Electrowinning Process Research Articles

Pemulihan Tembaga Larut secara Elektrolisis pada Limbah Larutan Tembaga-Nitrat Pengrajin Pemurnian Emas Perhiasan di Kota Makassar

This research is aimed to recovery of copper that has been dissolved in the copper-nitrate wastewater from gold jewelry purification, with a content concentration 5318.52 mg/l of Cu, which can be obtained pure copper powder of high economic value and can contribute to a decrease in weight metal content copper on the wastewater before discharge to urban drainage. The method used is the recovery process by electrolysis or electrowinning process that using liberation cell, which uses a single pair of stainless steel electrode with copper (SS-Cu), a single pair of graphite electrodes with copper (G-Cu), also multi pairs stainless steel electrode with copper (MSS-Cu). Single-electrode pair was examined by varying the voltage and current values at time variation of process, while for many electrode pairs by varying the process time at constant voltage and current values. The recoverable amount of copper was measured by weighing the mass changes at the cathode and the copper content test of the solution using Atomic Absorption Flame Emission Spectrophotometer. Laboratory test results show the decreasing maximum content for each pair, respectively 66.60% for the SS-Cu, 49.38% for the G-Cu, and 78.94% for the MSS-Cu. With reference to the effectiveness of multi-electrode cell liberation, there are business opportunities for wastewater treatment to find powder copper that can accompany the business of gold jewelry purification.

Chemical and biological approach to remove Mn from aqueous solution

Abstract Many approaches have been proposed to remove manganese from public supply waters as well as from acid mine drainage. This study investigated the removal of high levels of soluble Mn (II), similar to forms found in acid mine drainage in Brazil, by using a manganese oxide (MnO2) residue from the electrowinning process and a Bacillus cereus strain isolated from mine water, immobilized or not in calcium alginate. Experimental data for manganese removal by MnO2 showed that a pseudo-second-order kinetic model conformed well to the equilibrium adsorption data and the Langmuir isotherm was suitable to describe this adsorption process. Thermodynamic analysis showed that the adsorption of Mn (II) using MnO2 was spontaneous and endothermic under the experimental conditions. The manganese removal by B. cereus was 75% and by the MnO2 residue was 96% at the end of nine days. The removal using MnO2 and B. cereus together reached 96%. Immobilization of MnO2 and B. cereus using alginate biopolymer was also investigated. After nine days, the removal by B. cereus reached 93% and B. cereus + MnO 2 reached 92%, both immobilizing in alginate. The immobilization promoted fewer changes in pH, which ranged from 7.5 to 8.5 during the experiments. The use of MnO2 alone or the use of B. cereus immobilized in alginate are two interesting alternative to remove high levels of manganese, however, only the last alternative is capable of maintaining an alkaline pH necessary to the process.

Parametric study for enhanced performance of Cu and Ni electrowinning

In this study, we performed an electrowinning process for effective removal of metals (Cu and Ni) in solution and their recovery as solid forms. A complete removal of Cu and Ni (1,000 mg/L) was observed during four times recycling test, indicating that our electrowinning system can ensure the efficient metal removal with high stability and durability. In addition, we investigated effect of operation parameters (i.e., concentration of boric acid only for Ni, variation of pH, concentration of electrolyte (H2SO4), and cell voltage) on the efficiency of metal removal (Cu and Ni) during the electrowinning. The addition of boric acid significantly enhanced removal efficiency of Ni as the concentration of boric acid increased up to 10 g/L. Compared to negligible pH effect (pH 1, 2, and 4) on the Cu removal, we observed the increase in removal efficiency of Ni as the pH increased from 1 to 4. The electrolyte concentration did not significantly influence the removal of Cu and Ni in this study. We also obtained great removal rates of Cu and Ni at 2.5 V and 4.0 V, which were much faster than those at lower voltages. Finally, almost 99% of each Cu and Ni (1,000 mg/L) was selectively removed from the mixture of metals by adjusting pH and addition of boric acid after the completion of Cu removal. The findings in this study can provide a fundamental knowledge about effect of important parameters on the efficiency of metal recovery during the electrowinning.

