Techno-Economic Analysis of Recycled Ionic Liquid Solvent Used in a Model Colloidal Platinum Nanoparticle Synthesis

Ionic liquids have garnered significant attention over the past 20 years as alternatives to conventional volatile organic solvents because they are non-flammable, have negligible vapor pressures, possess high thermal and chemical stabilities, and can potentially be recycled. A more recent use of ionic liquids is their application as a solvent in the synthesis of colloidal inorganic nanoparticles; however, a major challenge in the adoption of ionic liquids is that they are generally more expensive than their traditional organic solvent counterparts. Herein, we provide insight into how recycling an ionic liquid solvent affects the product characteristics in a model colloidal platinum nanoparticle synthesis, the structure of the ionic liquid through each recycle, and the overall cost of nanoparticle fabrication using a techno-economic analysis. Using a standard ionic liquid, 1-butyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide (BMIM-NTf₂), as the solvent for a Pt nanoparticle synthesis, we demonstrate that the ionic liquid can be recovered and reused through multiple successive reactions following the initial reaction with virgin, or as-purchased, ionic liquid. The use of recycled ionic liquid does not cause any degradation in the product quality or change in nanoparticle morphology. Techno-economic analysis of this synthesis method revealed that, through ionic liquid recycling, nanoparticle preparation using BMIM-NTf₂ can achieve a cost that is not only competitive but also potentially lower than that of the conventional organic solvent, 1-octadecene.