A fundamental study on recovery of copper with a cation exchange membrane: Part 1 — Ion exchange equilibria between cupric and hydrogen ions

It is possible to concentrate metal ion against the gradient of its concentration through a cation exchange membrane. The membrane has a high ion exchange capacity and is hydrophilic, therefore a rapid transfer rate of ions is expected. Ion exchange equilibrium data between cupric and hydrogen ions for sulfuric and nitric acid systems are obtained and analyzed quantitatively for concentrations of dissociated cupric and hydrogen ions.     

Mechanistic study of active transport of copper (II) using LIX 54 across a liquid membrane

The present work describes the mechanism of active transport of copper(II) through an immobilized liquid membrane (ILM) containing LIX 54 (β‐diketone) dissolved in Iberfluid as mobile carrier. An uphill transport model has been described and equations have been derived taking into account aqueous boundary layer diffusion and liquid membrane diffusion as simultaneous controlling factors. In the present model, various cases were discussed using the carrier LIX 54 and different chemical species; the diffusional membrane resistance for lower and higher concentrations of extractant was evaluated. The diffusion coefficients were observed to decrease with increase in ­the extractant concentration, ranging from 4.1 × 10⁻³ to 1.65 × 10⁻² mol dm⁻³ Plotting [Cu]₀−[Cu]_t vs time resulted in a slope of [HR]₀A/2Δ_orgV taking into account the complex species, CuR₂, in the membrane. The mass transfer coefficient (Δ_org ⁻¹), the diffusion coefficient of the metal carrier species (D_org) and the thickness of the aqueous boundary layer were calculated from the proposed model for LIX 54. More than 90% of the Cu(II) could be separated using LIX 54 in the presence of various metals such as Ni, Co(II) and Zn. © 2000 Society of Chemical Industry     

New liquid membrane technology for simultaneous extraction and stripping of copper(II) from wastewater

In this paper, a new liquid membrane technique, hollow fiber renewal liquid membrane (HFRLM), is presented, which is based on the surface renewal theory, and integrates the advantages of fiber membrane extraction, liquid film permeation and other liquid membrane processes. The results from the system of CuSO₄+D2EHPA in kerosene+HCl show that the HFRLM process is very stable. The liquid membrane is renewed constantly during the process, the direct contact of organic droplets and aqueous phase provides large mass transfer area. These effects can significantly reduce the mass transfer resistance in the lumen side. Then the mixture of feed phase and organic phase flowing through the lumen side gives a higher mass transfer rate than that of stripping phase and organic phase, because the aqueous layer diffusion of feed phase is the rate-controlling step. The overall mass transfer coefficient increases with increasing flow rates and D2EHPA concentration in the organic phase, and with decreasing initial copper concentration in the feed phase. The overall mass transfer coefficient also increases with increasing pH in the feed phase, and reaches a maximum value at pH of 4.44, then decreases. Also, there is a favorable w/o volume ratio of 20:1 to 30:1 for this process. Compared with hollow fiber supported liquid membrane and hollow fiber membrane extraction processes, HFRLM process has a high mass transfer rate. Mathematical model for the HFRLM process based on the surface renewal theory is developed. The calculated results are in good agreement with experimental results under the conditions studied.     

Dual-phase membrane reactor for hydrogen separation with high tolerance to CO2 and H2S impurities

Catalytic membrane reactors based on oxygen-permeable membranes are recently studied for hydrogen separation because their hydrogen separation rates and separation factors are comparable to those of Pd-based membranes. New membrane materials with high performance and good tolerance to CO₂ and H₂S impurities are highly desired. In this work, a new membrane material Ce_0.85Sm_0.15O_1.925–Sr₂Fe_1.5Mo_0.5O_6-δ (SDC–SFM) was prepared for hydrogen separation. It exhibits high conductivities at low oxygen partial pressures, which is benefit to electron transfer and ion diffusion. A high hydrogen separation rate of 6.6 mL cm⁻² min⁻¹ was obtained on a 0.5-mm-thick membrane coated with Ni/SDC catalyst at 900°C. The membrane reactor was operated steadily for 532 h under atmospheres containing CO₂ and H₂S impurities. Various characterizations reveal that SDC–SFM has good stability in the membrane reactor for hydrogen separation. All facts confirm that SDC–SFM is promising for hydrogen separation in practical applications. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1088–1096, 2019     

