Efficiently and greenly removal of EVA encapsulant from photovoltaic modules: A sequential swelling-dissolution approach

As the photovoltaic (PV) industry continues to grow rapidly, there is a growing demand for efficient and environmentally friendly recycling solutions for end-of-life modules.

A key technical barrier is the removal of the ethylene-vinyl acetate (EVA) encapsulant, which impedes the reclamation of valuable materials. This study introduces an sequential swelling-dissolution approach for the complete and green removal of EVA from crystalline silicon PV modules. A pre-treatment step utilizing limonene, a bio-based solvent, effectively swells the cross-linking EVA network, facilitating the detachment of the backsheet and enhancing the accessibility of the encapsulant. A solution of sodium hydroxide (NaOH) in benzyl alcohol (BA) is employed to thoroughly dissolve the swollen EVA from the solar cell surface. The effects of various parameters, including temperature, reaction time, stirring speed, solid-liquid ratio, reagent concentration, and module piece size, on backsheet detachment and EVA removal efficiency were systematically investigated. Characterization techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Gas Chromatography-Mass Spectrometry (GC-MS) were utilized to analyze the cleaned cell surfaces, the chemical integrity of the solvents post-reaction, and the composition of the backsheet. The results demonstrate that this sequential chemical process can achieve near-complete EVA removal (e.g., 99.76 % removal in 50 min under optimized dissolution conditions) in under 1.5 h at moderate temperatures. FTIR analysis indicated the potential for solvent reuse. SEM imaging confirmed the cleanliness of the retrieved silicon wafers. The underlying mechanisms of EVA swelling by limonene and subsequent saponification and dissolution in NaOH-BA are also discussed.