Abstract
Abstract Polyvinyl alcohol (PVA), a high molecular polymer, has good barrier property, acid or alkali resistance and degradability, which could be used as personal radiation protective equipment and pollution control articles in the nuclear industry, resulting in degradable radioactive technical wastes after use. The degradation treatment process of PVA degradable technology waste can realize validity separation of radionuclides and reduce the output of radioactive solid waste. In this study, MnxOy/γ-Al2O3, CuxOy/γ-Al2O3, FexOy/γ-Al2O3 and FexCuyMnzOw/γ-Al2O3 nanoparticles were prepared by the impregnation-calcination method, which were used as catalysts for the oxidative degradation of ultra-high concentration PVA organic waste solution, and the effects of initial pH of polyvinyl alcohol (PVA) solution, hydrogen peroxide (H2O2) dosing, catalyst dosing and initial concentration of PVA solution on the degradation of PVA were analyzed. The results showed that the best overall degradability was achieved by using FexCuyMnzOw/γ-Al2O3 nanoparticles as catalysts with the initial reaction concentration of PVA at 1%, the initial pH of the solution at 3, the reaction temperature at 60 °C, the catalyst dosage at 0.5 g/L and the H2O2 dosage at 60 mL/L. At this time, the concentration decrease rate of PVA could reach more than 95 %, the viscosity average molecular weight of degradation products reached 1395, the molecular weight decrease rate reached 99 %, and the degradation products mainly included butanone, benzaldehyde, hexanal, acetic acid and other unsaturated small molecules. In addition, the mechanism of hydroxyl radical generation by nanoparticles catalyzing hydrogen peroxide was discussed, and the reaction pathway of oxidative degradation of PVA macromolecules by hydroxyl radicals was proposed, which provided a reference for volume reduction treatment of PVA degradable waste in nuclear industry.
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