## 3 Results and Discussion
### FTIR Analysis of H\({}_{2}\)O\({}_{2}\) Pre-Oxidation Effects and Treatment Efficiency  
The introduction of H\({}_{2}\)O\({}_{2}\) significantly improved the treatment process through pH regulation and enhanced oxidation. Without H\({}_{2}\)O\({}_{2}\), high-concentration PVA solutions (5-7 g/L) showed reduced pH values (pH 7-8), potentially affecting ferrite formation and PVA removal efficiency. After H\({}_{2}\)O\({}_{2}\) addition, pH levels remained around 12 across all concentrations, providing more favorable conditions for ferrite formation. FTIR spectral analysis, as shown in Figure 5, revealed significant changes in the C-O stretching vibration peak at 1100 cm\({}^{-1}\) across all concentrations. At lower concentrations (3-4 g/L), this characteristic peak intensity notably decreased, indicating H\({}_{2}\)O\({}_{2}\)-promoted C-O bond cleavage in PVA molecules. Absorption peak changes in the 700-900 cm\({}^{-1}\) and 1200-1500 cm\({}^{-1}\) regions became more pronounced, suggesting that H\({}_{2}\)O\({}_{2}\) affected both PVA main chain structure and side chain oxidative degradation. Although spectral changes were relatively minor at higher concentrations (6-7 g/L), treatment efficiency still improved compared to experiments without H\({}_{2}\)O\({}_{2}\).  
Figure 4: Visual comparison of ferrite treatment results at different PVA concentrations (3–7 g/L) with and without H\({}_{2}\)O\({}_{2}\) pretreatment, demonstrating the effects on deposit formation, phase separation, and precipitate characteristics.  
The mechanism of H\({}_{2}\)O\({}_{2}\) action under alkaline conditions involves H\({}_{2}\)O\({}_{2}\) dissociation at pH 12 generating HO\({}^{2-}\), which reacts with Fe\({}^{2+}\) to produce hydroxyl (-OH) and superoxide (O\({}^{2-}\)) radicals. These active radicals attack C-O bonds in PVA molecules, promoting bond cleavage. Subsequently, degraded PVA fragments more readily coordinate with iron ions, facilitating ferrite formation. Quantitative evaluation at the highest PVA concentration (7 g/L) demonstrated that single ferrite treatment achieved 37% COD removal. Implementation of a two-stage treatment strategy significantly improved COD removal to 83%. This enhancement likely results from initial H\({}_{2}\)O\({}_{2}\) pre-oxidation and ferrite treatment breaking down PVA macromolecular structure, producing more easily degradable intermediates that readily coordinate with iron ions during the second treatment phase.  
The H\({}_{2}\)O\({}_{2}\) pre-oxidation approach in our study offers distinct advantages over previously reported PVA treatment methods. While previous research [22,23] focused on complete PVA degradation using persulfate-based oxidation, our approach combines partial oxidation with ferrite formation, achieving both treatment efficiency and valuable material recovery. Our two-stage treatment strategy achieved 83% COD removal for 7 g/L PVA, which is comparable to more energy-intensive methods like UV/H\({}_{2}\)O\({}_{2}\)[11], but with the added benefit of producing recoverable magnetic materials. This represents a significant advancement over conventional electrocoagulation methods [21], which achieve PVA removal but do not facilitate resource recovery.  
Figure 5: FTIR spectra of PVA solutions (3–7 g/L) after H\({}_{2}\)O\({}_{2}\) pre-oxidation and ferrite treatment, showing characteristic peak changes at 1100 cm\({}^{-1}\) (C–O stretching), 700–900 cm\({}^{-1}\), and 1200–1500 cm\({}^{-1}\) regions.