Electrolysis of iron with oxygen gas evolution from molten sodium borate electrolytes

ABSTRACT

Molten oxide electrolysis can be used to reduce the carbon dioxide emissions from ironmaking. In this paper, we electrochemically decompose iron oxide (Fe₂O₃) into iron (Fe) and oxygen (O₂) using boron trioxide and sodium oxide (B₂O₃–Na₂O) as the molten oxide electrolyte at 1000°C that is less than the temperature of other molten oxide electrolysis. The formation of Fe at the cathode and O₂ at the anode is identified by analysing products from both electrodes. The results suggest that the cathodic current efficiency of electrolysis at 2 V is about 54.7%, energy consumption is about 5.27 kW h kg^–1 of Fe at 2 V electrolysis, and purity of the reduced Fe was more than 97 mol.%. With respect to the process temperature and product yield, B₂O₃–Na₂O molten oxide has potential as a supporting electrolyte to reduce Fe₂O₃ to Fe without consuming any carbon.

KEYWORDS:

• Molten oxide electrolysis
• carbon-free ironmaking process
• metal extraction
• oxygen evolution
• sodium borate
• high current efficiency
• low energy consumption
• thermogravimetric analysis

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the POSCO [Grant number 0642-20190003].