Preparation of NaA zeolite molecular sieve based on solid waste fly ash by high-speed dispersion homogenization-assisted alkali fusion-hydrothermal method and its performance of ammonia-nitrogen adsorption

Abstract

A high-speed dispersion homogenization-assisted alkali fusion-hydrothermal method was successfully developed for the preparation of NaA zeolite molecular sieve with excellent adsorption performance for ammonia nitrogen using solid waste fly ash. The zeolite molecular sieve, prepared at a calcination temperature of 700 °C and a crystallization temperature of 80 °C, was identified as NaA zeolite molecular sieve through XRD and SEM tests, exhibiting a uniform and ordered cubic crystal structure. The result of BET analysis indicates that the NaA zeolite molecular sieve has a specific surface area of 288.219 m2/g and a plentiful pore structure. The effect of pH, adsorption time, and initial concentration of ammonia nitrogen on the adsorption capacity of NaA zeolite molecular sieve was also investigated. The fitting analysis of experimental adsorption data using adsorption kinetics and isotherm models indicates that the kinetic adsorption of ammonia nitrogen solution by zeolite molecular sieve follows the second-order kinetic model more closely. The Langmuir model shows a better correlation than the Freundlich model, suggesting that the adsorption of ammonia nitrogen solution by the zeolite molecular sieve is mainly based on the surface-uniform monolayer physical adsorption process. Under the conditions of pH = 7 and an initial ammonia nitrogen concentration of 100 mg/L, the adsorption capacity of the zeolite molecular sieve for ammonia nitrogen within 60 min can reach 27.5 mg/g, showing excellent adsorption performance. This study establishes a vital research foundation for the utilization of fly ash and the treatment of ammonia nitrogen wastewater, with great ecological and social benefits.