Solar-Assisted Photocatalytic Degradation of Emerging Pollutants and Disinfection by TiO2/Reduced Graphene Oxide Composites in Water and Wastewater

Photocatalytic water treatment represents a promising strategy for the simultaneous removal of chemical and biological contaminants, although the development of efficient, stable, and reusable photocatalysts remains a challenge. In this work, nanosized TiO2–reduced graphene oxide (rGO) composites containing 1 and 5 wt.% rGO were prepared by mechanical mixing and evaluated for water decontamination under artificial and natural solar irradiation. The photocatalytic performance was first assessed through methylene blue degradation and subsequently for the simultaneous removal of organic microcontaminants (sulfamethoxazole, trimethoprim, and imidacloprid) and Escherichia coli inactivation in isotonic water (IW) and urban wastewater secondary effluent (UWW). Different photocatalyst concentrations (0–1000 mg L−1) were investigated and compared with commercial TiO2-P25. The TiO2/rGO composites exhibited effective dye degradation, pollutant removal, and microbial inactivation. The best performance was achieved with TiO2/rGO 5 wt.% at 500 mg L−1 in IW, enabling >80% removal of contaminants and >5 log E. coli inactivation within 15 min of solar treatment. Similar trends were observed in UWW, although with slower degradation kinetics. Furthermore, the composites maintained their photocatalytic activity over ten consecutive reuse cycles under natural sunlight and showed no ecotoxic effects toward Aliivibrio fischeri. These results demonstrate the potential of TiO2/rGO nanocomposites as efficient and reusable photocatalysts for sustainable water treatment applications.