Visible-light photocatalytic degradation of methyl orange over spherical activated carbon-supported and Er3+:YAlO3-doped TiO2 in a fluidized bed

BACKGROUNDPowdered photocatalyst by doping TiO2 with upconversion luminescence agents achieved visible light induced photocatalysis. However, slurry photocatalysts are difficult to recover from the treated liquor. In the present study, spherical activated carbon (SAC)-supported and Er3+:YAlO3-doped visible-light responsive photocatalyst (Er3+:YAlO3/TiO2-SAC) was synthesized and characterized. The photocatalytic performance of photocatalyst was examined for degradation of methyl orange (MO) in a liquid-solid fluidized bed photoreactor under visible-light irradiation. RESULTSTwo notable UV emission peaks at 320 and 360nm were observed for Er3+:YAlO3 by visible light excitation, which were assigned to the transition of (P3/2I15/2)-P-2-I-4 and (D5/2I11/2)-D-4-I-4, respectively. An optimum 8h photodecolorization efficiency of 65.3% was obtained from the fluidized bed with reaction rate constant 22.17mgL(-1)h(-1). The degradation rate first increased and then decreased with the increasing expansion ratio, and the optimum expansion ratio was found to be 130%. CONCLUSIONOptical characterization revealed that Er3+:YAlO3 could convert incident visible-light to UV, which can then be utilized by TiO2 for photocatalysis. The visible light generated by Er3+:YAlO3 emissions were not used by TiO2 because of its high band gap. The photocatalytic degradation of MO in the fluidized bed photoreactor followed the Langmuir-Hinshelwood kinetics model. (c) 2014 Society of Chemical Industry