Catalytic performance of electronic waste-derived gold nanoparticles for the reduction of p-nitrophenol†

Abstract

Current methods for producing gold nanoparticles (AuNPs) typically involve solutions containing 50 to 27 000 ppm of gold. These precursor solutions are derived from purified ore material and are not representative of waste-derived gold-containing solutions, which generally range from 20 to 30 ppm. Electronic waste (e-waste) is an increasing global concern due to the presence of various toxic substances that can leach into the environment and pose risks to human health. However, e-waste also represents a rich source of precious metals, including Ag, Pd, and Au. Here, we report the synthesis of AuNPs derived from AuCl₄⁻ or AuI₄⁻ at concentrations typical of e-waste streams, as well as from printed circuit board (PCB) e-waste samples. The AuNPs, ranging from 3 to 30 nm in diameter, are deposited onto commercially available cellulose fibres by a reductive deposition method using hydrazine hydrate. The catalytic performance of the AuNPs was evaluated in the reduction of p-nitrophenol to p-aminophenol in the presence of NaBH₄. The AuNPs derived from e-waste on cellulose exhibited higher turnover number (TON) and turnover frequency (TOF) compared to commercially available 30 nm AuNPs and previously reported AuNPs on cellulose, possibly due to trace amounts of palladium present. This study demonstrates that AuNPs can be efficiently synthesised from e-waste streams and provides proof-of-concept evidence that the gold in bulk e-waste can serve as a valuable source of high-value catalysts.