Controllable Synthesis of Biodegradable Lignin‐Grafted polyAA / AM Microspheres for Soil Remediation

ABSTRACT Biodegradable water‐absorbing resins hold significant potential in mitigating soil‐related issues and advancing sustainable agriculture. Lignin, being abundant, eco‐friendly, and biodegradable, possesses multiple active functional groups in its molecular structure, making it an ideal raw material for developing high‐performance superabsorbent resins. To further improve water absorption efficiency, dispersibility, and soil compatibility, lignin‐based polyacrylamide superabsorbent resin microspheres were successfully synthesized via suspension polymerization. The resulting microspheres exhibited an average particle size (D50) of 13.64 μm, with absorption capacities of 664 g/g in distilled water and 188 g/g in 0.09% NaCl solution. Moreover, the adsorption capacities for heavy metal ions‐Cu 2+ , Cd 2+ , and Ni 2+ ‐were measured at 146.4, 97.99, and 89.09 mg/g, respectively. After three absorption‐desorption cycles, the saturated liquid absorption capacity remained at 68% of its initial value. Treatment of soil with the resin microspheres for 30 days resulted in a volume expansion from 400 to 490 mL, representing a 22.5% increase. The resin also demonstrated favorable biodegradability in soil, with a degradation rate of 47.2% over 28 days, thereby minimizing the risk of long‐term secondary contamination. These findings indicate that lignin‐poly (acrylic acid‐acrylamide) superabsorbent resin microspheres hold considerable promise for applications in modern sustainable agriculture.