Use of Phytic Acid for the Removal of Iron in Hot Acidic Leachate from Zinc Hydrometallurgy

In zinc hydrometallurgy, hot-acidic leaching of calcines leads to Fe/Zn solutions in sulfuric acid medium. Three distinct processes have been previously developed to remove iron: jarosite, goethite and hematite. Each process displays their own drawbacks: important loss of zinc (jarosite, goethite), significant environmental impact of residue (jarosite) or economic cost (hematite). The work reported herein investigated the possibility of using phytic acid, a compound extractable from cereals, to remove iron. Precipitation was studied first at the laboratory-scale using DOE methodology and then with a laboratory pilot. At pH = 2.1, we showed that it is possible to remove up to 99.5% of iron with a loss of zinc equal to 0.6% and a residual concentration of Fe-III of 130 mg L-1. Even if the amount of residue is more important than in the jarosite process, leaching tests showed that iron phytate could be stored in less drastic conditions than jarosite.

Automated summary

This study investigated the possibility of using phytic acid to remove iron in zinc hydrometallurgy. Results showed that at pH = 2.1, up to 99.5% of iron could be removed with a loss of zinc equal to 0.6%. Even though the amount of residue is higher, iron phytate could be stored in less drastic conditions than jarosite.