Purification of Nickel Sulfate by Batch Cooling Crystallization

AbstractCooling crystallization was successfully carried out in a batch cooling crystallizer from impure acidic solutions to recover nickel as nickel sulfate salt with three different cooling rates. The compositions of the solutions included impurities of sodium, magnesium, chloride, and sulfuric acid to mimic industrial nickel electrowinning process solutions. The results show that NiSO4·6H2O mainly crystallized, and its solubility and purity decreased with the increase in the mass ratio of chloride to sulfate. Cooling rates did not have a significant influence on crystal purity; however, it did affect the filter cake moisture; lower moisture can be obtained with a lower cooling rate. The sequence of impurity removal efficiency from high to low was Cl > Na > Mg.

Review of Progress on Computational Modeling and Simulation of the Zinc Electrowinning Production Process

Zinc is an important energy material in the battery industry. Modeling and simulation are less expensive and more efficient ways to study and optimize the zinc electrowinning process. A critical review of research related to models and simulations of this process is presented herein, along with associated equations and methodologies. These equations or models are categorized into four different but closely related types: empirical equations for current efficiency prediction, equations for the related parameters in the electrowinning process, fundamental electrochemical models, and computational fluid dynamics (CFD) models. These equations or models are focused on certain aspects of the zinc electrowinning process and are applied under specific conditions. However, most of them are simplified, and many significant aspects of the zinc electrowinning process are ignored, limiting their accuracy. Promising future developments regarding modeling and simulation of the zinc electrowinning process are discussed.

Nickel production from laterites using electro metal electrowinning (EMEW) process

Laterite with low-grade nickel (< 0.5%) was very difficult to process using pyrometallurgy technique. One method which able to process this laterite is solvent extraction process. This process also able to separate cobalt from nickel solutions. The aqueous phase of solvent extraction process which has a high nickel content able to collect using electrowinning methods. Electrometal-electrowinning (EMEW) method is one of the electrowinning methods which has better performance to collect metal from solution. In this work, laterite was leached using H2SO4 then was extracted using Cyanex 272 in toluene as an organic solvent. In this research, the effect of a voltage, a duration time of operation, a concentration of boric acid and a temperature on EMEW process were studied and were optimized using Taguchi method.

The effect of magnetic field and operating parameters on cathodic copper winning in electrowinning process

Current efficiency and quality of deposited copper are important parameters in copper electrowinning industries. The effects of imposing an external magnetic field, Fe3+ and Cu2+ mass concentrations and electrical current density on the current efficiency, the thickness of the cathodic copper sheet and its morphology in copper electrowinning process were studied at different experimental operating conditions in a cuboid cell. A full factorial design of experiment is applied here to relate current efficiency and the standard deviation (STDEV) of the thickness with and without magnetic field, Fe3+ concentration (2.5 and 3.5 g/L), Cu2+ concentration (35 and 40 g/L) and electrical current density (150 and 220 A/m2) with constant acid concentration of 175 g/L at temperature of 40 °C for a synthetic electrolyte. Scanning electron microscope (SEM) is applied in studying the surface morphology of the deposited cathodic copper in all tests. The obtained results indicated that the presence of the magnetic field and increasing Fe3+ concentration could decrease the current efficiency up to 17 and 7%, respectively. While increasing Cu2+ concentration and electrical current density increased the current efficiency. Presence of magnetic field, increasing Fe3+ concentration and electrical current density increased the thickness uniformity of copper sheets. Investigation of SEM surface images revealed variations in these main parameters had different effects on deposited cathodic copper morphology.

