Cathodic Deposition Of Copper Research Articles

Enhanced recovery of high purity Cu powder from reclaimed copper smelting fly ash by NH3·H2O–NH4Cl slurry electrolysis system

Reclaimed copper smelting fly ash (RCA) is a residue produced during the smelting process of waste miscellaneous copper, containing heavy metals such as Cu, Zn, and Cd. In this study, a slurry electrolysis system was used to recover Cu from RCA. The results showed that the recovery efficiency, current efficiency, and purity of Cu on cathode were 97.11 %, 91.22 %, and 98.47 %, respectively, when the concentration of NH3·H2O was 2 mol/L, the concentration of NH4Cl was 1 mol/L, the concentration of CuSO4·5H2O was 20 g/L, the solid-liquid ratio was 50 g/L, the electric current density was 30 mA/cm2 and the reaction time was 2 h. The content of Zn in the RCA decreased from 144.54 mg/g to 23.7 mg/g and Cd from 0.72 mg/g to 0.005 mg/g after slurry electrolysis, and other heavy metals in the RCA also decreased. The potential difference that occurs between the two poles under the NH3·H2O slurry electrolysis system promotes the leaching of Cu from the RCA, while the leached Cu2+ combines with NH4+ to form the Cu–NH3 complex (Cu(NH3)42+, Cu(NH3)2+), thus increasing the current efficiency and promoting the cathodic copper deposition. The high-purity Cu obtained at the cathode belongs to the face-centered cubic structure (111), (200) and (220) of the Cu crystalline surface. This study provides a new method for the resourceful recovery of copper from RCA.

A Mechanistic Understanding of Electrochemical Bistability Induced By the Presence of 1,10-Phenanthroline in the Cathodic Deposition of Copper

We report herein a precise control of the electrochemical bistability induced by surface area changes during the cathodic deposition of copper. Small additions of 1,10-phenanthroline (Phen) in the reaction media present an inhibiting effect on the global rate mainly due to the adsorption of protonated Phen. The increase of its concentration favors a shrinkage of the bifurcation diagram and shifts it to less negative potentials. The dynamic instability is verified by impedance measurements, and a negative impedance is clearly found. We calculated the apparent molar mass of the adsorbents using in situ gravimetric monitoring in the electrochemical experiments, and the results indicate that mass changes occur mainly due to the reduction of copper from bivalent ions dissolved in the reaction media. Importantly, the adsorption of protonated Phen molecules does not show a considerable contribution in mass variations but prevents the formation of a copper course grained morphology over the surface. Imaging analysis indicates finer nodulations at the lower branch compared to the upper branch in the bistability domain. On the basis of these observations, a kinetic mechanism is proposed and a good agreement is obtained between the apparent molar mass extracted from experiments and the theoretical values. Altogether, our results contribute to a detailed physicochemical description of the nonlinear behavior, bringing new insights about this reaction and pointing out the possibility to design switchable surface electrodes by taking advantage of the bistable behavior.Rospendowiski, J.; Pinto, M. R.; Hessel, C.; Sitta, E.; Nagao, R. ACS Omega 2018, 3, 13636.

Protective properties of superhydrophobic coatings on copper and steel obtained by electrochemical method

Superhydrophobic coatings are obtained by cathodic deposition of copper or nickel on a copper plate with treatment with an ethanol solution of highest carboxylic acids with a long hydrocarbon radical simultaneously or sequentially. They are characterized by a contact angle of water wetting of the order of 155...160°.These coatings protect the copper substrate from corrosion in conditions of 100% humidity for 100...180 days, while maintaining the contact angle within 152…154°. There is no mass loss. The influence of the reversal of the current during electrolysis on the value of the contact angle of wetting is investigated. SEM images of superhydrophobic coatings are presented, indicating multilevel roughness. Superhydrophobic coating on carbon steel is obtained by cathodic deposition of nickel and subsequent surface treatment in an ethanol solution of myristic acid and annealing at 60° for two hours. The influence of the duration of electrolysis on the value of the contact angle of wetting is estimated. Its value is in the range of 151…154°. Exposure of a coated steel plate for 50 days in conditions of 100% humidity is characterized by the absence of weight loss and maintaining the contact angle up to 154°.

