Removal of As(V) from aqueous solution by activated carbon-based hybrid adsorbents: Impact of experimental conditions

Abstract

In this study, apricot stone based activated carbon (IAC) was modified with iron (oxy-hydr)oxides to produce effective hybrid adsorbents for arsenic removal from aqueous medium. For this purpose, Fe2+ loaded activated carbon (IAC-Fe(II)) and Fe3+ loaded activated carbon (IAC-Fe(III)) were produced by precipitation method. As(V) adsorption on each adsorbents was investigated at three levels of pH (3.0, 5.0 and 7.0), initial As(V) concentration (0.5, 4.5 and 8.5 mg L-1) and temperature (298, 318 and 3381K). As(V) adsorption capacities of IAC, IAC-Fe(II) and IAC-Fe(III) were found to be 0.034, 2.023 and 3.009 mg g(-1), which represented 15.00%, 9834%, and 99.05% As(V) removal efficiency, respectively. As(V) adsorption kinetics of hybrid adsorbents were investigated and it was found that IAC-Fe(III) required less contact time than IAC-Fe(II). Thermodynamic parameters such as Gibbs free energy (Delta G degrees), entropy (Delta S degrees) and enthalpy (Delta H degrees) were calculated from experimental isotherm at different temperatures. The value of Delta H degrees for arsenate adsorption on IAC-Fe(II) was positive that indicates endothermic nature of the adsorption process. On the other hand, IAC-Fe(III) had negative value of Delta H degrees that indicates exothermic nature of arsenate adsorption. The equilibrium data for both hybrid adsorbents fitted well to Freundlich and Dubinin-Radushkevich. The As(V) adsorption on hybrid adsorbents had high values of correlation coefficient (R-2) and low values of chi-square (chi(2)) for all adsorption isotherm model except Langmuir isotherm, indicate that adsorption of As(V) on hybrid adsorbents takes place on multi-layer. (C) 2013 Elsevier B.V. All rights reserved.