Selective flotation separation of bastnaesite from calcite using p-methyl/methoxy benzohydroxamic acid collectors

In this paper, the flotation performances of benzohydroxamic acid (BHA) and its derivatives, p-methyl-benzohydroxamic acid (PMBHA) and p-methoxy-benzohydroxamic acid (PMOBHA) towards bastnaesite and calcite were investigated. The micro-flotation results indicated that the three collectors returned an excellent flotation selectivity against calcite, and their collecting ability towards bastnaesite followed the sequence of PMBHA > PMOBHA > BHA. PMBHA achieved the effective flotation separation of bastnaesite from calcite under pH 8.0–11.0. The findings of adsorption capacity and zeta-potential inferred that PMOBHA exhibited the strongest adsorption affinity to bastnaesite, followed by PMBHA, and then BHA, corresponding to their electron donating ability as-calculated by density functional theory (DFT). While, the dynamic froth stability and contact angle showed that the foaming ability of the three collectors and their hydrophobization towards bastnaesite surface were in order of PMBHA > PMOBHA > BHA, which originated from the hydrophobicity difference reflected by the calculated LogP values. Their collecting power was consistent with the hydrophobization ability rather than the adsorption affinity. For the chemisorption of the three hydroxamic acids on bastnaesite surface was strong enough, their hydrophobicity and foaming power might play an important role for their collecting ability. PMBHA was an excellent candidate collector for bastnaesite flotation.