Wide-area surface decontamination is crucial in the event of a sudden release of radioisotopes to the public, such as during nuclear accidents or terrorist attacks. Although various strippable coatings demonstrate effective removal performance in the nuclear industry, they are not ideal for wide-area decontamination in such emergencies. These coatings typically become radioactive waste after use, leading to high disposal costs, and they are often difficult to remove completely from porous surfaces.
Our group has recently developed a series of reversibly cross-linkable complexes between polyvinyl alcohol (PVA) and borate (B(OH)₄^-), designed for easy removal from surfaces. This approach aims to reduce radioactive waste treatment costs and enable potential reuse. The PVA–borax-based coatings from previous studies are cost-effective, easy to manufacture, and leave no residual contaminants on porous surfaces after removal. Additionally, borax provides Na⁺ ions, which can exchange with Cs⁺ ions via ion exchange. However, the effectiveness of such coatings under low-temperature conditions has not been thoroughly investigated.
In this study, we developed a peelable coating with a subzero freezing point to ensure effective decontamination in cold environments. To achieve this, partially hydrolyzed poly(vinyl acetate) (PHPVAc) and borate were used, with a water/ethanol mixture as the solvent to improve performance at subzero temperatures. In this system, two separate solutions—one containing PHPVAc loaded with an adsorbent and the other containing borate—are simultaneously applied to contaminated surfaces. This forms a viscous coating with a three-dimensional gel network via reversible borate–diol ester bonding, which adheres to the surface and adsorbs Cs-137. The embedded adsorbent enhances the removal efficiency of Cs-137 even at a low temperature of −9 °C. Moreover, the coating can be easily removed by rinsing with water and leaves no residue, even on porous surfaces such as cement, due to the reversible nature of the PVA–borate complexation.
Therefore, this hydrogel system shows strong potential for the decontamination of hazardous contaminants, including radionuclides, from porous surfaces under low-temperature conditions.

Hee-Man Yang

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