Optimization and Interpretation of Fenton and UV/Fenton Processes for Degradation of Syringyl Lignin

Abstract

The performances of syringyl lignin degradation by using Fenton and UV/Fenton processes were investigated in a self-designed cylindrical reactor. Many factors including pH, dosage of H2O2, concentration of Fe2+ initial concentration of syringyl lignin, reaction time and UV irradiation were optimized to reach the removal efficiency of syringyl lignin up to 87.5%. Specifically the optimum reactor time was 60 min, dosage of H2O2 was two times of its theoretical quantity and molar ratio of [Fe2+]/[H2O2] was 1:50 at pH 3. Furthermore, introducing UV-light into the Fenton system significantly improved the decomposition of syringyl lignin with the removal efficiency of 100% in first 30 min. In addition, the degradation mechanism of syringyl lignin by Fenton process was discussed in detail by using UV-visible spectroscopyand TOC analysis. It was found that syringyl lignin was oxidized by electron transfer of complex intermediates which contained high valence iron in homogeneous Fenton system.