Abstract: In order to improve the molecular weight and application of lignin, trimethyl quaternary ammonium salt of lignin-sodium alginate polyampholyte (QL-SA) was prepared with trimethyl quaternary ammonium salt of lignin (QL) and sodium alginate (SA) by crosslinking, and glutaraldehyde was selected as the cross linker in present study. Based on the nitrogen content and flocculate ability on the acid black ATT, the reaction conditions were optimized. The QL-SA with high quality could be obtained as the QL and SA with mass ratio 2:1 were crosslinked by 4% glutaraldehyde at 70℃ for 4 h. For the QL-SA obtained under this optimum condition, the decolorization rate of acid black ATT was 90.08%. The solubility and amphoteric polymer characteristics, ie, isoelectric point, was also investigated. Its structure was analyzed by FT-IR, TG and DSC. The results revealed that QL and SA were grafted successfully, the nitrogen content reduced from 4.21% to 3.69%, and the thermal stability of QL-SA was superior to that of QL and SA. Its isoelectric point was 5.76, and ranged from 4 to 10. The QL-SA was an amphoteric compound.

Key words: trimethyl quaternary qmmonium salt of lignin(QL), sodium alginate(SA), polyampholyte, crosslinking reaction