The mechanism of separating hematite from kaolinite by shear-flocculation and the reason responsible for the selectivity of shear-flocculation was studied by using diffuse reflectance infrared Fourier transform (DRIFT...The mechanism of separating hematite from kaolinite by shear-flocculation and the reason responsible for the selectivity of shear-flocculation was studied by using diffuse reflectance infrared Fourier transform (DRIFT) spec-troscopy, which was found to be effective for analysing adsorbed oleate species on the highly absorbing mineral hematite. The spectra suggest that chemisorption of oleate on hematite took place under shear-flocculation condition and that the chemisorbed species was bridged bidentate, corresponding to a peak at 1580 cm-1. Dimers of oleic acid, corresponding to a peak at 1710 cm-1, adsorbed via hydrocarbon chain association with the chemisorbed oleate. The coexistance of physically adsorbed oleic acid dimers and chemisorbed oleate ions made the surface of hematite hydrophobic, which would remain under the shear field. Under the same condition , the surface of kaolinite did not adsorb oleic acid or oleate and remained hydrophilic. The shear field of sufficient magnitude made the hydrophobic ultrafine particles of hematite to aggregate, whereas the hydrophilic ultrafine particles of kaolinite remained suspended in solution. This explains the mechanism of selective shear-flocculation of hematite from kaolinite.展开更多
文摘The mechanism of separating hematite from kaolinite by shear-flocculation and the reason responsible for the selectivity of shear-flocculation was studied by using diffuse reflectance infrared Fourier transform (DRIFT) spec-troscopy, which was found to be effective for analysing adsorbed oleate species on the highly absorbing mineral hematite. The spectra suggest that chemisorption of oleate on hematite took place under shear-flocculation condition and that the chemisorbed species was bridged bidentate, corresponding to a peak at 1580 cm-1. Dimers of oleic acid, corresponding to a peak at 1710 cm-1, adsorbed via hydrocarbon chain association with the chemisorbed oleate. The coexistance of physically adsorbed oleic acid dimers and chemisorbed oleate ions made the surface of hematite hydrophobic, which would remain under the shear field. Under the same condition , the surface of kaolinite did not adsorb oleic acid or oleate and remained hydrophilic. The shear field of sufficient magnitude made the hydrophobic ultrafine particles of hematite to aggregate, whereas the hydrophilic ultrafine particles of kaolinite remained suspended in solution. This explains the mechanism of selective shear-flocculation of hematite from kaolinite.
