Superfund Research Program
Chemical Intervention Strategies
Project Leader: Timothy D. Phillips
Grant Number: P42ES004917
Funding Period: 2000-2008
Final Progress Reports
Year: 2007 2004
The major objectives of the Chemical Intervention Strategies project were to:
- develop and characterize sorbents for the sequestration and removal of arsenic and selected organic compounds from water;
- use the most effective sorbent(s) to conduct in vivo intervention studies, applying enterosorption methods in animals exposed to these environmental contaminants via tainted foods and water.
Sorbents from various mineral classes and different iron oxides synthesized in the lab were screened for their ability to sorb As(III) and As(V) from water applying single concentration sorption protocols. From this initial study, the arsenic binding of selected sorbents was further characterized using full isothermal analysis to determine their affinity and capacity for As. Ferrihydrite and other selected sorbents, were then tested for their ability to protect Hydra Attenuata, an organism susceptible to arsenic toxicity. Ferrihydrite, at 0.5%, w/w, was confirmed to protect hydra from arsenic toxicity at 200 and 2.5 times the minimal affective concentration (MAC) of As(III) (1.0 ppm in water) and As(V) (100 ppm in water), respectively. These experiments suggest that sorbents that bind arsenic can also protect susceptible organisms such as hydra from arsenic toxicity. Ferrihydrite was further encapsulated into chitosan gel beads, which have been shown to bind a variety of metals and arsenic. The addition of ferrihydrite (1/1 with chitosan) was found to increase the binding of As(III) and As(V) by 34.1% and 10.0%, respectively, versus chitosan control beads. The binding of arsenic to ferrihydrite was also examined using a simulated GI model. The results of these experiments show that ferrihydrite binds arsenic with high capacity in a simulated stomach and intestine. Throughout these experiments dissolved iron from ferrihydrite remained low with a maximum extrapolated dose of Fe equal to the same as found in 3 ounces of spinach. In vitro studies are still ongoing and will be followed by animal studies to verify ferrihydrite’s apparent safety and efficacy. Other studies will focus on the development of porous composite materials for the removal of other toxic metals and target organic compounds.