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

Abstract

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.

Metals Production, CO2 Mineralization and LCA

“…Examples are silver NPs in hospital cotton (bed sheets and lab coats), gold NPs in solar energy collectors, nickel NPs for catalysts, zinc NPs as flame redardants in plastics like PP, or copper NPs in water giving a nanofluid with improved cooling performance. Besides the summary in [14], more details on LCA work were given in [29] and [31] with focuses on energy use and comparisons of conventional methods (wet chemistry) for metallic NP production, respectively. For the analysis of carbonation of Mg(OH) 2 with CO 2 in the BF top gas, where in parallel the CO/water shift reaction supplies CO 2 for subsequent mineralization, a simulation study was made using Aspen Plus (AspenTech, Bedford, MA, USA) (v.8.2 and later v.9.0).…”

The Advantages of Spark Discharge Generation for Manufacturing of Nanoparticles with Tailored Properties

“…The same is true for the inert carrier gas that is not consumed and that could be fully recycled. In addition, a life cycle analysis comparing nanoparticles produced by electrical discharge and chemical synthesis methods shows that the previous have a lower environmental impact, in most categories [24].…”

Energy Efficiency and Scalability of Metallic Nanoparticle Production Using Arc/Spark Discharge

“…For silver, however, it may be challenging to be competitive with conventional (wet chemistry) NP production, due to the high SEC for producing Ag NP with the arc or spark process. Nonetheless, the use of an arc or spark discharge system offers the opportunity of substituting for the use complex chemicals in wet routes, as we analysed and reported earlier [27]. The life cycle impact contributions for NP metal production using an arc discharge depends on SEC and consumption of carrier gas (in this study a 99.5% recycling efficiency is assumed), besides the life cycle impact for producing the input metal which is independent of the scale of NP production.…”

“…For silver, however, it may be challenging to be competitive with conventional (wet chemistry) NP production, due to the high SEC for producing Ag NP with the arc or spark process. Nonetheless, the use of an arc or spark discharge system offers the opportunity of substituting for the use complex chemicals in wet routes, as we analysed and reported earlier [27].…”

“…The environmental impact caused by production process infrastructure, however, was considered to be outside the scope of the current study. The life cycle impact of producing pure metal NPs using the arc and spark methods and comparing the life cycle impact with (wet) chemical or other more conventional methods of producing similar NPs was published earlier by Slotte et al [27].…”