Purification Processes\nfor Generating Cationic Lignin-Acrylamide\nPolymers

Purification is an essential step in many polymerization\nprocesses\nfor fabricating highly pure polymers. This study considered various\npurification methods for purifying the product of lignin, acrylamide\n(AM), and diallyl dimethylammonium chloride (DADMAC) copolymerization\nreactions at a laboratory scale. The charge density, yield, molecular\nweight, and solubility analyses confirmed that ethanol extraction\nand membrane filtration were the most effective processes for producing\nlignin-p(AM)-p(DADMAC). The <sup>1</sup>H NMR analysis revealed that\nthe membrane dialysis effectively removed unreacted AM and DADMAC\nmonomers from the reaction medium. The produced samples of the ethanol-extraction\nand dialysis processes had higher solubility and yield compared to\nthe product of the acidification process. Thermogravimetric studies\nconfirmed that the ethanol-extracted and dialyzed samples had a degradation\ntemperature (220 °C) higher than that of the acidified samples\n(160 °C). The rheological studies confirmed that the viscosities\nof the polymer solutions were influenced more by the solubility than\nby the molecular weight of the generated polymers within the molecular\nweight range examined in this study. The flocculation studies confirmed\nthat the ethanol-extracted and dialyzed polymers were more effective\nflocculants than the acidified samples for the particles of a kaolinite\nsuspension. Based on the above results, membrane filtration with a\nlarger pore size could be an environmentally friendly method for effectively\npurifying lignin-p(AM)-p(DADMAC).