Hydrometallurgical Process for Zinc Recovery from C.Z.O. Generated by the Steelmaking Industry with Ammonia–Ammonium Chloride Solution

In this research, some experimental steps were investigated to recover zinc contained in crude zinc oxide (C.Z.O.). In the first stage, the C.Z.O. was treated in NH3–NH4Cl–H2O solution to dissolve the metals. The optimized leaching conditions in batch experiments were obtained: agitation speed 250 rpm, concentration of ammonia and ammonium chloride 2.5 mol/L and 5 mol/L, respectively, time 30min, temperature 40 °C, and L/S = 6 mL/g. The extraction percentage of zinc was over 81% under the optimized leaching conditions. The kinetic study indicates that zinc extraction from the C.Z.O particles was very rapid. In the second stage, the solution from the leaching process was purified by adding zinc dust to the solution. The Cu, Cd, Pb, Sb, and As could be reduced to levels of 0.03, 0.09, 0.87, 0.22, and 0.12 mg/L after the purification process. Finally, the electrowinning process was used to recover dissolved Zn from the final solution. The zinc content in the electrowon zinc was more than 99.99%.

Evaluation of the Sustainable Efficiency of two Manufacturing Processes using Life-Cycle Assessment and Efficiency Analysis

The global demand for raw materials is increasing consistently in the modern world such that a resource efficient handling becomes more and more important in today’s manufacturing processes. Therefore, re-manufacturing of degraded products and components is a major step within a sustainable manufacturing strategy. This paper shows an approach to evaluate and to compare the sustainability of two manufacturing processes using life-cycle assessment on the one hand and efficiency analysis methods on the other. In a first step, the two processes were analysed regarding their environmental impact in 13 different effect categories using the life-cycle assessment software GaBi. Data envelopment analysis (DEA) as well as TOPSIS were utilized to evaluate and to compare these results regarding sustainable efficiency in a second step. The analysis is done within the case study “Recycling of lead anode”. The evaluation of a new developed concept for an automated process, in comparison to a manual process, to recycle lead anodes, which were subjected to heavy wear during the electrowinning process of non-ferrous metals like copper, nickel or zinc, is in focus.

Modeling Nickel Electrowinning with Electrode Diaphragms Based on Nernst-Plank Equation and a Volume Force Form of Darcy's Law

The Ni electrowinning process with electrode diaphragms was simulated with an Electrochemical-Computational Fluid Dynamic model by considering a two-phase flow, mass transport, and electrochemical reactions. The effects of electrode diaphragms on the fluid flow, concentration, voltage drop, and current distribution were analyzed based on the simulation results. Results show that the electrode diaphragms have significant effects on the fluid flow and voltage drop in the electrolyte. The electrode diaphragms greatly reduced the strong convective flow caused by rising bubbles in the cell, and thus reduce the transport of H+ (generated at the anode) to the cathode. Based on this model, the effects of different operating parameters on the electrolyte potential and cathode current distribution have been analyzed. The results show that the cell temperature of 60°C, Ni concentration of 80 g/L, and a relatively low current density are the most favorable compared with other settings in the simulation for decreasing the electrolyte voltage drop and reducing the roughness of the deposition.

Electrodeposition of indium from the ionic liquid trihexyl(tetradecyl)phosphonium chloride.

The electrochemical behavior of indium in the ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) was studied. Cyphos IL 101 first had to be purified, as the impurities present in commercial Cyphos IL 101 interfered with the electrochemical measurements. Electrochemical deposition of indium metal from this electrolyte occurs without hydrogen evolution, increasing the cathodic current efficiency compared to deposition from water and avoiding porosity within the deposited metal. Indium(iii) is the most stable oxidation state in the ionic liquid. This ion is reduced in two steps, first from indium(iii) to indium(i) and subsequently to indium(0). The high thermal stability of Cyphos IL 101 allowed the electrodeposition of indium at 120 °C and 180 °C. At 180 °C indium was deposited as liquid indium which allows for the easy separation of the indium and the possibility to design a continuous electrowinning process. On molybdenum, indium deposits as liquid droplets even below the melting point of indium. This was explained by the combination of melting point depression and undercooling. The possibility to separate indium from iron and zinc by electrodeposition was tested. It is possible to separate indium from zinc by electrodeposition, but iron deposits together with indium.

