Life Cycle Impact Assessment of Iron Oxide (Fe3O4/γ-Fe2O3) Nanoparticle Synthesis Routes

The synthesis of superparamagnetic iron oxide nanoparticles (FeOx-NPs) has rapidly developed over the past decade due to their wide-ranging applications in research and technology. However, at present there exists very limited knowledge about the environmental impacts of the various input materials and the energy required for different FeOx-NP synthesis approaches. In this study, we used cradle-to-gate life cycle assessment (LCA) to analyze and compare the environmental impacts of FeOx-NPs produced via seven common synthesis routes. Four different functional units (i.e., mass, mean particle size, specific surface area, and saturation magnetization) were used to normalize the environmental impacts and evaluate the corresponding changes. Overall, physical and biological synthesis routes exhibited high environmental impacts due to their higher input material and energy requirements. Interestingly, biological syntheses had the highest environmental impacts due to their reliance on bacterial culture media. All of the chemical synthesis routes had lower environmental impacts except the thermal decomposition method, which had higher environmental impacts due its use of non-polar organic solvents during synthesis. The lab-scale LCA inventory data and analysis presented here addresses the existing data gaps and helps guide future research for FeOx-NP synthesis under industrial conditions. The information generated by this effort aids in the identification of environmentally friendly and sustainable production pathways for FeOx-NPs.