Performance evaluation of mixed metal oxide anodes for zinc electrowinning

Authors: Rossetto de Menezes, Daniela
Advisor: Darvishi Alamdari, Houshang
Abstract: The adoption of Mixed Metal Oxide (MMO)-coated anodes in zinc electrowinning cellhouses would provide energy savings and resolve operational issues related to lead corrosion by-products. But a major concern is that commercially available MMO anodes could deteriorate prematurely in typical zinc electrolytes, due to intense MnO2 deposition. In this context, the present study investigated the relationship that Mn2+ concentration in zinc electrolytes affects the characteristics of MnO2 deposits and, consequently, the integrity of three types of IrO2- bearing MMO anodes. For this purpose, firstly, an exploratory anode performance assessment was conducted to monitor the anode potentials and the MnO2 formation rates in the medium term, as a function of Mn2+ concentration. Then, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the anode samples after 72-hour galvanostatic polarization tests at different Mn2+ concentrations. The results have suggested that MnO2 deposits developed different morphologies and induced different anode deterioration processes, depending on the Mn2+ concentration and the anode type. In particular, anodes type “D” were covered by MnO2 films that would easily chip off after reaching a critical thickness, thus producing induced stresses. According to SEM images, these MnO2 pieces detached take out MMO coating fragments adhered to them. Meanwhile, MnO2 clusters of elongated crystallites developed over anodes “E” and “F”, and they were found to induce ruptures throughout the MMO coatings. Considering these results and specific criteria to define the Mn2+ tolerance levels of these anodes, a financial analysis was proposed for screening the most suitable anode type for industrial use, based on both the anodic potential demonstrated and the manganese control strategy required for its satisfactory operation.
Document Type: Mémoire de maîtrise
Issue Date: 2021
Open Access Date: 19 July 2021
Grantor: Université Laval
Collection:Thèses et mémoires

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