| Summary: | Ludwigite ore is a typical intergrown mineral resource found in China. Reductive soda-ash roasting followed by water leaching is an innovative process for the high-efficiency separation and recovery of boron and iron. In this study, the co-conversion mechanism of boron activation and iron reduction during soda-ash reductive roasting for boron-bearing iron concentrate was clarified. When the boron-bearing iron concentrate was reduced in the presence of Na<sub>2</sub>CO<sub>3</sub>, szaibelyite (Mg<sub>2</sub>(OH)(B<sub>2</sub>O<sub>4</sub>) (OH)) was activated to sodium metaborate (NaBO<sub>2</sub>) and, meanwhile, magnetite (Fe<sub>3</sub>O<sub>4</sub>) was reduced to metallic iron (MFe). Boron activation promoted iron-oxide reduction effectively, while the latter could only slightly influence the former. The promotion occurred through (1) a facilitated generation of sodium magnesium silicate (Na<sub>2</sub>MgSiO<sub>4</sub>) and a hindering of the formation of olivine (Mg<sub>x</sub>Fe<sub>2-x</sub>(SiO<sub>4</sub>)). (2) The newly generated NaBO<sub>2</sub> promoted iron-oxide reduction. (3) The low melting point of the NaBO<sub>2</sub> (966 °C) favored particle migration, which accelerated metallic iron particle aggregation.
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