-immiscible organic nitriles selectively extract copper(I) chloride as CuCl from aqueous chloride solutions. The distribution coefficients for the extraction of metal chlorides are in the order Ni 2+ ⪡ Fe 2+ < Na + < Cu 2+ ≈ Co 2+ < Cu + ⩽ Fe 3+. The equilibrium Cu 2+ + Fe 2+ ⇌ Cu + + Fe 3+ lies strongly to the right in nitrile solutions containing a small amount of water. When volatile nitriles containing some water are used as extractants, CuCl may be recovered from the organic phase by stripping the solvent with steam. Pure CuCl, suitable for reduction to electrolytic-grade copper, is precipitated from the residual aqueous phase. A process is demonstrated for the recovery of pure CuCl from chalcopyrite concentrate, in which a two-stage, iron(III), copper(II) chloride leach is used to maximize the amount of CuCl relative to CuCl 2 formed in solution.

Heat content and thermal electromotive force of the molten system, AgCl + CuCl

Measurements have been made of the heat content and thermal e.m.f. of AgCl, CuCl and of mixtures of these compounds.Heat content measurements were made in the temperature range 350 to 950 K by drop calorimetry. Results for the pure compounds agree well with the recent measurements of Thompson and Flengas. The integral heats of mixing calculated from the data are small (∼–0.5 kJ mol–1 at 750 K and 0.5 mole fraction). The variation of the specific heat of the liquid mixtures with mole fraction is anomalous, and may indicate complex formation in the melts.Measurements of the initial thermal e.m.f. (θ) were made with reversible electrodes. A recent extension of the Wagner–Pitzer approximation was used to calculate the heterogeneous contribution to θ. The heat of transport term, ∑i(tiQ*i/zi) has been calculated from the homogeneous contribution, θhom, for each composition studied. It varies from about 9.9 kJ mol–1 for pure AgCl to 14.6 kJ mol–1 for pure CuCl. The heat of transport term was also estimated from the temperature dependence of θhom and the results are consistent with the values calculated directly. A simple model is presented which accounts qualitatively for the variation of ∑i(tiQ*i/zi/zi) with composition. The data of Sinistri, Pezzati and co-workers on other binary halide systems are reconsidered in terms of this model.

ChemInform Abstract: REACTIVITY AND CATALYTIC ACTIVITY OF COPPER CHLORIDES PART 4, ELECTRICAL PROPERTIES AND ACCEPTOR LEVELS PRODUCED IN CUCL BY CL2 GAS

AbstractMessungen der elektrischen Leitfähigkeit, der Thermo‐EMK und der Transportzahlen von reinem oder mit Cl2‐Gas behandeltem CuCl im Bereich von 24‐240°C zeigen, daß die beobachteten Erscheinungen weniger auf elektronischer als auf ionischer Leitung beruhen, abgesehen von den Messungen an reinem CuCl oberhalb 140°C. Zwei Akzeptorniveaus bei 0,51 und 0,88 eV oberhalb des Valenzbandes werden nachgewiesen.

Reactivity and catalytic activity of copper chlorides. Part 4.—Electrical properties and acceptor levels produced in CuCl by Cl2 gas

Studies of electrical conductivity, thermoelectric power and transport numbers in CuCl, pure or after exposure to Cl2 gas, in the range 24–240°C, have shown that all phenomena observed are caused by electronic rather than ionic conduction, except in pure CuCl above about 140°C. Two acceptor levels are identified, at 0.51 and 0.88 eV above the valence band. The former is attributed to cation vacancies; the latter, tentatively, to anion interstitials. For high concentrations of cation vacancies, the conduction below 100°C is predominantly by electrons in a narrow band at the acceptor level, the activation energy of this “hopping” process being 0.36 eV. The difference between the two acceptor levels is briefly discussed in terms of ligand field splitting of the Cu 3d orbitals.

Optic phonons in mixed crystal of CuClCuBr

Optic phonons in CuClCuBr mixed crystals have been studied by means of Raman scattering and infrared absorption measurements. It is concluded that this system belongs to the two-mode type. The observed behaviour of the phonon mode is accounted for by the modified random-element-isodisplacement model fairly well. In connection with this interpretation, the origin of the double peak in the pure CuCl is discussed.