Comparative assessment of solvent chemical delamination of end-of-life solar panels

This work investigates the use of toluene, d-limonene and three deep eutectic solvents (based on choline chloride, urea and zinc chloride) for the delamination process of recovered and de-glassed end-of-life solar panels. The organic solvents that have been previously investigated for delamination such as toluene and trichloroethylene are generally hazardous and fossil fuel derived. To evaluate and compare the effectiveness of separation of alternative solvents to toluene, solar panel laminates recovered from end-of-life solar modules were exposed to the respective solvent at 30 degrees C, 90 degrees C and (for deep eutectic solvents) 160 degrees C for 30 - 60 min at each temperature. After chemical treatment the recovered photovoltaic material and encapsulant was sieved into the size fractions > 1.0 mm, 1.0 - 0.5 mm and < 0.5 mm before being oxidised at 550 degrees C to quantify the remaining encapsulant in each fraction by mass change. It was found that d-limonene has a similar degree of separation as toluene. Moreover, d-limonene showed an improved recovery of up to 4.5 times more photovoltaic cell material below the 1.0 mm size fraction making it a more effective alternative. No discernible effects were observed for either of the three deep eutectic solvent combinations tested. The experimental data obtained was used to model and compare a separation process based on toluene and d-limonene, with maximal solar photovoltaic cell recoveries of 10 % for toluene delamination and 39 % for d-limonene delamination in size fractions < 1.0 mm.