Study of the Adsorption of L-Phenylalanine, L-Tryptophan, and L-Tyrosine from Aqueous Samples by Fe3O4 Modified Magnetic Nanoparticles with Ionic Liquid

Abstract

<span style="font-family: Times New Roman;">Fe₃O₄ nanoparticles and their binary mixtures ([C₈MIM]-Fe₃O₄) with 1-Octyl-3-methylimidazolium bromide were prepared and characterized as ionic liquid for using in the adsorption of phenylalanine, tryptophan, and tyrosine. The characteristics of [C₈MIM]-Fe₃O₄ nanoparticles were investigated via using TEM, XRD and FTIR techniques. The pH of the point of zero charge (pH_pzc) of both Fe₃O₄ and [C₈MIM]-Fe₃O₄ were obtained based on the experimental curves corresponding to the immersion technique. Experimental results were obtained under optimum operational conditions of: nanoparticle amount of 0.015 g and a contact times of 5, 10, 15 minutes for tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe), respectively, when initial concentration of each amino acid was 5.0×10⁻⁴ mol L⁻¹. The isotherm evaluations revealed that the Freundlich model attained better fits to the equilibrium data than the Dubinin-Radushkevich model. The maximum obtained adsorption capacities of Tyr, Trp and Phe were 12.74, 3.55 and 35.62 mg amino acid per gram of adsorbent, respectively. The applicability of pseudo-first order and pseudo-second order kinetic models was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium adsorption capacity and correlation coefficients. Furthermore, the adsorption processes were found endothermic. Both phenylalanine and tyrosine were desorbed from [C₈MIM]-Fe₃O₄ nanoparticles by using NaOH aqueous solution with concentrations of 1.0 and 2.0 mol L⁻¹, respectively. Tryptophan was completely desorbed in the presence of a mixture of 1.0 mol L⁻¹ NaCl and 1.0 mol L⁻¹NaOH. The nanoparticles thus were recycled. </span>