The hydrophobization enhancement mechanism of a novel Gemini hydroxamic acid for ilmenite flotation

Abstract

In this study, a novel Gemini hydroxamic acid collector N,N′-bis[(3-hydroxyamino)-propoxy]-N,N′-dihexyl dithiooxamide (DSHPA) was firstly synthesized and used for ilmenite flotation. The micro-flotation results showed that DSHPA achieved 64.8 % flotation recovery difference between ilmenite and titanaugite in artificially mixed minerals, which was better than benzohydroxamic acid (BHA), octyl hydroxamic acid (OHA) and sodium oleate (NaOL), resulting in the effective separation between ilmenite and titanaugite. Contact angle tests showed that the surface hydrophobicity of ilmenite was significantly enhanced after treatment with DSHPA. In situ AFM images, FTIR, and XPS further confirmed the extensive adsorption of DSHPA molecules on the ilmenite surface. Moreover, the adsorption of DSHPA on ilmenite was markedly stronger than on titanaugite, providing strong evidence for its effectiveness in the selective separation of ilmenite from titanaugite. XPS and DFT calculations demonstrated that two hydroxamic acid groups were the active centers of DSHPA, which could separately bind to Fe and Ti on the ilmenite surface with forming two five-member rings. As result, “H” shape hydrophobic structure consisting of two C₆ hydrophobic chains and a closed “Loop” structure between two five-member rings formed on DSHPA-treated ilmenite surface rendered an improved hydrophobicity of the ilmenite surface. Combined with DSHPA’s suitable foaming ability, DSHPA exhibited better flotation performance than NaOL, BHA and OHA. The results of this study provide valuable insights into the molecule design of functional surfactant that can finely regulate the hydrophobicity of surface, which sheds light on improving separation efficiency among various substances in a broad range of engineering applications.