E. Konadu-Yiadom, C.G. Anderson
Colorado School of Mines,
United States
Keywords: monazite, flotation, phosphonic acid, rare earth elements
Summary:
INTRODUCTION: Collectors such as phosphonic acids, fatty acids and hydroxamic acids are necessary in flotation to increase the surface hydrophobicity of valuable minerals and reduce the difference between the surface hydrophobicity of valuable and gangue minerals. The application of organic phosphonic acid ligands/collectors were evaluated as promising alternatives to hydroxamic acids for monazite flotation. This poster investigated the performance of different classes of organic phosphonic acid collectors for monazite flotation and studies their collecting ability and mechanism of adsorption on the surface of monazite to bridge the knowledge gap. Materials and Methods: A 150-mg synthetic monazite sample was conditioned in 50-mL collector solutions of HPA and OPA for 3 days at specific pH values using pH modifiers. At the end of conditioning time, foaming agent MIBC was added and the mixture stirred for 5 mins after which it was transferred into the flotation cell. Flotation was conducted for 5 mins. Finally, the foam product and the product remaining in the cell were separately dried and weighed. The mass recovery rate and grade of concentrate were calculated. RESULTS: Maximum monazite recovery for HPA was 95 % at pH 2 which later decreased to 65% at pH 7 and 35% at pH 11. A similar trend was observed in the case of BPA as recovery decreased with increasing pH. There was no recovery at pH 11. The results of both types of collector microbubble flotation experiments demonstrated that the recovery of monazite can reach approximately 95% at an HPA dosage of 10 mM, whereas the recovery was only 76% at an OPA dosage of 10 mM. In conclusion: pH plays a key role in rare earth flotation with optimum floatability dependent on pH. Phosphoric acid ligands work best at acid pH values with highest recovery at pH 2. Both C-4 and C-6 showed good recovery rate at acidic pH, however, at pH 11, no concentrate was obtained for C4. Optimizing flotation parameters can lead to improved recovery. Phosphoric acid collector has shown promising results