Zirconosilicate Sorbent Based on Waste Fly Ash Cenospheres for Cesium Immobilization in a Ceramic Form

Hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase, 95.4 wt %; (SiO₂/Al₂O₃)_glass, 3.1 wt %) isolated from coal combustion fly ashes were used to prepare composite sorbents containing a sorption-active component based on framework zirconosilicates. The synthesis products were characterized by X-ray powder diffraction (XRD), electron microscopy−energy-dispersive X-ray spectral analysis (SEM−EDX), and low-temperature nitrogen adsorption; their Cs⁺ sorption properties were studied. The prepared zirconosilicate material exhibits a high distribution coefficient in Cs⁺ sorption from aqueous solutions (ca. 10³–10⁴ mL/g) and a stable sorption capacity due to decationization. The usability of spark plasma sintering (SPS) technology to provide high-density mineral-like ceramics based on the zirconosilicate sorbent for cesium immobilization was investigated. Dilatometric, structural, and porosity analyses were performed for ceramics sintered at various temperatures (800–1000°C).