BACKGROUND: The plasmon-induced photocatalytic reduction of bromate (BrO3-) was investigated in visible-light irradiated Au-Ag-AgI/Al2O3 suspension. The Br-3(-) reduction process was studied in detail. RESULTS: The catalyst was found to be highly effective for the reduction of Br-3(-) from pH 3 to 6. An enhancement of the electrical interaction between Br-3(-) and the positively charged surface of the photocatalyst favored adsorption and reduction of Br-3(-). Organic compounds such as ethanol could react as sacrificial electron donors with excited holes (h(+)) on the metal nanoparticles (NPs) to accelerate electron transfer, inhibiting the release of metal ions and the recombination of h(+) and electrons, hence promoting photocatalytic reduction of Br-3(-). Electron quenching and cyclic voltammetry studies under a variety of experimental conditions verified that Br-3(-) trapped conduction band electrons of AgI from the excited metal NPs were reduced, competing with O-2. CONCLUSION: The photocatalyst Au-Ag-AgI/Al2O3 exhibited particularly good reduction of Br-3(-) under visible-light irradiation. The Br-3(-) reduction was highly favored at acidic condition due to the greater adsorption of Br-3(-) onto the catalyst. This finding indicates that this visible-light-driven catalyst could be applied to the reduction of some oxidative pollutants or even simultaneous removal of both oxidative and reductive pollutants. (C) 2013 Society of Chemical Industry