Effect of monovalent, divalent and trivalent ions on the grinding efficiency of bentonite-containing ores

• The presence of bentonite in the ore adversely affects grinding performance. • Higher valence number of grinding additives improves grinding performance. • Slurry viscosities were reduced after adding the grinding additives. • Settling rates were higher in the presence of the grinding additives. Grinding efficiencies of bentonite-containing ores have been rarely investigated in the literature even though bentonite is found in various ores such as refractory and free-milling gold ores. In this work, the influence of the cation valency of grinding additives on the grinding behaviour of bentonite-containing ores has been studied. The results indicate that the presence of bentonite in the ore requires more energy for grinding compared to grinding in its absence. It was found that the particle size for the same energy consumption during grinding of the bentonite slurry decreased in the following order with cation addition: Al 3+ > Mg 2+ > K + . The additions of Al 3+ ions particularly reduced the repulsive forces between bentonite particles as confirmed using the zeta potential measurements. Therefore, the ore-bentonite slurries in the presence of Al 3+ significantly reduced shear forces between particles, leading to improved settling rates and grinding performance. This paper illustrates how the valency number of added grinding additives can substantially alter slurry chemistry, thereby enhancing grinding performance.