Enhancement of 2-hydroxy-3-naphthyl hydroxamic acid adsorption on bastnaesite and monazite surfaces using H2O2 pre-oxidation for improved flotation process

Abstract

Rare earth elements have been widely applied in various sectors. Bastnaesite and monazite are crucial rare earth minerals, and flotation is a vital technique for recovering fine-grained rare earth minerals and separating them from associated gangue minerals such as fluorite and apatite. Flotation collectors play a key role in selectively adsorbing valuable minerals, enhancing their surface hydrophobicity, which has prompted considerable research interest. However, the interaction between minerals and reagents relies on the reactivity and selectivity of the reagent groups, as well as the reactive properties of the surface atoms of the minerals. This study proposes the use of H₂O₂ oxidation to enhance the flotation process of rare earth minerals. The flotation experiments demonstrated that pre-adding H₂O₂ before introducing the flotation collector significantly improved the grade and recovery of rare earth concentrates. The adsorption mechanisms of 2-hydroxy-3-naphthyl hydroxamic acid collector on rare earth mineral surfaces before and after H₂O₂ pre-oxidation were studied. The 2-hydroxy-3-naphthyl hydroxamic acid interacts with Ce³⁺ on the surface of unoxidized rare earth minerals, forming chelate compounds with five-membered ring structures. The H₂O₂ exhibited potent oxidizing properties and oxidized the Ce³⁺ on the bastnaesite and monazite surfaces to more stable Ce⁴⁺, which demonstrated stronger binding capability with hydroxamic acid.