Removal of hexavalent chromium from aqueous solutions using barks of Acacia albida and leaves of Euclea schimperi

Abstract

Removal of hexavalent chromium ions (Cr(VI)) from aqueous solutions by adsorbents prepared from barks of Acacia albida of Fabaceae family and leaves of Euclea schimperi of Ebenaceae family has been studied by batch adsorption technique. Double-beam UV-visible spectrophotometer was used to monitor the concentration of Cr(VI). The influence of contact time, initial chromium ion concentration, pH and adsorbent dose on the efficiency of adsorption process was studied. Among the studied parameters, pH was found to be the most influential. At the optimum pH (pH 2), 98.47 and 97.39 % removal of Cr(VI) was achieved using the adsorbents prepared from barks of A. albida and leaves of E. schimperi, respectively. After determining the optimal conditions for maximum adsorp- tion, the applicability of the biosorbents was tested on real samples. The results indicate that these adsorbents can be employed as low-cost alternatives to commercial adsor- bents for the removal of Cr(VI) from effluents. Adsorption isotherms and kinetic parameters were also studied. The results showed that the adsorption of Cr(VI) by these adsorbents follow Langmuir adsorption isotherm. The kinetics of the adsorption process follows the pseudo-sec- ond-order kinetic model.