Life cycle assessment of nanoadsorbents at early stage technological development

Increasing pressure to the environment due to human activities manifests the necessity of applying new approaches to determine the environmental impact of a new product before scale-up. Nanoadsorbents as an emerging product and a special application of nanomaterial play an important role in the control and removal of environmental pollutants. This application is still an emerging technology at the early stages of development. Hence, the heart of this study enables an environmental assessment of nanoadsorbents as an emerging product. In addition, the environmental impacts of synthesized adsorbents including cumulative energy demand, climate change, water use, human toxicity, and ecotoxicity are investigated by a stepwise procedure during their synthesis processes, regarding their potential to remove mercury from polluted water. Accordingly, characterization results showed that although the process of the functionalization of nanoadsorbents leads to the increase of the adsorption capacity of nanoadsorbents, it is also paired with a significant enhancement of negative environmental impacts. The results of t-test comparing the cradle-to-use life cycle impacts of studied impact categories for 1 kg Hg removal between MGO-NH-SH and Fe3O4@SiO-NH-SH estimated approximately 37, 34, 40, 31, and 26% more for climate change, water use, cumulative energy demand, human toxicity, and ecotoxicity, respectively for the latter. Hence, according to the results, Fe3O4@SiO-NH-SH revealed the larger environmental impacts from the same functional unit, 1 kg Hg removal, compared with MGO-NH-SH. Finally, not only does this study represents the LCA of two different kinds of mercury adsorbents, but it also provides a guideline for determining the environmental impacts of similar nanoadsorbents.