Transport Of Copper Ions Research Articles

Chemical Kinetic Approach To The Mechanism Of Coupled Transport Of Cu(II) Ions Through Bulk Liquid Membranes

Transport of copper(II) ions through bulk liquid membranes is studied in various experimental conditions. The results obtained are analyzed by using the concepts and methods of chemical kinetics. This approach allowed kinetic equations to be established which are sufficiently general to account for a large variety of transport kinetics (steady or nonsteady state, first or zeroth order, diffusion or reaction controlled, reversible or irreversible), to identify clearly the rate-determining steps, and to propose a detailed mechanism at the molecular level. The important role played by the interfaces is also demonstrated.

Transcriptional regulation and function of the copper ion transport machinery: [formula omitted] University of Michigan Medical School. Ann Arbor, MI 48109-0606

Transcriptional regulation and function of the copper ion transport machinery: [formula omitted] University of Michigan Medical School. Ann Arbor, MI 48109-0606

Spectrochemical Characterization of Benzotriazole on Copper

The spectroelectrochemical behavior of Cu in 1 M sodium acetate solution, pH 5.8, alone and in the presence of benzotriazole (BTA) was investigated by cyclic voltammetry, impedance spectroscopy, and Raman spectroscopy. Impedance spectra are characterized by two time constants relating to charge transfer and transport of copper ions through the surface film, the latter being the rate‐determining factor. The finite diffusion impedance is analyzed using a diffusion factor (B), which is a function of the diffusion layer thickness (d) and the diffusion coefficient (Df) for species. The analysis suggests that changes in the film thickness can be monitored in situ by impedance spectroscopy. The values of Df and concentration of species (cf) in the film formed in the presence of 1 M BTA were estimated to be of the order 10−14 cm2 s−1 and 10−6 mol cm−3, respectively. The results indicate that the film formed at higher inhibitor concentration and longer immersion time behaves almost like an ideal capacitor. Its thickness (up to 20 nm) and protection against corrosion increase by increasing the BTA concentration and immersion time. The results obtained by Raman spectroscopy confirm the model for the complex Cu(I)BTA in which overlap of Cu sp‐hybrid atomic orbitals with the N‐hybridized lone‐pair atomic orbital occurs.

Comparison of carrier-facilitated copper(II) ion transport mechanisms in a supported liquid membrane and in a plasticized cellulose triacetate membrane

Transport of copper ions through a plasticized cellulose triacetate membrane containing lauric acid as carrier and tris(2-ethylhexyl)phosphate (TEHP) as plasticizer has been investigated. A comparative study of transport mechanism across such a membrane and a supported liquid membrane (SLM) containing the same carrier in THEP has been made. In both cases, transport mechanisms were controlled by the diffusion of 1:2 metal/carrier complex in the membrane and of copper ions through the aqueous diffusion layer at the source/membrane interface. Diffusion coefficient in the cellulose triacetate membrane, after normalization, was found to be 22 times lower than in the corresponding SLM.

The transport of Cu(II) through a sulfonated styrene/divinylbenzene copolymer membrane

The transport of copper (II) ions through sulfonated styrene/divinylbenzene copolymer ion permeable membranes under Donnan dialysis conditions has been investigated. The flux increases strongly with the copper (II) ion concentration and temperature. The other cation transported through the membrane and its concentration can also have some influence but it is relatively small.

Coupled transport of copper through different commercial supports containing LIX 984 as carrier

The coupled transport of copper(II) ions through a supported liquid membrane containing LIX 984 as the mobile carrier dissolved in kerosene has been studied. Many commercial membrane supports were investigated at different stirrer speeds in a permeation cell. An equation describing the permeation rate has been derived, taking into account stagnant layer aqueous diffusion and liquid membrane diffusion. By means of this treatment the copper overall transfer resistance and the experimental determination of the effective porosity factor (e/τ), for each support have been performed. The Accurel® 2E-PP membrane showed a relatively high value of e/τ (0.91), which makes this membrane an adequate support when the transport properties of the supported liquid membrane are concerned.

