Utilização de adsorvente natural para remoção de ferro (ii) de solução aquosa-tratamento cinético e equilíbrio termodinâmica

Abstract

In this study were performed the kinectics, isotherms and thermodynamics of the adsorption of the ions Fe(II) from aqueous solutions using natural peanut shell as adsorbent. All experiments were stirred at 120 RPM and tested concentrations of 3 to 10 mg L -1 for pH testing used a ratio of 20 g of adsorbent to 1 L solution of Fe (II ), for the adsorption kinetics a ratio of 2.5 g L -1 and the isotherms a ratio of 2 g L -1 . It was evaluated the influence of three temperatures different, 25°C, 35°C e 45°C, on the adsorption of Fe(II). The increase in the temperature until 45°C increased the adsorption capacity of the peanut shell, indicating endothermic adsorption. The adsorption kinetics was analyzed using the Pseudo-First Order model, Pseudo-Second Order model and Intraparticle Diffusion. The Pseudo-Second Order model exhibited the best correlation coefficient (0,99) and proved the most efficient in describing the adsorption rate. In the Intraparticle Diffusion, the best correlation coefficient occurred in the last adsorption stage (0,99), indicating the ruling stage as the final equilibrium phase. Langmuir, Freundlich, Langmuir-Freundlich and Radke-Prausnitz isotherms were used to describe the adsorption equilibrium of Fe(II) at different temperatures. Freundlich, Langmuir-Freundlich and Radke-Prausnitz isotherms demonstrated the best correlation coefficient (0,99). The thermodynamics parameters of Gibb’s free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also analyzed. The negatives values of ΔG° confirms the viability and spontaneity of the adsorption process by peanut shell.