Removal of Antimony by Volatilization from Photovoltaic Glass with Sucrose under Anoxic Environment

In the recycling of photovoltaic (PV) modules, promoting the recycling of PV glasswhich accounts for approximately 60% of the total module weightis crucial. However, PV glass contains antimony (Sb) to enhance its transmittance, and this antimony poses a barrier to recycling in float baths. In this study, we investigated the feasibility of removing Sb from PV glass by volatilization using chloride and reductive methods. We also estimated the reactions using thermodynamic equilibrium calculations and evaluated the volatilization mechanism of Sb from PV glass. The results showed that, unlike conventional chloride volatilization and chloride reduction methods, operation under a non-oxygen atmosphere and the use of sucrose as a reducing agent are important for Sb removal by volatilization. The degree of influence of each experimental condition on Sb volatilization was highest for the gas atmosphere (N2) and sucrose, followed by heating temperature and C/Sb molar ratio. Under experimental conditions used in this study, heating time is considered to have a low degree of influence. The optimal conditions for Sb volatilization in the experiments were a heating temperature of 1100 °C, a heating time of 120 min, and a C/Sb molar ratio of 224, which yield a Sb volatilization rate of 92.6%. By contrast, thermodynamic equilibrium calculations showed that at a heating temperature of 500 °C, the Sb volatilization rate was 100%, and at a C/Sb molar ratio of 11.2, the rate was 92.8%. These results suggest that the heating temperature and C/Sb molar ratio can be reduced by increasing the reactivity of the sample. PV glass after heating is considered recyclable as raw material for flat glass and can be used as antimony-free or low-antimony glass material. Therefore, the Sb volatilization removal method developed in this study is expected to significantly reduce barriers to recycling.