Synthesis of Zeolite A from Natural Ca-Bentonite Using a Direct Alkali Hydrothermal Approach

Abstract

Ca-bentonite can be converted into zeolite A via hydrothermal alkaline treatment by varying the synthetic parameters. This paper focuses on the effects of SiO₂/Al₂O₃ molar ratio, Na₂O/SiO₂ molar ratio, reaction temperature, reaction time on the synthesis of zeolite A. Phase-pure zeolite A was synthesised under optimum conditions of 3Na₂O:0.25Al₂O₃:1SiO₂:150H₂O by heated at 90°C for 12 h, whose shape and average crystal sizes are the cube of 1∼3 μm by the SEM micrograph. Compared with chemical synthesis method, one-step alkali fusion method has the advantages of low cost, simple operation, short time etc, which are worthy of further consideration in industrialization.

Keywords:

• Ca-bentonite
• zeolite A
• alkali hydrothermal
• synthesis