Study of oleic acid-induced hydrophobic agglomeration of apatite fines through rheology

The useful mineral apatite in phosphate ore has a fine embedded particle size, requiring fine grinding for monomer dissociation, which will lead to a large number of fine apatite generation, resulting in low flotation efficiency and other problems. In this study, the effects of pH, agent concentration and stirring rate upon agglomeration behavior and rheological properties of fine apatite were investigated. The reasonable agglomeration mechanisms were proposed by means of Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), zeta potential analysis. Moreover, the interaction between particles was evaluated by using the rheological parameter apparent viscosity, and the internal connection between fine apatite agglomeration and pulp rheology was revealed. The results indicate that at an oleic acid (OA) concentration of 400 mg/L, stirring rate of 500 rpm, and pH of 9, the average particle size (d_mean) of apatite increases from the original 7.37 μm to 104.7 μm, and the apparent viscosity rises from 2.18 mPa·s to 17.40 mPa·s. In the process of fine apatite agglomeration, OA is adsorbed onto the surface of apatite particles through chemical complexation, which makes the apatite surface hydrophobic, and thus causing agglomeration between apatite particles due to hydrophobic attraction. In addition, the flotation models of apatite were proposed before and after agglomeration, and there is a correlation among particle agglomeration, apparent viscosity and particle interactions, forming a triangular relationship similar to an “iron triangle”. This study provides novel insights into the regulation of hydrophobic agglomeration of fine particles.