Abstract
Impurities and additives play a key role in copper electrodeposition, in particular in upstream processes such as electrowinning or electrorefining. One common impurity is iron, mostly present as iron species Fe(II) in highly concentrated sulfuric acid solutions and in a cathodic environment. Herein, the kinetics of copper electrodeposition from such solutions have been investigated using a copper rotating disk electrode and alternating current voltammetry (ACV). For a concentration of proton of 1.84 M and a concentration of Fe(II) ions of 0.054 M, the deposition kinetics are slow enough to separately observe the two electron transfer steps involved in copper reduction: an observation unique to ACV. The results suggest that Fe(II) ions affect the electrodeposition kinetic by slowing down reaction kinetics, in particular slowing the second electron transfer reaction.
Highlights
Wagner, Mary-Elizabeth, Rodrigo Valenzuela, Tomas Vargas, Melanie Colet-Lagrille, and Antoine Allanore
Advancing the understanding of copper electrodeposition kinetics in a concentrated sulfuric acid electrolyte is beneficial at multiple stages of copper life cycle
Electrodeposition in concentrated solutions at 25◦C.— Figure 1 shows the DC signal measured during copper electrodeposition in a solution with 0.63 M Cu(II) and 1.84 M H2SO4, concentrations representative of industrial practices
Summary
Mary-Elizabeth, Rodrigo Valenzuela, Tomas Vargas, Melanie Colet-Lagrille, and Antoine Allanore. Various factors influencing copper electrodeposition have been reported in conditions simulating the low pH, high copper concentration electrolytes common in industrial conditions.[4,5,6] In upstream steps such as electrowinning or electrorefining, solution additives play an important, though only marginally understood, role in the final deposit quality. Additives encompass both inevitable impurities inherited from the raw minerals and carried along with copper during the smelting process,[7] as well as impurities purposely added to improve the deposit properties.[8] The outcome on deposit quality varies widely,[6,7,8,9,10] with additives exhibiting either a positive or negative effect on copper growth. The situation is further complicated for copper electrodeposition in concentrated electrolyte, where a four-step mechanism, commonly referred to as
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