Copper Differentially Regulates the Activity and Degradation of Yeast Mac1 Transcription Factor

Copper is an essential metal ion that is toxic when accumulated to high intracellular concentrations. The yeast Mac1 protein is a copper-sensing transcription factor that is essential for both the activation and inactivation of genes required for high affinity copper ion transport. Here we demonstrate that in response to low copper ion concentrations Mac1 protein is rendered inactive for copper transporter gene transcription. Under high copper ion concentrations Mac1 is degraded in a rapid, copper-specific manner. This degradation is critical to prevent copper toxicity that would otherwise result from sustained expression of the copper transport genes. These results demonstrate that nutritional and toxic copper concentrations elicit distinct fates for the Mac1 copper-sensing transcription factor and establish a new mechanism by which trace metals regulate gene expression.

Stability of supported liquid membranes containing Acorga P-50 as carrier

The coupled transport of copper(II) ions through supported liquid membranes (SLM) was examined in zeroth order steadystate kinetic regime using Acorga P-50 as carrier. SLM life-times were estimated using a new method based on kinetic analysis. The influence of different experimental conditions on the transport rate allowed to establish various factors determining membrane stability. SLM life-time seems to depend in a clearcut way on both the type of polymeric support and the nature of liquid membranes suggesting that solute-solvent (and polymer solvent) interactions play a dominant role in membrane stability. It was shown that water transport, if any, occurs only through empty pores of the polymeric support. No clear effect of osmotic pressure gradient on liquid membrane stability was found.

Equilibrium and Kinetic Studies of Copper Ion Uptake by Calcium Alginate

Equilibrium and kinetic experiments of copper ion uptake by calcium alginate beads were carried out under different values of pH, ionic strength, initial concentration of copper ion, and amount of calcium alginate. The removal efficiency increases with increasing pH and decreasing ionic strength and initial concentration. The removal of copper occurs rapidly in the first hour, followed by a slow process that takes about 15 h. The copper ion uptake becomes faster with increasing pH and decreasing initial copper concentration and ionic strength. Mass transport of copper ions plays an important role in the kinetics of uptake. Equilibrium experiments show that surface complex formation is the major mechanism for copper ion uptake. Modeling of equilibrium and kinetics was also conducted based on a surface complexation approach. Modeling results showed that the two-pK Basic Stern model can successfully describe the effect of pH on equilibrium uptake. A diffusion-controlled model can also predict the effect of pH on the kinetics.

Cloning and characterization of corA, a gene encoding a copper-repressible polypeptide in the type I methanotroph, Methylomicrobium albus BG8

In an attempt to identify proteins involved in copper transport in the type I methanotroph Methylomicrobium albus BG8, copper-regulated polypeptides were examined. One major copper-repressible membrane polypeptide of approx. 28 500 Da was identified and designated CorA. The gene encoding this polypeptide was isolated and sequenced, and it shared a low identity with a calcium channel protein. An insertion mutation in corA of M. albus BG8 grew very poorly, suggesting that CorA is important for growth of this methanotroph. CorA may be involved in transport of copper and/or other divalent metals ions in M. albus BG8.

A surface coverage model for pulse-plating of binary alloys exhibiting a displacement reaction

Models for the prediction of the composition of pulse-plated copper-nickel alloys in the presence and absence of a displacement reaction during the pulse off-time are reviewed and critically evaluated. For very long and very short pulse off-times the composition of copper-nickel alloys deposited from electrolytes containing an excess of nickel ion is entirely controlled by mass transport of copper ion. At intermediate pulse off-times, however, the kinetics of nickel dissolution play a role. A modified model is proposed which takes into account the role of surface coverage by copper for the rate of nickel dissolution. Assuming a step function for the variation of surface coverage with off-time the model predictions can be fitted to experimental data using the critical off-time which corresponds to a change in surface coverage from zero to one as adjustable parameter. The model is used to estimate for different experimental conditions the amount of copper leading to a suppression of the displacement reaction. More copper is deposited by the displacement reaction in sulfamate than in citrate electrolytes.

