Enhancing Salt‐Resistance in Agricultural Superabsorbent Polymers: First Incorporation of Silica Gel Into Sodium Alginate‐g‐Poly(Sodium Acrylate‐co‐Acrylamide) Composite

A novel superabsorbent composite based on sodium alginate (SA), acrylic acid (AA), acrylamide (AM), and silica gel (SG) was synthesized via free‐radical solution polymerization. The first incorporation of SG into an alginate‐based system was systematically optimized using single‐factor experiments and an orthogonal array design. Under optimal conditions (AA 10 g, AM 2 g, MBA 0.15 g, SG 4 wt%, neutralization degree 75%, initiator 0.5 wt%, reaction temperature 70°C), the composite achieved swelling capacities of 920.1 ± 15.2 g/g in deionized water and 135.2 ± 3.8 g/g in 0.9 wt% NaCl solution. The incorporation of 4 wt% SG enhanced the saline water absorption by approximately 14.6% compared to the SG‐free counterpart. FTIR provided supportive evidence for hydrogen bonding between SG silanol groups and polymer chains. BET analysis confirmed increased porosity upon SG addition (surface area increased from 12.4 to 38.7 m 2 /g). A 30‐day soil burial test revealed a mass loss of 42.3%, indicating partial biodegradability under soil burial conditions. The composite exhibits promising water retention and salt‐resistant swelling, suggesting potential applications in agriculture and hygiene products where moderate biodegradability is acceptable. Further long‐term degradation studies are recommended.