The photocatalytic interaction of Cr(VI) ions and phenol on polymer-modified TiO2 under visible light irradiation

To investigate the interaction of Cr(VI) and phenol in the photocatalytic process, the photocatalytic reaction of the mixed solution of these two pollutants was carried out using poly(fluorene-co-thiophene) modified TiO2 photocatalyst and visible light. In this mixed system, the removal efficiency in the presence of Cr(VI) and phenol were higher than that produced by individual systems, indicating a synergetic effect between the reduction of Cr(VI) and degradation of phenol. In the mixed system, Cr(VI) ions were reduced by the photo-generated electrons, and phenol was oxidized by photo-generated holes. In the presence of Cr(VI) ions, both the photocatalytic degradation and mineralization efficiency of phenol were promoted, but the promoting role was not the same. There was an optimum value of phenol/Cr(VI) molar ratio (1: 1) in the degradation process. If the ratio was less than 1 : 1, the promoting effect decreased slowly but was still fairly distinct. The mineralization efficiency of phenol increased gradually with the increasing concentration of Cr(VI) ions, but when phenol/Cr(VI) was less than 1 : 1, the rate of increase became slower.