Objective To improve the degradation and renewable capacities of superabsorbent polymers (SAPs), we developed a SAP using natural fucoidan, a polysaccharide rich in hydrophilic L-fucose units and sulfated groups as a feedstock.

Method A fucoidan biological SAP was synthesized via aqueous solution polymerization by grafting natural fucoidan onto acrylic acid (AA) monomers using ammonium persulfate (APS) as the initiator and N,N'-methylenebis(acrylamide) (MBA) as the crosslinker. The preparation process was optimized through single-factor experiments. The product was characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). A pot experiment was conducted to evaluate the effect of the SAP on cabbage growth.

Result The optimal mass ratio of fucoidan to AA was 1∶7.5, with a neutralization degree of 70%, and APS and MBA dosages of 3.0% and 0.2% of AA mass, respectively. The SEM analysis revealed a porous and loose network structure, while FTIR confirmed the formation of a graft copolymer of fucoidan and AA. The water absorption ratios of the SAP in deionized water and 9 g∙L⁻¹ NaCl solution were 420.9 and 63.8 g∙g⁻¹, respectively. After six cycles of absorption and drying, the water absorption ratio remained 70.8% of its initial value. Additionally, soil amended with 6 g∙kg⁻¹ SAP significantly enhanced Chinese cabbage growth, increasing total biomass by 105.5% and soil moisture content by 8.98% (P < 0.05).

Conclusion The fucoidan biological SAP exhibits excellent water absorption and reusability, significantly promoting plant growth when applied to soil. This study provides foundational data for the development and agricultural application of algal-derived SAP.