Radiation-induced degradation of polyvinyl alcohol in aqueous solutions

Abstract

The degradation of polyvinyl alcohol (PVA) by γ-ray irradiation was investigated. Degradation efficiency of PVA was influenced by several factors, such as initial PVA concentration, dose rate, pH, and the addition of H 2O 2. The degradation kinetics depended on initial PVA concentration and dose rate. At a relatively lower PVA concentration, e.g., 180 mg/L, and a higher dose rate, e.g., 55.7 Gy/min, the degradation followed pseudo-first-order kinetics. On the contrary, at a higher PVA concentration, e.g., 500 mg/L, but a lower dose rate, e.g., 12.1 Gy/min, a pseudo-zero-order reaction occurred. The removal of PVA was more effective under acidic or alkaline conditions than that under neutral conditions. At a certain dose rate there was an optimal dosage of H 2O 2 to facilitate the degradation of PVA. For instance, at a dose rate of 17.2 Gy/min, the optimal H 2O 2 dosage was found to be about 2.5 mmol/L. Radical scavenging experiments, total organic carbon determination, and FTIR analysis on the degradation products demonstrated that PVA radiolysis was initiated by OH and H , leading to chain scission and formation of ketones/enols. Ultimately, complete mineralization of PVA was achieved.