Surfactant-assisted synthesis of Mo-doped TiO2/FAC (fly ash cenosphere) for degradation of methylene blue dye under visible light irradiation

Methylene blue (MB) is extensively used in the textile industry; meanwhile, it is also one of carcinogenic and mutagenic pollutants. The removal of MB from wastewater by photocatalytic decomposition under visible light irradiation is a very important method. In this work, a photocatalyst of Mo-doped TiO 2 coated on fly ash cenosphere (CTAB-Mo-TiO 2 /FAC) was prepared by a sol-gel method and modified by hexadecyl trimethyl ammonium bromide (CTAB). Compared to TiO 2 /FAC and Mo-TiO 2 /FAC (without CTAB), it was featured by low bandgap and strong light absorption ability. More importantly, the light absorption range broadened from 200 to 400 nm to 200–800 nm, which could absorb visible light . Besides, after adding CTAB, the Mo 6+ could more easily dope into the TiO 2 lattice and cause crystal distortion, which exposed more oxygen vacancies . Oxygen vacancies could generate abundant reactive radicals to enhance the photocatalytic activity . At CTAB-Mo-TiO 2 /FAC dosage of 2 g/L, 99.75% of MB was removed in an initial MB concentration of 0.03 mmol/L with a pH of 7.0 under visible light irradiation of 60 min, whereas that of Mo-TiO 2 /FAC and TiO 2 /FAC was only 42 % and 24 %, respectively. The photodynamic parameter of CTAB-Mo-TiO 2 /FAC (0.066 min −1 ) is about 3 times of Mo-TiO 2 /FAC (0.023 min −1 ), 8.3 times of TiO 2 /FAC (0.008 min −1 ).