Towards net-zero adsorbents: a multi-factor selection approach considering performance, life cycle assessment, and end-of-life scenarios
摘要
Activated carbon (AC) is a highly versatile adsorbent widely used in water and wastewater treatment due to its strong adsorption capabilities. However, conventional coal-derived AC has raised significant environmental concerns, necessitating the development of more sustainable alternatives such as pine-bark-derived adsorbents (PBAs). This study proposes a multi-criteria selection framework that integrates conventional physical and adsorption capacity-based evaluation with environmental sustainability considerations. By combining these criteria, the framework enabled the identification of adsorbents that offer optimal performance while minimizing their environmental impacts. Of the evaluated PBAs, that dual activation of both NaOH and HCl (PB-NH) was found to be the most effective option, with superior adsorption capacity and a lower environmental footprint. Life cycle assessment (LCA) was conducted using both mass-based and adsorption capacity-based functional units to comprehensively evaluate the sustainability of the PBAs. In addition to conventional midpoint impact categories, this study quantified the cumulative energy demand and endpoint impacts. This study also critically assessed the environmental impacts of AC activation using various physical and chemical strategies to benchmark PB-NH against alternative adsorbents, while a prospective scale-up LCA framework was employed to investigate the optimization of AC production at an industrial scale. Finally, end-of-life assessment was employed to determine the extent to which emissions can be mitigated using different disposal methods for the adsorbent. By combining experimental analysis with LCA modeling, this study provides a systematic and quantifiable approach for the development of sustainable adsorbents.