Highly efficient and green separation of iron from complex low-grade polymetallic ore via hydrogen-based mineral phase transformation

Abstract

The Bayan Obo low - grade polymetallic ore (BOLPO) is a complex polymetallic resource that has accumulated over decades. Conventional mineral processing struggles to meet specifications. In this study, a hydrogen - based mineral phase transformation (HMPT) technique was introduced. Using HMPT at 425 °C for 30 min, CO and H2 in a ratio of 1:3, 20% concentration, and a product grind size below 38 μm with 95% content, an iron concentrate achieved 65.56% grade and 93.68% recovery. x - ray diffraction, x - ray photoelectron spectroscopy and scanning electron microscopy with energy dispersive x - ray spectroscopy analyses showed selective phase transformation of iron to magnetite in BOLPO during HMPT, avoiding excessive wüstite formation, and no phase transformation of quartz, rare earths or fluorite was observed in the products. Vibrating sample magnetometer analysis showed improved magnetic properties, with saturation magnetization increasing from 7.25 A·m2·kg−1 to 47.28 A·m2·kg−1. HMPT selectively separates high - grade iron from low - grade polymetallic ores without compromising the subsequent recovery of rare earths and fluorite in non - magnetic components.