Research Snapshot:
Chemical Regeneration of Granular Activated Carbon

Significance

EPA’s Office of Research and Development (ORD) has developed a method for treating contaminated fluids through adsorption of the contaminant onto a sorbent - granular activated carbon - to concentrate the contaminant, and subsequently transform it into less toxic byproducts.  Research has focused on methyl tert-butyl ether (MTBE), a gasoline additive, but this method is applicable to a broad range of organic contaminants.  An advantage to this technology is that the sorptive capacity of the carbon can be re-established (i.e., reused), which reduces costs for water treatment.  Additionally, this technology may represent a viable, green alternative to conventional thermal methods, which consume large quantities of fossil fuel and yield large quantities of greenhouse gases.

Summary

Granular activated carbon (GAC) is a broad-spectrum adsorbent used to purify air, water, and waste water, and is commonly used in the US. Activated carbon is used to purify liquids and gases through adsorptive treatment where organic pollutants are adsorbed or immobilized, and concentrated on the activated carbon. Once fully adsorbed with the contaminants, the GAC is exhausted or “spent” such that it cannot adsorb any additional contaminants. The GAC must then be regenerated.

Fenton-driven regeneration of the spent GAC involves the reaction between iron surfaces on the GAC and hydrogen peroxide.  To do this, the unit is taken offline, and hydrogen peroxide is recirculated through the GAC, which reacts with the iron on the GAC, creating reactive intermediates that oxidize the contaminants.  This oxidative treatment transforms the contaminants into less toxic byproducts.  Chemical regeneration of the GAC can be carried out on-site, and in situ, thereby allowing reuse of the GAC to achieve treatment objectives.

One treatment goal is to deploy this technology in a funnel and gate hydraulic configuration in the subsurface (i.e., in situ treatment); thus far it has been tested at pilot-scale in above-ground applications.  While the technology is highlighted here for use in ground water remediation, it can also be potentially used in other applications including waste water and drinking water treatment.

Additional Information

• Huling, S.G., Ko, S., Park, S., and Kan, E. 2010. (In Review) “Persulfate-driven oxidation of contaminant-spent granular activated carbon.” Wat. Res.
• Huling, S. and Hwang, S. 2010. Iron amendment and Fenton oxidation of MTBE-spent granular activated carbon, Wat. Res. (44)8, 2663-2671.
• Huling, S.G., Kan, E., Wingo, C. 2009. “Fenton-driven regeneration of MTBE-Spent granular activated carbon – Effects of particle size and Iron Amendment Procedures”. J. Appl. Cat. B: Environ. 89, 651-657.
• Kan, E. and Huling, S.G. 2009. “Effects of temperature and acidic pre-treatment on Fenton-driven oxidation of MTBE-spent granular activated carbon”. Environ. Sci. Technol. 43 (5), 1493-1499.
• Huling, S.G., K.P Jones, and T. Lee. 2007. “Iron Optimization for Fenton-Driven Oxidation of MTBE-Spent Granular Activated Carbon.” Environ. Sci. Technol. 41(11), 4090-4096.
• Huling, S.G., P.K. Jones, W.P. Ela, and R.G. Arnold. 2005. “Fenton-Driven Chemical Regeneration of MTBE-Spent Granular Activated Carbon”. Water Research. (39)2145-2153.
• Patent Information: U.S. Patent and Trademark Office - Patent Nos. 6,663,781 and 7,335,246.

CONTACTS
Scott Huling: huling.scott@epa.gov or (580) 436-8610