Leaching of immobilized cesium from NaOH-activated fly ash-based geopolymers. (October 2022)

• Record Type: Journal Article
• Authors: Jain, Shubham; Banthia, Nemkumar; Troczynski, Tom
• Is Part Of: Cement & concrete composites. Volume 133(2022)
• Publication Date: 2022-10
• Subjects: Immobilization -- Hazardous radioactive nuclear waste -- Leaching kinetics -- Leaching mechanism -- Leachability index -- Pollucite; Composite-reinforced concrete -- Periodicals; Concrete -- Periodicals; Composite materials -- Periodicals; Composites de ciment -- Périodiques; Béton -- Périodiques; Composites -- Périodiques; Béton léger -- Périodiques; Cement composites; Composite materials; Composite-reinforced concrete; Concrete; Lightweight concrete; Periodicals; Electronic journals; 620.135
• DOI: 10.1016/j.cemconcomp.2022.104679
• Languages: English
• ISSNs: 0958-9465

Abstract

Abstract: This study investigated the effects of cesium (Cs) dosage (2–20 wt.%) and curing time (7–180 days) on the leaching behavior and immobilization of Cs in NaOH-activated fly ash-based geopolymers (FA-GP). The Cs leaching behavior and leachability index ( LX ) were evaluated per ANS-16.1. FA-GP were characterized using XRD and N2 adsorption-desorption isotherms. The results revealed that Cs dosage affects the resulting phases and pore structure of FA-GP and influences the Cs immobilization. The higher Cs dosage (≥8 wt.%) provides conditions for in-situ pollucite crystallization within the FA-GP matrix (cured at 90 °C for 7 days) and significantly enhances Cs immobilization ( LX values from 11.5 to 14.5). Cs leaching resistance of FA-GP cured at 22 °C improved with curing time. Diffusion was determined to be the primary leaching mechanism. The results advocate the use of FA-GP as an effective immobilization material, mainly containing a high concentration of Cs. Graphical abstract: Image 1 Highlights: Cesium dosage and curing time affected cesium immobilization in fly ash geopolymers. High cesium dosage (≥8 wt.%) aided formation of in-situ pollucite in geopolymers. Leaching resistance of geopolymers cured at 22 °C improved with curing time. Diffusion was determined to be the primary leaching mechanism.