Natural convection mass and heat transfer at a horizontal spiral tube heat exchanger

The free convection mass and heat transfer (by analogy) behavior of a spiral tube was studied by an electrochemical technique which involved measuring the limiting current of the cathodic deposition of copper from acidified CuSO4. Variables studied were tube diameter (d), tube separation (s) and physical properties of the solution. The data were correlated for the conditions 1.4×106<Sc⋅Gr<5.74×108 by the equation: Sh=0.01 Sc⋅Gr0.29sd−0.5.A comparison of the present data with the data previously obtained for helical tubes and horizontal tubes was made. The importance of the present work for predicting the rate of diffusion controlled metal finishing processes which may be performed on the spiral tube during fabrication such as electroplating, etching, electroless plating and electropolishing was highlighted. Also potential application of the present data for predicting the rate of heat transfer at the outer surface of the spiral tube heat exchanger under stagnant conditions or under weak forced convection where natural convection contributes a great deal to the rate of transfer was pointed out.

Mass transfer characteristics of a flow-by fixed bed electrochemical reactor composed of vertical stack stainless steel screens cathode

Mass transport properties of a flow-by fixed bed electrochemical reactor composed of a vertical stack of stainless steel nets operated at a batch-recycle mode were characterized using cathodic deposition of copper as a test reaction. The electrochemical reactor was operated at constant potential in which reduction of copper happened under mass transport control. This potential was selected from the application of hydrodynamic voltammetry using a borate/chloride solution as supporting electrolyte on stainless steel rotating disc electrode. A linear relationship was observed between the flow rate and the mass transfer coefficient. The electrochemical reactor was efficient in removing copper and able to reduce the levels of this metal to lower than 0.4 ppm starting from an initial concentration of 49.7 ppm at 80 min using a ratio of cathode volume/catholyte volume equal to 0.0075. A mathematical correlation between the Sherwood number and Reynolds number were obtained which characterized the mass transport properties of the reactor as follows: Sh = 0.2254Re0.4228Sc1/3.

Emergency of electrochemical bistability in the cathodic deposition of copper

Nanostructured metallic multilayers in the electrodeposition of copper can be spontaneously synthetized when the system is kept far from thermodynamic equilibrium. We have focused on the understanding of how blocking agents, mainly induced by strong adsorption, can tune the thickness of these self-organized layers, therefore, altering the total surface area. For this purpose, we perturbed the electrodeposition of copper on acidic media with small amounts of o-phenanthroline (phen). Indeed, the addition of phen gives rise to a distinct current-potential profile. A negative differential resistance (NDR) and hysteresis are observed in the cyclic voltammograms. The appearance of the NDR is attributed to the adsorption of some species in lower potentials, which suppresses the copper electrodeposition. The hysteresis, in its turn, indicates that the system has two stable steady states for the same set of controlling parameters, the so-called bistability (BS). We have monitored the bistability domain by mapping the bifurcation diagrams Rext (external resistance between the working and reference electrodes) vs. potential obtained from the experimental data for different concentrations of phen. We have also performed EQCN, SEM and EIS measurements in order to investigate the phenomena involved in the appearance of bistability. We have suggested a physical-chemical mechanism in attempt to explain which substances act as the surface-blocking agents.

Tuning Electrochemical Bistability by Surface Area Blocking in the Cathodic Deposition of Copper.

We report herein a precise control of the electrochemical bistability induced by surface area changes during the cathodic deposition of copper. Small additions of 1,10-phenanthroline (Phen) in the reaction media present an inhibiting effect on the global rate mainly due to the adsorption of protonated Phen. The increase of its concentration favors a shrinkage of the bifurcation (saddle-node) diagram and shifts it to less negative potentials. The dynamic instability is verified by impedance measurements, and a negative impedance is clearly found. We calculated the apparent molar mass of the adsorbents using in situ gravimetric monitoring in the electrochemical experiments, and the results indicate that mass changes occur mainly due to the reduction of copper from bivalent ions dissolved in the reaction media. Importantly, the adsorption of protonated Phen molecules does not show a considerable contribution in mass variations but prevents the formation of a copper course grained morphology over the surface. Imaging analysis indicates finer nodulations at the lower branch compared to the upper branch in the bistability domain. On the basis of these observations, a kinetic mechanism is proposed and a good agreement is obtained between the apparent molar mass extracted from experiments and the theoretical values. Altogether, our results contribute to a detailed physical chemical description of the nonlinear behavior, bringing new insights about this reaction and pointing out the possibility to design switchable surface electrodes by taking advantage of the bistable behavior.

