Design of optimal electrolyte circulation based on the kinetic modelling of copper dissolution in silver electrorefining

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2020-09-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
Series
Hydrometallurgy, articlenumber 105403
Abstract
Copper is the major impurity dissolved in silver electrorefining which potentially accumulates in the electrolyte during the process and co-deposits onto the cathode surface, decreasing the product quality. The study investigated the dissolution kinetics of copper in silver electrorefining as a function of wt%Cu in the industrial electrolyte ranges of 40–100 g/dm3 [Ag+], 5–15 g/dm3 [HNO3] and 20–60 g/dm3 [Cu2+] at 25–45 °C. The results showed that Cu dissolved at a higher rate in comparison to silver and that the two kinetic models developed have good accuracy and validity. From the models, optimal electrolyte circulation parameters were simulated to avoid [Cu2+] accumulation in the electrolyte. As a conclusion, processing 1% Cu anodes at the critical [Cu2+]/[Ag+] ratio of 0.8 in the electrolyte requires an inlet of [Ag+] of 2.3–3.3 and tolerates [Cu2+] of 0.14–0.47 times that of the [Ag+] and [Cu2+] in the bulk electrolyte, respectively. Furthermore, electrolyte with higher [Ag+] provides the benefit of reduced electrolyte circulation flowrate and increased tolerance of wt%-Cu in the silver anodes.
Description
Keywords
Copper dissolution, Model-bassed process design, Silver electrorefining
Other note
Citation
Aji , A , Hamuyuni , J , Aromaa , J , Wilson , B P & Lundström , M 2020 , ' Design of optimal electrolyte circulation based on the kinetic modelling of copper dissolution in silver electrorefining ' , Hydrometallurgy , vol. 196 , 105403 . https://doi.org/10.1016/j.hydromet.2020.105403