Validation and Implementation of Cold Purification Cake Leaching in Ammoniacal Carbonate Solutions at Hindustan Zinc Hydro Refineries

  • Sundar S. Sombhatla
  • Ashish Kumar
  • Kiran Kr. Rokkam
Technical Paper


Cold purification cake generated during the purification of zinc leachate mainly contains copper 30–40% along with zinc 10–20% and cadmium up to 2%. Photomicrographs of purification cake indicated the major presence of copper in metallic/oxidized form. In the present work, ammoniacal carbonate leaching of purification cake followed by solvent extraction using diketone-based solvent has been studied under the influence of various parameters, viz. temperature, agitation, pulp density, ammonia, CO2 dosages, solvent concentration and impact of w/s zinc on leaching and solvent extraction. Leaching kinetics were determined based on shrinking core model. Chemical reaction at unreacted core was found to be the rate controlling step. The estimated activation energy was found to be 24 kJ/mol. Leached copper was extracted by solvent extraction with a β-diketone-based solvent and was stripped with sulfuric acid as concentrated copper sulfate solution. The above-established R&D findings were successfully implemented in the commercial plant with a treatment capacity of two tons of cold purification cake per batch.


Ammoniacal leaching Kinetics Solvent extraction Activation energy 

List of symbols


Pre-exponential factor in Arrhenius equation


Stoichiometric coefficient in Eq (8)


Concentration of fluid reactant (mol/m3)


Effective diffusivity (m2/s)


Activation energy (J/mol)


Liquid–solid mass transfer coefficient (m/s)


Apparent rate constant for product layer diffusion (s−1)


Apparent rate constant for surface chemical reaction (s−1)


Intrinsic reaction rate constant


Mole gas constant (8.3145 J/(mol K))


Time (h or s)


Temperature (K)/° centigrade


Fraction of extraction


Density of solid


Initial particle radius (m)



The authors would like to acknowledge Hindustan Zinc Limited for providing a fostering environment for this research and permission to publish the data.


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Copyright information

© The Indian Institute of Metals - IIM 2018

Authors and Affiliations

  • Sundar S. Sombhatla
    • 1
  • Ashish Kumar
    • 1
  • Kiran Kr. Rokkam
    • 1
  1. 1.Central Research and Development LaboratoryHindustan Zinc LimitedUdaipurIndia

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