Sustainable Recycling of Silicon from End-of-Life Photovoltaic Panels for the Synthesis of Porous Cordierite Via Bischofite-Assisted Chlorination

Abstract

The rapid increase in electronic waste, driven by the widespread use of electronic devices, poses significant environmental challenges due to its classification as hazardous waste. Among these, end-of-life solar panels present a growing concern, as improper disposal can lead to the release of toxic pollutants. Recycling these panels not only prevents environmental contamination but also optimizes resource and energy use. This study focuses on repurposing silicon from discarded panels to synthesize cordierite, a material with industrial applications. The synthesis process involves the thermal treatment of silicon obtained from waste panels, combined with kaolinitic clay and bischofite, which acts as a chlorinating agent. Non-isothermal experiments were conducted within a temperature range of 20–900 °C to evaluate the effects of temperature on the reaction process and impurity behavior. Additionally, isothermal experiments were performed to assess the impact of reaction time. The reaction mechanism was also analyzed. The results revealed that cordierite begins to form at 700 °C through the reaction of evolved mullite and enstatite in a chlorine atmosphere. At 600 °C, iron impurities in the clay undergo chlorination, forming volatile FeCl₃. Optimal conditions for the process were identified at 900 °C with a reaction duration of 120 min, enabling the selective synthesis of cordierite and the effective removal of iron and vitreous silica impurities.