Synthesis of activated carbon-supported nano copper oxide and its inactivation performance on Escherichia coli in water

Copper oxide (CuO) is limited in inactivating bacteria due to the deficiency of active Cu(I) that can catalyze dissolved oxygen to produce reactive oxygen radicals. A novel sterilization agent was developed to inactivate Escherichia coli (E. coli) by loading nano copper oxide onto activated carbon (nCuO/AC) with a facile impregnation method. Surface techniques proved that CuO with a size of 100–200 nm was evenly loaded on AC surface, which improved its dispersity and reactivity. XPS analysis further revealed a cycle of surface-bonded Cu(II) to Cu(I) in the nCuO matrix that was driven by reducing groups on AC surface such as hydroxyl. The resultant Cu(I) activated dissolved oxygen to produce reactive oxygen species for bacterial inactivation. Superoxide radical (•O2–) was proved to be the primarily oxidative species during the sterilization process by EPR analysis and quenching investigations. Therefore, the nCuO/AC achieved an enhanced inactivation efficiency of 6.0 log CFU/mL as compared to those of 1.1 and 0.4 log CFU/mL by the nCuO and AC, respectively. The above sterilization reaction was pH-dependent and high inactivation efficiency could be achieved under neutral conditions. Additionally, the nCuO/AC exhibited excellent stability with an inactivation efficiency of 5.4 log CFU/mL after 4 cycles. Spent nCuO/AC showed great potential in renewability because it could inactivate 5.5 log CFU/mL of E. coli by peeling off residual nCuO on AC surface with sulfuric acid and reloading new nCuO through impregnation, with a regeneration rate up to 97.2 %. The above results demonstrated that nCuO/AC could be a promising bactericidal material for water treatment.