Contact Displacement of Copper at Copper Plating of Carbon Steel Parts

The process of the contact displacement of copper by the carbon steel surface in a low-concentrated sulfate electrolyte and in electrolytes containing copper complexes with glycine, tartrate, and ethylenediaminetetraacetate is studied. The method of analyzing the particular reactions of interaction between a steel surface and copper-containing electrolytes in the absence of current is applied. The parameters of the contact exchange kinetics are determined with computer processing of the arrays of the coordinates of the particular polarization dependences of cathodic copper deposition in the electrolytes and the anodic dissolution of steel in the corresponding background solutions, as well as of the chronopotentiograms of steel samples in the electrolytes under study. The values of the contact exchange current density and the relation between the areas of the cathode and anode surface sections are calculated as a function of the steel substrate potential and the steel–electrolyte contact time. The influence of the nickel sublayer thickness on the kinetics of the contact exchange in a low-concentrated sulfate electrolyte is shown.

Cathodic deposition of copper on polyaniline-coated textiles from a citrate bath: effects of electroplating conditions

Copper electrodepostion on polyaniline (PANI)-covered poly(ethylene terephthalate) (PET) textiles was realized galvanostaticly in a plating solution containing sodium citrate. Electrochemical behaviors of Cu deposition on PANI/PET electrodes in citrate baths were studied by measuring the cathodic polarization curves. Electroplating conditions such as concentrations of copper sulfate, sodium citrate and sodium sulfate, pH value, current density as well as the concentration ratio of oxidation/monomer for PANI formation were determined by comparing the polarization curves and the current efficiency results. The surface morphologies of Cu/PANI/PET formed under the different current density were evidenced by scanning electron microscopy. In addition, the conductivity of the synthesized films was also measured with a four-probe method and the lowest sheet resistance of 100 mΩ/sq was presented at 60–80 mA cm−2, in which the maximum current efficiency reached up to 85 %. The deposition mechanism that the reductions of copper ions and PANI layers occurred in parallel, and the growth of copper crystals performed at the polymer surface were deduced.

FREE CONVECTIVE MASS TRANSFER BEHAVIOR OF FINNED TUBES

Rates of natural convective mass transfer at vertical and horizontal finned cylinders were determined by an electrochemical technique that involved measuring the limiting current of the cathodic deposition of copper from acidified copper sulfate solution. Variables studied were fin spacing (s), fin diameter (d), and physical properties of the solution. For vertical and horizontal finned tubes it was found that the mass transfer coefficient increases with increasing fin height and decreases with increasing fin separation. Rates of mass transfer at vertical and horizontal finned tubes were found to be higher than that at unfinned (plain) tubes by an amount ranging from 44% to 96%. Although the degree of mass transfer enhancement by fins is higher at vertical cylinders, horizontal finned cylinders have higher mass transfer coefficients than vertical finned cylinder under the same conditions. Mass transfer data at vertical finned cylinders were correlated by the equation while mass transfer data at horizontal finned cylinders were correlated by the equation Implications of the present study for determining the rate of diffusion-controlled metal finishing processes that are conducted during the fabrication of finned tubes such as electroplating, electroless plating, etching, electro-polishing, and pickling were noted. Also, the importance of the present results for design and operation of electrochemical reactors fitted with fins (baffles) was highlighted. The possibility of using the derived equations in predicting rates of heat transfer in solutions of high Pr by analogy with mass transfer was outlined.

The Effect of Tellurium Presence in Anodic Copper on Kinetics and Mechanism of Anodic Dissolution and Cathodic Deposition of Copper

The Effect of Tellurium Presence in Anodic Copper on Kinetics and Mechanism of Anodic Dissolution and Cathodic Deposition of Copper

Electrochemical Characterization of Mass Transport in Porous Electrodes

Mass transport in reticulated vitreous carbon electrodes in flow by mode has been studied with the cathodic deposition of copper as a model reaction. Two methods characterizing mass transport are being compared. The first one relies on determination of the electrorecovery kinetics under mass-transfer limiting conditions in galvanostatic mode. The second method is the determination of the limiting current by a linear potential sweep technique. This technique has been modified to allow for a more unambiguous limiting current determination. In some cases, the modified linear sweep technique can also be used to measure the influence of a gaseous reaction side products on mass transport.

