Surface hydrophobicity of sub-bituminous and meta-bituminous coal and their flotation kinetics

Abstract

This paper discusses the relationships between the surface properties of the sub-bituminous and meta-bituminous coal and their flotation properties. Additionally, it was investigated whether the flotation kinetic constants, obtained using various flotation kinetic models, can be used for prediction of the flotation response. Both coal samples had the very similar amount and type of impurities as confirmed by XRD. FTIR, contact angle, zeta potential and SEM measurements were used to study the coal surface properties. It was found that the meta-bituminous coal was significantly more hydrophobic than the sub-bituminous coal and the coal surface roughness was significantly more pronounced in the case of the sub-bituminous coal than that in the case of the meta-bituminous coal. For these reasons, the recovery of the meta-bituminous coal by flotation was dramatically higher than that of the sub-bituminous coal even in the presence of collector. Six flotation kinetic models successfully predicted the flotation data. Nevertheless, the modified first-order model was the only model that can be used to explain the flotation responses under a wide range of the experimental conditions. The reason is that for most flotation kinetic models, used in this study, particularly in the case of the sub-bituminous coal, the flotation rate constants decreased with increasing in collector dosage while the opposite is true in the case of the flotation recoveries.