Visible　light　photoreduction　of　toxic　Cr(VI)　over　TiO2　was　achieved　through　surface　modification　with　small　molecular　weight　organic　acids　(SOAs)　as　sacrificial　organics.　Because　neat　anatase　TiO2　is　active　only　under　UV　light　irradiation　(lambda　＜　387　nm),　no　photoreduction　of　Cr(VI)　was　observed　in　TiO2　dispersions　being　irradiated　with　visible　light　(lambda　＞　420　nm).　However,　when　a　small　amount　of　colorless　SOAs　was　added　into　the　TiO2　dispersion,　a　charge-transfer-complex　(CTC)　was　formed　between　TiO2　and　SOA,　which　was　sensitive　to　visible　light　irradiation　and　induced　the　photo-oxidation　of　SOA　and　photoreduction　of　Cr(VI).　It　was　observed　that　about　95%　of　added　Cr(VI)　(0.2　mmol　L-1)　was　removed　in　the　visible　light-illuminated　TiO2　(1.0　g　L-1)　dispersions　at　pH　3.0　within　2　h　by　adding　0.2　mmol　L-1　tartaric　acid　as　a　SOA.　The　SOA-induced　photoreduction　of　Cr(VI)　proceeded　via　a　CTC-mediated　path,　being　governed　by　chemical　structures　of　sacrificial　SOAs.　A　higher　energy　of　the　highest　occupied　molecular　orbital　or　lower　ionization　potential　of　SOAs　is　favorable　to　electron　transfer　within　TiO2-SOA　complex,　thereby　accelerating　the　photoreduction　of　Cr(VI).　The　Cr(VI)　removal　was　further　enhanced　by　increasing　SOA　concentration　and/or　decreasing　solution　pH.　(C)　2010　Elsevier　B.V.　All　rights　reserved.