Synthesis of eco-compatible bimetallic silver/iron nanoparticles for water remediation and reactivity assessment on bromophenol blue

In the last decade, zero-valent iron nanoparticles (nZVI) have been applied for groundwater remediation and they proved to be effective towards a wide range of contaminants, both organic and inorganic. One of the critical aspects related to the synthesis of this material concerns the use of borohydride, which increases the cost of the final product and generates toxic borates. In this paper, a new synthesis method of bimetallic nanoscale zero-valent silver/iron (nZVSI), its properties and its reactivity towards a model compound are presented. The novel synthesis protocol employs benign hydrosulfite as reducing agent and it is of easy implementation and scalability. The resulting nanoparticles have narrow size distribution and show appropriate colloidal stability. They consist of a core of zerovalent iron and a thin shell of iron oxide, while silver is homogeneously distributed within the material. The nanoparticles showed effective reactivity, able to degrade bromophenol blue with suitable kinetics and using a low amount of material. Additionally, the bimetallic nanomaterial significantly outperformed nanometric zero-valent silver (nZVS) and nZVI obtained with the same protocol. The proposed synthesis would allow to significantly reduce the environmental and health impact of the stage prior to product application via injection in the subsoil. Also, the simplicity and the safety of the proposed synthesis procedure would allow the production of the bimetallic reactant directly on-site, thus streamlining the remediation process and maximizing its efficiency.