Investigating the Effect of Microwave Pretreatment on Bastnasite Grinding for Comminution Energy Reduction and Rare Earth Recovery

This study explored the impact of microwave pretreatment on the grinding efficiency of bastnaesite ore using a stirred mill. Bastnaesite ore was prepared using a staged crushing and sieving process, followed by microwave pretreatment in a specially designed microwave furnace system. Representative samples of the crushed ore underwent stirred mill grinding, with power draw measurements recorded and adjusted to reflect only the specific energy input required for grinding. Particle size distribution was analyzed periodically using laser particle size analysis. In addition, a Box–Behnken design was used to statistically assess the effects of various parameters on the results, ensuring a robust analysis of the factors influencing energy consumption and particle size reduction. The findings reveal that microwave pretreatment significantly influenced specific energy and product P80, with SEM analyses showing increased microcracking and porosity and XRD analyses suggesting possible mineralogical alterations. This enhancement was also proved via statistical tools and analyses such as Design Expert software Ver. 13 and ANOVA. In summary, the research concludes with the following critical points: (1) Microwave pretreatment was found to reduce the energy consumption required for bastnaesite grinding by 27%. (2) Following pretreatment, bastnaesite achieved a 25% finer product size under identical grinding conditions. (3) Structural and compositional changes in bastnaesite after grinding were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. (4) Based on these analyses, potential mechanisms for the observed energy savings and product size reductions have been suggested. Additionally, we have enhanced the Abstract to better highlight the methods used in the study. This investigation not only advances our understanding of microwave-assisted comminution but also opens avenues for future research on optimizing and implementing this technique in large-scale mining operations.