Investigation of the kinetics and the morphology of cementation products formed during purification of a synthetic zinc sulfate electrolyte
Journal article, 2018

© 2018 In zinc production, the purity of incoming zinc solution is of great importance. The presence of cobalt in the electrolyte used for zinc production lowers the current efficiency of zinc deposition and affects the purity of the zinc product. For this reason, cobalt must be removed from the electrolyte prior to zinc electrowinning. Cobalt removal is commonly achieved by the addition of metallic zinc dust through a process called cementation. The mechanism by which cementation occurs is not well understood. Parameters, such as cementation time, temperature, solution pH, concentration of activators, concentration of zinc ions in the electrolyte were investigated in this study. It was concluded that cobalt cementation could be described by a first order rate equation with an activation energy of 45 kJ/mol. Temperature played a significant role on the kinetics while the presence of hydrogen, intermediate compound formation, and zinc ions inhibited the cobalt cementation. Cu/Sb activators were cemented within the first 90 s and gave synergistic effect on cobalt cementation. Surface compounds on the cementation product were identified as mainly Zn(OH)2and ZnSO4. Redissolution of cobalt did not occur from cemented cobalt but from dissolution of intermediate Co(OH)2and CoSO4salts.

Zinc

Metallurgy

Activators

Cementation

Mechanism

Author

Toni Karlsson

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Nuclear Chemistry

Yu Cao

Chalmers, Industrial and Materials Science, Materials and manufacture

Yuda Chryspian Colombus

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Nuclear Chemistry

Britt-Marie Steenari

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Nuclear Chemistry

Hydrometallurgy

0304-386X (ISSN)

Vol. 181 169-179

Subject Categories

Inorganic Chemistry

Other Chemical Engineering

Other Chemistry Topics

DOI

10.1016/j.hydromet.2018.09.007

More information

Latest update

10/17/2018