Natural Cellulose-Chitosan Cross-Linked Superabsorbent Hydrogels with Superior Swelling Properties

Abstract

We have developed a new, aqueous-based process for production of superabsorbent materials that is catalyst-free and eco-friendly as the superabsorbent was derived from two completely biodegradable polymers with water as the only byproduct. The new hydrogels were obtained by cross-linking partially oxidized bleached kraft pulp fibers with carboxymethylated chitosan. In distilled water, the maximum water retention value (WRV) of the cross-linked hydrogels reached 610 (g/g gel), which is several times higher than any neat cellulose-based superabsorbent material reported in the literature. In saline water, the WRV of the new hydrogels (85 g/g) doubled that of commercial gels (40–50 g/g). In the presence of potassium or ammonium cations, the WRV increased further to reach 91 and 96 g/g, respectively. Gels only lost 5–10% of their reswelling capacity when reused four consecutive times. The hydrogels had high porous architecture and specific surface area that facilitates rapid mass penetration in superabsorbent applications. Due to their superior swelling properties, reusability, and biodegradable nature, the new hydrogels could serve as strong candidates to replace synthetic petroleum-derived polymers and find uses in high-value hygiene, food, agricultural, and pharmaceutical products.