Adsorptive Removal of Pentavalent Arsenic from Aqueous Solutions by Granular Ferric Oxide

R. Zakhar, J. Derco, F. Čacho and O. Čižmárová

Abstract
Arsenic contamination of water resources, which is characterized by strong carcinogenic and toxic impacts, is a global problem. Therefore, the present study is focused on the isotherm and kinetic studies of pentavalent arsenic As(V) adsorption with initial concentration of 1 000 µg L−1 from aqueous solutions onto granular ferric oxide (GFO). Adsorption experiments were carried out by batch method, and the equilibrium and kinetic data were evaluated by the Langmuir, Freundlich, Dubinin-Radushkevich, Redlich-Peterson and Sips isotherm model, and pseudo-first and pseudo-second order kinetic model. The results obtained from this study imply that the adsorption of As(V) onto GFO was favourable, physical and multilayer process. The Sips and Redlich-Peterson isotherm and the pseudo-first order kinetic model gave the best fit to experimental data according to the values of correlation coefficient. The maximum theoretical adsorption capacity from Langmuir isotherm model was determined to be 1 900 µg g−1. In addition, the impact of different operating conditions such as As(V) initial concentration, adsorbent dose, agitation speed, pH, temperature, and presence of phosphates and silica on adsorption capacity of GFO was also investigated. As(V) was efficiently recovered from GFO by 0.1 M NaOH desorbing solution during the three adsorption-desorption cycles.

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Keywords
adsorption, arsenic, granular ferric oxide, isotherm models, kinetic models, regeneration