Swift sono-hydrothermal synthesis of pure NaX nanocrystals with improved sorption capacity from industrial resources

Synthesis of nanocrystalline zeolite with high purity from industrial resources like fly ash is extremely challenging and it takes days to synthesize even macro-size zeolite with high purity and realistic sorption capacity under conventional alkaline activation method. In present work, sono-hydrothermal method has been found to be really rapid and yielded high pure NaX nanocrystals with high sorption capacity in 20 min of ultrasonic irradiation from differently sources fly ashes with Si/Al ratio less than 3. Average crystal size of synthesized X type nanozeolite was found to fall between 19 and 27 nm. and high sorption properties were observed towards different metal ions such as Zn²⁺, Cu²⁺, Cd²⁺, Pb²⁺, Ni²⁺, Ca²⁺, and Mg²⁺ as well as various organic dyes such as methylene blue, crystal violet, indigo carmine, and congo red. All the nanocrystalline zeolites X were found to be superior to other low cost adsorbents including the commercially available zeolite X towards various metal ions and dyes. Highest adsorption capacities were found for the Pb²⁺ and crystal violet among all metal ions and dyes (a maximum of 171.23 mg g⁻¹ for Pb²⁺ and 149.36 mg g⁻¹ for crystal violet).