Probing the Effect of Water Recycling on Flotation through Anion Spiking Using a Low-Grade Cu–Ni–PGM Ore: The Effect of NO₃⁻, SO₄²⁻ and S₂O₃²⁻

• Main Authors: Mathew Dzingai, Malibongwe S. Manono, Kirsten C. Corin
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Minerals
• Subjects: froth flotation; ion accumulation; ion concentration spiking; ionic strength; water recycling
• Online Access: https://www.mdpi.com/2075-163X/11/4/340
• ISSN: 2075-163X

Water scarcity necessitates the recycling of process water within mineral processing practices. This may however come with its disadvantages for unit operations such as froth flotation as this process is water intensive and sensitive to water chemistry. It is therefore important to monitor the water chemistry of the recycle stream of process water and any other water source to flotation. Monitoring the concentrations of the anions in recycled process water is therefore important to consider as these are speculated to impact flotation performance. Batch flotation tests were conducted using synthetically prepared plant water (3 SPW) with a TDS of 3069 mg/L as the baseline experiment. 3 SPW contained 528 mg/LNO₃⁻ and 720 mg/L SO₄²⁻, other anions and cations, and no S₂O₃²⁻.Upon spiking 3 SPW with selected anions, viz, NO₃⁻, SO₄²⁻ and S₂O₃²⁻, it was noted that NO₃⁻ and SO₄²⁻ exhibited threshold concentrations while S₂O₃²⁻ did not show a threshold concentration for both copper and nickel grade. Spiking 3 SPW with 352 mg/L more of NO₃⁻ to a total 880 mg/L NO₃⁻concentration resulted in the highest copper and nickel grade compared to 3 SPW while increasing the S₂O₃²⁻ from 60 to 78 mg/L increased nickel and copper grade. 720 to 1200 mg/L SO₄²⁻ and 528 to 880 mg/L NO₃⁻ were deemed the concentration boundaries within which lies the threshold concentration above which flotation performance declines with respect to metal grades, while for S₂O₃²⁻ the threshold concentration lies outside the range considered for this study. Anion distribution between the pulp and the froth did not seem to impact the recovery of copper or nickel. Notably, the correlation between the concentrate grades and anion distribution between the froth and the pulp seemed to be ion dependent.