BiOI photocatalysts with tunable morphologies from 2D laminar structure to 3D hierarchitectures have been prepared by a hydrothermal or solvothermal way using four kinds of solvents: water, ethanol, ethylene glycol and glycerol (these solvents are abbreviated as H2O, ETH, EG, and GLY hereinafter). The viscosity of the solvents plays a key role to the evolution on the morphologies and performances of BiOI samples. The BiOI synthesized in GLY exhibits excellent visible-light photocatalytic performances toward As(III), which is highly increased to that of N-TiO2. Further investigation reveals that the surface characteristics of BiOI nanosheets, the thickness of the nanosheets, and the way by which they integrate together play important roles in photocatalytic reaction process. The main active species is detected as O-center dot(2)-. Considering about the practical use, the BiOI synthesized in GLY is also work under illumination of natural sunlight, and total arsenic concentration can be decreased even below 10 mu g/L from 1 mg/L As(III) aqueous solution within 3 h, which has reached the drinking water standard (0.01 mg/L). Moreover, its stable performance also shows its great potential application value in the wastewater treatment. (C) 2013 Elsevier B.V. All rights reserved.