A techno-economic approach to guide the selection of flow recyclable ionic liquids for nanoparticle synthesis

Abstract

Ionic liquids (ILs) are an important class of solvents that can be sustainable alternatives to conventional volatile organic solvents owing to their non-flammability, negligible vapor pressures, and high thermal and chemical stabilities. While several advantages to employing ILs as reaction solvents in colloidal inorganic nanoparticle syntheses have been demonstrated, their significantly higher purchase costs compared to traditional organic solvents creates a large barrier in utilizing them at scale. However, a unique characteristic of ILs is their potential to be recycled and reused in subsequent nanoparticle reactions, which may offer a potential cost offset by reducing the amount of solvent needed over the lifetime of a process. Herein, we report an experimentally guided, early-stage techno-economic analysis of a model platinum nanoparticle synthesis using a matrix of six different ILs as the reaction solvent. A continuous flow membrane separation system was used for the purification of the ILs using acidified water, allowing both water-immiscible and water-miscible ILs to be recycled. Unsurprisingly, each of these ILs have different bulk prices, however, this synthesis-driven economic analysis revealed the impact of the synthetic consequences of varying the IL solvent system, such as different nanoparticle yields and variable solvent recoveries based on their water miscibility.