The Electrochemical Performance and Reaction Mechanism of Coated Titanium Anodes for Manganese Electrowinning

In this paper, electrochemical performance of coated titanium anodes in the manganese electrowinning process are investigated. The turbid anolyte can be avoid by using coated titanium anodes compared to conventional Pb anodes, and the generation of manganese dioxide (MnO2) on anode can be also reduced. The deposited manganese dioxide layer on coated titanium anodes are uniform and compact after electrolysis by using Scanning electron microscopy (SEM), which is totally different from that on Pb anodes. The possible mechanism involving permanganate ion is proposed and confirmed by Square wave voltammetry (SWV) and in-situ ultraviolet-visible spectrophotometry (UV-VIS). Moreover, the cell voltage for coated titanium anodes is about 270 mV lower than that of traditional Pb anodes, exhibiting well energy saving effect. Linear sweep voltammetry and Tafel curves show that coated titanium anodes have lower Tafel slope and possess a better catalytic property for oxygen evolution reaction. Finally X-ray photoelectron spectroscopy (XPS) analysis manifests the Ru element can be oxidized to a higher valence state and has a blocking effect for active oxygen. Our results here offer some basic electrochemical data for the anode in electrolytic manganese system, and provide a promising path for replacing Pb anodes in electrolytic manganese industry.

Process mineralogy of refractory gold ore in thiosulfate solutions

A mineralogical characterization was carried out in samples of refractory gold ore with 59 g/ton, according to fire assays, which were taken from a previous leaching process with ammonium thiosulfate. The potential window used to evaluate the cathodic and anodic processes was chosen knowing that gold and copper reduction, and thiosulfate and Cu(I) species oxidation occurs in it. The leaching process consisted of a pretreatment of the mineral (in ammonium hydroxide and copper sulfate during 12 h with and without air bubbling) followed by leaching (in ammonium thiosulfate solution and EDTA at a pH ∼ 10 during 24 h with mechanical stirring at a rate of 250 rpm) which rendered a gold-release of 81.57%. When oxidants and stabilizers like Cu(II), NH3 and EDTA are present in thiosulfate based leaching solutions, the chemistry turns complex, and the partial reduction of copper, and redissolution of gold may occur. This fact and the low gold concentration make the electrowinning process especially difficult. Characterization techniques such as polarized light microscopy, X-Ray Diffraction, Rietveld quantification, and Automated Digital Imaging System, were chosen to track the process mineralogy of the sample, and the results prior to the leaching revealed association, size, and shape of each mineral occurrence; it was found that the mineral composition was pyrite crystals, exhibiting subhedral and inequigranular morphology (75%); galena crystals (10%); sphalerite (1.8%); chalcopyrite and arsenopyrite crystals (<3%); and free gold (<1%). The rest of the sample was comprised of aluminosilicate phases such as quartz and muscovite. After the leaching process, the main feature found was some accumulation of individual pyrite grains with corrosion grooves, and decrease in the particle size; on the other hand, the dissolution of the accompanying phases, with respect to the galvanic interactions, evidenced the next sequence of dissolution: I/E = pyrite > galena > M3 > sphalerite. Rietveld quantification suggested changes in the ratio of the main phases: pyrite decreased from 75.6% up to 65.7%; quartz increased from 21.1% up to 31.3%; galena decreased from 10.4% up to 7.6%; sphalerite decreased from 1.8% up to 1.1%. It is worth saying that the presence of precipitated amorphous phases was not observed.

