Performance of UV/S2O82− process in degrading polyvinyl alcohol in aqueous solutions

This study evaluates the performance of UV/S2O82− process in degrading polyvinyl alcohol (PVA) in aqueous solutions. The effects of pH, Na2S2O8 dose, initial PVA concentration, and addition of inorganic anions on the degradation efficiency of PVA were determined. The degradation efficiency of PVA followed the order pH 3 > pH 7 > pH 11. Additionally, higher Na2S2O8 dose and lower initial PVA concentration were associated with high degradation efficiency of PVA. Moreover, adding Cl− and NO3− reduced the degradation efficiency of PVA. Radical scavenging tests adopted to identify predominant radicals reveal that SO4− was the predominant radical at pH 3, but OH was the predominant radical at pH 11. At pH 3, an Na2S2O8 dose of 1.00 mM, an initial PVA concentration of 20 mg/L, and a temperature of 25 °C, the degradation efficiency of PVA in the absence of inorganic anions was 97% with the observed degradation rate coefficient of 0.3785 min−1, as measured after 10 min. Comparison with heat/S2O82− process reveals that UV/S2O82− process can enhance the degradation of PVA at ambient temperature, suggesting that UV/S2O82− process would be alternative to degrade PVA in aqueous solutions.