Heavy metal removal using alkali activated kaolinite in the Cao-Al2O3-Sio2- H2O system

Abstract

The transformation of kaolinite was examined at 175°C for 24 h in the CaO-Al2O3- SiO2-H2O (CASH) system, which is important in cement science and especially in, cement chemistry and is closely related to the pozzolanic reaction, the CaO-aggregate reaction and the glass fibre reinforcement of hardened cement. The hydration products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transformed infrared spectroscopy, Magic Angle Spinning Nuclear Magnetic Resonance and thermogravimetric analysis in order to elucidate their mineral chemistry and microstructure. Results reveal that several poorly crystalline phases were formed, with un-reacted Ca(OH)2 appearing at shorter reaction times. Hydrogarnet tends to form more rapidly than tobermorite. It was transformed into aluminium-substituted tobermorite with curing time. A batch experimental study confirmed that kaolinitebased calcium silicate hydrates are effective for the treatment of acid mine drainage, particularly in removing metal ions and ammonium