Fluorite flotation separation from bastnaesite via an eco-friendly polymer as a depressant and insight into its mechanism of adsorption

Fluorite and bastnaesite are significant mineral resources, but they have comparable surface characteristics, making flotation separation challenging. An eco-friendly polymer depressant was used in this study, causticized cassava starch (CS), for flotation separation of fluorite and bastnaesite. Experimentation, molecular dynamics modeling, and characterization evaluation are used to identify the CS flotation adsorption process on minerals. These findings suggest that hydroxyl groups on CS branches can be weakly adsorbed on fluorite and bastnaesite surfaces by forming OH⋯F hydrogen bonds. CS belongs to causticized starch, which may adsorb on surfaces in a specific manner bastnaesite by developing the R′–CH2–O–Ce-R″ complex. Under the action of chemical adsorption and hydrogen bond adsorption, the adsorption energy of CS in bastnaesite is much larger than that in fluorite, which is −83.16 kJ/mol and −28.38 kJ/mol respectively. After a large amount of CS adsorption, the hydrophilicity of bastnaesite is awfully enhanced and the floatability is decreased. With intentionally mixed materials, flotation separation may provide a concentrate with 82.23 % CaF2 grading and 90.04 % CaF2 recovery. This study provides an idea for separating fluorite and rare earth by preferential flotation of fluorite and selective inhibition of bastnaesite.