Solvent-free synthesis of nano-cancrinite from rice husk ash

The solvent used in the hydrothermal synthesis of zeolites is a major obstacle to achieve green and sustainable methods of synthesis, so the development of environmentally friendly zeolite synthesis technology has aroused widespread concern. As a solid waste, it still has a challenge for zeolites synthesis from rice husk ash by solvent-free method to increase its recovery rate and economic value. Our approach focused on reutilization of rice husk ash by converting it to cancrinite without employing solvents. The raw and as-synthesized products were characterized by XRD, XRF, SEM, FT-IR, UV-Raman, and BET analysis. The influence of Na₂CO₃·10H₂O/SiO₂ molar ratio and synthesis time on cancrinite crystal growth and properties was evaluated by various analytical methods. The results suggested that the optimal conditions of Na₂CO₃·10H₂O/SiO₂ and synthesis time for the cancrinite synthesis were 0.3 and 72 h, at this condition, the size of cancrinite was about 200 nm, the BET surface area was estimated to 59.909 m²/g, and the external surface area was 55.456 m²/g, which indicate the cancrinite was a good mesoporous material. From this study, it could be known that the synthesis process of cancrinite by solvent-free route was an amorphous sodium aluminosilicate phase followed by sodalite and finally cancrinite, which is different from the traditional hydrothermal method.