Natural (Clinoptilolite) and Synthetic (NaP1) Zeolites in the Adsorption Process for the Removal of Acid Black 1 Dye from Aqueous Solutions

This study investigates the adsorption of Acid Black 1 (ABk 1) dye onto natural clinoptilolite (CLIN) and synthetic NaP1 zeolites under various conditions of adsorbent dose (5, 10, 20 g/L), dye concentration (1–1000 mg/L), and contact time (5–1440 min). The adsorption data were analyzed using Freundlich and Langmuir isotherms, as well as pseudo-first-order and pseudo-second-order kinetic models. Both linear and nonlinear regression methods were applied to assess the model fit. The results showed that CLIN exhibited maximum adsorption capacities of 35.32 mg/g, 21.9 mg/g, and 9.39 mg/g at doses of 5 g/L, 10 g/L, and 20 g/L, respectively. For NaP1, the corresponding values were 28.44 mg/g, 12.46 mg/g, and 9.11 mg/g. The pseudo-first-order model described adsorption at low dye concentrations and short contact times, while the pseudo-second-order model successfully explained adsorption across all tested conditions. These findings suggest that both zeolites, particularly CLIN, are effective adsorbents for ABk 1 dye removal, presenting a valuable solution for wastewater treatment applications.