Modification and application of collectors for fine-grained ilmenite flotation: a review

Ilmenite is the essential feedstock for titanium metal and its oxides (mainly titanium dioxide), accounting for approximately 90 % of global titanium resources. However, as high-grade titanium resources are continuously exploited, ilmenite is increasingly exhibiting lower grades, fine dissemination sizes, and a more complex mineralogical composition. Consequently, conventional gravity-magnetic separation fails to achieve efficient recovery, especially for fine-grained ilmenite (−0.074 mm). Flotation, offering superior selectivity and separation efficiency, has thus become a pivotal technology for recovering fine-grained ilmenite. This paper systematically summarizes the types, properties, and action mechanisms of collectors for fine-grained ilmenite flotation. Carboxylic acid collectors are widely used for their strong collecting power, but their limited selectivity and poor low-temperature performance limit their use. In contrast, hydroxamic acid and phosphonic acid collectors exhibit higher selectivity at the expense of relatively weaker collecting power. To mitigate these limitations, researchers have modified collectors by incorporating hydrophilic substituents (amide, dithiocarbamate, amino, ester groups, and metal ions) or reconstructing the hydrophobic R-groups via double bonds and isomers. Alternatively, researchers mix multiple types of collectors for synergistic flotation. Modified collectors exhibit enhanced collecting power, superior selectivity, broad pH adaptability, and improved aqueous solubility. Based on a critical analysis of existing studies, this review proposes prospective directions for collector modification to provide theoretical insights and forward-looking guidance for the efficient flotation recovery of fine-grained ilmenite.