A simple synthesis of nitrate cancrinite from natural bentonite

A nearly pure, pale brown, spherical, nitrate cancrinite zeolite was successfully synthesized from natural bentonite as starting material with acidic activation treatment via hydrothermal method at 368 K for 24 h. The effect of different NaOH concentrations (pH at around 12) was investigated without addition of silica and aluminum sources. The effect of different NaOH concentrations (pH at around 12) was investigated without addition of silica and aluminum sources. The final products were characterized by powder X-ray diffraction, scanning electron microscopy, elemental and thermal analyses, infrared (IR) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area measurements. While the Si/Al ratio of ideal cancrinite is 1.0, the Si/Al ratio of the product framework is approximately 1.76, apart from trace components. Unique single nitrate band was observed in both IR and thermogravimetric measurements, indicating that pure cancrinite was synthesized. This study showed that pure nitrate cancrinite was obtained with NaOH concentrations from 8 to 12 M, independent of NaOH contents on crystallization. Through this study, we proposed a simple synthesis method for pure nitrate cancrinite from bentonite for the purpose of recycling natural clay minerals.