Ionic diffusion and local hopping in copper chalcohalide glasses measured using 64Cu tracer and 129I-Mössbauer spectroscopy

For the first time, 64Cu tracer measurements of ionic diffusion were performed for several copper-rich glass compositions in the CuIAs 2Se 3, CuISbI 3As 2Se 3, CuIPbI 2As 2Se 3, CuIPbI 2SbI 3As 2Se 3 and Cu 2SeAs 2Se 3 systems. In accordance with previous a.c. impedance results and Wagner d.c. polarization measurements, it was found that pure Cu + ion-conducting glasses (50CuI17PbI 233As 2Se 3 and 50CuI20PbI 210SbI 320As 2Se 3) exhibit the highest copper tracer diffusion coefficients, D Cu , and the lowest diffusion activation energies. The values of D Cu at room temperature are higher by 4.5–5.5 orders of magnitude than those in an As 2Se 3 glass. The Haven ratio, H R , is found to be 0.52–0.61 (ternary glass) and 0.93–1.00 (quaternary glass). Short-range diffusional displacements of the iodide ions induced by the hopping Cu + ions are also detected in the CuIPbI 2SbI 3As 2Se 3 glassy system using 129I-Mössbauer spectroscopy in the temperature range of 4.2 to 305 K. The activation energy of local hopping, E h ≈ 0.31 eV, is very similar to that of bulk ionic conductivity (0.37 eV) and copper diffusion (≈ 0.33 eV). In contrast to CuI-based vitreous alloys, 50Cu 2Se50As 2Se 3 glass exhibits D Cu that are two to five orders of magnitude lower, and the copper ion transport number, t Cu + , is between 10 −3 and 10 −4 in the temperature range 140–170 °C.

Ion transport studies in calcium alginate gels by magnetic resonance microscopy

Polyelectrolyte biopolymers such as calcium alginate are becoming increasingly important for the recovery of heavy metals from aqueous solutions. To understand the mechanism of ion transport in these biopolymer systems, the transport of copper ions into calcium alginate gels was investigated using proton nuclear magnetic resonance (NMR) microscopy. Copper ion transport was imaged using an inversion recovery technique which utilizes the paramagnetic effect of copper on water proton relaxation times. Diffusion experiments were performed in a diffusion cell designed to approximate a semi-infinite slab geometry at temperatures between 278 and 313 K using copper reservoir concentrations between 10 and 60 mM. The diffusion coefficient of copper in these gels was calculated from the NMR data to fit a combined diffusion-reaction model involving a diffusion term ( D) and a kinetic binding term ( k). At 23 °C, the diffusion coefficients in 1, 2, and 3% (w/v) gels were 3.1 · 10 −10, 2.0 · 10 −10, and 1.4 · 10 −10 m 2/s, respectively. The activation energy for diffusion in the 2% (w/v) gel was 28 kJ/mol.

Coupled transport of copper through different types of liquid membranes containing Acorga P-50 as carrier

The coupled copper ion transport through bulk and supported liquid membranes containing Acorga P-50 as carrier has been examined. The influence of membrane material (organic solvent, carrier concentration, polymeric support) aqueous donor (initial copper concentration) and acceptor (acid concentration) phase compositions has been established. It was found that copper ion fluxes through supported liquid membranes change in the same way as bulk transport fluxes under the influence of the various external factors studied, independently of kinetic regime used. A new method is proposed for estimating diffusion layer thickness in bulk liquid membranes and for characterizing unknown porosity of polymeric supports.

Transport and separation of cobalt, nickel and copper ions with alamine liquid membranes

AbstractThe transfer and separation of Co(II), Ni(II) and Cu(II) ions across a flat‐sheet supported liquid membrane containing Alamine 336 as the mobile carrier dissolved in kerosene solvent has been investigated. Both the Alamine composition in the organic solution and the hydrochloric acid concentration in the feed solution have a marked effect on Co(II) and Cu(II) transport. A maximum flow of these ions at 50% of Alamine in the diluent was obtained. Ni(II) ion was not transported in the whole range of experimental conditions studied and good separation from Co(II) and Cu(II) could thus be performed. With decreasing hydrochloric acid concentration in the feed solution the separation factor of Cu(II) from Co(II) increases thus decreasing the Cu(II) recuperation factor.

