Removal of Cr (VI) from aqueous solutions by Acacia nilotica bark.

Removal of hexavalent Cr from aqueous solutions by bark of Acacia nilotica L. was studied in batch process. Different parameters of adsorption viz. effect of pH, effect of dose and effect of contact time were studied. The percentage removal of Cr (VI) from synthetic sample was found to be 89.0 and 93.1% for 1.0 mm and 0.3 mm Acacia bark carbon (ABC) respectively and 60.9% and 68.1% for 1.0 mm and 0.3 mm Acacia bark untreated (ABU) respectively, in 30 min contact time. The optimum pH for both adsorbents was found to be 2.0 and adsorption equilibrium was found to be 30 min. for both adsorbents. The adsorption process was found to follow first order rate mechanism as well as Freundlich isotherm.