Mechanism demystification and factor optimization of uranium decontamination on fabrics via supercritical CO2: Role of off-line prepared additives

Supercritical CO 2 (SC-CO 2 ) technology promises to overcome the trade-off between secondary waste volume and decontamination efficiency in traditional radioactivity decontamination methods. However, attempts to use this technology for decontaminating uranium-contaminated fabrics have remained unexplored. Hence, we investigated the role of additives in decontaminating uranium-contaminated fabrics using SC-CO 2 technology, with particular emphasis on off-line versus in-situ preparation methods. Additives prepared via the off-line method, comprising H(NO 3 ) · TBP complexes, demonstrated superior efficiency owing to immediate solubility and reactivity in SC-CO 2 . Molecular dynamics (MD) simulations also supported these experimental observations by visualizing the microstructural evolution of the additive molecules. The factors, including pressure (20 MPa) and temperature (343 K), were optimized, achieving up to 97.4 % decontamination efficiency in 40 min. The radioactivity of the fabric surface was reduced to the level that allowed for reuse in the nuclear field. Notably, the mechanism analysis revealed the transformation of uranium contaminants from UO 2 (OH) 2 to UO 2 (NO 3 ) 2 · 2TBP complexes, which were efficiently dissolved in SC-CO 2 . Furthermore, the technology demonstrated high versatility, successfully decontaminating various fabric types and real radioactive samples, achieving results suitable for reuse in the nuclear field. These findings suggest that SC-CO 2 , when combined with optimized additives, offers an environmentally sustainable and highly effective method for uranium decontamination in the nuclear industry.