Palladium metal oxide/hydroxide clustered cobalt oxide co-loading on acid treated TiO2 nanorods for degradation of organic pollutants and Salmonella typhimurium inactivation under simulated solar light

Abstract

Here, metal oxides/hydroxide (MO = (PdO)n·[Pd(OH)2]m, Co(OH)2, and (PdO)n·[Pd(OH)2]m/CoO, n > m) clusters were successfully co-loaded on the surface of acid-treated molten salt fluxed TiO2 nanorods (ATO-NRs) via conventional wet impregnation. The synergistic effect of palladium oxide/palladium hydroxide and cobalt oxide [((PdO)n·[Pd(OH)2]m/CoO)] co-loading on ATO-NR demonstrated by the photocatalytic degradation of Orange II dye, bisphenol A and S. typhimurium inactivation under mimicked and unfiltered solar light (Xe arc lamp) radiation. Optimum [((PdO)n·[Pd(OH)2]m/CoO)] co-loaded ATO-NRs exhibited significantly higher degradation efficiency (Orange II (91%) and BPA (97%) within 30 min of treatment) over (PdO)n·[Pd(OH)2]m (n > m) and CoO/ATO-NRs under Xe arc lamp light radiation. Also, optimal sample showed higher inactivation efficiency for S. typhimurium than (PdO)n·[Pd(OH)2]m (n > m)/ATO and CoO/ATO-NRs under UVA light radiation, however, the photocatalytic mechanisms for S. typhimurium inactivation was different than the BPA. Photoelectrochemical analyses demonstrated that the significantly accelerated charge-transfer process in metal oxides/hydroxide cluster [(PdO)n·[Pd(OH)2]m/CoO] co-loaded ATO-NRs leading to higher degradation efficiency than other studied samples. Radical trapping supports h+ and O2− as major reactive species, with OH playing a secondary role in Orange II and BPA degradation. Cell membrane interruption by reactive oxygen species (ROS) and reactions of photocatalyst with the –NH and –COOH group of protein and metalloproteins, nucleic acid in bacterial cells could be the main cause in S. typhimurium disinfection. Plausible charge transport pathways were proposed for photocatalytic degradation of organic pollutants and bacterial inactivation over the (PdO)n·[Pd(OH)2]m/CoO/ATO-NR’s.