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Biosorption of cadmium (II) from aqueous solutions by natural and modified non-living leaves of Posidonia oceanica

Meseguer, Víctor F., Ortuño, Juan F., Aguilar, M. Isabel, Pinzón-Bedoya, Martha L., Lloréns, Mercedes, Sáez, José, Pérez-Marín, Ana B.
Environmental science and pollution research international 2016 v.23 no.23 pp. 24032-24046
Fourier transform infrared spectroscopy, Gibbs free energy, Posidonia oceanica, adsorption, aqueous solutions, biosorbents, biosorption, cadmium, calcium, hydrochloric acid, ions, kinetics, leaves, magnesium, models, pH, potassium, sodium, sorption isotherms
Natural, HCl-treated, and formaldehyde-treated non-living leaves of Posidonia oceanica, a marine plant, were investigated as potential biosorbents to remove Cd²⁺ from aqueous solutions. The studied biosorbents were characterized by elemental analysis and Fourier transform infrared spectroscopy (FTIR) and it was observed that the adsorption capacity of the biosorbents strongly depended on the pH, increasing as the pH rises. The adsorption process was fast. The adsorption kinetic was analyzed using five kinetic models: pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, and Bangham models. The adsorption isotherms were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich, Sips, Redlich-Peterson, and Toth models. The maximum biosorption capacity was attained by the biosorbent treated with HCl (1.11 mmol g⁻¹). The distribution equilibrium constant and the Gibbs free energy change were calculated. The effects of the presence of Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions in the solution on Cd²⁺ uptake were studied. Results indicate that non-living leaves of P. oceanica, natural or treated, can be considered as effective and low-cost biosorbents for the removal of cadmium from aqueous solutions.