Sustainable silver recovery by chemical treatment of metal rich fines from solar panel waste

Abstract

Solar photovoltaic power generation has seen rapid growth worldwide which is also giving rise to large amount of waste solar panels at end of life. Due to lack of clear strategy to recycle the waste solar panels, most will end up in landfill causing severe environmental impact and loss of valuable resources like silver, copper, aluminium, and silicon. Recovery of silver from waste solar panels is of particular interest as silver is a fast depleting and valuable resource. In this work, c-Si EoL panels were collected and post removal of junction box and aluminium frames, the laminates were shredded to obtain required size grading. The crushed material was sieved and segregated into five size fractions (F1- F5). Analysis of XRD patterns confirmed presence of metals only in the portion below 300 μm (F4 & F5). The XRF analysis confirmed 0.85 wt% of silver in the metal rich fines (<150 μm). A lab-scale process was developed to recover silver from the metal rich fraction (F5) by leaching with Nitric acid. Acid concentration of 6 M HNO₃, leaching time 60 min and temperature 60 °C were established as the optimum conditions for complete recovery of silver from the fines. The proposed process for recovery of silver can provide an economic incentive to the solar waste recycling process, as it is focused on fines (comprising of 5 % of the crushed laminates). This approach cuts down the processing and transportation cost of recycling EoL solar panels, validating the commercial viability of the size fraction based approach.