Bimetallic FeO(x)–MO(x) Loaded TiO(2) (M = Cu, Co) Nanocomposite Photocatalysts for Complete Mineralization of Herbicides

[Image: see text] A series of monometallic and bimetallic cocatalyst(s), comprising FeO(x), CuO(x), CoO(x), FeO(x)–CuO(x), and FeO(x)–CoO(x) loaded TiO(2) catalysts prepared by the surface impregnation method, were investigated for the photocatalytic mineralization of the widely used four herbicides: 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). It was found that FeO(x)–CoO(x)/TiO(2) showed the highest photocatalytic efficiency toward mineralization of selected herbicides. FeO(x)–CoO(x)/TiO(2) achieves 92% TOC removal in 180 min, representing nearly three time activity of the benchmark PC50 TiO(2). From XPS analysis, FeOOH, CuO, and CoO were determined to be loaded onto the TiO(2) surface. The outstanding photocatalytic performance of the optimized FeO(x)–CoO(x)/TiO(2) sample for herbicides mineralization is due to an increased charge separation and enhanced hydroxyl radicals production monitored by diverse spectroscopies. Based on the proposed charge transfer mechanism, FeO(x)–CoO(x) cocatalyst species accelerate the transfer of photogenerated holes on TiO(2), thus facilitating hydroxyl radicals production.