Salt-Resistant Swelling Behavior and Methylene Blue Adsorption Performance of Chitosan-Modified Poly(acrylic acid-acrylamide-sodium styrene sulfonate) Superabsorbent Resin

Abstract In response to the escalating global water pollution problem, a three-dimensional crosslinked poly(acrylic acid-acrylamide-sodium styrene sulfonate)/chitosan (P(AA-AM-SSS)/CTS) composite superabsorbent resin was successfully synthesized via inverse suspension polymerization. A series of systematic experiments were performed to elucidate the effects of initiator dosage, crosslinker content, and monomer composition on the network structure, swelling behavior, and adsorption performance. Through controlled optimization of the polymerization conditions, a structurally stable three-dimensional polymer network was established. Under optimized conditions, the composite resin exhibited a high swelling capacity of 1233.7 g/g in deionized water and 137.3 g/g in saline solution, demonstrating effective enhancement of both water absorbency and salt tolerance. Meanwhile, the material maintained favorable water retention at 60°C, achieving a water retention rate of approximately 85%, and displays outstanding reswelling capability. Thermogravimetric analysis revealed a residual mass of 42.9% at 600°C, indicating enhanced thermal stability. In addition, adsorption experiments toward the cationic dye methylene blue were systematically conducted under varying adsorbent dosage, contact time, temperature, and initial dye concentration. The optimized composite achieved a maximum adsorption capacity of 874.6 mg/g under the studied conditions. Therefore, the incorporation of sulfonic acid groups and chitosan-based structural regulation into the superabsorbent resin network enables the simultaneous improvement of water absorbency, salt tolerance, and dye adsorption performance, indicating its potential applicability in wastewater treatment.