Carbon-based composites in advanced wastewater treatment: A life cycle assessment of TiO2 and GO-TiO2 solar photocatalysis

The increasing deterioration of freshwater bodies has prompted the development of legislation for priority substances (PSs) and contaminants of emerging concern (CECs). In parallel, advanced treatment processes have been investigated to remove these contaminants from wastewaters and the assessment of the potential impacts of some of these processes has been performed throughout their life cycle. In this paper, a comparative life cycle assessment of the solar heterogeneous photocatalysis treatment of secondary urban wastewater using a carbon-based composite (consisting of graphene oxide and titanium dioxide, GO-TiO2) or commercially available titanium dioxide material (TiO2–P25) as photocatalysts is conducted. It was found that the solar/GO-TiO2 treatment, which implements GO-TiO2 synthesized by the liquid phase deposition method, has higher potential impacts than the solar/TiO2 option in all categories assessed under the present conditions due to the high potential impacts of the GO-TiO2 synthesis method (i.e., using ammonium hexafluorotitanate and boric acid as precursors to obtain TiO2 in the composite). A composite prepared with TiO2–P25 and GO via a mechanical process seems to be a better solution to reduce all potential environmental impacts, but the resulting photocatalytic activity should also be considered before reaching a decision.