Abstract: Abstract:Lignin is a complex, three-dimensional aromatic polymer which contributes to a significant value of COD, chromaticity and POP_S in wastewater of the pulp and paper-making industry. In order to develop an economically effective and environmentally friendly technology for lignin degradation, synergetic lignin degradation combining electrochemical oxidation (ECO) with biodegradation (BD) was proposed. Firstly, the electrochemical pretreatment of lignin solution was studied by galvanostatic electrolysis using Ti/Sb-SnO₂ as the anode and sodium sulphate as the electrolyte. Response Surface Methodology (RSM) was employed to optimize the ECO-BD process of lignin degradation. Current intensity of 8.64 mA/cm², electric quantity of 20.00 kC and concentration of Na₂SO₄ of 0.15 mol/L were taken as the optimum conditions. Under the optimum conditions, a COD_Cr removal rate of 59.31% and specific energy consumption (SEC) of 28.87 kW·h/kg were obtained for 1g/L lignin solution. Secondly, FTIR and GC-MS analysis showed that ECO can effectively degrade the structures of phenolic hydroxyl and chromophoric groups of lignin. Electro-oxidative conversion of lignin was initiated with the breaking of lignin polymer on account of ether linkage flouting into monomers, and was followed by their oxidation to quinones. Finally, quinones underwent opening of the aromatic rings to produce dicarboxylic acids, or were further mineralized to CO₂ and H₂O. After ECO, the biodegradability of lignin increased from 0.20-0.25 to 0.31-0.37. Therefore, the following bio-degradation time was significantly decreased. In conclusion, ECO can destroy the recalcitrant bonding structure of lignin to produce biodegradable intermediates. ECO-BD could be an economically effective and environmentally friendly method for lignin degradation.