Enhanced flotation separation of fine ilmenite from titanaugite using 5-alkyl salicylhydroxamic acid

To enhance the flotation separation of fine ilmenite and titanaugite, three novel alkyl salicylhydroxamic acids, 5-isopropyl salicylhydroxamic acid (ISHA), 5- tert -butyl salicylhydroxamic acid (TBSHA), and 5- tert -amyl salicylhydroxamic acid (TASHA), were developed. Flotation results showed that the three collectors were superior to SHA under neutral conditions, with ISHA giving the highest separation efficiency. DFT calculations, microcalorimetry, and contact angle measurements revealed that introducing alkyl groups into the SHA structure enhanced its hydrophobicity and the electron-donating ability of the hydroxamic acid group, while preserving the intrinsic selectivity of SHA, thereby strengthening ilmenite flotation. Dynamic froth stability tests showed that the ISHA system exhibited lower froth stability than the TBSHA and TASHA systems, which may reduce froth entrainment of titanaugite and thus contribute to better separation performance. In-situ AFM imaging and zeta potential measurements indicated that ISHA adsorbed more strongly on ilmenite than on titanaugite. FTIR and XPS analyses confirmed that the two O atoms in the hydroxamic acid group of ISHA strongly chelated with Fe on ilmenite, but interacted weakly with Ca and Mg on titanaugite. The number of active Fe sites on ilmenite was significantly higher than that on titanaugite, enabling selective ISHA adsorption. This study provides a new design strategy for developing efficient collectors for titanium resources and offers an important reference for green separation technologies.