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


Material Science & Engineering International Journal
Carlos A  Ríos,1,2 Craig D Williams,2 Michael A Fullen2
Industrial University of Santander
Craig D Williams, The University of Wolverhampton
Michael A Fullen, The University of Wolverhampton

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 andthermogravimetric analysisin order to elucidate their mineral chemistry and microstructure. Results reveal that several poorly crystalline phases were formed, with un-reacted Ca(OH)2appearing 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 kaolinite-based calcium silicate hydrates are effective for the treatment of acid mine drainage, particularly in removing metal ions and ammonium.

Keywords

Kaolinite; CASH system; Cement; Calcium silicate hydrates; Hydrogarnet; Tobermorite; Geothermal; Calcium silicate hydrate; Metakaolinite; Zeolite; Chronology; Gehlenite hydrate

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