Hydrometallurgical recycling of surface-coated metals from automobile-discarded ABS plastic waste

The ammoniacal leaching of surface-coated metals from automobile-discarded ABS plastics followed by their recovery through solvent extraction has been investigated. The leaching of ABS (typically containing 4.1% Cu, 1.3% Ni, and 0.03% Cr) could efficiently dissolve the ammine complexes of Cu and Ni, leaving Cr unleached as fine particles. The optimization studies for achieving the maximum efficiency revealed that the leaching of metal ions in different ammoniacal solutions follows the order CO32− > Cl− > SO42−. The leaching carried out in a carbonate medium by maintaining the total NH3 concentration 5.0 M at a NH4OH/(NH4)2CO3 ratio of 4:1, pulp density of 200 g/L, agitation speed of 400 rpm, temperature of 20 °C, and time of 120 min yielded the optimum efficiency of >99% Cu and Ni (i.e., 8.14 g/L and 2.57 g/L, respectively, in the leach liquor). Subsequently, the solvent extraction of metals from ammoniacal leach liquor as a function of extractant (LIX 84-I) concentration and organic-to-aqueous (O:A) phase ratio was examined. Based on the extraction data, a three-stage counter-current extraction at O:A = 1:1 was validated using 0.8 M LIX 84-I, yielding the quantitative extraction of both metals into the organic phase. Thereafter, the stripping of metals in acid solutions indicated that 0.5 M H2SO4 could quantitatively strip Ni from the loaded organic phase; however, ∼27% Cu was also co-stripped. The rest of Cu from the Ni-depleted organic phase was separately stripped with 1.0 M H2SO4 that can be directly sent to the electrowinning process. On the other hand, the co-stripped metals from the acidic solution can be easily separated, again using LIX 84-I as the extractant, by adopting the pH-swing method. Finally, a process has been proposed for the hydrometallurgical recovery of surface-coated metals from waste ABS plastics; that does not affect the physicochemical characteristics of the polymer substances for their reuse.

Non-Precious Group Metal Electrocatalysis of Sulfite Electro-Oxidation Reaction for Gold Electrowinning Processes

The electro-oxidation of sulfite and its radicals has a wide range of applications from gold electrowinning to wastewater treatment, hydrogen production and in the food industry (1-4). While efforts have been made to study the electro-oxidation of sulfite ions on noble metals (e.g. Au) as well as carbon surfaces, metal oxides in general have not been thoroughly investigated for this electrochemical reaction (1, 5). During gold recovery from thiosulfate solutions, Au+ ions are reduced to Au from the thiosulphate gold complex on the cathode while oxygen evolution occurs on the anode via the following reactions (6): Au(S2O3)2 3- + e- = Au + 2S2O3 -2, E0= 0.15 V (1) 4OH- = 2H2O + O2 + 4e-, E0= 0.4 V (2) To drive the cathodic reaction, high current densities are used, which result in high anodic potentials on the stainless-steel anodes. Such high anodic potentials may cause transpassive corrosion of the anode as well as significant, and undesirable, changes in solution chemistry (7). This study systematically investigated the effect of operating factors on the corrosion behavior of stainless steel anodes in thiosulfate solutions during gold electrowinning. Further, novel non-precious group materials such as manganese oxides and perovskites were used as electrocatalysts for sulfite electro-oxidation to ultimately enhance the activity and long-term durability of the anodes in the gold electrowinning process (8). A 2n half-fraction factorial design study was performed to find the effect of five important parameters involved in the gold electrowinning process (i.e. thiosulfate concentration, sulfite concentration, sulfate concentration, temperature and applied anodic current density), on the anodic potential of the stainless steel anode. As shown in the Fig. 1A, increasing the sulfite concentration and temperature of the gold electrowinning solution lead to a low anodic potential of 550 mV which is about 250 mV lower than the transpassive corrosion potential for the 316 stainless steel anodes. To further reduce the anodic potential and employ the high sulfite concentration (i.e. 3000-32000 ppm) in the gold electrowinning solution, non-precious metal oxides were tested to facilitate the electrowinning process by catalyzing the following sulfite electro-oxidation reaction instead of the oxygen evolution reaction (eq. 2): SO3 2- + 2OH- = SO4 2- + H2O + 2e-, E0= -0.93 V (3) Fig. 1B shows that a combination of manganese oxide and perovskite electrocatalysts provides promising electrocatalytic activity and durability for sulfite electro-oxidation (i.e. up to 500 mV lower onset-potential over 7 hours of testing at 3.5 mAcm-2) compared to the Ni, commercial Ag/AgO, Pt, carbon, commercial Pb-2 wt% Ag and stainless steel electrodes tested here. Fig. 1 A) Surface plot produced from the 2n half-fraction factorial design study on the effect of five electrowinning parameters on the performance of 316 stainless steel gold electrowinning anode. B) A comparison between the electrocatalytic activity of various electrocatalyst materials for sulfite electro-oxidation in a solution of 100 ppm NaCl + 3000 ppm Na2SO4 + 32000 ppm Na2SO3 at 3.5 mA cm-2 and 45 °C. All MnO2-based catalysts are under the license with Catalyst Square Materials Ltd (8).

