Abstract
In this study, an alumina (Al) anode, a lead cathode, and insoluble catalytic cathodes (IrOx, PdOx, TaOx, and SnOx) were used as electrodes to enhance zinc recovery. The traditionally used iron electrode and insoluble catalytic electrodes were also used to compare the recovery yield when different types of electrodes were subjected to the same amount of energy. The lead electrode showed over 5000 Ω higher electrode resistance than did the insoluble catalytic electrode, leading to overpotential requiring higher electrical energy. As electrical energy used by the lead and the insoluble catalytic electrodes were 2498.97 and 2262.37 kwh/ton-Zn, respectively, electrical energy can be reduced by 10% when using an insoluble catalytic electrode compared to that when using a lead electrode. Using recovery time (1–4 h) and current density (100–500 A/m2) as variables, the activation, concentration polarization, and electrode resistance were measured for each condition to find the optimum condition for zinc recovery. A recovery yield of about 77% was obtained for up to 3 h of zinc recovery time at a current density of 200 A/m2, which is lower than that (about 80%) obtained at 300 A/m2. After 3 h of recovery time, electrode resistance (Zn concentration reduction, hydrogen generation on electrode surface) and overpotential increase with time decreased at a current density of 200 A/m2, leading to a significant increase in zinc recovery yield (95%).
Highlights
The zinc smelting process, urban mining, and plating industries produce zinc solutions containing various impurities (F, Cl, Mn, As, Mg, and Ca); methods to recover high-purity zinc from these solutions are actively being researched [1]
The recovery time and current density of insoluble catalytic electrodes were used as variables to measure activation, concentration polarization, and electrode resistance in order to find the optimum condition for zinc recovery
The Galvanic measurement method was used in the condition where the Al electrode was the anode and lead or an insoluble catalytic electrode was the cathode with the same electrode surface area
Summary
The zinc smelting process, urban mining, and plating industries produce zinc solutions containing various impurities (F, Cl, Mn, As, Mg, and Ca); methods to recover high-purity zinc from these solutions are actively being researched [1]. Limitations of lead electrodes require a high overpotential, which contributes to the high electric cost and produces precipitates due to the low erosion resistance, reducing the electrode lifespan [7]. In a IrOx/Ti electrode, Mn in the electrolyte is electrodeposited in an oxide form at the cathode surface to increase cell resistance, while F ions corrode the coated catalyst at the cathode surface, critically reducing the electrode efficiency and lifespan [14]. Design factors for the zinc recovery process include the zinc purity, cathode cell voltage, electrical energy, pH, current density, zinc concentration, recovery temperature, and electrode spacing. The recovery time and current density of insoluble catalytic electrodes were used as variables to measure activation, concentration polarization, and electrode resistance in order to find the optimum condition for zinc recovery
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