Work

Engineering an amphiphilic guar gum/xanthan gum complex for enhanced methylene blue removal: Experimental and molecular insights

Year: 2026

Type: article

Abstract: Bio-based adsorbent hydrogels were developed by chemically functionalizing guar gum (GG) through amidation with octadecylamine, producing a hydrophobically modified derivative (NGG). NGG was subsequently combined with xanthan gum (XG) to form NGG/XG polysaccharide complex networks. Structural, morphological, and thermal analyses confirmed successful amidation, along with reduced crystallinity, increased surface porosity, and improved thermal stability compared with native GG. The NGG/XG complexes exhibited strong pH-responsive swelling, reaching a maximum water uptake of 923% at pH 2. Their adsorption performance was evaluated using methylene blue (MB) as a model cationic dye. At pH 2 and 298 K, the NGG/XG system achieved a high experimental adsorption capacity of 248 mg g⁻¹ for an initial MB concentration of 50 mg L⁻¹ and adsorbent dose of 0.1 g L⁻¹. The pseudo-first-order kinetic model and Langmuir isotherm model best described the adsorption for the MB solution with a maximum adsorption capacity of 230 mg g⁻¹. Thermodynamic analysis indicated spontaneous (ΔG° = −2.28 to −2.62 kJ mol⁻¹), mildly endothermic (ΔH° = +0.95 kJ mol⁻¹), entropy-driven adsorption (ΔS° = +0.011 kJ mol⁻¹ K⁻¹). DFT, NCI-RDG, and QTAIM analyses revealed complementary polar, electrostatic, hydrogen-bonding, and hydrophobic/dispersion interactions, supporting a cooperative multisite physisorption mechanism. These findings highlight NGG/XG as promising, pH-responsive adsorbents for wastewater remediation.

Source: Desalination and Water Treatment

DOI: 10.1016/j.dwt.2026.101968