Electrodeposition of iron from aqueous bath towards zero-carbon ironmaking: Effect of phosphorus on product purity and energy efficiency

Abstract

Electrodeposition of iron from aqueous bath was a promising technology for ultra-low carbon ironmaking. However, the P impurity leached from iron ore co-deposited with Fe in the electrodeposition process, leading to a serious decline of Fe product quality. In this study, the effects of the electrodeposition parameters on the Fe purity and the current efficiency were investigated, and the P-Fe co-deposition behavior was examined by electrochemical characterization. The results showed that higher P/Fe ratio in the electrolyte was unfavorable for the Fe purity. The P content in the electrodeposited product decreased, while the current efficiency of Fe electrodeposition increased with the increase of the electrodeposition temperature and current density. Although higher H₂SO₄ concentration improved the Fe purity, the Fe current efficiency was reduced. It was attributed to the charge transfer resistance and the inhibitory effect of P on Fe electrodeposition. The electrodeposited Fe product with a purity of 99.31 % and a P content of 0.09 % was prepared at 200 mA cm^-2, 80 °C, and 4.5 g/L H₂SO_4, when the P/Fe ratio was 1:100 (P = 150 mg/L). The structural analysis of electrodeposited products showed that P may be deposited in the lattice interstitial space of iron and exist as interstitial solid solution.