Decolorization of molasses-based distillery wastewater by means of pulse electro-Fenton process

The decolorization of actual molasses wastewater using the electro-Fenton (EF) process was investigated. The optimization of decolorization was performed by means of a Box-Behnken design (BBD), with the operating parameters studied being the applied voltage, H2O2 dosage and reaction time. The results showed that the color removal efficiency reached 88.50% under the optimal conditions, in which 2.86 V, 15.8% H2O2/wastewater ratio and 90.7 min reaction time were applied. The pulse electro-Fenton (PEF) process using the applied voltage and reaction time in the obtained optimal condition was performed afterward. The effects of pulse frequency, pulse duty cycle, electrode distance, H2O2/wastewater ratio and H2O2 stepwise addition were studied. From the results, under the optimal conditions of 2.5 kHz pulse frequency, 25% pulse duty cycle, 2 cm electrode distance and 15.8% H2O2/wastewater ratio, the color and COD removal efficiencies reached 89.59% and 40.71%, respectively. Under these conditions, the PEF process could reduce the energy consumption by at least 75% compared with the regular EF process. Additionally, compared with stepwise addition, the single step addition of H2O2 was more effective in color removal.