Study On Enzymatic Polymerization Of Lignin In Paper Mill Effluent

As one of the main pollution sources of water, pulping and papermaking effluent has become a serious problem in the development of papermaking industry. In this paper, a new method was developed. It was confirmed that coniferin could polymerize with lignin model compound. Coniferin could also used to treat wastewater of paper mill successfully.In this research work,β-O-4 type lignin model compound (i.e. guaiacyglycerol-β-guaiacyl ether) was synthesized with a modified method. The synthesis method of an important intermediate,i.e. 4-(α-bromoactyl)-guaiacol was improved.β-O-4 type lignin model compound (i.e. guaiacyglycerol-β-guaiacyl ether) yield reached 80%. The combination of infrared spectra, 1H-NMR analysis was used to identify the chemical structure of the product and related precursors.This paper adopted Stable isotope(13C) enrichment technique and combining with nuclear magnetic resonance (13C-) to discover the structure of lignin and its biosynthesis mechanism. First, we synthesized coniferins-[α-13C] which are lignin precursors: The structure was confirmed by its melting point, NMR analysis and FT-IR spectra. It was found that acetylated Glucoferulic acid as intermediate could react with pyridine solvent to form a relative stable salt because of alkaline characteristic of pyridine.The lignin model compound of guaiacylglycerol-β-guaiacyl ether was treated with coniferin catalyzed by laccase. The reaction products were analyzed by 13C-NMR, FT-IR and GPC. The formation mechanism of the products structure was also explored. It was found number average molecular weight (Mn) was increased from 420 to 3200~8670 and the main structures wereβ-O-4, coniferyl alcohol etc. There were some minor substructures such as vanillin, phenylpropane units withα-methylene. It was proved that coniferin could polymerize with lignin model and become macromolecule products. As a result the lignin can be removed though precipitate and flocculation.The results showed that both the concentration of lignin and chroma were reduced significant. The concentration of lignin decreased from 0.73g/L to 0.078g/L and the chroma from 500 to 18.