Synthesis and Sorption Properties of Microsphere Zeolite Materials Based on Coal Fly Ash Cenospheres with Respect to Cs⁺ and Sr²⁺

Abstract—The effect of the hydrothermal synthesis conditions (temperature, duration, mixing), composition, and presynthetic processing of narrow fractions of cenospheres of fly ash, which act as a template and source of Si and Al, on the production of microspherical zeolite materials of the given structural type in the Na₂O–H₂O–(SiO₂–Al₂O₃)_glass of two molar compositions is studied. The synthesis products are characterized by XRD, SEM-EDS, and low-temperature nitrogen adsorption, and their sorption properties in relation to Cs⁺ and Sr²⁺ are studied. The factors contributing to the predominant formation of NaX zeolite of the faujasite structural type are revealed. It is established that zeolite products based on cenospheres with a glass phase content of about 95 wt % demonstrate the highest sorption parameters, including the maximum capacity for Cs⁺ and Sr²⁺ of up to 250 and 180 mg/g, distribution coefficient of about 10⁴ and 10⁶ mL/g, and degree of extraction of 99.1 and 99.9%, respectively.