Kinetics and Equilibrium Studies on the Adsorption Performance of Methylene Blue onto Terracotta Clay

ABSTRACT Methylene blue (MB), a toxic, carcinogenic, and persistent dye, has constantly contaminated aquatic systems, posing serious risks to human health and environmental safety. In this study, the potential of natural raw terracotta clay, herein termed (RTC), to effectively sequester cationic MB dye from aqueous solution was evaluated. Effects of variations in sorption time (5–180 min), adsorbent dosage (0.01–1.0 g), initial adsorbate concentration (2–50 mg/L), adsorbate pH (2–12), temperature (298–323 K), and water chemistry were investigated for its successful removal in batch experiments. The optimum pH for MB adsorption was attained at 10. The kinetic data were best fit by the pseudo‐second‐order model, while the Langmuir isotherm model justified the state of equilibrium data. RTC achieved a maximum adsorption capacity of 23.10 mg/g at 298 K. Thermodynamics investigations revealed that the reactions were viable, spontaneous, and exothermic. The clays’ characterization revealed that it was crystalline and mesoporous. Furthermore, RTC demonstrated consistent performance in removing MB from aqueous solution over five consecutive regeneration cycles, indicating its good reusability. RTC is thus suited for the cost‐effective and environmental friendliness removal of MB from aqueous solutions.