Synthesis of pure zeolite P2 from calcium silicate hydrate; tobermorite

Abstract

Calcium silicate hydrate phases offer the possibility to become potential zeolites precursors due to its high silica contents. Pure calcium silicate hydrate phase; tobermorite (Ca5Si6O16(OH)2·4H2O), was prepared by hydrothermal method at 175°C. Tobermorite was sucssefully converted to Zeolite P2 for the first time via refluxing in 3 M NaOH solution and in the presence of Al source. Sodium hydroxide removed calcium ions from the interlayers of calcium silicate phase and form mesoporous zeolite. The pure zeolite was obtained after extraction of Ca(OH)2 with sugar solution. The zeolite products were characterized by using X-ray diffraction spectroscopy (XRD) and Scanning Electron Microscopy (SEM) with microanalysis (EDX). The Si/Al molar ratio of zeolite P can be controlled by vering the initinal Si/Al molar ratio. The cationexchange capacity (CEC) of the produced zeolite P was higher than those produced from fly ash.