New insights into the impact of acid surface pretreatment on the flotation of three classified ilmenites

[Display omitted] •Three ilmenites had different flotation recoveries.•Acid surface pretreatment enhanced the floatability of three ilmenites.•Fe3+ ion was the active sites chemisorbed with NaOL in ilmenite flotation.•Fe, Ti, and Mg elements became active sites after acid surface pretreatment.•Acid surface pretreatment increased the distribution densities of main elements. The effect of acid surface pretreatment on the flotation behaviors and surface properties of three classified ilmenites was studied with sodium oleate (NaOL) collector. Three ilmenites had different flotation recoveries in the range from 38% to 64% at the NaOL concentration of 1.0 × 10−4 mol·L−1. After acid surface pretreatment, their flotation recoveries all reached the maximum of over 82%, and the NaOL adsorption and the surface hydrophobicity increased to a close level. XPS analyses proved that the acid surface pretreatment changed the active sites chemisorbed with NaOL collector from Fe3+ ion to Fe3+, Fe2+, Ti4+, and Mg2+ ions on three ilmenite surfaces due to the dissolution of elements. Meanwhile, the XPS and AFM analysis results confirmed that after surface dissolution of elements, the action strengths and distribution densities of the main Fe and Ti elements with collector were enhanced on three ilmenite surfaces. Hence, their floatability all enhanced greatly.