Mass Transfer at a Vertical Oscillating Screen Stack in Relation to Catalytic and Electrochemical Reactor Design

The aim of the present work is to improve the performance of the parallel plate catalytic and electrochemical reactor in conducting diffusion controlled reactions by using parallel oscillating vertical arrays of closely packed screens. To this end, rates of mass transfer at oscillating vertical single screen and arrays of closely packed screens were studied by measuring the limiting current of the cathodic deposition of copper from acidified copper sulfate. Variables studied were amplitude and frequency of vibration, screen mesh number, and number of screens per stack. The mass transfer data at a single vibrating screen were correlated by the equation: Sh = 0.73Sc0.33Rev0.38. Increasing mesh number of the screen was found to increase the mass transfer coefficient, while increasing the number of screens per stack decreased the mass transfer coefficient below single screen value. The enhancement ratio between oscillating screen array and oscillating vertical plate (the volumetric mass transfer coefficient ratio) ranged from 11.7 to 27.87 depending on the operating conditions. Electrical energy consumption of the present reactor was found to be lower than the value reported in the literature for electrowinning of copper using traditional parallel plate reactor. In view of this, the possibility of using oscillating vertical screen stack in building high space-time yield modular parallel plate electrochemical reactor suitable for wastewater treatment, electroorganic synthesis, and electrochemical energy storage via redox cells was noted. Also, the possibility of using the present geometry in building catalytic reactors suitable for conducting diffusion controlled liquid–solid reaction was highlighted.

Effect of pitch-to-diameter ratio on the natural convection heat transfer of two vertically aligned horizontal cylinders

Natural convection heat transfer experiments were conducted for two parallel horizontal cylinders using various pitch-to-diameter ratios ( P/ D) from 1.02 to 9 for the Prandtl numbers between 2014 and 8334 and Rayleigh numbers between 7.3×10 7 and 4.5×10 10. Based upon analogy concept, mass transfer rate were measured instead of heat transfer rates by measuring the limiting current of the cathodic deposition of copper from acidified copper sulfate solution. The mass transfer rates for the lower cylinders were unaffected by the presence of the upper cylinders, and agreed well with the prediction from existing heat transfer correlations developed from a single horizontal cylinder. The Nusselt number ratios of the upper to lower cylinders increased with P/ D. The ratios were less than 1 at P/ D values less than about 1.5 for laminar flows, but the ratios were almost 1 at a P/ D very close to 1 for turbulent flows. The variation of the ratios with P/ D becomes steep with higher Prandtl numbers, which is confirmed by numerical simulations using the FLUENT program. The plating pattern that appeared on the surface of the cylinder revealed local mixed convection heat transfer. The area covered by thin lines, denoting the flow separation on top of the upper cylinder, increased for laminar but decreased for turbulent flow due to the laminarization phenomena in turbulent mixed convection.

Study of the rate of diffusion controlled liquid–solid reactions accompanied with gas generation in batch fixed bed reactor in relation to wastewater treatment

Factors affecting the rate of liquid–solid diffusion controlled reactions at gas evolving fixed bed reactor were studied by measuring the mass transfer coefficient of cathodic copper deposition from acidified CuSO4 above the limiting current where simultaneous H2 evolution takes place in a reactor packed with either cylinders or Rasching rings with no net electrolyte flow. Variables studied were particle size, bed height and H2 discharge velocity. The rate of mass transfer was found to be proportional to the square root of H2 discharge rate. Bed height and particle size were found to have a negligible effect on the rate of mass transfer. For a given set of conditions the mass transfer coefficient at a fixed bed of cylinders is higher than that at a fixed bed of Raschig rings. A mathematical model based on bombardment of the mass transfer surface by high kinetic energy bubbles is presented to explain the results. Mass transfer data at the cylinder bed reactor were correlated by the equationJ=1.58(Re⋅Fr)−0.166While the data at a fixed bed of Raschig rings were correlated by the equationJ=1.4(Re⋅Fr)−0.162Practical applications of the results in the design and operation of fixed bed electrochemical and catalytic reactors used in wastewater treatment were highlighted.

Effect of electrode pulsation on the rate of simultaneous electrochemical recovery of copper and regeneration of ferric salts from dilute solutions

The effect of vertical plate electrode pulsation on the rate of cathodic copper deposition and anodic oxidation of ferrous sulphate was studied in a divided cell. Electrode oscillation was found to enhance the rate of diffusion controlled copper deposition and ferrous sulphate anodic oxidation by a factor ranging from 1.9 to 7.8 compared to the natural convection value depending on the vibration velocity. Electrode pulsation was found to increase the current efficiency of copper deposition from 52% to 98%, while the current efficiency of anodic oxidation of FeSO 4 increased from 35% to 92% depending on the vibration velocity. Also, electrode vibration was found to decrease electrical energy consumption of copper deposition from 4 to 1.56 kWh/kg; for anodic oxidation of FeSO 4 electrode vibration reduces energy consumption from 3.35 to 1.25 kWh/kg depending on vibration velocity. The importance of the present results for treating dilute solutions containing copper and ferrous ions such as printed circuit etching solution, pickling waste solutions, chemical machining waste solution, mine drainage water, leaching liquor obtained by leaching low grade copper sulphide ore by ferric salts was highlighted. The present technique has the advantage of recovering a precious metal and recycling a valuable chemical in one step, this satisfies the policy of zero discharge industry.

