Removal of fine quartz from coal-series kaolin by flotation

Coal-series kaolin (CSK) in Xuzhou, Jiangsu Province of Eastern China was characterized by chemical analyses, X-ray diffraction (XRD) and zeta potential measurement as well as by scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS). The authigenic ultrafine quartz grains ( d 90   =   15.8   μm) closely associated with this CSK sample was the major impurity mineral, which cannot be separated from kaolin by screening and size classification process. This work investigated the separation of fine quartz from kaolin by flotation. Single mineral flotation tests indicated that effective separation of quartz from kaolin was possible with acidic pH value (pH   =   3), depressant of starch and collector of dodecyl amine (DDA). Rougher flotation tests of coal-series kaolin revealed that the SiO 2 /Al 2 O 3 weight ratio of the concentrate was qualified for industrial applications in the presence of 160   g/t starch and 100   g/t DDA, at acidic pH pulp. A specially designed two-stage cleaner flotation flowsheet increased the concentrate recovery from 37.26% to 46.55% compared to a rougher flotation process.