Solar module recycling based on oxidative liquefaction

<p class="p1"><span class="s1">Researchers have developed a low-temperature, hydrogen peroxide-mediated oxidative liquefaction process to recycle end-of-life solar panels by selectively breaking down polymers into useful chemical feedstocks. The proposed method reduces energy consumption, eliminates hazardous solvents, and minimizes landfill waste compared to traditional recycling techniques.</span></p><p>Researchers at <a href="https://www.pv-magazine.com/2025/01/07/storing-photovoltaic-thermal-energy-with-volcanic-tuff-stones/" rel="noopener" target="_blank">Xi'an Jiaotong University</a> in China have developed a novel end-of-life (EoL) solar module recycling process that uses oxidative liquefaction (OL) at comparatively low temperatures to exploit selective oxidative degradation chemistry.</p>
<p>“Oxidative liquefaction is an aqueous hydrogen peroxide (H₂O₂)-mediated thermochemical process previously applied to composite wind turbine blade recycling,” said researcher <span class="hover:entity-accent entity-underline inline cursor-pointer align-baseline"><span class="whitespace-normal">Xing Fu</span></span>. “The ecological advantage stems from lower operating temperatures and the potential for process heat recovery from exothermic H₂O₂ decomposition and polymer oxidation reactions.”</p>
<p>The study used 250 W silicon-based monocrystalline PV panels, which were cut into 1 cm × 1 cm chips and used as feedstock. The experiments were conducted in a 510 mL stainless-steel Parr reactor using aqueous H₂O₂ as the oxidizing agent. While pressure and reaction time were held constant at 32 bar N₂ and 90 minutes, three variables were investigated: temperature (210 C, 260 C, and 310 C), H₂O₂ concentration (30%, 48%, and 65%), and waste-to-liquid ratio (12.5%, 25%, and 37.5%).</p>
<p>Before and after treatment, the PV waste and reaction products were characterized using proximate and ultimate analysis, SEM-EDS, FTIR spectroscopy, and thermogravimetric analysis (TGA/DTG). After each reaction, solid and liquid products were separated by filtration. Solid residues were analyzed for polymer degradation, while liquid products were characterized by gas chromatography with flame ionization detection (GC-FID) to identify and quantify oxygenated carbon compounds (OCCs). Statistical optimization and model validation were subsequently performed.</p>
<p>TGA/DTG results showed that EVA decomposes in two stages. Operating at 210–310 °C allowed the researchers to target the first stage, in which acetic acid and other useful intermediates are released, while avoiding the second stage at around 385 °C, where the polymer backbone undergoes complete breakdown and combustion. Response surface methodology (RSM) and ANOVA-based optimization identified the optimal operating conditions as 245 C, 32% H₂O₂ concentration, and a 13% waste-to-liquid ratio. Under these conditions, the process achieved 88.4% total polymer degradation and an oxygenated carbon compound yield of 52.8 mg per gram of PV waste.</p>
<p>“Normalized energy consumption at optimal conditions (1.95 kWh/kg PV waste) is 46–65% lower than comparable pyrolysis and supercritical delamination processes, primarily due to lower operating temperatures and partial recovery of exothermic heat from H₂O₂ decomposition,” the academics said. “Preliminary ecological indicators show that OL reduces landfill burden to around 11.6 wt% of PV input, eliminates hazardous solvent use, and generates recoverable liquid chemical feedstocks.”</p>
<p>In conclusion, Fu noted that scale-up analysis identifies staged H₂O₂ injection, continuous plug-flow reactor design, and heat integration as the primary engineering challenges for industrial implementation.</p>
<p>The new recycling tech was presented in “<a href="https://www.sciencedirect.com/science/article/pii/S2352492826005921" rel="noopener" target="_blank">Oxidative Liquefaction as a Sustainable Route for End-of-Life Photovoltaic Panel Recycling: Process Optimization, Ecological Indicators, and Scale-Up Assessment</a>,” published in <em>Materials Today Communications. </em></p>