Electrochemical deposition of zero-valent iron from alkaline ceramic suspensions of Fe2-xAlxO3 for iron valorisation

Electrochemical reduction of iron oxides into zero-valent iron (ZVI, Fe0) is a promising alternative to the traditional methods used for iron production. The electrochemical deposition of Fe0 from hematite and hematite-based Fe2−xAlxO3 ceramic in alkaline suspensions (10 M of NaOH) was assessed at relatively low temperature (90 °C). Ceramic compositions aimed to mimic the main components of red mud waste from the alumina refining industry for iron valorisation purposes. The impact of aluminium content on the electroreduction and microstructure of the deposited Fe0 films was demonstrated and discussed. Trapping and following the leaching of the aluminium species during deposition causes drastic morphological changes and induces significant porosity. Faradaic efficiencies of the reduction to Fe0 were found to decrease from 70% to 32% for Fe2O3 and Fe1.4Al0.6O3, respectively. The results highlight possible effects imposed by aluminium presence during Fe0 electrodeposition for future iron recycling from, for example, red mud or other aluminium containing wastes by electrowinning in alkaline conditions.