Project Title: Using flotation to recover monazite from a heavy mineral sands zircon waste stream
Supervisors: Dr Megan Becker; Prof B Palsson (Lulea University of Technology, Sweden); Prof J-P Franzidis; Prof Dee Bradshaw
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, and creating a potential REE by-product, from the Namakwa Sands operation in Northern Cape. 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
was likely to constitute a major challenge in achieving flotation selectivity. A statistical screening design was applied to find the most relevant flotation
parameters flowed by a full factorial design to optimise the flotation conditions. The most promising results showed that monazite could be successfully removed
from the zircon reject 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 needed to validate these results on a larger scale. Miss Tranvik was a visiting student from Lulea University of Technology,
and spent six months carrying out her experimental programme at UCT.