The removal of COD from bleaching effluents by Fenton's reagent: Effect of system parameters and kinetic study



Fenton's reagent was now being used as a post-treatment procedure to eliminate the intractable pollutants in the bleaching effluents from pulp mills. To establish cost-efficient operating conditions for the application of Fenton's reagent, the effects of operating conditions such as the dosages of H2O2, the molar ratio of [Fe2+]/[H2O2], the value of solution pH and the system temperature on the removal of COD were evaluated systematically. The results showed a suitable operating condition that yields 88.7% of COD removal was obtained at [H2O2] = 4COD(mM L−1), [Fe2+]/[H2O2] = 20:1, pH3, 90°C, reaction time 120 min. A kinetic study was carried out using a modified pseudo-first-order model. The results showed the COD removal for bleaching effluents by Fenton's reagent followed the first-order reaction kinetics, and the activation energy Ea was detected to be 1.68 kJ mol−1 based on the experiments performed at different temperatures. In addition, the results of GC/MS analysis showed organic pollutants in effluents were degraded into organic acids of lower molecular weight under the attack of hydroxyl radicals generated in Fenton's reaction. The results of biodegradability assay indicated the bio-toxic substances in the bleaching effluents were eliminated. © 2010 American Institute of Chemical Engineers Environ Prog, 2011