Adsorption of Chromium (VI) from Aqueous Solution by Acacia Tree (Acacia tortilis) Charcoal

Abstract

The adsorption of chromium (VI) ions from aqueous solution by charcoal from acacia (Acacia tortilis) tree were studied in a batch adsorption system. Various parameters such as the effect of initial chromium concentrations, pH, and contact time on Cr (VI) removal were investigated. The removal of Cr (VI) ions was observed to increase with contact time, and reduced with increasing initial chromium concentration. The optimum pH for chromium (VI) removal was attained between pH 5.0 and 6.0. Simulation kinetic models results showed that the pseudo-second–order kinetic model (R2>0.983) best describes the kinetic sorption of Cr (VI) ions onto the acacia charcoal. Moreover, the Langmuir and Freundlich models agreed very well with experimental data with a regression coefficient of 0.999 and 0.998, respectively. Desorption studies using nitric acid (HNO3) indicated high capability of chromium regeneration with desorption of higher than 92% being observed. Use of acacia tree charcoal for adsorption of Cr (VI) ions in this study exhibited high potentials for chromium ions removal from aqueous solution. These results suggest that acacia tree charcoal can be employed as an efficient adsorption for Cr (VI) removal in contaminated waters and can be utilized for recovery of chromium. Results from this study can be utilized in assessing the effectiveness of acacia tree charcoal for Chromium heavy metal at the field scale.