Pretreatment of Polyvinyl Alcohol-Containing Desizing Wastewater by the Fenton Process: Oxidation and Coagulation

To remove polyvinyl alcohol (PVA) and improve the biodegradability of the desizing wastewater, the Fenton process was developed to treat the PVA-containing desizing wastewater. Effects of operational parameters (i.e., n (Fe2+):n (H2O2) molar ratio, H2O2 dosage, initial pH, and reaction time) on the treatment efficiencies of the Fenton process were investigated. Under the optimal conditions, the high chemical oxygen demand (COD) (i.e., 50.9%) and turbidity (i.e., 99.8%) removal efficiencies were obtained by the Fenton process. Meanwhile, PVA concentration in the wastewater was decreased from 326 +/- 15 to 16 +/- 2 mg/L, and its removal efficiency reached about 95.1%. According to results from two control experiments, it is clear that the high treatment efficiency was mainly attributed to the combination action of oxidation (hydroxyl radical, HO center dot) and coagulating sedimentation (Fe2+/Fe3+). In addition, the Fourier transform infrared spectroscopy analysis results showed that PVA was decomposed and transferred into the small molecule organic acids, which resulted in the rapid increase of BOD5:COD (B:C) ratio from 0.25 to 0.51 after 120-min treatment by the Fenton process. Therefore, the Fenton process was an effective method for pretreatment of desizing wastewater before biological treatment.