Flocculant study for neutral and leached slurries from ore processing of pressurised alkali leaching-based plant

This study evaluates the filtration and settling performance of four commercially available polymeric flocculants (FL-1 to FL-4) for treating neutral and alkaline leach slurries generated during the pressurised alkali leaching of uranium-bearing ores. Laboratory-scale filtration and sedimentation tests were performed under conditions representative of industrial plant operations. Among the flocculants investigated, FL-3 delivered the best overall performance for neutral slurry, achieving the highest filtration rate of 651.62 kg/m².h at an optimum dosage of 40 mg/kg and exhibiting the most rapid settling behaviour. In the case of alkaline leach slurry, FL-3 again produced the highest filtration rate before washing (630.9 kg/m².h). However, FL-2 showed superior washing efficiency, reducing the residual dissolved U₃O₈ concentration in the filter cake to 0.88 mg/kg following carbonate–bicarbonate washing. The results demonstrate that flocculation performance is governed by both polymer properties and slurry chemistry, particularly in highly alkaline systems containing elevated concentrations of carbonate and sulfate ions. The enhanced separation efficiency observed with selected flocculants is attributed primarily to polymer bridging and electrical double-layer compression, which promote the formation of larger and more permeable flocs. The findings provide valuable practical insights for selecting flocculants and optimising solid–liquid separation processes in uranium extraction circuits operating under alkaline carbonate leaching conditions.