Efficient and selective gold recovery from electronic wastewater by synergistic effect between Fe3O4 nanoparticles and quaternary ammonium salt

Recovering gold from electronic wastewater is of great significance in alleviating the shortage of metal resources and reducing environmental pollution, especially considering the increasing number of discarded electronic devices. However, the ultra-low concentration of gold and the competitive interference of various metals pose significant challenges. In this work, we used Fe 3 O 4 nanoparticles and quaternary ammonium salt to recover gold from electronic wastewater. The method achieved a gold recovery efficiency of 98.2 % within just 3 min. The mechanism of gold recovery was investigated using techniques such as SEM, EDX, FT-IR, XPS, and XRD. The Au (III) ions were complexed with tetrabutylammonium nitrate to form the [N 4444 ][AuCl 4 ] complex, and this complex then aggregated with Fe 3 O 4 nanoparticles to form nanoclusters, while Fe (II) ions on the surface of Fe 3 O 4 nanoparticles reduced the Au (III) ions to Au (0). This study proposed a mechanism of complexation-aggregation-reduction-separation to recover gold. On application to a simulated electronic wastewater, the method exhibited excellent selectivity for Au (III), achieving a recovery efficiency of 99.1 %. The regeneration of Fe 3 O 4 nanoparticles can be readily performed by ultrasound, retaining a 96.7 % recovery rate of Au (III) even after six consecutive cycles. This study proposed the combination of Fe 3 O 4 nanoparticles and quaternary ammonium salt for gold recovery, which provided an environmentally friendly solution to address the increasing demand for precious metal resources in industry.