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Adsorptive removal of rhodamine B from textile wastewater using water chestnut (Trapa natans L.) peel: adsorption dynamics and kinetic studies

Khan, Tabrez A., Nazir, Momina, Khan, Equbal A.
Toxicological and environmental chemistry 2013 v.95 no.6 pp. 919-931
Gibbs free energy, Trapa natans, adsorbents, adsorption, aqueous solutions, biosorbents, correlation, enthalpy, models, sorption isotherms, wastewater
Water chestnut peel, an agricultural bio-waste, was used as a biosorbent for removal of rhodamine B (RhB), basic textile dye, from an aqueous solution. The effects of various experimental parameters were studied. The equilibrium data correlated well with a Freundlich isotherm (R ² = 0.98–0.99) followed by a Halsey isotherm model (R ² = 0.98–0.99) which indicated heterogeneity of the adsorbent surface and multilayer adsorption of RhB dye onto the water chestnut peel waste (WCPW). High correlation coefficients (R ² = 0.99) together with close agreement between experimental q ₑ (0.4–1.7 mg g ⁻¹) and calculated q ₑ (0.4–2.5 mg g ⁻¹) suggested that the adsorption process followed pseudo-second-order kinetics, with k ₂ values in the range of 52–3.4 × 10 ⁻¹ g mg ⁻¹ min ⁻¹ at different concentrations. The overall mechanism of adsorption was controlled by both liquid-film and intra-particle diffusions. The negative values of change in Gibb's free energy (−Δ G ⁰ = 19.2–29.2 kJ mol ⁻¹) and positive values of change in enthalpy (Δ H ⁰ = 30.9–117.6 kJ mol ⁻¹) revealed the process to be spontaneous and endothermic. WCPW was found to be an effective adsorbent for removal of RhB, a cationic dye, from an aqueous solution.