Search Results (7)

The oxygen-evolving IrO₂-Ta₂O₅/Ti anode (OEA), primarily used in electrolyzers for plating, metal powder production, electrowinning (EW), and water electrolysis, is analyzed. This study focuses on the distribution of oxygen evolution reaction (OER) activity and the associated operational loss over the randomized OEA texture. The OER activity and its distribution across the IrO₂-Ta₂O₅ coating surface are key factors that influence EW operational challenges and the lifecycle of OEA in EW processes. To understand the OER activity distribution over the coating’s randomized texture, we performed analyses using anode polarization in acid solution at both low and high (EW operation relevant) overpotentials and electrochemical impedance spectroscopy (EIS) during the OER. These measurements were conducted on anodes in both their as-prepared and deactivated states. The as-prepared anode was deactivated using an accelerated stability test in an acid solution, the EW simulating electrolyte. The obtained data are correlated with fundamental electrochemical properties of OEA, such as structure-related pseudocapacitive responses at open circuit potential in the same operating environment. OER and Ir dissolution kinetics, along with the physicochemical anode state upon deactivation, are clearly characterized based on current and potential dependent charge transfer resistances and associated double layer capacitances obtained by EIS. This approach presents a useful tool for elucidating, and consequently tailoring and predicting, anode OER activity and electrolytic operational stability in industrial electrochemical applications. Full article

The leaching of Cu in ammoniacal solutions has proven an efficient method to recover Cu from waste printed circuit boards (WPCBs) that has used by many researchers over the last two decades. This study investigates the feasibility of a counter-current leaching circuit that would be coupled with an electrowinning (EW) cell. To accomplish this objective, the paper is divided into three parts. In Part 1, a leaching kinetic framework is developed from a set of experiments that were designed and conducted using end-of-life waste RAM chips as feed sources and Cu(II)-ammoniacal solution as the lixiviant. Various processing parameters, such as particle size, stirring rates, initial Cu(II) concentrations, and temperatures, were evaluated for their effects on the Cu recovery and the leaching rate. It was found that the particle size and initial Cu(II) concentration were the two most important factors in Cu leaching. Using a 1.2 mm particle size diameter and 40 g/L of initial Cu(II) concentration, a maximum Cu recovery of 96% was achieved. The Zhuravlev changing-concentration model was selected to develop the empirically fitted kinetic coefficients. In Part 2, kinetic data were adapted into a leaching function suitable for continuously stirred tank reactors. This was achieved via using the coefficients from the Zhuravlev model and adapting them to the Jander constant concentration model for use in the counter-current circuit model. Part 3 details the development of a counter-current circuit model based on the relevant kinetic model, and the circuit performance was modeled to provide a tool that would allow the exploration of maximum copper recovery whilst minimizing the Cu(II) reporting to electrowinning. A 4-stage counter-current circuit was modeled incorporating a feed of 35 g/L of Cu(II), achieving a 4.12 g/L Cu(II) output with 93% copper recovery. Full article

This study aimed to recover copper and gold from a waste printed circuit board (WPCB) using monosodium glutamate (MSG) supplemented with a clean oxidizer(s) under 30 °C, 150 rpm, and an initial pH of 7.00. The solder mask of WPCBs needed to be removed before leaching. At the first leaching, 93% of copper was selectively leached from solder–mask–free WPCBs within 3 h using 0.75 M MSG with 0.50% (w/v) ${\mathrm{H}}_2{\mathrm{O}}_2$. Then, gold (86%) was extracted from the first residue for 3 h by 1 M MSG with 0.25% (w/v) ${\mathrm{H}}_2{\mathrm{O}}_2$. In the downstream process, 98–100% copper could be directly recovered within 5–6 h from the first leachate by electrowinning (EW). However, gold in the second leachate required separation and purification processes before EW. At 4 h, 98% gold was adsorbed onto the activated carbon. Most impurities were removed from gold-loaded activated carbon by pre-elution using 0.05 M EDTA for 0.5 h without gold release. Afterward, 99% gold was eluted by diluted aqua-regia within an hour. Finally, the gold could be harvested perfectly using EW for 2 h. This complete copper and gold recycling process delivers an innovative concept for hydrometallurgical study and has the potential to develop into a practical industry. Full article

