Lignin‐Based Microgels by Inverse Suspension Polymerization: Syntheses and Dye Removal

AbstractLignin, as a sustainable building block, has become popular in developing the hydrogel absorbents since the last two decades. Herein, lignosulfonate‐graft‐poly[acrylamide‐co‐(acrylic acid)], LS‐g‐P(AAm‐co‐AA) microgels are synthesized by inverse suspension, a well‐known and practical industrial process. Taking advantage of a chain transfer reaction with lignosulfonate (LS), no modification of lignin is therefore required. LS is confirmed to incorporate in the microgels as evidenced by elemental analysis, FTIR, DOSY 1H NMR, and XPS spectroscopies. Microgel particles with a high percent LS grafting are obtained by decreasing the monomer concentration in the disperse phase. Additionally, the LS‐g‐P(AAm‐co‐AA) microgels containing LS promote thermal stability and render the faster and stronger methylene blue (MB) adsorption. The adsorption kinetics and isotherms understudy indicate that the adsorption behavior of MB on the microgels follows the pseudo‐second order and Langmuir model. It is found that the LS‐g‐P(AAm‐co‐AA) microgels can take up MB with 154 mg g−1 of adsorption capacity. More importantly, the LS‐g‐P(AAm‐co‐AA) microgels can be degraded by laccase enzyme derived by fungi in nature.