Flotation separation of fluorite from calcite and quartz using 1-hydroxyoctane-1,1-bisphosphonic acid

Sodium oleate (NaOl) is commonly regarded as a kind of collector with strong recovery ability for fluorite flotation. However, its limited selectivity for fluorite and gangue had affected the production of higher-grade fluorite. In this investigation, 1-hydroxyoctane-1,1-bisphosphonic acid (HOBA) was employed as a potential alternative, offering greater efficiency. Micro-floatation experiments confirmed that HOBA could offer better selectivity than NaOl. Moreover, the interaction mechanisms between HOBA or NaOl and the mineral surfaces of fluorite, calcite, and quartz were systematically studied during the flotation process. Contact angle, zeta potential analyses revealed stronger adsorption on fluorite by HOBA compared to calcite and quartz, which can be attributed to its superior selectivity. FTIR and XPS analyses indicate that this selectivity arises from the chemisorption of reagents on fluorite. DFT calculations further demonstrated that HOBA exhibited the stronger selective adsorption on fluorite than that on calcite and quartz surfaces compared to NaOl, due to its more binding sites, supporting IR and XPS results. Additionally, the electronic structure analysis implies that HOBA should is likely bonded to the mineral surfaces through chemisorption as ionic bonds.