Electroless copper plating using Fe as a reducing agent

Although the electroless plating method is known to be an effective method for obtaining fine wiring in particular, 1 mol hydrogen gas is generated during 1 mol Cu deposition, and voids are generated in the wiring when electroless Cu plating is applied to fine wiring. To avoid the hydrogen evolution, the possibility of performing electroless Cu plating was confirmed using an inexpensive Fe^II compound as a reducing agent. The bath contains CuSO₄, FeSO₄, NaCl, ethylenediamine, sodium citrate, polyethylene glycol (PEG), and 2,2′-bipyridine. Under optimal conditions, over 1.7 μm of copper deposit with a smooth surface was obtained after 3 h of plating, which did not contain iron as an impurity. The electrical resistivity of the copper film is about 3-4 μΩ cm corresponding to that of electroplated copper films.     

Adsorption and reaction induced morphological changes of the copper surface of a methanol synthesis catalyst

The morphology (surface structure) of the copper component of an industrial Cu/ZnO/Al₂O₃ methanol synthesis catalyst has been studied by carbon monoxide temperature programmed desorption (CO TPD). The initial state morphology produced by hydrogen reduction at 513 K showed evidence of the existence of Cu(111), Cu(110) and Cu(211) surfaces. Surface oxidation of the copper by CO₂ decomposition at 213 K followed by CO reduction at 473 K did not reproduce the initial state morphology, most of the Cu(110) surface being lost; at the same time there was a six-fold increase in the surface population of the (211) face. This new surface produced by CO₂ decomposition at 213 K and CO reduction at 473 K was considerably less active in its ability to decompose CO₂ at 213 K. Treatment of it with hydrogen at 513 K for 16 h caused the surface to reconstruct almost completely to its original state, with the Cu(110) face reappearing and the Cu(211) face being reduced in population to roughly its original value. The ability of the copper to decompose CO₂ was proportionately restored. It is evident that in the synthesis of methanol using CO/CO₂/H₂ mixtures over Cu/ZnO/Al₂O₃ catalysts, the morphology of the surface of the copper will be in a continuous state of restructuring, which, depending on the conditions, has the potential to result in chaotic behaviour. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrogen-ion transport numbers in cation exchange membrane determined by emf method

The electromotive force of the membrane cells /Hg/Hg₂SO₄/H₂SO₄, a′/ lon exchange Nafion membrane /H₂SO₄ a″/Hg₂SO₄/Hg/ with different solution concentrations from 0.01 to 2 mol kg^?1 H₂O were measured. On that basis the apparent transport number of H⁺-ions and its dependence on external electrolyte concentration were determined. The dependence was then used for the calculation of both the transport number of H⁺-ions and the water transference numbers. It was found that the apparent transport number of H⁺-ions decreases with increasing external concentration while the transport number of H⁺-ions and the transference number of water remain constant up to concentrations of 1.2 moles kg^?1 h₂O.     

Potassium sorbate solutions as copper chemical mechanical planarization (CMP) based slurries

Copper depassivation and repassivation characteristics in potassium sorbate solutions, subsequent to mechanical abrading are reported. The identification of copper repassivation kinetics obtained subsequent to mechanical damage of copper protective films formed in sorbate based solutions is discussed. The repassivation rate of copper in sorbate based solutions was measured by means of a slurryjet system capable of measuring single particle impingments on microelectrodes. Copper repassivation rates measured by this slurryjet system in sulfate solutions containing 10 g L⁻¹ potassium sorbate were found to be in the range of 0.5-1.5 ms. An increase in the potassium sorbate concentration leads to a decrease in copper repassivation time at potentials ranging from 200 to 600 mV_Ag/AgCl. The impingement angle between the copper surface and a single abrasive particle has no impact on copper repassivation time nor peak current (I_max) values. XPS studies revealed that copper passivation in potassium based solution was due to the formation of a thin film which is constituted of: Cu₂O, Cu(OH)₂ and Cu(II)-sorbate, while copper(II)-sorbate is mainly present at the top levels of the passive film. It is therefore recommended that the use of potassium sorbate as a passivating component in conjunction with the addition of strong oxidizing agents in chemical mechanical planarization (CMP) slurry design should be considered.     

