Enhanced dye adsorption via pectin/pullulan/kaolinite nanocomposite for wastewater treatment applications

Toxic dyes in wastewater threaten the environment and public health making their effective removal essential. In the present study, a novel Pectin/Pullulan/Kaolinite nanocomposite hydrogel was synthesized via chemical cross-linking of pectin, pullulan, and NaOH-intercalated kaolinite. The resulting hydrogel exhibited enhanced mechanical integrity, superior swelling capacity (1797%), and excellent dye adsorption performance. Comprehensive characterization was performed using FTIR, TGA, BET, XRD, and FESEM-EDX. Adsorption studies were carried out under varying experimental parameters, including initial dye concentration, solution pH, temperature, adsorbent dosage, ionic strength, and contact time. The nanocomposite hydrogel demonstrated q_max of 205.57 mg/g for CV and 689.65 mg/g for CR. Optimal removal efficiencies of 93.8% for CV and 84.8% for CR were achieved under specific conditions: for CV at pH 9, 40 °C, 0.5 g adsorbent, 50 mg/L dye concentration, and 300 min contact time; and for CR at pH 5, 40 °C, 0.5 g adsorbent, 10 mg/L dye concentration, and 240 min contact time. Adsorption isotherm and kinetic data were best described by the Langmuir model and pseudo-second-order kinetics, respectively. Thermodynamic analysis further confirmed the exothermic and spontaneous nature of dye adsorption. These results highlight the efficiency of PC/PL/KaO hydrogels for dye removal in wastewater treatment.