## 1 Introduction
Electrocoagulation, as an emerging electrochemical treatment technology, has demonstrated effectiveness in treating various wastewaters through the generation of metal ions from sacrificial anodes to form hydroxides for pollutant removal [21]. In the field of advanced oxidation processes, the persulfate-based system has emerged as a promising oxidant owing to its strong oxidation potential, chemical stability, and versatile activation mechanisms through thermal-, Fe2+-, and zero-valent iron (Fe(0))-mediated pathways [22]. Studies have shown that thermally activated persulfate can completely degrade PVA within 30 min at 60 \({}^{\circ}\)C, while at room temperature, Fe2+- or Fe(0)-activated persulfate systems achieve complete PVA degradation within 2 h [23]. The Fe(0)-activated system demonstrates superior treatment efficiency, primarily attributed to its sustained release of Fe2+, maintaining persulfate activation efficiency. Gas chromatography-mass spectrometry analysis reveals that the main intermediate product of persulfate oxidation of PVA is vinyl acetic acid, which is more biodegradable than PVA due to its lower molecular weight and unsaturated carboxylic acid structure. This indicates that persulfate oxidation significantly enhances the biodegradability of PVA wastewater, creating favorable conditions for subsequent biological treatment [24]. Several limitations exist in applying persulfate oxidation to treat high-concentration PVA wastewater from 3D printing. The thermal activation process exhibits high efficiency but remains energy-intensive and impractical for industrial applications. The understanding of Fe\({}^{2+}\) and Fe\({}^{(0)}\) activation efficiency and mechanisms under high PVA concentrations is still insufficient [25]. The process is further complicated by the potential self-scavenging reactions of excess Fe\({}^{2+}\), which can reduce overall oxidation efficiency. The ferrite process, initially developed for heavy metal removal [26; 27; 28], has shown promise in organic pollutant treatment due to its ability to form easily separable magnetic precipitates. This process involves the co-precipitation of Fe\({}^{2+}\) and Fe\({}^{3+}\) ions under alkaline conditions to form ferrite (Fe\({}_{3}\)O\({}_{4}\)). Spinel ferrite nanoparticles (SFNPs), with their unique superparamagnetic properties, high adsorption capacity, and surface-area-to-volume ratio, demonstrate significant potential in water treatment [29; 30; 31]. The ferrite structure, with the general formula MFe\({}_{2}\)O\({}_{4}\) (M = Mn, Fe, Co, Ni, Cu, Zn, etc. ), not only exhibits excellent magnetic properties but can also be surface-modified to enhance selectivity and adsorption performance for pollutants. Studies have shown that SFNPs effectively remove both organic and inorganic pollutants. For instance, Fe\({}_{3}\)O\({}_{4}\)-chitosan composites achieve adsorption capacities of 1215 mg/g for azo dye acid orange 7, significantly higher than traditional adsorbents like activated carbon (391 mg/g) and graphene oxide (144.92 mg/g), while achieving over 95% removal efficiency for heavy metals such as Pb\({}^{2+}\) ions [32; 33; 34]. The ferrite process combines the advantages of precipitation separation and magnetic recovery, demonstrating unique potential in treating complex wastewaters. In situ-generated ferrite materials exhibit smaller particle sizes (50-300 \(\upmu\)m) and larger specific surface areas (>200 m\({}^{2}\)/g) compared to traditional prefabricated ferrites, with abundant active functional groups on their surfaces, leading to superior pollutant removal performance [29]. For instance, the in situ ferrite process achieves over 95% removal efficiency for methylene blue dye within 5 min, with an adsorption capacity of 347.82 mg/g, significantly surpassing traditional adsorbents such as activated carbon (164.9 mg/g), graphene oxide (144.92 mg/g), and bio-adsorbents like cellulose citrate [30].