Pongamia oil cake (POC), a bio-residual waste is obtained during the production of biodiesel as a byproduct. This is used as biosorbent to evaluate the removal of chromium (VI) ions from an aqueous synthetic solution. The effects of various process parameters such as pH, contact time, initial chromium ions concentration and adsorbent dosage have been investigated. The FT-IR and SEM analysis of the adsorbents was done in the native- and Cr(VI)-loaded state, to explore the position of the functional groups available for binding of chromium ions and the structural morphology of the studied adsorbents respectively. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm were used to study the adsorption mechanism, and it was found that the equilibrium data was better represented by the Freundlich isotherm. The maximal removal of hexavalent chromium ion was found to be at a pH of 2.0 within 2 h. The sorption kinetic follows the pseudo second order kinetic model. The Cr(VI) ions bound to the biosorbent could be effectively removed, using dilute H2SO4 (0.05 mM). The ability of POC to adsorb Cr(VI) ions in packed column was also investigated through the column studies. Bed Depth Service Time model and the Thomas model were used to analyze the experimental data and evaluate the model parameters. POC was shown to be a promising adsorbent for removal of Cr(VI) ions from aqueous solutions. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 342–352, 2014
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