RECYCLING SILICON FROM SECONDARY SOURCES: WASTE SOLAR WAFERS AND DIAMOND WIRE SAW KERF SLURRY IN PHOTOVOLTAIC INDUSTRY

Abstract

The surge in global interest in installing solar panels in recent years has been remarkable, in 2022, 250.000 MW of new capacity, primarily silicon (Si) based cell technology was installed (Chowdhury et al. 2020). Only in the past few years, there has been a substantial amount of solar panels, installed in the only 2000´s reaching end-of-life (EoL), with the big wave of EoL panels approaching.  In 2050, there will be approximately 7 million tonnes of EoL panels. This implies the potential recovery of 7.000 to 70.000 tonnes of silver (Ag) and 210.000 to 350.000 tonnes of Si (Weckend et al. 2016).  Without a comprehensive strategy for recycling them, we face the prospect of accumulating a mountain of EoL solar panels in the coming decades.

Moreover, during the slicing of purified silicon ingots into wafers, the process of cutting multi-crystalline silicon ingots generates up to 40% Si kerf slurry waste. The rapid expansion of the global photovoltaic (PV) industry has resulted in a significant increase in diamond-wire saw kerf slurry waste. To reduce the costs of producing crystalline Si and mitigate environmental pollution caused by EoL solar panels and Si kerf slurry, recycling these materials has become imperative.  In this work, the recycling of Si from waste solar wafers and Si kerf slurry in the solar industry are investigated using both pyrometallurgical and hydrometallurgical methods.