Hledat publikace

The leaching behaviour of three metakaolinite-rich materials prepared from granulated kaolin and two kaolinitic claystones in alkaline solutions at room temperature was investigated with the aid of centrifugal separation of clear supernatant from the reaction mixture. Two types of alkaline solutions (sodium or potassium hydroxide and sodium or potassium silicate solution) with two solid/ liquid weight ratios (0.04 and 0.65) were tested in a large time interval (5?min to 336?h). The metakaolinite-rich materials were characterized by XRD, XRF, BET and MIP. Al and Si concentrations in supernatant were analysed using an inductively coupled plasma optical emission spectrometer (ICP-OES), the solid phases were identified by X-ray diffraction. All three metakaolinite-rich input materials are leachable in the applied alkaline solutions, almost independent of the character of the calcined kaolinitic materials, including both less expensive claystones. The concentrations of dissolved Al and Si were mostly higher in an alkaline solution with sodium than with potassium cations. Alkali silicate solutions showed a significantly higher extent of leaching in comparison with alkaline hydroxide solutions. The solids remaining after the leaching in hydroxide solutions showed a presence of zeolites and carbonates, which, was not the case with alkaline silicate solutions.