Hybrid colloidal suspensions tailored as gels to remove radioactive bitumen stains

Vacuumable gels have been developed in the nuclear industry to decontaminate solid surfaces with little or no mechanical operations and without producing any liquid effluents. These gels can be spread on the contaminated surface and rapidly trap the radio-contaminants by sorption after corroding the substrate down to several tens of microns if necessary. The gel then dries and eventually fractures into a non-powdery solid that is easily removable by brushing or vacuum cleaning. This process was initially developed for the nuclear decontamination of metallic surfaces but innovative formulations are being developed for wide range of applications. This paper introduces two such formulations designed to remove sticky organic layers, bitumen in this study. We show that adding an organic bio-solvent, limonene, allows bitumen layers to be dissolved, absorbed in the liquid state into the gel matrix, and then removed from the substrate as solid waste after drying. Substituting an organic co-solvent (ethanol) for some of the limonene improves the overall efficiency of the process by decreasing the drying time of the gel and limiting the diffusion of the dissolved bitumen without affecting the dissolving power of the gel. Finally, the performance of these gels is demonstrated for the removal of nuclear contaminated (¹³⁷Cs) bitumen stains.