Decoupling Network Architecture and Sorption Mechanisms in Cellulose–Alginate and Carboxymethylcellulose–Alginate Hydrogels

Abstract Understanding how network architecture governs the properties of polysaccharide-based hydrogels is essential for designing sustainable functional materials. This study investigates structure–property relationships in renewable cellulose/alginate (CEL/AL) and carboxymethylcellulose/alginate (CMC/AL) hydrogels using adsorption experiments as mechanistic probes of network organization, hydration behavior, and adsorbate transport. Structural analyses revealed distinct architectures: CEL/AL retained partial cellulose crystallinity and localized chain ordering despite presenting a heterogeneous porous morphology, whereas CMC/AL exhibited a predominantly amorphous structure associated with greater chain flexibility, higher carboxylate functionality and greater hydration capacity. These structural and chemical differences strongly influenced diffusion pathways and sorption behavior. Adsorption kinetics showed pseudo-second order behavior for methylene blue adsorption in both hydrogels and for Cd2+ adsorption in CMC/AL, while Cd2+ uptake in CEL/AL followed pseudo-first order kinetics. Isotherm analyses indicated Freundlich behavior for methylene blue adsorption onto CEL/AL and Langmuir/Sips behavior for Cd2+, whereas CMC/AL followed the Sips model for both contaminants. Dubinin–Radushkevich analysis indicated differences in the model-derived adsorption energy between CEL/AL and CMC/AL. Both hydrogels achieved removal efficiencies above 50%, highlighting their potential for water treatment. The results indicate that chemical functionality, network organization, and hydration state jointly influence sorption behavior and functional performance.