Using central composite experimental design to optimize the degradation of black liquor by Fenton reagent

Abstract We investigated the advanced oxidation of the black liquor effluent from the pulp and paper industry using the dark Fenton reaction in a lab-scale experiment based on central composite experimental statistical design. The independent variables considered for the optimization of the oxidative process were temperature, H 2 O 2 and Fe(II) concentrations, for a black liquor with a chemical oxygen demand (COD) of 628 mg·L −1 O 2 at pH = 3. The response functions were the decrease in COD, aromatic content (UV 254 ) and lignin content (UV 280 ). The methodology lets us identify and statistically evaluate the effects and interactions of the study variables and their roles in the efficiency of the treatment process. In the optimization, the correlation coefficients for the model (R 2 ) were 0.954 for COD, 0.936 for UV 254 and 0.945 for UV 280 . Optimum reaction conditions at pH = 3 and temperature = 298 K were [H 2 O 2 ] = 44.1 mM and [Fe(II)] = 4.655 mM. At these optimal conditions, the molar ratio H 2 O 2 /Fe(II) was 9.5. Under these conditions, 90 min of treatment resulted in a 94.8% decrease in COD, an 80.9% decrease in UV 254 and an 85.6% decrease in UV 280 .

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