Selective Separation Behavior and Study on the Interaction Mechanism of 2-Hydroxy-3-Naphthylmethyl Hydroxamic Acid and Cassiterite

Abstract

In this study, the performance of 2-hydroxy-3-naphthylmethyl hydroxamic acid (NHA) in cassiterite flotation was investigated. The aim was to understand the mechanism of action of NHA for the first time. The effect of NHA as a collector in the flotation separation of cassiterite, calcite, and quartz was investigated via microbubble flotation experiments. The experimental results showed that the maximum recovery of cassiterite in the presence of NHA was 91.76%. This was attributed to the selective adsorption of NHA on the cassiterite surface. NHA showed a stronger collection performance for cassiterite than calcite and quartz. Therefore, the mechanism of NHA-cassiterite interaction was investigated using zeta potential, the logarithmic solubility plot (LSD), Fourier Transform Infrared (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscope (SEM) analyses. This study introduces a new adsorption process and mechanism for the NHA-based adsorption of cassiterite. The results show that, under neutral conditions, the solute components of cassiterite surface lattice ions mainly exist in the form of Sn–OH complexes. Chemisorption occurs between cassiterite and NHA which is adsorbed onto the cassiterite surfaces through interaction with O sites, rather than Sn sites as is traditionally expected. Further, the hydroxyl and hydroxyl groups of NHA are chemically coordinated with Sn–OH on the surface of cassiterite to form a six-membered chelate ring. This proposed mechanism can be extended to most systems in which metal ions interact with hydroxamic acids bearing hydroxyl groups. This contributes to a better understanding of the activation mechanism of hydroxamic acid collectors in cassiterite flotation.