Gas permeability of wet cation exchange membranes

The permeation of CO₂ across a Nafion cation exchange membrane in different hydrated forms is studied. The water solvent linked to the ion exchanging sites of the charged membranes forms a liquid supported membrane in which the transport of the polar gas is enhanced. This effect is still higher when the dry membrane is swollen in a Li₂CO₃ solution which increases the carbonate/bicarbonate anion concentration in the wet membranes and reduced the effectiveness of the Donnan co-ion exclusion from the membrane phase.     

EFFECTIVE DIFFUSION COEFFICIENTS OF COPPER IN MACROPOROUS CHELATING ION EXCHANGE RESIN D751

Kinetic data on the macroporous chelating ion exchange resin D751 containing iminodiacetic acid as ligand are presented. The experimental systems are R-Na / Cu(N0₃)₂, R₂Cu/HNO₃and R-(Na+H) / Cu(NO₃)₂. Sorption and desorption rates of copper were measured in batch experiments by using a three-necked flask as the reaction vessel. The effective diffusion coefficients of copper have been calculated.     

Hydrogen generation in a Pd membrane fuel processor: assessment of methanol-based reaction systems

The feasibility of a Pd membrane fuel processor that integrates several methanol-based chemistries and hydrogen purification steps is assessed. The assessment involves membrane reactor simulations to determine the effects of operating and design parameters on performance metrics including hydrogen utilization, hydrogen productivity, device volume, and Pd requirements. Methanol decomposition (direct and oxidative) on Pd/SiO₂, methanol steam reforming (MSR) on Cu/ZnO/Al₂O₃, and methanol partial oxidation (MPOX) on Cu/Al₂O₃ are evaluated. The membrane reactor model includes detailed treatments of the catalytic kinetics from the literature, accounts for reaction on the Pd membrane and hydrogen permeation inhibition by site blockage, among other features. The simulations reveal that a maximum in the hydrogen productivity occurs at an intermediate value of the space velocity, implying a trade-off between reactor size, methanol conversion and hydrogen utilization. The assessment involves a determination of the Pd membrane surface to reactor volume ratio that maximizes productivity and the requisite Pd to realize that productivity. We show that MSR on Cu/ZnO and MPOX on Cu are promising reaction systems to practice the membrane concept for fuel processing, whereas direct methanol decomposition is reaction limited, making it infeasible. Several approaches for improving membrane fuel processor performance are evaluated and discussed. We show that oxygen addition can increase the hydrogen productivity in the Pd system, while water addition is beneficial for the MPOX system. The extent of enhancement in both cases depends on supply rate and kinetic factors.     

Efficient diffusion barrier layers for the catalytic growth of carbon nanotubes on copper substrates

We have investigated the growth of carbon nanotube (CNT) films on copper substrates by the catalytic chemical vapour deposition route. Ferrocene was used as the catalyst precursor and toluene was the carbon feedstock. The copper substrates were coated with nitride and oxide amorphous ceramic barrier coatings in order to prevent diffusion of the iron catalyst during growth. It was found that virtually no CNT grew on pure copper, but long and densely packed mats of CNTs could be grown on TiN-coated copper. Copper substrates coated with SiN_x and In₂O₃:Sn (ITO) also showed better results than pure copper, although the CNT density was much lower than that obtained from TiN/Cu. Auger electron spectroscopy (AES) showed that Fe diffusion occurred into SiN_x/Cu and ITO/Cu substrates, which partially inhibited its catalyst activity. In contrast, AES did not detect the presence of diffused Fe into the TiN coating. The estimation of the diffusion coefficient by AES depth profiles for Fe in SiN_x, was 3 · 10⁻³ nm² s⁻¹. This value establishes an upper limit for Fe diffusion on substrates for proper nanotube nucleation and growth. Secondary ion mass spectrometry provided complementary information on the composition profiles with depth.     

