Life cycle assessment of a nanomaterial-based adsorbent developed on lab scale for cadmium removal: Comparison of the impacts of production, use and recycling

Abstract

Many nanoadsorbents are reported in the literature, exhibiting remarkable properties in the removal of low concentrations of toxic metals. However, their environmental performance has not yet been well studied. A life cycle assessment (LCA) was carried out for a previously reported nanomaterial-based adsorbent, silicate-titanate nanotubes chitosan beads (STNTs-Ch beads), used to remove cadmium from wastewater. The environmental impacts associated with the synthesis of the nanomaterial and the final adsorbent, including use and recycling, were evaluated. The hotspot of the process was the synthesis of the nanomaterial, mainly due to high electricity consumption, suggesting that energy use must be reduced in the scaling up. The chemicals used may become an environmental problem once electricity consumption in the process is optimised on a large-scale process. The environmental impacts associated with the synthesis and the use of the process were compared with granular activated carbon (produced on industrial scale), a resin based on titanium dioxide (pilot scale), and an adsorbent based on a residue after alginate extraction (laboratory scale). Granular activated carbon had the lowest impacts, suggesting again that optimisation of energy and chemicals should be prioritised in the production of emerging materials. • LCA was carried out for a nanomaterial-based adsorbent for treating Cd in water. • The hotspot of the process was the synthesis of the nanomaterial STNTs. • Reduced and fossil-free electricity will significantly improve the carbon footprint. • The amounts of NaOH and TiO 2 may also be considered in scale-up. • Recycling the nanoadsorbent significantly reduced its environmental impacts.