Facile Hydrothermal Synthesis of Zeolitic ANA Membrane from Raw Kaolin
The present paper reported a preparation of zeolitic ANA (analcime) membrane on porous ceramic support by in situ synthesis method using raw kaolin as SiO2 and Al2O3 source with the molar composition of Al2O3 ∙ 2.3SiO2 ∙ 3.6Na2O ∙ 140.4H2O at hydrothermal temperature 200ºC. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the ANA membrane. The effects of aging time and hydrothermal time on the synthesis were investigated. The porous ceramic supports were prepared by adding 10.0 wt% of cristobalite and varying an amount of pore formers (activated carbon and calcite) by sintering at 1400ºC. This resulted in the high crystallinity of ANA observed on the support which was prepared from mixing of 2.5 wt% of activated carbon and 2.5 wt% of calcite. In addition to aging, it was observable that small crystals seemed to spread completely on the support within 3 days of aging. It seems that the longer the hydrothermal time is, the more obvious the crystals tightly bound with the support becomes.