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

Particular macroshape structures of zeolite are required in numerous application fields to avoid secondary powder pollution. In this paper, a NaP zeolite block with high strength was successfully fabricated from fly ash-based geopolymer through in situ hydrothermal process. The results of SEM and XRD confirmed that the alkalinity, crystallization time and temperature of the hydrothermal system played an important role in controlling the morphology and crystallinity of final samples. Under the optimal hydrothermal conditions (100 °C, 2.0 mol/L NaOH solution, 24 h), the NaP zeolite block exhibited a distinct diamond ball-like shape and sharp edges with good crystallinity. In addition, the BET specific surface area, the average mesopores diameter and the compressive strength of NaP zeolite block were respectively 50.46 m2/g, 11.06 nm and 23.21 MPa.