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Rice UniversityCBEN
Center for Biological and Environmental Nanotechnology

Arsenic Removal Using Nanoscale Magnetite: Lab Scale to Pilot Scale

Silica-coated magnetite nanoparticle (16 nm core; 34 nm shell).

Silica-coated magnetite nanoparticle (16 nm core; 34 nm shell).

Arsenic is widespread in the earth’s crust and affects millions globally via dissolution into groundwater from arsenic-containing minerals and ores in the subsurface (Ferguson and Gavis 1972).  The International Agency for Research on Cancer recognizes that long term exposure to arsenic in drinking water elevates cancer rates of the skin, lungs, urinary bladder, and kidneys, in addition to several skin diseases (International Agency for Research on Cancer 2004; 2004).  As a result of the growing body of knowledge on the effects of arsenic, the US EPA began enforcing a reduced maximum contaminant limit for arsenic of 10µg/l in January of 2006.

Large scale drinking water treatment plants can remove arsenic economically by relying on traditional FeCl3 or alum coagulation and flocculation, followed by sedimentation or filtration (Feenstra, Erkel et al. 2007).  However, that technology is not easily scaled down.  Thus in the last decade, much research has been conducted on iron and iron-oxide based sorbents, that would enable arsenic treatment at smaller scales (Mohan and Pittman 2007).
Nanomagnetite is an iron-oxide sorbent which, displays high affinity for both As(III) and As(V) and, as the most magnetic natural mineral on earth, can be manipulated by a low-strength magnetic field (Harrison, Dunin-Borkowski et al. 2002; Yavuz, Mayo et al. 2006).  However, little has been done beyond batch studies to determine more ideal design and operating conditions of a nanomagnetite-based treatment method that could disseminate into wide use.

This past year, with a focus on direct application, the Tomson group advanced batch isotherm, lab-scale column, and pilot-scale field research for nanomagnetite enhanced sand filtration to remove arsenic and other heavy metals from drinking water.

Participating Researchers: