Poly(vinyl alcohol)-borax complex-based spray coating for the decontamination of radioactive Cs from wide-area surfaces

A spray coating based on an adsorbent/polyvinyl alcohol (PVA)-borax complex was developed to remove radioactive cesium from surfaces by adsorption for wide-area surface decontamination. Two aqueous solutions of borax and PVA containing adsorbents, namely, Prussian blue, bentonite, and sulfur-zeolite, were simultaneously sprayed on surfaces, which subsequently self-generated a gel-like coating via a borate-diol ester bond between borax and PVA. The spray coating adhered adequately to vertical surfaces for at least 1 h due to its good viscoelasticity and displayed 137Cs removal efficiency (56.966%) twice that of a commercial strippable coating (DeconGel, 27.248%) on porous cement surfaces because the sulfur-zeolite in the coating has an excellent Cs distribution coefficient (4.768 × 106 mL/g). In addition, our coating could be easily removed from the surface after use by simply rinsing with water, and it left no residue, even on a porous surface such as cement, due to the reversible PVA-borax complexation. In contrast, commercial strippable coating and chemical gels leave a residue. Moreover, the used adsorbent that captured 137Cs could be easily separated using simple filtration for a direct solidification procedure before final disposal/storage, whereas the commercial strippable coating and chemical gels require expensive treatment, such as incineration, to remove organic components. In a demonstrative test using a commercial spray-coater, the spray coating exhibited a fast spray rate (1.25 m2/min), high stability (>1 h), and easy removal by simply rinsing with tap water.