Adsorption of cationic dye from aqueous solutions using benzyl trimethylammonium-exchanged sodalite zeolite

The adsorption of methylene blue dye from aqueous solutions was investigated using a modified sodalite zeolite using a modified zeolite, prepared by treating sodalite-type zeolite with benzyl trimethylammonium chloride (BTMAC). Various characterisation techniques were used to compare the adsorption performance of modified and unmodified zeolites, including elemental (CHNS), spectral (FT-IR), XRD, XRF, surface morphology (SEM) and surface area (BET). Adsorption studies were performed to evaluate the effects experimental conditions like pH of solution (2–10), temperature (303–333 K), contact duration (0–250 min), initial dye concentration (20–160 ppm), stirring rate (200–1000 rpm), and adsorbent dosage (0.02–0.10 g). The experimental data aligned well with a first-order quartic model. Modified zeolite exhibited higher dye removal efficiency (~91%) than pristine Zeolite (~81%). The adsorption equilibrium data fit Langmuir, Freundlich, Temkin, and Dubinin – Radushkevich (D-R) isotherms, with the Langmuir providing the best correlation. Kinetic experiments revealed that the pseudo-first-order model best defined the adsorption mechanism. Thermodynamic analysis revealed negative values for ΔG° (−3.62 to −1.63 and −4.80 to −2.90 KJ/mol), ΔS° (−68.19 and −62.31 J/mol·K), and ΔH° (−25.31 and −23.63 KJ/mol), confirming that the adsorption process is exothermic and spontaneous. These findings suggest modified zeolite is a more efficient adsorbent for cationic dye removal than pristine Zeolite.