A fully bio-derived superabsorbent polymer based on sodium alginate and konjac glucomannan

Superabsorbent polymers (SAPs) derived from sodium alginate have attracted considerable attention. However, their practical application is limited by poor saline absorption and water retention. In this study, a fully biomass-derived SAP was fabricated from sodium alginate and konjac glucomannan via a two-step crosslinking strategy using CaCl₂ and borax as crosslinkers. The microstructure, chemical structure, thermal stability and composition of the optimized SAP were characterized in detail. The dual-crosslinked network, formed through Ca²⁺-carboxylate coordination and dynamic borate ester bonds, enhanced saline tolerance while maintaining structural integrity. The partial disruption of the Ca²⁺ crosslinking network by Na⁺ ions relaxed the polymer network to facilitate saline uptake, whereas reversible borate ester bonds enabled network rearrangement and water retention. The optimized SAP exhibited absorption capacities of 35.87 g/g in 0.9 wt% NaCl solution, 18.43 g/g in artificial urine, outperforming most fully biomass-based SAPs and the commercial acrylate-based SAP. Notably, its saline water retention ratio reached 65.07% after centrifugation. Moreover, the optimized SAP achieved an 85.24% biodegradation within 28 days. In summary, the fully biomass-based dual-crosslinked SAP simultaneously improves saline absorbency, water retention, and biodegradability, highlighting its strong potential for hygiene product applications.