Preparation of faujasite block from fly ash-based geopolymer via in-situ hydrothermal method

In this study, a faujasite block with certain compressive strength was successfully fabricated from fly ash based geopolymer via in-situ hydrothermal method. The effects of various factors, such as the SiO2/Al2O3 molar ratio of the geopolymer, the concentration of NaOH, crystallization time and crystallization temperature of the hydrothermal curing solution on the structure and morphology of the hydrothermal products were investigated. SEM and XRD results confirmed that these factors played essential roles in controlling the morphology and crystallinity of the hydrothermal products. The optimum faujasite block showed an octahedral shape and sharp edges with good crystallinity. In addition, the BET specific surface area, the total pore volume and the compressive strength of the faujasite block were 136.23 m(2)/g, 0.14 cm(3)/g and 5.14 MPa, respectively. The optimum conditions for the synthesis of faujasite block were SiO2/Al2O3 molar ratio of 4.0, NaOH solution concentration of 1.0 mol/L, and 24 h for crystallization at 70 degrees C. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.