Comparative Studies on the Bioremediation of Hexavalent and Trivalent Chromium using Citrobacter freundii: Part I-Effect of parameters controlling Biosorption

Document Type : Original Research Paper


Department of Materials Engineering and Indo-French Cell for Water Sciences, Indian Institute of Science, Bangalore, 560012, Karnataka, India


The potential of Citrobacter freundii, a Gram negative bacteria for the remediation of hexavalent
chromium (Cr(VI)) and trivalent chromium (Cr(III)) from aqueous solutions was investigated. Bioremediation
of Cr(VI) involved both biosorption and bioreduction processes, as compared to only biosorption process
observed with respect to Cr(III) bioremediation. In the case of Cr(VI) bioremediation studies, about 59 %
biosorption was achieved at an equilibrium time of 2 h, initial Cr(VI) concentration of 4 mg/L, pH 1 and a
biomass loading of 5x1011 cells/mL. The remainder, 41 %, was found to be in the form of Cr(III) ions owing to
bioreduction of Cr(VI) by the bacteria resulting in the absence of Cr(VI) ions in the residue, there by meeting
the USEPA specifications. Similar studies were carried out using Cr(III) solution for an equilibrium time of 2
h, Cr(III) concentration of 4 mg/L, pH 3 and a biomass loading of 6.3x1011 cells/mL, wherein a maximum
biosorption of about 30 % was achieved.