Life cycle indicator comparison of copper, silver, zinc and aluminum nanoparticle production through electric arc evaporation or chemical reduction

Ways to produce metallic nanoparticles and the scale-up of these processes have seen increased interest as the industrial application of nanoparticles continues to grow. Their feasibility from an environmental point of view can be assessed by means of life cycle analysis (LCA). In this work two methods of metallic nanoparticle production, by evaporation/condensation of metal using electrical arc discharge reactors or by chemical reduction of metal salts in aqueous solutions or dry solid/solid mixtures, are evaluated based on the life cycle indicators. The evaporation of metal using electrical discharge reactors is a method studied in the European Commission 7th Framework Program “BUONAPART-E.” The environmental impact of the two different nanoparticle production approaches is here compared for four metals: copper, silver, zinc and aluminum. The chemical routes of producing nanoparticles require several different chemicals and reactions, while the electrical discharge routes use electricity to evaporate metal in a reactor under inert atmosphere. The nanoparticle production processes were modeled using “SimaPro” LCA software. Data for both the chemical production routes and the arc routes were taken from the literature. The choice of the best route for the production of each metal is strongly dependent on the final yield of the metallic nanoparticles. The yields for the chemical processes are not reported in the open literature, and therefore the comparisons have to be made with varying yields. At similar yields the electrical process has in general a lower environmental footprint than the studied chemical routes. The step or chemical with the greatest environmental impact varies significantly depending on process and metal being studied.