Removal of Rhodamine B from water using natural clay: a study on adsorption kinetics, thermodynamics, and environmental impact

Abstract

ABSTRACT This study investigates the adsorption capabilities of natural clay for the removal of Rhodamine B (RhB) from water, emphasising its potential as a cost-effective and sustainable solution for water treatment. The adsorption process was studied at three temperatures, focusing on kinetics, thermodynamics, and equilibrium. UV Vis spectrophotometry confirmed that natural clay achieved a remarkable RhB removal efficiency exceeding 97%. Factors such as initial concentration, adsorbent dosage, and temperature significantly influenced the adsorption efficiency. Thermodynamic analysis revealed negative Gibbs free energy values (−26.27, −27.50, and −28.80 kJ/mol) across the tested temperatures (14°C, 24°C, and 34°C), indicating the spontaneous and favourable nature of RhB adsorption onto clay surfaces, which is further enhanced by higher temperatures due to its endothermic nature. Equilibrium data fitting favoured the Freundlich isotherm model, suggesting heterogeneous adsorption, while kinetics were best described by the pseudo-second-order model. Optimal conditions for maximum RhB removal were identified as 40 minutes contact time, initial pH 3.71, and 0.5 grams of adsorbent. These findings underscore natural clay’s potential for large-scale water treatment applications, offering both environmental benefits and economic viability as a sustainable solution to mitigate industrial dye contamination in water sources.