UV/S₂O₈^2- process for degrading polyvinyl alcohol in aqueous solutions

This investigation evaluates the effectiveness of the UV/S₂O₈^2- process in the degradation of polyvinyl alcohol (PVA) in aqueous solutions without adjusting their pH. The effects of UV wavelength and Na₂S₂O₈ dosage on the efficiency of degradation of PVA were examined. The efficiency of degradation of PVA under UV-254nm exceeded that under UV-365nm. A larger Na₂S₂O₈ dosage was associated with a higher efficiency of degradation of PVA under UV-254nm irradiation. However, an excessive Na₂S₂O₈ dosage inhibited the degradation of PVA by the UV-365nm/S₂O₈^2- process. Both UV-254nm/S₂O₈^2- and UV-365nm/S₂O₈^2- processes exhibited pseudo-first-order kinetics. SO₄^- was detected by performing quenching studies using specific alcohols, revealing that SO₄^- was found to be the predominant radical in the UV-254nm/S₂O₈^2- process. Additionally, the presence of inorganic anions with various effects inhibited the degradation of PVA by the UV-254nm/S₂O₈^2- process. Complete degradation of PVA (20mg/L) was achieved within 5min under UV-254nm using an Na₂S₂O₈ dosage of 0.12g/L in the absence of inorganic anions, indicating that UV irradiation to activate S₂O₈^2- promotes the degradation of PVA in aqueous solutions without adjusting their pH.