Sundar S. Sombhatla, Kiran Kr. Rokkam, Ashish Kumar, Sheeba Mashruwala, Akhilesh Shukla
Manganese is frequently found, as a naturally associated element with lead-zinc ores. During the
processing of Zinc concentrates with high manganese content, the selective sulphate leaching of zinc
from concentrate is not possible and eventually ends up with extraction of manganese along with
other minor impurities in to the zinc leachate. The manganese and magnesium levels in zinc hydrorefineries
of Hindustan Zinc have increased above acceptable limits and resulting in an adverse impact
on cell house performance. Due to limited capacity of continuously operated Magnesium Removal
(MR) bleeding section alternative routes for reducing Mn in the zinc sulphate solution have
been explored. The focus is mainly laid on using selective oxidants to oxidize and precipitate manganese
from zinc leach solution. In this regard, KMnO4 has been selectively preferred for Mn reduction,
by taking account of reagent consumption as well as operational lenience.
Consumption of MnO2 for oxidizing ferrous to ferric ions in leaching circuit was identified as another
source of manganese increase. This problem was related to the roaster calcine with high sulphide
sulphur content. Therefore, the usage of MnO2 slurry was unavoidable in leaching circuit along with
air and oxygen sparging. “Sodium persulphate (SPS)”, a powerful oxidizing agent, was explored to
replace MnO2 slurry in leaching; SPS has additional advantages in oxidizing ferrous ions to ferric
along with “sodium sulphate” generation, a prime reagent used for iron precipitation in the form of
Jarosite.
Above improvements, together with additional operational disciplines, have led to an appreciable
control over manganese levels in purified solution and an improvement in cell house performance.