Improvement in efficiency of lignin degradation by Fenton reaction using synergistic catalytic action

Lignin is a complex aromatic compound and a by-product from the wood pulping process. We used a central composite design to assess the efficiency of synergistic catalysts (Fe-0, Fe2+ and Fe3+) and H2O2 in the Fenton process for removal of lignin, aromatic compounds, and chemical oxygen demand (COD) from lignin solution. Results showed that the Fe-0 and H2O2 concentration were the most significant variables in lignin degradation by Fenton reaction, while Fe2+ and Fe3+ concentration were the next most important variables. The highest removal efficiencies were obtained with concentration levels of 7.61 mg/L Fe-0, 9.89 mg/L Fe2+, 14.27 mg/L Fe3+, and 376.88 mg/L H2O2 at pH 3.0 and 35 degrees C. Under these optimal conditions, the efficiencies of removal of lignin, aromatic compounds, and COD were 98.45%, 82.63%, and 100%, respectively, while the removal rates of lignin and aromatic compounds were 23.73 mg/L/h and 27.75 mg/L/h, respectively. The optimization results revealed that using synergistic catalysts in the Fenton reaction was more effective in treating wastewater and resulted in decreased cost and time. (C) 2015 Elsevier B.V. All rights reserved.