Studies of natural kaolinite and its modified forms

Modified forms of the natural and annealed at 700°C kaolinite have been fabricated by treatment using hydrochloric acid of different concentrations. The resulting samples were investigated using X-ray fluorescence spectroscopy, X-ray diffraction analysis, IR spectroscopy, and positron annihilation spectroscopy, scanning electron microscopy, etc. The dependencies of elements contents, dye adsorption, specific surface area, and specific internal volume on the concentration of hydrochloric acid have been determined. It has been demonstrated that the changes in the structure of annealed kaolinite were significantly increased by the increase of the concentration of acid, and also there were proportional changes in the values of specific surface area, internal volume, and dye adsorption. Changes in the structural parameters of natural kaolinite depend on the acid concentration in a less degree. Modification with acid results in obtaining solutions that contain metal chlorides. Precipitation of these metals in the form of oxides on the surface of kaolinite particles results in fabrication of new sorbents, whose yield is close to the quantitative one, whereas the kaolinite sorption characteristics become improved. Further kaolinite modification by cellulose under similar conditions results in fabrication of a new, more efficient sorbent. It has been demonstrated that natural kaolinite treated with 12% hydrochloric acid had lower friction coefficient than the annealed one.