Optimization of integrated electrochemical oxidation and biodegradation (EO-BD) for Kraft lignin

BACKGROUND: The effluent from pulp and paper mills is difficult to treat effectively via conventional biochemical processes due to the high concentration of lignin and its derivatives. In this study, the integration of electrochemical oxidation and biodegradation (EO-BD) for Kraft lignin (KL) was proposed to potentially enhance the efficiency of the treatment. Typical anodes, titanium based antimony doped tin dioxide electrodes (Ti/Sb-SnO₂), were used in the pre-degradation of KL solution (1000 mg L^-1), followed by post-biodegradation using aerobic flora as inocula. Response surface methodology (RSM) was applied to optimize the EO-BD of KL. RESULTS: The optimum conditions obtained via RSM were: current density 3.68 mA cm^-2, electric quantity 14.49 kC and pH 9.0. Under these conditions, the maximum chemical oxygen demand (COD) removal rate and minimum specific energy consumption were predicted by the correlation developed to be 70.83% and 28.84 kWh kg^-1 COD, respectively, which agreed well with the experimental data. The results of gas chromatography-mass spectrometry (GC-MS) analysis indicated that KL was partially degraded by EO, which was beneficial to the subsequent biodegradation. CONCLUSION: This study validated the technical feasibility of adopting the EO-BD process to enhance KL degradation.