Much more attentions were paid to the anatase TiO2 than rutile due to its higher photoactivety with a larger band gap. However, it is usually ignored that the relative narrow band gap of rutile TiO2 benefits to the increasing in the responsive wavelength range. In this work, spherical activated carbonsupported Er3+:Al2O3-doped rutile TiO2 (Er3+:Al2O3/TiO2-SAC) was synthesized by a sol-gel method using tetrabutyl titanate as titanium precursor, and erbium nitrate and aluminum nitrate as dopant sources. Long-wavelength visible light from a light-emitting diode source was upconverted to ultraviolet light and short-wavelength visible light by Er3+ dopant, which could then be absorbed by the synthesized photocatalyst that contained rutile TiO2. This resulted in higher photocatalytic activity of samples with rutile than those with anatase. A response surface methodology based on the central composite design model was used to determine the optimum synthesis conditions: Er concentration, 0.07 mol%oo; Al concentration, 0.08 mol%; and calcination temperature, 700 degrees C. The catalyst achieved a 90.0% removal efficiency for methyl orange (MO) with a reaction rate of 18.98 x 10(-3) min(-1) at an initial MO concentration of 500 mg L-1 in 2 h under visible-light irradiation. (C) 2015 Elsevier B.V. All rights reserved.