Optimized Alginate-Glycerol Nano-hydrogel Composites for Enhanced Methylene Blue Removal: Kinetic and Isotherm Analysis

Abstract

This work systematically investigated the adsorption of methylene blue (MB) onto sodium alginate-glycerol nano-hydrogel composites (SA/G-NH), with special emphasis on the influence of glycerol content on the mechanical and adsorptive properties. Hydrogels having 20 wt% and 40 wt% glycerol were synthesized and characterized. Dynamic mechanical analysis (DMA) showed that the hydrogel of 20 wt% glycerol had a higher storage modulus (G′ = 2.41 ± 0.13 kPa) and exhibited more consistent viscoelastic behavior than the sample with 40 wt% (G′ = 1.78 ± 0.21 kPa), thus demonstrating enhanced mechanical stability (p < 0.99), which indicates the predominance of the chemisorption mechanism. Isotherm evaluations suggested that the Langmuir model fitted the equilibrium data well (R² = 0.9364), with maximum adsorption capacity (q_m) calculated to be 11.9332 mg/g for the 20 wt% hydrogel. Each of the experiments was performed in triplicate, and results are reported as mean ± standard deviation. It is concluded from the findings that SA/G-NH hydrogels, particularly at 20 wt% glycerol, show promise as efficient and robust adsorbents for MB removal from aqueous media. The results accentuate the pivotal effect of glycerol amount on tuning the mechanical and adsorption prowess of the hydrogels and pave the pathway toward their use for environmental remediation on a statistically validated basis.