Towards cleaner production – Using flotation to recover monazite from a heavy mineral sands zircon waste stream

• Published in: Minerals engineering Vol. 101; pp. 30 - 39
• Main Authors: Tranvik, E., Becker, M., Pålsson, B.I., Franzidis, J.-P., Bradshaw, D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2017
• Subjects: Design of experiment; Mineral Processing; Mineral sands; Mineralogy; Mineralteknik; Rare earth elements; Statistical analysis; Surface coatings; Statistical analysis; Rare earth elements; Mineralogy; Surface coatings; Mineral sands; Design of experiment; pH
• ISSN: 0892-6875; 1872-9444; 1872-9444
• DOI: 10.1016/j.mineng.2016.10.011

•Selective separation of monazite from zircon at pH 10 with an oleate collector.•Monazite flotation selectivity is highly pH dependent.•Importance of mineralogy for characterisation of surface coatings.•Effective scoping of multiple factors with DOE approach and statistical analysis. In line with the principles of cleaner production, the removal of monazite via reverse flotation was investigated with a view to reducing the radioactivity of a heavy mineral sands waste stream. Another benefit was to create a potential REE by-product from the Namakwa Sands operation in South Africa. Understanding the mineralogy of the zircon waste stream was essential owing to the cemented nature of the deposit and the potential impact of surface coatings on the flotation performance. SEM, QEMSCAN and optical microscopy showed that amorphous SiO2 was the most abundant surface coating associated with both monazite and zircon, which is likely to constitute a major challenge in achieving flotation selectivity. A D-optimal statistical screening design was applied to find the most relevant flotation parameters and a full factorial design to find the optimal flotation conditions. The most promising results showed that monazite could be successfully removed from the zircon waste with an oleate collector at pH 10. The selectivity was found to be highly dependent on pH, with no selectivity at pH 9 and no mineral flotation at pH 11. Further work is recommended to confirm and optimise these conditions and test them on a larger scale.