The flotation tailings obtained from Bor Copper Mine contain pyrite (FeS₂) and chalcopyrite (CuFeS₂), these sulfide minerals are known to promote acid mine drainage (AMD) which poses a serious threat to the environment and human health. This study focuses on the treatment of mine tailings to convert the AMD supporting minerals to more stable forms, while simultaneously valorizing the mine tailings. A combination of hydrometallurgical processes of high-pressure oxidative leaching (HPOL), solvent extraction (SX), and electrowinning (EW) were utilized to recover copper from mine tailings which contain about 0.3% Cu content. The HPOL process yielded a high copper leaching rate of 94.4% when water was used as a leaching medium. The copper leaching kinetics were promoted by the generation of sulfuric acid due to pyrite oxidation. It was also confirmed that a low iron concentration (1.4 g/L) and a high copper concentration (44.8 g/L) obtained in the stripped solution resulted in an improved copper electrodeposition current efficiency during copper electrowinning. Moreover, pyrite, which is primarily in the mine tailings, was converted into hematite after HPOL. A stability evaluation of the solid residue confirmed almost no elution of metal ions, confirming the reduced environmental loading of mine tailings through re-processing. Full article

Zinc recovery from spent pickling acids (SPAs) can play an important role in achieving a circular economy in the galvanizing industry. This work evaluates the scale-up of membrane-based solvent extraction technology aimed at the selective separation of zinc from industrial SPAs as a purification step prior to zinc electrowinning (EW). The experiments were carried out at a pilot scale treating SPAs batches of 57 to 91 L in a non-dispersive solvent extraction (NDSX) configuration that simultaneously performed the extraction and backextraction steps. The pilot plant was equipped with four hollow fiber contactors and 80 m² of total membrane area, which was approximately 30 times higher than previous bench-scale studies. Tributylphosphate diluted in Shellsol D70 and tap water were used as organic and stripping agents, respectively. Starting with SPAs with high Zn (71.7 ± 4.3 g·L⁻¹) and Fe (82.9 ± 5.0 g·L⁻¹) content, the NDSX process achieved a stripping phase with 55.7 g Zn·L⁻¹ and only 3.2 g Fe·L⁻¹. Other minor metals were not transferred, providing the purified zinc stripping with better quality for the next EW step. A series of five consecutive pilot-scale experiments showed the reproducibility of results, which is an indicator of the stability of the organic extractant and its adequate regeneration in the NDSX operation. Zinc mass transfer fluxes were successfully correlated to zinc concentration in the feed SPA phase, together with data extracted from previous laboratory-scale experiments, allowing us to obtain the design parameter that will enable the leap to the industrial scale. Therefore, the results herein presented demonstrate the NDSX technology in an industrially relevant environment equivalent to TRL 6, which is an essential progress to increase zinc metal resources in the galvanizing sector. Full article

In the Pyror process, electrowinning (EW) is used to recover acid and iron from spent leaching solutions (SLS), where a porous Terylene membrane acts as a separator between the cathode and anode. In this study, a novel anion exchange membrane (AEM)-based EW process is benchmarked against a process without and with a porous Terylene membrane by comparing the current efficiency, specific energy consumption (SEC), and sulfuric acid generation using an in-house constructed EW flow cell. Using an FAP-PK-130 commercial AEM, it was shown that the AEM-based process was more efficient than the traditional processes. Subsequently, 11 novel polybenzimidazole (PBI)-based blend AEMs were compared with the commercial AEM. The best performing novel AEM (BM-5), yielded a current efficiency of 95% at an SEC of 3.53 kWh/kg Fe, which is a 10% increase in current efficiency and a 0.72 kWh/kg Fe decrease in SEC when compared to the existing Pyror process. Furthermore, the use of the novel BM-5 AEM resulted in a 0.22 kWh/kg Fe lower SEC than that obtained with the commercial AEM, also showing mechanical stability in the EW flow cell. Finally, it was shown that below 5 g/L Fe, side reactions at the cathode resulted in a decrease in process efficiency, while 40 g/L yielded the highest efficiency and lowest SECs. Full article

The influence of adsorbate (D2EPHA and kerosene) on the process of zinc electrowinning from sulfuric acid electrolytes was analyzed. The main objective was to critically compare three factors: (1) Three types of activated carbon (AC); (2) adsorption temperatures and contact time; and (3) zinc recovery efficiency. The results showed that organic components reduced the efficiency of zinc recovery. Moreover, wood-based ACs had a higher adsorption capacity than coal- and coconut-based ACs. To maintain a removal efficiency of 99% or more, wood-based ACs should constitute at least 60% of the adsorbate. The temperature of adsorption did not affect the removal efficiency. Additionally, the feeding rate of adsorbate in the solvent was inversely proportional to the removal efficiency. A feeding rate of the liquid pump of over 3 mL/min rapidly increased the delta pressure. For the same contact time, 99% of adsorbate removal occurred at 1 mL/min compared to approximately 97% at 0.5 mL/min. In the presence of 100 mg/L zinc, with increasing adsorbate from 0–5%, the recovery efficiency of zinc decreased from 100% to 0% and the energy consumption increased from 0.0017–0.003 kwh/kg zinc. Considering the energy consumption and zinc deposit mass, 0.1% of the adsorbate is recommended for zinc electrowinning. Full article