Abstract
Chemically, biologically, or radiologically contaminated surfaces can be treated using colloidal “vacuumable” gels containing alumina particles as a thickening agent, decontaminating solutions to inhibit/eliminate biological and chemical contaminants, and Pluronic PE 6200 as a surfactant to adjust the gel’s physicochemical properties. These gels have been shown to remain efficient even after prolonged storage. In the present study, the properties of gels with different surfactant concentrations were monitored over several months using rheological analyses, contact angle measurements, and ion chromatography. Results show that the surfactant reacts with the hypochlorite ions in the decontaminating solution. This leads to sedimentation, which modifies the rheological properties of the gel. Increasing the surfactant concentration ensures the physicochemical properties of the gel are preserved for longer, but because the surfactant reacts with the hypochlorite ions, the concentration of the latter decreases drastically and thus so do the decontamination properties of the gel. There is therefore a trade-off between the efficiency of the gel against chemical and biological contamination at a given time and how long its physicochemical properties are preserved, with the optimal balance depending on its intended use.
Highlights
Colloidal gels are complex fluids that can be used to decontaminate solid surfaces [1,2,3,4,5,6,7,8]
To ensure that the gel can be applied by spraying, the gel should behave as a shear-thinning fluid as it passes through the spraying nozzle, and it should have a sufficiently high yield stress to remain in place once spread in a millimeter-thick layer on a vertical surface
Once spread on the surface, the gel absorbs or dissolves the contaminant before drying out, producing only solid waste, such that no effluent post-treatment is required. This technology has been adapted for CBR decontamination, with a highly basic solution containing hypochlorite ions used to inhibit biological and chemical contamination
Summary
Colloidal gels are complex fluids that can be used to decontaminate solid surfaces [1,2,3,4,5,6,7,8]. Similar gels have been formulated for the chemical, biological, and radiological (CBR) decontamination of solid surfaces [2,4], with hypochlorite ions and sodium hydroxide added to the decontaminating solution to treat biological and chemical contamination. Solid contaminants such as radioactive or biological particles are absorbed, while chemical and ionic nuclear contaminants are solubilized and neutralized either by oxidation (hypochlorite) or by hydrolysis (sodium hydroxide). A mechanism is proposed to explain the role of the surfactant concentration on the rheological and chemical aging of CBR gels
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