The photocatalytic degradation of a cyanobacterial toxin, microcystin-LA (MC-LA), was studied in aqueous solutions under both simulated solar light and visible light irradiation. Neat TiO2 and carbon-based TiO2 materials, prepared with carbon nanotubes (CNT) or graphene oxide (GO), were compared. The highest photocatalytic activity was obtained with a GO-TiO2 composite comprising 4 wt.% of carbon content (GO-TiO2-4). Complete conversion of MC-LA was achieved under solar light irradiation in 5 min. GO-TiO2-4 was also active under visible light illumination, with 88% of MC-LA removal in 2 h.The high photocatalytic activity of GO-TiO2-4 was attributed to the optimal assembly and interfacial coupling between the TiO2 nanoparticles and the GO sheets that can effectively inhibit electron/hole recombination. Reaction intermediates of MC-LA photocatalytic degradation were also identified by LC/Q-TOF and LC/MS/MS, most of them resulting from the attack of hydroxyl radicals to the MC-LA molecule under solar light irradiation. (C) 2015 Elsevier B.V. All rights reserved.