Grinding-aid effect on the colour properties (Ry, whiteness and yellowness) of calcite in stirred media milling

This study investigates the influence of some chemical additives such as methanol, ethanol, sodium oleat, chloroform and sodium hexametaphosphate (SHMP) on the dry fine grinding of calcite (X50= 33 µm) using a stirred media mill. The experiments were carried out by a batch operation, and the change in colour properties (Ry, whiteness and yellowness) of calcite powder. The results showed that the chemical additives promote the fine grinding of calcite obtained with ethanol and methanol at a range of 0.5%. Ry and whiteness values of the ground calcite products very slightly increased from 94.10 and 87.04 to 94.76 and 87.75 respectively with grinding aid (ethanol) increased from 0% to 1%. Ry value was affected slightly adversely with sodium oleat, chloroform and SHMP indicating that the quality of colour of calcite deteriorates. It was also found that ΔRy increases with increasing amount of grinding aids from 0% to 0.5% for methanol and ethanol, indicating that the quality of colour of calcite heals.