Electrodeposition of Indium from a Phosphonium-Based Ionic Liquid

Electrochemical deposition of indium metal from aqueous electrolytes is challenging as it occurs simultaneously with hydrogen evolution. The evolution of hydrogen can compromise cathodic current efficiency and can cause porosity of the deposited metal, but it can be avoided by using ionic liquid electrolytes. The high thermal stability of ionic liquids allows for high-temperature electrodeposition on a liquid cathode, offering several advantages over a solid electrode, such as easier separation of electrolysis products and the possibility to design a continuous electrowinning process. In this paper, the electrochemical behavior of indium in the ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) was studied at 120 °C and 180 °C. Indium metal was electrodeposited on platinum and molybdenum substrates and on a liquid indium cathode at 180 °C. Impurities present in commercial Cyphos IL 101 interfered with the measurement of the electrochemical window, so that it had to be carefully purified. The electrochemistry of indium in Cyphos IL 101 was studied by cyclic voltammetry, QMCB, rotating disk and rotating ring disk voltammetry. InCl3 concentration between 10 and 400 mM in Cyphos IL 101 were used in this study. Therefore, the major indium(III) species in solution corresponds to the [InCl6]3– complex. Using the Levich equation, a diffusion coefficient of (7.5 ± 0.1) 10–12 m2 s–1 at 120 °C was calculated for [InCl6]3–. It was found that indium(III) is the most stable oxidation state in the ionic liquid. This ion is reduced via a two-step process, going from indium(III) to indium(I) and subsequently to indium(0). The disproportionation of indium(I) to indium(III) and indium(0) was clearly illustrated. During cyclic voltammograms, the anodic and cathodic peak potentials was found to depend on the scan rate. As the scan rate increases, the separation between the anodic and cathodic peaks becomes greater, indicating that the deposition of indium is irreversible or quasi-reversible. The indium electrodeposits were characterized by SEM-EDS. When depositing indium on molybdenum substrates, the deposition of spherical indium droplets was observed, even at temperatures substantially below the melting point of indium (see figure). The probable mechanism behind this deposition morphology will be explained. Figure 1

Regeneration of Sn4+ from Sn2+ solution during electrowinning process using anion exchange membrane

ABSTRACTElectrowinning process to regenerate Sn4+ from Sn2+ in HCl solution using an electrowinning cell with anion exchange membrane was proposed to suggest a novel recycling process to recover Sn. During the tests, the effects of initial Sn2+ concentration on the regeneration of Sn4+ were investigated under the following condition; 7,000 mg/L, 10,000 mg/L, and 13,000 mg/L of Sn2+, 1 M HCl, 250 A/m2 of current density, graphite anode, titanium cathode, room temperature, and 2 h. Electro-deposited Sn on the cathode showed dendritic structure regardless of the Sn2+ concentration and no change of Sn concentration was observed in the anolyte. Leaching tests were performed using the anolyte, obtained from the electrowinning tests, to examine the amount of regenerated Sn4+ concentration during electrowinning process. Based on the results of Sn leaching tests, it was found that 84.44%, 81.03%, and 79.43% of Sn4+ were regenerated from 7,000 mg/L, 10,000 mg/L, 13,000 mg/L initial concentration of Sn2+ solution, respectively. Consequently, it was found that the regeneration of Sn4+ can occur during the electrowinning process at the same time with Sn recovery and Sn4+ can be reused as an oxidant to leach Sn successfully.

