Life cycle indicator comparison of copper, silver and zinc nanoparticle production through electric arc/spark 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 nanoparticles production, by evaporation/condensation of metal using electrical arc/spark discharge reactors or by chemical reduction of metal salts in aqueous solutions, 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 three metals: copper, silver and zinc.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/spark routes was taken from 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 can vary significantly depending on process and metal being studied. For copper and zinc nanoparticle production the main source of CO2 emissions is the production of electricity or the production of the reducing agent, for the electrical discharge and chemical methods, respectively. For silver particles it is the production of pure silver in both cases.