Flotation behavior of pyrite in sub-bituminous and meta-bituminous coals with starch depressant in a microflotation cell

Removal of pyrite from coals is very important to reduce the emission of SO2 during coal combustion. The selective flotation of pyrite from coal is challenging due to the hydrophobic nature of both coal and pyrite particles. The surface properties of coal vary significantly with the degree of coalification. The present paper investigates the flotation behavior of pyrite from sub-bituminous and meta-bituminous coal which has different ranks and surface properties. XRD, XPS, contact angle, UV–visible spectroscopy, SEM and zeta potential measurements were used to characterize their differences in mineralogy and surface chemistry. The classical first-order model and the potential flow model were used for flotation kinetic studies and to back-calculate the induction times, respectively. Efficient selective flotation of pyrite from the sub-bituminous and meta-bituminous coal was observed in the presence of potassium amyl xanthate collector and starch depressant. The flotation recoveries of pyrite from the sub-bituminous coal and the meta-bituminous coal were over 95%, with pyrite grade of over 95% in the concentrates