Diffusion coefficient of hydrogen in a Pd-Ag membrane: Effect of hydrogen solubility

The permeabilities of hydrogen through a Pd₇₅-Ag₂₅ membrane have been measured at temperatures ranging from 423 to 573 K and under hydrogen pressure differences ranging from 69 to 256 kPa. From the available literature solubility data a neural network model has been developed in order to simulate the variation of the hydrogen content in the alloy as a function of pressure and temperature. Then, from steady state permeability measurements and calculated solubilities, the diffusion coefficients of hydrogen have been computed. At a given temperature, the diffusion coefficient has been found to decrease with the hydrogen content (0.1 ≤ n = H/M ≤ 0.37). A simple relation is then suggested to predict the variation of the diffusion coefficient on both temperature and hydrogen content. To account for the variation of the diffusion coefficient with n, the integration of Fick's law of diffusion has been performed numerically, resulting in non-linear profile of hydrogen content through the membrane under steady state permeation.     

Effects of specific adsorption of copper (II) ion on charge transfer reaction at the thin film LiMn2O4 electrode/aqueous electrolyte interface

This study investigated the effect of a specific adsorption ion, copper (II) ion, on the kinetics of the charge transfer reaction at a LiMn₂O₄ thin film electrode/aqueous solution (1 mol dm⁻³ LiNO₃) interface. The zeta potential of LiMn₂O₄ particles showed a negative value in 1 × 10⁻² mol dm⁻³ LiNO₃ aqueous solution, while it was measured as positive in the presence of 1 × 10⁻² mol dm⁻³ Cu(NO₃)₂ in the solution. The presence of copper (II) ions in the solution increased the charge transfer resistance, and CV measurement revealed that the lithium insertion/extraction reaction was retarded by the presence of small amount of copper (II) ions. The activation energy for the charge transfer reaction in the solution with Cu(NO₃)₂ was estimated to be 35 kJ mol⁻¹, which was ca. 10 kJ mol⁻¹ larger than that observed in the solution without Cu(NO₃)₂. These results suggest that the interaction between the lithium ion and electrode surface is a factor in the kinetics of charge transfer reaction.     

Mechanistic study of cobalt,nickel and copper transfer across a supported liquid membrane

The mechanism of cobalt, copper and nickel transport through supported liquid membranes containing di(2-ethylhexyl)phosphoric acid as a mobile carrier has been studied. An equation describing the permeation rate has been derived, taking into account stagnant layer aqueous diffusion, interfacial resistance due to solvatation reaction and liquid membrane diffusion as simultaneous controlling factors. The validity of this model is evaluated with experimental data of mass transfer coefficient measured employing a permeation cell. For these ions it was found that at low stirring conditions the stagnant layer resistance mainly controlled the processes, but it is controlled by diffusion of the ion complex through the supported liquid membrane when the stagnant layer resistance is negligible.     

Explosive compaction of nano-alumina particle-reinforced copper alloy

This paper is intended to describe manufacturing of a nano-alumina particle-reinforced copper alloy with better strength and high-temperature properties than those of pure copper. A new preparation technique is proposed, which includes three processes: mechanical alloying, hydrogen sintering, and explosive compaction. Cu/α-Al₂O₃ bulk samples with a density of 97.86% of the theoretical density and hardness of H _V = 112 are obtained. The microstructure study indicates that α-Al₂O₃ particles are dispersed in the copper matrix and still keep the nanometer scale. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 133–135, January–February, 2008.     

