Leachability of the metakaolinite-rich materials in different alkaline solutions

Publication date: Available online 27 September 2019Source: Materials Today CommunicationsAuthor(s): Jan Kohout, Petr Koutník, Petr Bezucha, Zdeňka KwoczynskiAbstractThe 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) and two solid/ liquid weight ratios (0.04 and 0.65) were applied in a large time interval (5 minutes to 336 hours). 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 often 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 content of zeolites and carbonates, which,...
Source: Materials Today Communications - Category: Materials Science Source Type: research