Enhanced grindability of bastnaesite ore by ex-situ CO2 treatment under the partial pressure of 0–100 psi

High grinding energy consumption has long constrained the sustainable development of mineral processing . This study introduces an innovative technology that employs ex-situ CO 2 treatment to enhance the grindability of bastnaesite ore. The grinding aid effect was evaluated under CO 2 partial pressures ranging from 0 psi to 100 psi using particle size distribution and the Bond work index (BWI), while the underlying mechanism was elucidated with various characterization techniques including inductively coupled plasma (ICP), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET). The optimal grinding aid effect was achieved at 100 psi partial pressure, 50 % slurry concentration, and 3 h reaction duration. Correspondingly, the P 80 of the grinding product decreased from 81.76 μm to 72.73 μm and the BWI of bastnaesite ore decreased from 6.96 kW·h/t to 6.30 kW·h/t, a reduction of 9.48 %. The grinding aid effect primarily resulted from the transformation of sparingly soluble carbonates like calcite and dolomite into more soluble bicarbonates, which created substantial cracks and pores, thereby reducing the ore's hardness and improving its grindability. By significantly saving grinding energy consumption while delivering environmental benefits, this technology exhibits great promise for further optimization and widespread adoption. • Ex-situ CO 2 treatment has improved the grindability of bastnaesite. • Ex-situ CO 2 treatment resulted in partial dissolution of carbonates. • The dissolution caused the ore particles to form more pores and cracks. • More pores and cracks led to a decrease in the hardness of the ore particles.