The improvement in whiteness index of calcite tailings using attrition-scrubbing process

ABSTRACT Calcium carbonate (CaCO3) is an essential mineral critical for various applications in many industries like plastic, rubber, paint, and paper manufacturing. However, salable CaCO3 products need to meet specific requirements. For the paint and paper manufacturing industries, the whiteness index (WI) of CaCO3 is an important property because it strongly influences the final color of paper and paint products. In this study, the effects of retention time and pulp density on the WI after attrition-scrubbing of calcite tailings were investigated. To increase the whiteness index, an attrition scrubber was used to remove impurities on the CaCO3 surface with different pulp densities—40, 45, 50, 55, 60, and 70% solids—and retention time—10, 15, 20, and 25 min—as process variables. The results of laboratory-scale experiments found that the attrition-scrubbing process improved the whiteness index of CaCO3 tailings and reduced its iron content. The optimum condition was at the pulp density of 55% solids, which was used in the pilot-scale experiments. The results of the pilot-scale tests were consistent with the laboratory-scale, indicating that the attrition-scrubbing process can be used to improve the quality of CaCO3 tailings.