Visible‐light photocatalytic degradation of methyl orange over spherical activated carbon‐supported and Er 3+ : YAlO 3 ‐doped TiO 2 in a fluidized bed

BACKGROUND Powdered photocatalyst by doping TiO 2 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 Er 3+ : YAlO 3 ‐doped visible‐light responsive photocatalyst (Er 3+ : YAlO 3 / TiO 2 ‐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. RESULTS Two notable UV emission peaks at 320 and 360 nm were observed for Er 3+ : YAlO 3 by visible light excitation, which were assigned to the transition of 2 P 3 /2 → 4 I 15 /2 and 4 D 5 /2 → 4 I 11 /2 , respectively. An optimum 8 h photodecolorization efficiency of 65.3% was obtained from the fluidized bed with reaction rate constant 22.17 mg L −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%. CONCLUSION Optical characterization revealed that Er 3+ : YAlO 3 could convert incident visible‐light to UV , which can then be utilized by TiO 2 for photocatalysis. The visible light generated by Er 3+ : YAlO 3 emissions were not used by TiO 2 because of its high band gap. The photocatalytic degradation of MO in the fluidized bed photoreactor followed the Langmuir–Hinshelwood kinetics model. © 2014 Society of Chemical Industry