Synthesis of hierarchical porous ceramsites loaded with GIS-P1 zeolite crystals for removal of ammonia nitrogen from aqueous solution

In this study, ceramsites loaded with GIS-P1 zeolite were prepared via high-temperature sintering and hydrothermal synthesis using fly ash as the raw materials. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to confirm the structure of the ceramsites; moreover, the transformation mechanism of zeolite was studied by Fourier transform-infrared and Raman spectroscopy. The specific surface area of zeolitization ceramsites increased to 40.86 m2/g from 0.59 m2/g of the basic ceramsites. The results showed that the removal rate was 93.6% for NH4+−N aqueous solution with an initial concentration of 50 mg/L. The results of kinetic and isothermal fitting showed that the adsorption process of NH4+−N by zeolitization ceramsites coexisted between physical and chemical adsorption. Furthermore, the results of density functional theory calculations and X-ray photoelectron spectroscopy analysis showed that ion exchange and pore adsorption were the main adsorption mechanisms of the zeolitization ceramsites. This study provides a new method to significantly improve zeolite ceramsites with large specific surface areas, which can easily separate NH4+−N from water. Moreover, it can realize the environmental protection purpose of “wastes-treat-wastes.”