Synthesis of magnesium aluminate spinel by calcination of aluminum recycled from discarded PV solar panels with bischofite

Abstract

Disposal of discarded photovoltaic solar panels has emerged as a significant environmental concern as they are classified as hazardous electronic waste. However, significant benefits can be gained by strategically recovering valuable materials from this waste. The objective of this study was to utilize aluminum recovered from the frame of a discarded PV solar panel to synthesize magnesium aluminate spinel (MgAl2O4). The synthesis method investigated involved chlorination roasting, employing bischofite (MgCl2·6H2O) as the chlorinating agent. Initially, the frame was separated from the discarded panel, size-reduced and subjected to leaching. The resulting powder was then mixed with bischofite. The mixture was calcined under isothermal and non-isothermal conditions to investigate the influence of temperature and reaction time on the synthesis.Additionally, the effect of the chlorination roasting atmosphere, including air and nitrogen atmospheres, was assessed. Different studies, including thermodynamic calculations, X-ray diffractometry (XRD), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) were conducted to elucidate the reactions and mechanism involved in the synthesis process. The results showed that AlOOH, Al2O3·H2O, Mg3(OH)5Cl·4H2O and Mg2(OH)3Cl·4H2O are the intermediate products generated during the synthesis process. Magnesium aluminate spinel begins to form at 700 °C, with the optimal operating conditions identified at 700 °C and 120 min.