High-efficiency methylene blue removal using a novel thiadiazole-functionalized chitosan–Noria composite: Synthesis, characterization, and adsorption mechanism

A novel composite adsorbent, CS@Noria@TDDT, was successfully synthesized by grafting 1,3,4-thiadiazole-2,5-dithiol onto a chitosan–glutaraldehyde–Noria framework to enhance the removal of methylene blue (MB) dye from aqueous media. The composite was comprehensively characterized using FTIR, XRD, SEM, XPS, and TGA, confirming successful integration of functional groups and improved thermal stability. Batch adsorption experiments were performed to evaluate the effects of pH (2–8), initial dye concentration (25–300 mg/L), contact time (1–180 min), adsorbent dosage (0.01–0.05 g), and temperature (25–45 °C). Optimal conditions (pH 8.0, 45 °C, 0.02 g adsorbent) yielded a maximum adsorption capacity (qₑ) of 169.76 mg/g and a removal efficiency of 96.44 %. The kinetic data best fit the pseudo-second-order model (R² = 0.999), indicating chemisorption. Isotherm analysis showed strong correlation with the Langmuir model (R² = 0.997), confirming monolayer adsorption. Thermodynamic parameters (ΔH° = +32.84 kJ/mol, ΔG° < 0) indicate that the process is endothermic and spontaneous. Additionally, the composite retained high performance over five consecutive adsorption–desorption cycles, with removal efficiency decreasing only slightly from 96.44 % to 94.00 %, confirming excellent reusability. These results underscore the potential of CS@Noria@TDDT as a highly efficient and sustainable adsorbent for cationic dye remediation in wastewater treatment.