Dynamics of extended space charge in concentration polarization

This paper is concerned with ionic currents from an electrolyte solution into a charge selective solid, such as an electrode, an ion exchange membrane or an array of nanochannels in a microfluidic system. All systems of this kind have characteristic voltage-current curves with segments in which current nearly saturates at some plateau values due to concentration polarization--formation of solute concentration gradients under the passage of a dc current. A number of seemingly different phenomena occurring in that range, such as anomalous rectification in cathodic copper deposition from a copper sulfate solution, superfast vortexes near an ion-exchange granule, overlimiting conductance in electrodialysis and the recently observed nonequilibrium electro-osmotic instability, result from formation of an additional extended space charge layer next to that of a classical electrical double layer at the solid/liquid interface or, rather, from the peculiar features of the extended space charge distinguishing it from that of a common diffuse electrical double layer. In this paper we discuss the nature and origin of the extended space charge and analyze its peculiar steady state and time-dependent properties important for understanding nonequilibrium electrokinetic phenomena in ionic systems.

The effect of bi presence as impurities in anodic copper on kinetics and mechanism of anodic dissolution and cathodic deposition of copper

The influence of Bi, as foreign metal atoms in anode copper, on kinetics and mechanism of anodic dissolution and cathodic deposition of copper in acidic sulfate solution was investigated using the galvanostatic single-pulse method. Results indicate that presence of Bi atoms in anode copper increases the exchange current density, as determined from the Tafel analysis of the electrode reaction, which is attributed to the increase of the crystal lattice parameter determined from XRD analysis of the electrode material.

Electrochemical modeling and study of copper deposition from concentrated ammoniacal sulfate solutions

A fundamental investigation of the electrolytic deposition of copper from concentrated aqueous ammoniacal solutions has been carried out based on the thermodynamic analysis of the system Cu–NH 3–H 2O. The speciation of copper vs. pH and redox potential was modeled in high ionic strength solutions, in which the activity coefficients of the system species were estimated according to the Modified Bromley's Methodology. The electrochemical behavior of the redox system Cu(0)/Cu(I)/Cu(II) in concentrated aqueous ammoniacal solutions was studied at pH = 9.5 and the cathodic reactions in these solutions were determined. It was found that metallic copper was formed under strongly reductive redox conditions, while under mildly reductive to mildly oxidative conditions the cuprous di-ammine complex species dominate. Under highly oxidative conditions the cupric tetra-ammine complex species predominated. According to the theory and results, the cathodic deposition of copper from concentrated aqueous ammoniacal solutions proceeds in a two-step reduction mechanism. The cupric ammine species are first reduced to cuprous di-ammine, which in turn is reduced to metallic copper. The electrochemical experiments revealed that copper deposition over time follows a sigmoid-type curve, verifying the two-step mechanism. The main feature of these sigmoid curves was the presence of an induction period with negligible copper deposition, followed by an acceleration period where the copper deposition rate gradually increased. By increasing the applied cell voltage, the induction period was significantly reduced or disappeared.

Free convective mass transfer at corrugated surfaces in relation to catalytic and electrochemical reactor design

The free convective mass transfer behavior of V-corrugated horizontal and vertical surfaces was studied by measuring the limiting current of the cathodic deposition of copper from acidified copper sulphate solution. Variables studied were peak-to-valley height and angle of the V-grooves, physical properties of the solution and vertical electrode height. For vertical corrugated surfaces, the data were correlated by the equation: S h = 0.78 ( S c ⋅ G r ) 0.26 while the data for the horizontal corrugated surfaces were found to fit the equation: S h = 1.64 ( S c ⋅ G r ) 0.23 A comparison with the free convection mass transfer behavior of flat plates shows that the mass transfer coefficient at vertical corrugated surface is higher than that at vertical flat plates. For horizontal surfaces the reverse is true. The importance of the present results to the design and operation of electrochemical reactors, membrane processes and catalytic reactors which employ corrugated surfaces to conduct diffusion-controlled processes is highlighted.