Transport of nickel and copper against a concentration gradient through a carboxylic membrane,based on poly(vinyl chloride)/poly(methyl methacrylate-co-divinylbenzene)

Carboxylic exchange membranes were prepared from poly(vinyl chloride)/poly(methyl methacrylate-co-divinylbenzene) (PVC) [poly(MMA-co-DVB]. Transport of nickel and copper against a concentration gradient through the membrane was investigated by using a system containing NiCl₂ or CuCl₂ aqueous solution on the left side (L) and mixed solution of NiCl₂ (or CuCl₂) and HCl on the right side (R) of the membrane. It was found that nickel and copper were actively transported through the membrane from the L to the R side during the first 5 h of the experiments. The rate of transport of the ions increased with increasing H⁺ ion concentration on the R side and the initial concentration of the metals ions on both sides. The highest rate of transport was observed when 0.1 mol/L MeCl₂ on the L side and 0.1 mol/L MeCl₂-0.5 mol/L HCl on the R side were used. The nickel and copper transport fractions were 34 and 24%, respectively. © 1996 John Wiley & Sons, Inc.     

Impedance investigation of the mechanism of copper electrodeposition from acidic perchlorate electrolyte

The mechanism of the copper electrodeposition from acidic perchlorate electrolyte has been investigated with polarization and impedance methods. The impedance of the copper electrode in copper perchlorate electrolytes has been measured as a function of frequency for different Edc overpotential values and different copper(II) ion concentrations. The relations between the shape of a complex plane impedance display and the copper electrode potential values as well as the concentration of CuII ion were analysed in terms of the electrode reaction mechanism. It is shown, that the presence of the intermediate cuprous ion and its sinusoidal change of transport rate is one of the main factors determining the depressed shape of the impedance arc. The quantitative relation between the faradaic impedance and the rates of electrode reaction rates was established. The impedance arc was simulated with a set of parameters involving: rate constants, Tafel slopes, diffusion coefficient of cuprous ion and double layer capacitance. The rate constants were calculated with respect to ECu2 + Cu00 as: k10 = 6.50 × 10−5 cm s−1, k20 = 0.139 cm s−1, k−20 = 1.88 × 10−7 mol cm−2 s−1.     

Separation of CO2 by 2-amino-2-methyl-1-propanol aqueous solution in microporous hydrophobie hollow fiber contained liquid membrane

The absorption of CO₂ from a mixture of CO₂/N₂ gas was carried out using a flat-stirred vessel and the polytetrafluoroethylene hollow fiber contained aqueous 2-amino-2-methyl-1-propanol (AMP) solution. The reaction of CO₂ with AMP was confirmed to be a second order reversible reaction with fast-reaction region. The mass transfer resistance in the membrane side obtained from the comparison of the measured absorption rates of CO₂ in a hollow fiber contained liquid membrane with a flat-stirred vessel corresponded to about 90% of overall-mass-transfer resistance. The mass transfer coefficient of hollow fiber phase could be evaluated, which was independent of CO₂ loading.     

Potential-pH diagrams for hydroxyl and hydrogen adsorbed on a copper surface

The principle of equilibrium potential-pH diagrams for two-dimensional layers adsorbed on metal surfaces in aqueous solution is applied to the case of hydrogen and oxygen species electroadsorbed on copper. The conditions of adsorption of species on copper surfaces in water may be predicted from thermodynamic calculations of the equilibrium potentials of the dissolved species/adsorbed species couples and drawing of potential-pH diagrams. Standard chemical potentials for hydroxyl chemisorbed on Cu(1 1 1) are derived from recent electrochemical data, while those for hydrogen chemisorbed on Cu(1 1 1) are derived from gas phase adsorption data. The E-pH relations associated with the equilibria between water and adsorbed hydroxyl, and between solvated protons and adsorbed hydrogen are given. The possible diagrams showing the E-pH domains of thermodynamic stability of the species adsorbed on a copper (1 1 1) surface (H₂O_ads, OH_ads and H_ads) in water are calculated at 25 °C and superimposed to the usual Pourbaix diagram for the Cu-H₂O system.