Mechanisms and factors influencing the removal/recovery of gold nanoparticles by thermally modified pyrite

Abstract The environmental effects of nanoparticles have attracted widespread attention. The removal and recycling of nanoparticles are crucial for both environmental protection and resource reuse. However, current removal and recycling methods are not yet mature, and there is a need to explore inexpensive materials for the efficient removal and recycling of nanoparticles. This study investigates the effects of pyrite species, thermal modification temperature, pH and ionic strength on the adsorption of gold nanoparticles (AuNPs) by pyrite. The experimental results demonstrate that the adsorption rate of artificially thermally modified pyrite is slightly faster than that of naturally thermally modified pyrite. However, the concentration of Fe ions dissolved from the artificially thermally modified pyrite is higher. Natural pyrite, when thermally modified at 400°C and 500°C, adsorbs 100% of AuNPs within 10 min. The lower the acidity of the system, the faster the adsorption rate. Conversely, an increase in ionic strength decreases the adsorption rate. Artificially thermally modified pyrite primarily adsorbs AuNPs through electrostatic gravitational attraction, which is supplemented by a significant amount of chemisorption. After four recycling cycles, the adsorption and desorption rates of AuNPs using artificially thermally modified pyrite were 92.1% and 94.2%, respectively, indicating excellent adsorption and recovery performance. The results of this study provide a new method for the recycling of nanoparticles and an experimental basis for the further application of thermally modified pyrite in environmental treatments.