Oxidative Liquefaction as a Sustainable Route for End-of-Life Photovoltaic Panel Recycling: Process Optimization, Ecological Indicators, and Scale-Up Assessment

End-of-life (EOL) photovoltaic (PV) panel recycling is impeded by the complex, multi-layer polymer composite architecture of silicon-based modules. This study investigates oxidative liquefaction (OL) as a chemical recycling pathway that is fundamentally distinct from conventional pyrolysis, hydrothermal treatment, and supercritical fluid approaches by operating at comparatively low temperatures (210–310°C) in the presence of aqueous H₂O₂ and exploiting selective oxidative degradation chemistry rather than purely thermal decomposition or high-pressure solvolysis. EOL PV waste was characterized via proximate/ultimate analysis, SEM-EDS, and FTIR spectroscopy. Thermal decomposition behavior was established by thermogravimetric analysis (TGA) and derivative TGA (DTG) at heating rates of 1–16 K/min under an inert argon atmosphere. The oxidative liquefaction process was systematically optimized using a combined Fractional Factorial Design (FFD) and Central Composite Design (CCD) over seventeen experimental runs spanning temperature (210–310°C), H₂O₂ concentration (30–65% v/v), and waste-to-liquid ratio (12.5–37.5%). ANOVA-based response surface models yielded R² = 0.962, adj-R² = 0.941 for total polymer degradation (TPD) and R² = 0.948, adj-R² = 0.921 for oxygenated carbon compound (OCC) yield. GC-FID characterization of liquid fractions identified principal OCCs including acetic acid, formic acid, acetaldehyde, propanoic acid, and methanol. FTIR analysis confirmed encapsulant decomposition via EVA acetyl-group cleavage and main-chain scission. Normalized energy consumption was determined to be 1.95 ± 0.09 kWh/kg PV waste at optimal conditions (245°C, 32% H₂O₂, 13% waste-to-liquid), representing a 46–65% reduction relative to established pyrolysis and supercritical delamination processes. Preliminary ecological indicators, including estimated CO₂ equivalent emissions and avoided landfill burden, are reported to contextualize the environmental benefit of this approach.