Two-step synthesis of a macroporous LTA zeolite sorbent by supercritical CO2 coating and hydrothermal conversion: Implementation in fixed-bed nuclear wastewater treatment

Fixed-bed sorption on solid substrate is a common approach to safely extract cationic radionuclides (such as 90Sr2+) from nuclear wastewater and minimize final waste volumes. This article describes the preparation and characterization of a new hierarchical zeolite-glass bead composite for this application. A homogeneous layer of microporous amorphous silica is deposited on the beads in supercritical CO2 and then transformed into a 1 mu m -thick LTA (Linde Type A) zeolite film (40 wt% of the composite) by hydrothermal treatment. Microstructural data show that this design improves the accessibility of the sorbent sites for Sr2+ cations. Batch sorption data in different types of simulated wastewater quantify the effects of competing cations and high salinity. Dynamic breakthrough experiments with simulated saline wastewater show that the proposed composite has delayed leakage and faster exchange kinetics than an existing commercial LTA-zeolite sorbent, which should translate into greater waste volume reduction in industrial fixed-bed extraction systems.