In this study, cobalt oxide doped nanoporous activated carbon (Co-NPAC) was synthesized and used as a heterogeneous catalyst for the Fenton oxidation of organic dye chemicals used in tannery process. The nanoporous activated carbon (NPAC) was prepared from rice husk by precarbonization followed by chemical activation at elevated temperature (600 degrees C). The cobalt oxide was impregnated onto NPAC and characterized for UV-visible, Fluorescence spectroscopy, FT-IF, HR-TEM, XRD, BET surface area and XPS analyses. The hydroxyl radical generation potential of Co-NPAC from hydrogen peroxide decomposition was identified (lambda(exi) 320 nm:), lambda(emi), 450 nm) by Excitation Emission Spectra (EES) analysis. The conditions for the degradation of tannery dyeing wastewater such as, Co-NPAC dose, concentration of H2O2, and temperature were optimized in heterogeneous Fenton oxidation process and the maximum percentage of COD removal was found to be 77%. The treatment of dyes in wastewater was confirmed through UV-Visible spectra, EES and FT-IR spectra analyses. (C) 2015 Elsevier Inc. All rights reserved.