Synthesis and characterization of Co-NPAC and in situ hydroxyl radical generation for the oxidation of dye laden wastewater from the leather industry

Abstract

Cobalt oxide supported on nanoporous activated carbon (Co-NPAC) could be utilized as a catalyst in the heterogeneous Fenton oxidation of organic dye chemicals in tannery wastewater. The nanoporous activated carbon (NPAC) was prepared from rice husk by precarbonization followed by chemical activation at an elevated temperature. The Co-NPAC was characterized using UV-visible, fluorescence and FT-IR spectroscopy, as well as TEM, XRD, BET surface area and XPS analysis. The role of Co-NPAC in generating a hydroxyl radical from hydrogen peroxide was verified using Excitation Emission Spectroscopy (EES) with λ_excitation and λ_emission at 320 nm and 450 nm, respectively. The parameters for the treatment of dye laden tannery wastewater, such as the dosage of Co-NPAC, concentration of H₂O₂, pH and temperature were optimized. The refractory organic compounds were estimated in terms of chemical oxygen demand (COD), and in tannery wastewater these were eliminated during the heterogeneous Fenton-like process by 78%. The characterization of the wastewater before and after heterogeneous Fenton oxidation was performed using UV-Visible spectroscopy, EES, and FT-IR spectroscopy. The Co-NPAC retained its catalytic activity for up to 5 cycles with the sustained generation of hydroxyl radicals.