Facile Synthesis of Ultrafine Akaganeite Nanoparticles for the Removal of Hexavalent Chromium: Adsorption Properties, Isotherm and Kinetics

Here, we report the preparation of rather spherical akaganeite (beta-FeOOH) nanoparticles with a mean diameter of similar to 5 nm by means of a hydrolysis procedure. The obtained material was widely characterized by several techniques such as X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The textural and surface properties were studied through the analysis of the surface area (BET), pore size distribution (BJH) and the point of zero charge, pH(PZC). The beta-FeOOH nanoparticles were used to evaluate the removal of Cr(VI) from aqueous systems. The results reveal that the optimal adsorption conditions were under acidic pH values (pH similar to 4.5). The adsorption kinetic data fit well with a pseudo-second-order model while the Langmuir isotherm describes the adsorption equilibrium conditions of the system. The maximum adsorption capacity of the beta-FeOOH was estimated in 56.5 mg/g from the Langmuir isotherm at 25 degrees C.