Effect of calcium/magnesium precipitates on galena flotation: Implications for water recycling in mineral processing

Abstract Environmental standards increasingly encourage water recycling in mineral processing. However, untreated recycled water often contains calcium and magnesium ions, among other species, which depress galena. One of the most important effects is the formation of precipitates that interact with the mineral surface, modifying its natural hydrophobicity. Sodium carbonate (Na 2 CO 3 ) has been proposed to remove these ions through the formation of insoluble species. This study evaluates the interaction between galena and the solids formed during the precipitation of Ca 2+ and Mg 2+ with Na 2 CO 3 and their influence on flotation performance. Contact angle, zeta potential, and microflotation tests were conducted to evaluate galena hydrophobicity and recovery. The results showed that calcium and magnesium strongly reduce the hydrophobicity of galena, while Na 2 CO 3 treatment mitigates this adverse effect. These findings suggest that water treatment using Na 2 CO 3 is a low-cost and practical strategy to improve flotation efficiency in circuits operating with recycled process water. Graphical abstract