Oil-assisted flotation of fine hematite using sodium oleate or hydroxamic acids as a collector

Micro-flotation and batch flotation tests were carried out on fine (-20 µm) hematite to investigate the influences of non-polar oil when sodium oleate, octyl hydroxamic acid, or oleoyl hydroxamic acid was used as a collector. Both micro-flotation and batch flotation tests were performed using single hematite mineral and/or artificial mixed minerals (hematite:quartz = 1:1), and kerosene was utilized as the neutral oil. The experimental results showed that the addition of a kerosene emulsion benefited hematite recovery in the micro-flotation tests where a froth layer did not exist. In the batch flotation where a froth layer existed, kerosene behaved differently when used in conjunction with the three collectors. Kerosene helped improve the batch flotation when sodium oleate or oleoyl hydroxamic acid was used as a collector. However, it reduced concentrate weight yield, grade and recovery to a noticeable extent when octyl hydroxamic acid was used as a collector, especially at low dosages. In addition, single hematite batch flotation kinetics tests coupled with water recovery measurement were carried out to study the role of kerosene at different collector dosages. It was observed that water drainage and the resulting froth destabilization by kerosene was dominant at low collector dosages, especially in the flotation using octyl hydroxamic acid. At higher collector dosages, the water drainage and froth destabilization effect by kerosene was possibly counter-balanced by the higher hematite surface hydrophobicity and bubble surface tension gradient, which led to more stable froth layer.