REMOVAL AND RECOVERY OF Cr(III) AND Cr(VI) WITH ALFALFA BIOMASS
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K. Dokken, 1K.J. Tiemann, 1G. Gamez, 1J.G. Parsons, 1I. Herrera, 2J.L. Gardea-Torresdey, and
N.E. Pingitore
1
Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968; 2Department of
Environmental Science and Engineering, University of Texas at El Paso, El Paso, TX 79968; and
3
Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968; 2Phone:
(915) 747-5359, 2E-mail: jgardea@utep.edu.
Contamination of ground and surface waters by trivalent and hexavalent chromium has become a
great health risk to the public due to increased industrial activity over recent years. Current
technologies used to remediate chromium contamination pose a threat to the environment and are
costly. A more environmentally friendly and cost-effective alternative utilizes plant or bacterial
matter as biosorbents for chromium remediation. Alfalfa is a possible biosorbent because of its
affinity for trivalent and hexavalent chromium under single-metal and mixed-metal conditions. In
addition, we have found that alfalfa reduces hexavalent chromium to trivalent chromium which was
characterized through x-ray absorption near-edge structure (XANES) spectroscopy and extended xray absorption fine-structure (EXAFS) spectroscopy. However, a problem commonly encountered
in ion exchange resins, as well as biosorbents like alfalfa, is the recovery of chromium after
adsorption. Some stripping agents provide low recoveries while others damage the biosorbent
which, in each case, affects recyclability of the biosorbent. In this study we investigated the use of
a wide array of stripping agents such as dilute acids and bases under batch experimental conditions.
Also, flow studies using silica-immobilized biomass were used to further investigate the ability of
various stripping agents to recover hexavalent and trivalent chromium. The results of these
experiments will be presented.
Key words: XANES, EXAFS, alfalfa, chromium, recovery, metal binding, stripping agents