Adsorption and electroreduction of hematite particles on steel in strong alkaline media

The aim of this work was to use various electrokinetic measurement techniques, from which zeta potential values were obtained, in order to investigate the behavior of the surface charge of hematite particles in highly concentrated electrolytes (up to 10 M) and to correlate these results with the electrochemical reduction of hematite in a strong alkaline media at 110 °C. Electrochemistry experiments showed that adsorption of hematite onto steel in this strong media was possible although weak, thus the electroreduction of hematite into elemental iron was observed. At alkaline pH, zeta potential measurements by electrophoresis in diluted media yielded coherent results, and in high concentration electrolytes, electroacoustic measurements allowed proving that over a concentration in [Na+] of 0.1 M, a charge reversal occurs. Zeta potential then remains slightly positive in the range of 0.1–10 M.

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► Adsorption of hematite onto steel is observed in strong alkaline solutions.
► Zeta potential of hematite in NaOH solutions up to 10 M was measured.
► A charge reversal of zeta potential occurs for [Na+] > 0.1 M.
► No electrostatic repulsion is expected between particles and electrode.