An Assessment of the Role of Combined Bulk Micro- and Nano-Bubbles in Quartz Flotation

Bulk micro-nano-bubbles (BMNBs) have been proven to be effective at improving the flotation recovery and kinetics of fine-grained minerals. However, there is currently no research reported on the correlation between the properties of BMNBs and flotation performance. For this purpose, aqueous dispersions with diverse properties were created by altering preparation time (0, 1, 2, 3, 5, and 7 min), aeration rate (0, 0.5, 1, 1.5, and 2 L/min) and aging time (0, 0.5, 1, and >3 min). Micro- and nano-bubbles were characterized using focused beam reflection measurements (FBRM) and nanoparticle tracking analysis (NTA), respectively. The micro-flotation of quartz particles was performed using an XFG-cell in the presence and absence of BMNBs with Cetyltrimethylammonium bromide (CTAB) as a collector. The characterization of bubble sizes showed that the bulk micro-bubble (BMB) and bulk nanobubble (BNB) diameters ranged from 1-10 mu m and 50-400 nm, respectively. It was found that the preparation parameters and aging time considerably affected the number of generated bubbles. When BNBs and BMBs coexisted, the recovery of fine quartz particles significantly improved (about 7%), while in the presence of only BNBs the promotion of flotation recovery was not significant (2%). This was mainly related to the aggregate via bridging, which was an advantage for quartz flotation. In comparison, no aggregates were detected when only nano-bubbles were present in the bulk solution.