Recovery and analysis of valuable materials from a discarded crystalline silicon solar module

Mechanical, thermal, and chemical treatments were employed on a discarded small-sized silicon solar module to recover valuable materials from it. Materials like glass, junction box, polymer back sheet, and aluminium frame were recovered without damage. Ethylene-vinyl acetate layer (EVA) was obtained through the treatment of the panel with toluene solution. Optimised solution of 2 M HCl was used for Pb and Sn stripping from connecting wires to recover Cu Strips. Pb was extracted as PbCl2 from the solution through precipitation in an ice bath. Sn was recovered as SnO2 and SnCl2 through electrolysis of the residual solution. Al from the back contact was recovered as Al(OH)3 through sequential treatment with KOH and H2SO4. The effect of the molar concentration of KOH solution on Al etching was also investigated, and it was found that the 2 M solution was optimal. An innovative and cost-effective approach was adopted for the recovery of silver. Ag extraction involved, the treatment of solar cell pieces with HNO3 acid followed by reduction of AgNO3 with the copper strips. As recovered Cu strips were reused for Ag recovery, it can be considered a cost-reducing step for the reported recycling process. At last, ARC coating was removed by employing an H3PO4 solution to get silicon wafer pieces. X-Ray Diffraction and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) were used for phase identification and purity of the recovered materials. An overall recovery rate of 92.4% is achieved. Environmental impact and revenue generation through the process is also discussed.