▎ 摘　　要

The removing of hexavalent chromium has received extensive attention. In this work, graphene oxide (GO) was modified by humic acid (HA), then the GO-HA composites were prepared using green methods. The sp(2) carbon system was increased markedly and the reduced GO (rGO) that with rough and porous structure was formed in GO-HA composites. GO-HA has a band gap of 2.73 eV and owned an adequate aqueous dispersion. The modification of HA enhanced the performance of GO for Cr(VI) photoreduction at environmental relevant pH. GO-HA could trigger the separation of photo-generated electrons/holes under irradiation with the incident wavelength lower than 455 nm. Wherein rGO sheets, as an electron carrier, allowed photo-excited electrons quickly transferred to Cr(VI) and caused the reduction. The center dot O-2(-) that from the excitation of HA with irradiation also could reduce Cr(VI). Meanwhile, photo-generated holes have ability to combine HA and water molecules. Hence, the depletion of photo-generated electrons and holes would enhance its catalytic ability via the separation of charge carriers. These data indicate that the modification with organic molecules is a convenient strategy to obtain GO-based catalysts, which may pave a way to new developments of the GO-based materials.