Electrochemical Oxidation of Covellite (CuS)in Alkaline Solution

The anodic oxidation of the surface of natural covellite in 0.1 M Na2B4O7 (pH 9.2) has been investigated using cyclic voltammetry, chronoamperometry, chronopotentiometry, electrode impedance spectroscopy, and X-ray photoelectron spectroscopy. At potentials < 0.48 V vs S.C.E. (saturated calomel reference electrode), copper dissolution occurred without copper (hydr-)oxide forming a passive film on the covellite surface; copper ion transport from the bulk covellite through a copper-depleted layer to the electrode/electrolyte interface was rate determining. In the potential range 0.48 to 0.92 V vs S.C.E., the copper(II) solubility was exceeded locally, so that a passivating copper (hydr-)oxide film covered the electrode surface. The oxidation process was then controlled by copper ion transport from the hulk covellite, through both a copper-depleted layer and a copper (hydr-)oxide film, to the electrode/electrolyte interface. The copper (hydr-)oxide film was thin and subsequently could be dissolved chemically in 1 min at open circuit potential. At potentials > 0.92 V vs S.C.E., the copper (hydr-)oxide film thickened, retarding the covellite anodic oxidation process; this film remained on the electrode surface for longer when the electrode was switched to open circuit potential. However, because a small amount of sulfur was oxidized to sulfate at the higher potentials, the passive layers were porous and showed a smaller polarization resistance.

Copper(II) and copper(I) complexes of “tweezer” ligands, influence of substituents on the transport of copper(II) ions across liquid membranes

“Tweezer” ligands obtained by the condensation of 2,9-diformyl-1,10-phenanthroline and o-substituted aromatic primary amines were used for the syntheses of copper(II) and copper(I) complexes. By varying the nature of the ortho substituent on the aromatic primary amine, several ligands were obtained which form 1:1 complexes. When the substituent was any one of the F, Cl, Br or CH 3 groups, monomeric complexes were obtained. With OCH 3 and SCH 3 groups as substituents the formation of loosely held dimers was proposed from spectral, ESR and magnetic results. Ligands of the latter type were shown to be effective carriers for the transport of CU + ions across organic liquid membranes.

Selective Transport of Copper(I, II), Cadmium(II), and Zinc(II) Ions through a Supported Liquid Membrane Containing Bathocuproine, Neocuproine, or Bathophenanthroline

Abstract Some selective transport systems for heavy metallic ions through a supported liquid membrane (SLM) containing a 2,2′-dipyridyl derivative ligand, 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline (bathocuproine), 2,9-dimethyl-1,10-phenanthro-line (neocuproine), or 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline), were investigated. The transport of copper(I, II), cadmium(II), zinc(II), lead(II), and cobalt(II) ions was accomplished with a halogen ion such as chloride, bromide, or iodide ion as a pairing ion species for any SLM. The ranking of the permeability of the metallic ions was Cu+,2+, Zn2+, Cd2+ ≫ Pb2+, Co2+. When the oxidation-reduction potential gradient was used as a driving force for metallic ions, the transport of Cu+ ion was higher than those of Cd2+ and Zn2+ ions for any SLM containing bathocuproine, neocuproine, or bathophenanthroline. On the other hand, in the transport system which used the concentration gradient of pairing ion species, the permeability of the Cu2+ ion decrease...

Leaching processes of the dicalcium silicate and copper oxide solidification/stabilization system

Cement based solidification/stabilization technology has been widely practiced for the treatment of inorganic hazardous wastes, especially metal‐bearing wastes. The advantage of using the solidification/stabilization process is that the mobility of the hazardous materials is greatly retarded in the final disposal sites. The purpose of this study is to assess the stability of a synthetic solid waste through the renewable leaching test. A major cement constituent, dicalcium silicate (C2S), was used as a model binder to react with copper oxide to form a solid waste matrix. The semi‐dynamic leaching test using 1 N acetic acid was employed to investigate the leaching characteristics of the C2S/CuO system. The results show that the dissolution of Ca(OH)2 is the primary mechanism for the destruction of the matrix, and the subsequent leaching of copper ion. The surface‐controlled dissolution reaction increases the pore size and porosity of the matrix, thus increasing the diffusion rate of copper ion transport. The C2S hydration product, silicate hydrate, might play a role in adsorbing the copper ion in the leaching system.

Investigation of the rate-limiting step of coupled copper ion transport through liquid membranes by means of variable speed experiments

Coupled transport of copper(II) ions through liquid membranes ( n-octane) containing Acorga P-50 as a carrier was examined using variable membrane stirring speeds. The linear dependence of the membrane entrance ( k 1d) and exit rates ( k 2a) on the stirring speed for two carrier concentrations suggests that the diffusion of the metal-carrier complex thorugh the narrow layers situated between the interfaces and the bulk of the membrane is the rate-determining step. The membrane was stable during the transport experiments (no leakage of carrier and carrier-metal complex to both aqueous phases and no supplementary water penetration into the membrane). This favours the interfacial character of the metal-carrier complexation reaction.