Electrochemical Evaluation of Lead Base Composite Anodes Fabricated by Accumulative Roll Bonding Technique
- PDF / 2,232,345 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 28 Downloads / 252 Views
þ 4Hþ þ 4e ! 2H2 O e ¼ 1:229 V/SHE
INTRODUCTION
HYDROMETALLURGICAL methods are commonly preferred to pyrometallurgical ones in metal extraction processes because of the latter’s higher energy consumption; higher costs of instruments, materials, and labor; environmental pollution; and poor recyclability. Cathodic reduction (electrowinning) of metals is one of the conventional hydrometallurgical methods used in the industrial scale production of bulk type and high purity metals such as Zinc and Copper. Sulfuric acid is one of the electrolytic solutions most generally used in numerous electrowinning industries and oxygen evolution is the main anodic reaction employed in these methods. The reaction is expressed by Relation [1] below[1]: 1 H2 SO4 þ O2 þ 2e $ SO2 4 þ H2 O 2
½1
This could be reduced to Relation [2] below:
MARYAM KARBASI, Ph.D. Candidate, is with the Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, P.O. Box. 15875-4413, Tehran, Iran. ESKZANDAR KESHAVARZ ALAMDARI, Associate Professor, is with the Department of Mining and Metallurgical Engineering, Amirkabir University of Technology and also with the Research Center for Materials and Mining Industries Technology, Amirkabir University of Technology. Contact Contact e-mail: [email protected] Manuscript submitted June 23, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
½2
The actual potential for these reactions is related to the associated polarization value. Polarization is a kinetic status of the system directly related to current density and productivity.[1] Polarization intensity is affected by temperature as well as the electrolyte’s composition and anodes properties.[2] However, reduction of the actual anodic reaction potential decreases energy consumption.[2] Therefore, the materials selected for anodes must have such outstanding characteristics as excellent electrical conductivity, electrocatalytic properties, high corrosion resistance, and dimensional stability for higher energy efficiency, more productivity, and lower maintenance costs.[1] Lead base compounds have been universally used as anodes in electrowinning industries.[2] Although these anodes enjoy such advantages as insolubility in sulfuric acid solutions, they are usually plagued with problems like high anodic overpotential, high energy consumption, anodic corrosion, dimensional instability, and increased maintenance costs.[1] These drawbacks have encouraged many researchers to focus on improvement of lead base anodes (Pb-Ag, Pb-Ag-As, and Pb-Ag-Sn (Tainton et al. before 1921), Pb-Tl (Fink et al. 1921), PbTl-Te-Ca (Bray 1942), Pb-Ag-Sn-Sb, Pb-Ag-Sn-Co (Yoshida et al. 1953), Pb-Ag-Ti (Kozin et al. 1977), and Pb-Ag-As (Tomas 1984)[1]). However, few achievements have been made in this regard that include electrochemical improvement[1] and utilization of
alloyed[3] and composited anodes.[4–8] Moreover, the use of lead base anodes has been restricted by various process disadvantages such as casting and rolling defects;[3,9–12] expensive methods
Data Loading...
