Nanoscale zero-valent iron in mesoporous carbon (nZVI@C): stable nanoparticles for metal extraction and catalysis

Abstract

Extraction of precious metals from low-level sources such as wastewater is of significance for water/wastewater treatment and resource recovery. Herein, we report a composite of nanoscale zero-valent iron in ordered mesoporous carbon (nZVI@C) for rapid reduction and immobilization of precious metals. The iron nanoparticles are anchored by the mesoporous carbon frameworks with active sites partially confined in the carbon cavities. This new material possesses a large surface area (∼500 m² g⁻¹) and highly ordered mesopores (∼5.2 nm). Small-sized (∼16 nm), uniformly dispersed and reactive iron nanoparticles are obtained for the first time. This material exhibits outstanding performance in gold (10 μg L⁻¹) extraction with >99.9% uptake in less than 5 min. The reclaimed gold nanoparticles are small (<6 nm), stabilized by the presence of both zero-valent iron and mesoporous carbon, exhibiting a high conversion (∼95%) and stability for catalysis. The material thus offers a new strategy for precious metal recovery, as well as the minimization of aggregation and deactivation of reactive nanoparticles.