An investigation of the effect of clay type on coal flotation along with DLVO theoretical analyses

Coals generally exist with clay minerals, which are very fine-sized minerals, and adversely affect the flotation of coal. For instance, they make the coal surface hydrophilic by coating coal surfaces and therefore, they inhibit bubble-particle attachment. Clay minerals can also cause over-consumption of reagents due to their high surface area. Additionally, clay minerals can transfer into the concentrate during the flotation process by entrainment because of their low weight and small particle size, and thus, increase pulp viscosity and changing froth stability. In this study, the influence of various clay minerals (kaolinite, illite, and bentonite) on the flotation behavior of coal sample was studied in detail by conventional flotation tests. In addition, the values obtained from flotation tests were correlated with theoretical energy barrier values established with classical DLVO theory based on zeta potential values of coal and clay samples measured at different pH values. According to the results of this study, no significant effect of clay minerals was observed on coal flotation. This was probably because of the high floatability of the coal used for this study. Both the results obtained from the experiments and theoretical analysis, DLVO calculations, showed that the type of clay mineral is the main indicator parameter for coal flotation