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

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.