Electrochemical oxidation of lignin by two typical electrodes: Ti/Sb-SnO2 and Ti/PbO2

The titanium based antimony doped tin dioxide electrode (Ti/Sb-SnO2) and titanium based lead dioxide electrode (Ti/PbO2) were used in the pre-degradation of a sodium lignosulphonate solution (2000 ppm). The performances of these two electrodes were compared by evaluating the change of water quality parameters (COD, biodegradability) and UV-Vis absorption. The parameters that influence effectiveness and efficiency of the pretreatment were investigated, including applied current, passed electric charge, solution temperature, and supporting electrolyte. Moreover, IR spectra, and GC-MS analysis were used for products analysis in order to explore the degradation mechanism. Results showed that the electro-chemical oxidation is a promising approach for the pretreatment of lignin, and the aerobic or anaerobic biodegradability was enhanced significantly. Quinones and low-chain carboxylic acid were identified as important intermediate and main products, respectively. The oxidation effectiveness depends strongly on the electrode material. The Ti/Sb-SnO2 exhibited a better ability of UV-Vis absorption decrease and COD removal, while the Ti/PbO2 had a better capability to enhance biodegradability. Such differences could be interpreted by the theory of selective and nonselective oxidation. (C) 2014 Elsevier B.V. All rights reserved.