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　O2-.　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　10μg/L　from　1mg/L　As(III)　aqueous　solution　within　3h,　which　has　reached　the　drinking　water　standard　(0.01mg/L).　Moreover,　its　stable　performance　also　shows　its　great　potential　application　value　in　the　wastewater　treatment.　©　2013　Elsevier　B.V.