Removal of chromium(VI) from aqueous solution by grain-less stalk of corn

BELLÚ, S. E.; GARCÍA, S. I.; GONZÁLEZ, J. C.; ATRIA, A. M.; SALA, L. F.; SIGNORELLA, S. R.

SEPARATION SCIENCE AND TECHNOLOGY

Taylor & Francis

Año: 2008 vol. 43 p. 3200 - 3220

0149-6395

Grain-less stalk of corn (GLSC) was tested for removal of Cr(VI) and Cr(III) from aqueous solution at different pH, contact time, temperature and chromium/adsorbent ration. The results show that the optimum pH for removal of Cr(VI) is 0.84, while the optimum pH for removal of Cr(III) is 4.6. The adsorption processes of both Cr(VI) and Cr(III) onto GLSC were found to follow first-order kinetics. Values of kobs of 0.037 and 0.018 min-1 were obtained for Cr(VI) and Cr(III) respectivelly. The adsorption capacity of GLSC was calculated from the Langmuir isotherm as 7.1 mgg-1 at pH 0.84 ofr Cr(VI) and as 7.3 mgg-1 at pH 4.6 ofr Cr(III) at 20oC.At the optimum pH for Cr(VI) removal, Cr(VI) reduces to Cr(III). EPR spectroscopy shows the presence of Cr(V) + Cr(III)-bound GLSC at short contact times and adsorbed Cr(III) as the final solution state of Cr(VI) -treted GLSC. The results indicate that, at pH aproximately 1, GLSC can completely remove Cr(VI) from aqueous solution through an adsorption-coupled reduction mechanism to yield adsorbed Cr(III) and the less toxic aqueous Cr(III), which can be further removed at pH 4.6