Catalytic reduction of Cr(VI) using recovered Silicon from end-of-life photovoltaic panels as a catalyst

As installed photovoltaic panels (PVP) approach their end of life, the need for a sustainable recovery plan becomes imperative. This work aims to reuse Silicon from End-of-Life PVP as a potential catalyst/photocatalyst for wastewater treatment. PVPs were pretreated thermally (550°C for 30 min). The resulting mixture of glass, silicon, electrodes, and ash was separated into different fractions in a trommel. Recovered Silicon flakes were washed with water, acetone, ΗΝΟ3, and HF in order to obtain pure Si. Then Si was etched through a single stage Ag-assisted Chemical etching process and doped with copper. Doping was performed in aqueous HF solutions containing CuSO4. Photocatalytic reduction of Cr(VI) in the presence of 5mM citric acid was carried out in a 600 mL batch reactor irradiated by a Xenon 150W arc lamp as well as under dark conditions. It was found that in the presence of 1.2 g/L of the Si catalyst, Cr(VI) at an initial concentration of 15 mg/L can be reduced below detection limit (>99%),under dark conditions in 90-240 min, depending on the pH of the solution. Irradiation, however, was shown to inhibit the process, contrary to previous reports that had not examined catalysis in the dark.