Packed bed column studies on Cr (VI) removal from tannery wastewater by neem sawdust

The removal of Cr (VI) from tannery wastewater by neem sawdust was investigated in a fixed bed column. The experiments were conducted to study the effect of important parameters such as bed depth (5-15 cm) and flow rate (5-15 ml min(-1)). The bed depth service time model (BDST) fit well with the experimental data. The adsorption capacity estimated from the BDST model was 33,009.9 mg g(-1). The column was regenerated by eluting chromium (VI) using 2 N NaOH after adsorption studies. The desorption of Cr (VI) failed to reach 100% in each cycle because some amount of adsorbed Cr (VI) got reduced to Cr (III) in the biosorbent surface and released into the aqueous phase. The effect of co-ions on adsorption of Cr (VI) was studied in column mode, where the breakthrough and the exhaustion time of the column decreased in the presence of co-ions. In the three cycles of biosorption, about 3.75 L of tannery effluent were treated to reach the chromium (VI) standard (0.1 mg L-1) established by the Central Pollution Control Board (CPCB). Neem sawdust proved to be the potential biosorbent for the removal of Cr (VI) from tannery effluents. (C) 2010 Elsevier B.V. All rights reserved.