## 1 Introduction  
Polyvinyl alcohol (PVA) plays a crucial role in the rapidly expanding 3D printing industry, particularly as a water-soluble support material for complex geometric structures [1]. The unique properties of PVA, including excellent water solubility, biodegradability, and mechanical strength, make it ideal for supporting overhanging features during the printing process of complex objects [2]. Once printing is complete, the PVA supports can be dissolved in water, leaving the main structure intact. With the widespread adoption of 3D printing technology in medical devices, construction, and industrial applications, the demand for PVA has increased significantly. Recent applications include patient-specific anatomical models in healthcare, lightweight structural components in automotive manufacturing, and intricate architectural prototypes in construction [3, 4, 5]. Unlike traditional textile and paper industries where PVA wastewater concentrations range from 0.1 to 1 g/L, 3D printing generates wastewater containing PVA concentrations as high as 20-35 g/L, presenting a new environmental issue [6, 7]. This higher concentration results from the complete dissolution of solid PVA supports in relatively small volumes of water during the post-processing phase of 3D printing. The treatment of such high-concentration PVA wastewater is particularly challenging due to PVA's unique molecular structure. Its carbon backbone with hydroxyl side groups creates excellent water solubility while imparting significant chemical stability. Conventional biological treatment methods are ineffective, as most microorganisms lack the enzymes necessary to break down the carbon-carbon bonds in PVA's main chain [8]. Additionally, PVA's high molecular weight and viscosity properties cause severe fouling in membrane filtration systems, reducing treatment efficiency by up to 85% [6]. The environmental impacts of untreated PVA wastewater are multifaceted and persistent. When discharged into aquatic environments, PVA requires extended periods for natural degradation, with studies showing half-lives exceeding 100 days in natural waters [7]. Its accumulation in water bodies increases viscosity, generates surface foam, and interferes with oxygen transfer, inhibiting aerobic microbial activity essential for ecosystem health. Furthermore, PVA has been shown to facilitate the mobilization and transport of heavy metals in sediments by forming complexes that increase metal solubility, potentially exacerbating environmental pollution. The final destination of PVA in the environment is particularly concerning, as it can eventually degrade into microplastics that may enter the food chain, posing risks to aquatic organisms and potentially humans [9]. Previous studies have revealed multiple solutions in treating high-concentration PVA wastewater. While biological treatment is environmentally friendly, even specialized bacterial strains achieve only 65% degradation efficiency for 5 g/L PVA, requiring treatment periods exceeding 15 days [10]. Advanced oxidation processes, such as UV/H2O2 systems, require 4.8 kWh/m3 energy consumption to treat 1 g/L PVA [11], making them cost-prohibitive. Membrane filtration technologies experience up to 85% flux decline when treating high-concentration PVA and face membrane fouling and high operational costs [12]. These technologies become even less efficient and more costly when dealing with high-concentration PVA wastewater from 3D printing. To address these issues, researchers have proposed various treatment methods, including photochemical degradation [13; 14; 15], ultrasonic technology [16], potassium permanganate oxidation [17], radiation degradation [18], and various adsorption materials [19]. Among these, photoelectrochemical treatment has gained attention due to its environmental friendliness and operational flexibility [20].