Application of supercritical CO2 for delaminating photovoltaic panels to recover valuable materials

The demand for photovoltaic panels has increased in recent years and the resources used in its production such as silicon, with high production costs and silver that is becoming scarce, in addition to the presence of toxic metals such as lead, highlight the importance of recycling of these materials. One of the main challenges for recycling is the delamination of the panels, for which supercritical fluids can be an effective option. Constituents of a photovoltaic module were analyzed using SEM/EDS, XRD, XRF, TGA, DSC, and FTIR techniques. The efficiency of the delamination process was evaluated using tests carried out at atmospheric pressure, in the presence of different cosolvents. Comparative tests were performed using supercritical CO2 (ScCO2). For both processes, after delamination, the components that still showed low release of adhered materials were processed in a planetary ball mill. Determinations were then made of the recovery and purity of the delaminated fractions, as well as the separation of the adhered materials. The best results for recovery and purity of the glass, metallic filaments, and backsheet were obtained using ScCO2 with toluene, together with planetary ball milling, achieving values over 96 %. For the solar cell and EVA (cell + EVA), the recovery was greater than 85 %, including high value materials such as Si and Ag. In addition to recovering high value metals and reducing the volume of solvent, the use of ScCO2 enabled delamination of the photovoltaic panel with a time around 3.5 times shorter than at atmospheric pressure.