The stability and decontamination of surface radioactive contamination of biomass-based antifreeze foam

Conventional water-based foam decontaminants used for the removal of radionuclides lose their efficacy in winter at temperatures below 0 degrees C. To address this problem, an antifreeze foam, with characteristics of good stability, high decontamination efficiency, less liquid waste generation, and excellent biodegradability, was developed using a biomass-based surfactant, a polysaccharide foam stabilizer, and an antifreeze agent. Furthermore, the surface tension, solution viscosity, foam stability, and decontamination of simulated radionuclides on different plates of a xanthan gum (XG)-stabilized antifreeze foam at temperatures ranging from -10 degrees C to 10 degrees C were investigated. Especially, the bulk-phase performance and stabilizing mechanism of the antifreeze foam were analyzed. Compared with the antifreeze foam without stabilizer, the half-life of the XG-stabilizing foam increases from 30.5 min to 2785 min, and the initial drainage time increases from 5 min to 383.5 min at -10 degrees C, which considerably extends the decontamination time and is conducive to improving the decontamination efficiency. Furthermore, the foam stability and bulk viscosity of the foam solution at a low shear rate exhibited a significant positive correlation. As a result, with decreasing the temperature, the viscosity of the XG-stabilized antifreeze foam solution increased leading to a better stability of foam at a lower temperature. The stabilizing mechanism of the XG stabilizer would possibly be the rigid chain structure of the XG molecule, which could lightly resist the contraction and bending of the molecular chain caused by Na+ originated from the surfactant sodium alpha-olefin sulfonate (AOS) and H+ originated from acidic chelator citric acid (CA) in the decontamination foam. Another probable stabilizing mechanism would be that the electrostatic repulsion generated by the negatively charged groups on the XG molecular chains could prevent the molecular aggregation and precipitation. Moreover, surface decontamination results revealed that the XG-stabilized antifreeze foam can remove >90% of the radionuclide contamination physically attached to surfaces of glass, stainless steel, white paint, green paint, and tile plate below 0 degrees C. Therefore, the antifreeze foam detergent exhibits good application potential for the decontamination of surface radioactive contamination in winter due to its excellent stability, high decontamination efficiency, and biodegradability.