Optimization of solar assisted heating system for electro-winning process in the copper complex

Through various solar assisted heating systems installed worldwide, large industrial scale applications include a very small fraction and further research is still needed in this area. Electrowinning in the copper complex is an industrial scale process that needs thermal energy for electrolyte heating. In this work, for the first time, the techno-economical assessment of using solar energy for this application is performed. Sarcheshmeh copper mine, Kerman, Iran is selected as the case study. System components are modeled and the annual performance is evaluated. To economically optimize the collector arrangement and sizes of storage tank and solar farm, a single-objective as well as a multi-objective genetic algorithm is used. Then, the effects of type and orientation of collector and heat transfer fluid on the system performance are studied. Results demonstrated that a system of 5000–6000 square meters of collectors (depending on the selected collector), facing south, 150–250 cubic meters of stratified storage tank with a height to diameter ratio of three can supply 40–78% of the total heat demanded. This leads to around a 970 tonnes reduction in carbon dioxide emissions each year, which is quite significant, especially in terms of reducing global warming. Payback period varies between 6 and 10 years.

Thermodynamically inert Sc2O3 ceramic crucible for electrowinning process in pyroprocessing

As an alternative to wet processing, pyroprocessing shows promise in recycling transuranic elements with high proliferation resistance. The ceramic crucible used in the electrowinning process is a critical issue encountered in pyroprocessing. These ceramic crucibles are frequently damaged by thermal stress and chemical reaction, which results in significant volumes of crucible waste that must be properly disposed. The volume of generated radioactive waste is a concern when dealing with nuclear power plants and decontamination issues. In this study, a chemically stable Sc2O3 crucible was developed, based on thermodynamic calculations, and sintered using a LiCl–KCl electrowinning system. Secondary ion mass spectroscopy was used to measure the intrusion depth of Li in the sintered ceramics. X-ray diffraction was used to measure the reactivity with ceramic and liquid Li.

Reclamation of copper from spent ammoniacal Printed Circuit Board (PCB) etch solutions

Ammoniacal spent etch liquors is a potential source for copper recovery. In the present investigation copper was extracted from spent ammoniacal PCB etch solutions using hydroxyoxime LIX 84I. Maximum extraction was observed at equilibrium pH of 8.9. Three counter-current stages were required for quantitative extraction of 51.8 g/L copper from the spent liquor using 50%v/v extractant at an O/A ratio of 1.5. It was also possible to achieve quantitative extraction with 20% v/v extractant concentration at an equilibrium pH of 8.9 and O/A ratio 4.5:1. Precipitation −stripping of the loaded organic phase using oxalic acid led to reclamation of copper as copper oxalate. Contacting the oil phase fully loaded with copper in 50% v/v extractant, with 1 M oxalic acid at equal O/A resulted in 77.4% copper getting stripped in first contact, quantitative stripping was achieved in the second contact with fresh acid. There was a close agreement between the experimental and predicted yields based on solubility plots developed for copper-oxalic acid system. Co-extracted ammonia to the organic phase was stripped as soluble ammonium oxalate offering an inherent advantage over the conventional stripping process where build-up of ammonium sulphate is observed during electrowinning process. Calcinations for three hours formed copper oxide, XRD and chemical analysis confirmed the formation of pure copper oxide. The copper present in waste etchant could thus be appropriately converted to value added product.