Aplicação de CO2 supercrítico na delaminação de um painel fotovoltaico visando a recuperação de materiais valiosos

Abstract

Photovoltaic panels are technologies that have been gradually increasing in the world market and, after their end of life, are considered as electronic waste. There are 250,000 metric tons of solar panel waste worldwide and that number will reach 78 million by 2050. Among some of the consequences of improper disposal of photovoltaic panels, there is the percolation of heavy metals in the soil, such as lead and cadmium, and consequent impact on water resources and also losses of aluminum and glass, important for the industrial market. In addition, there are losses of metals with high added value, such as silicon and silver. The importance of recycling photovoltaic panels meets the need to restore these materials to the production process. The technology of supercritical fluids has been presented as an interesting technique for the recycling and extraction of several materials due to the high solvation power and low viscosity. It is advantageous to use this technology when the extraction object has high added value, as is the case with the photovoltaic plate. The separation of the module layers with supercritical fluids allows components to be reused in new materials. One of the major difficulties in recycling solar panels is the delamination of their constituents. Thus, this work aimed to analyze the efficiency of supercritical technology with carbon dioxide (CO2) in the delamination of photovoltaic panels through the application of different cosolvents and the use of a planetary ball mill to enable exposure and access to high-value metals to be recycled. Several samples of a Canadian Solar model cs6Pp-265p photovoltaic plate were used. Toluene was used in the delamination of the photovoltaic module with supercritical CO2 (ScCO2) and comparatively in the system at atmospheric pressure. The variables pressure, temperature, solid:liquid ratio (S:L) and time were analyzed. The recovery efficiency and purity of the materials obtained after the process were carried out. The constituents of the photovoltaic module were subjected to analyzes of SEM/EDS, XRD, XRF, TGA, DSC and FTIR. ScCO2 showed advantages in terms of solvent volume and time when compared to the system at atmospheric pressure. After 60 min in ScCO2 and in the planetary ball mill, the recovery was close to 100% for the fractions of glass, metallic filament and protection sheet. The recovery of the solar cell and EVA was over 85%, which is satisfactory and allows the recovery of silicon and silver, metals of high value for the market. In addition, this reuse reduces the extraction of raw materials, bringing economic and environmental benefits.