电化学氧化与生物法联合降解木质素

为开发经济和环境安全的木质素降解技术,采用ECO-BD(electrochemical oxidation and biodegradation, 电化学氧化与生物降解)工艺联合降解木质素,以Ti/Sn-SbO₂电极为阳极,无水Na₂SO₄为电解质,在恒电流条件下,应用响应面法得到ECO-BD联合降解木质素的最佳电化学条件:电流密度为8.64 mA/cm2,电量为20.00 kC,c(Na₂SO₄)为0.15 mol/L. 在该条件下,ECO-BD对1 g/L木质素溶液的COD_Cr去除率为59.31%,单位能耗为28.87 kW·h/kg. 采用傅里叶变换红外光谱及气相色谱-质谱对ECO-BD联合降解木质素过程中的降解产物进行分析发现,ECO能有效地破坏木质素的酚羟基结构及发色基团,木质素多聚体的醚键先被断裂形成单体,随后芳环结构被氧化生成醌类化合物,再进一步开环和裂解生成小分子酸类或被矿化成CO₂和H₂O；电解后溶液生化可降解性由0.20~0.25升至0.31~0.37,缩短了后续生物降解时间. 研究显示,ECO能先行打断抵御微生物攻击的木质素顽固键合结构,有利于后续BD消除残余碎片,实现木质素的ECO-BD高效低成本降解. 

Combined Degradation of Lignin by Electrochemical Oxidation and Biodegradation (ECO-BD)

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.