Influence and optimization of hydrogen-based mineral phase transformation on grinding characteristics of polymetallic oxide and recovery of valuable elements by response surface methodology

The complex polymetallic ore of Bayan Obo is rich in valuable elements, but difficult to utilize. Hydrogen-based mineral phase transformation (HMPT) is an efficient and eco-friendly technology for processing refractory ores. In this study, the process parameters of HMPT were optimized using response surface methodology (RSM). The effects of reaction temperature, reaction time, and H₂ concentration on grinding efficiency, energy consumption, and iron recovery were studied using Box-Behnken Design (BBD). The phase transformation and microstructural characteristics of the ore were analyzed. The results indicate that temperature and H₂ concentration are key factors influencing specific power consumption in grinding and iron recovery rate. Using the characteristic parameter T, which represents the ratio of specific power consumption to iron recovery rate, as the evaluation index, the optimal HMPT conditions were determined: temperature of 500℃, time of 20 min, and H₂ concentration of 30 %. XRD and SEM-EDS analysis results indicate that after HMPT treatment, hematite is more likely to transform into magnetite, and additional cracks appear on the surface of the mineral particles, explaining the improved grinding and separation effects. This provides theoretical guidance for the low-energy consumption and high-efficiency HMPT processing in the industrialization of complex polymetallic ore.