Iontech provides a hydrometallurgical approach for zinc production, which generally consists of the following steps:
In this stage the zinc oxide is separated from the other calcines via leaching with sulphuric acid. Thereby the zinc content dissolves whereas iron precipitates and lead and silver remain undissolved.
Solution concentration and purification
The dissolved solution contains some impurities which need to be eliminated in order to obtain a high-purity zinc product at the electrowinnig stage. In the more standard way the purification is done through cementation by adding zinc dust to the solution. In the other way for purification and concentration, ion exchange or solvent extraction are used. In the technological approach, proposed by Iontech, this step is done in more advanced manner, namely by using the very promising combination of ion exchange and solvent extraction processes.
The obtained from previous stage purified solution passes an electrolytic process where the solution is electrolyzed between lead alloy anodes and aluminium cathodes. An electrical current is circulated through the electrolyte by applying an electrical voltage between the anode and cathode causing the zinc to deposit on the aluminium cathodes in high purity. The deposited zinc may be High Grade (HG) 99.95% or Special High Grade (SHG) 99.99% of zinc.