SYNTHETIC CLAY REMOVES RADIUM FROM WATER AND SOIL

[Susan Gawarecki <loc@ICX.NET>]

I always like to see good geology news.

--Susan Gawarecki



>From Penn State's Sci-Tech NewsWire (4/27/01)

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SYNTHETIC CLAY REMOVES RADIUM FROM WATER AND SOIL



An inexpensive, synthetic clay may one day help provide radium free

drinking water and clean up radium-contaminated mine and mill

tailings according to a Penn State researcher.

        Radium, a natural decay product of uranium, is often found in

the southwestern United States where large deposits of uranium are

mined, but is also present in many other areas in  rocks and soils.

Coal and phosphate processing also produce tailings that contain

radium.

        "Areas like Pennsylvania, which have a known radon problem,

will also have radium in their soils and perhaps in their water

supplies," says Dr. Sridhar Komarneni, professor of clay mineralogy

both with Penn State's College of Agricultural Sciences and Materials

Research Institute.  "At least 25 water systems in Wisconsin have had

problems with radium in their drinking water."

        Federal regulations limit the amount of radium in drinking

water to 5 pico Curies per liter of water.  A pico Curie is a

trillionth of a Curie and is a million times less than the radiation

produced by the radium on a wrist watch face.  Current methods to

remove radium are complicated and expensive.

        Komarneni, working with Naofumi Kozai, a visiting scientist

from the Japan Atomic Energy Research Institute and William J.

Paulus,  master's degree recipient, now at General Motors

Corporation, tested a variety of synthetic micas for radium removal,

but found that sodium-4 mica was the best synthetic clay for this

purpose.  The researchers reported on this work in the April 12

issue of the journal Nature.

         Natural mica is a mineral containing a combination of

aluminum, silica, magnesium and potassium.  The mineral is found in

sheets and has a structure like the pages of a book.  The sheets are

bonded to each other to form a solid, layered mass.

        Natural mica has a closed structure with all the spaces

between layers filled and is not a good ion exchange media, says

Komarneni.  Sodium-4 mica, like natural mica, contains aluminum,

silica and magnesium, but each potassium atom is replaced by two

sodium ions, and fluorine is also added.  The two sodium ions take up

more space than the potassium ion and the layers of mica become

offset, creating a space to capture water and radium.

        "Sodium-4 mica has an interlayer spacing of 2.6 angstroms,

too small to capture ions of hydrated sodium, calcium, magnesium or

potassium," says Komarneni.  "Radium, however, is less hydrated and

therefore small enough to fit between the layers as are barium,

copper, nickel and zinc."

        These other transition metals are not usually found in great

abundance in radium- contaminated water or in tailings containing

radium, so they would not compete for space between the layers.  When

the mica is filled with radium, a shift in the layers occurs and the

atoms of radium are trapped between the layered structure.

        "Once the radium is trapped, it will not leave the mica,"

says Komarneni.  "Disposal and storage requirements would then depend

only on the radioactivity of the material and not whether radium

could leach out of the clay.  Very low level radioactive clay could

simply be buried."

        If the mica is only partially filled with radium at the time

of disposal, then heating to above 212 degrees Fahrenheit will lock

the radium in place.

        Sodium-4 mica is easily synthesized by heating kaolinite -- a

naturally occurring clay with an equal ratio of silicon and aluminum

-- with magnesium oxide and sodium fluoride to about 1500 degrees

Fahrenheit.

        "Clays are already being synthesized for cosmetics, pigments

and catalyst substrates," says Komarneni.  "The cost of manufacture

is probably around $2 per pound."

        Sodium-4 mica could be used in conventional ion exchange

columns to remove radium from water, but would first need to be

pelletized.  To immobilize radium from mine or mill tailings, simply

mixing the clay with the tailings is sufficient.

        The clay could also line ponds that receive radium containing

tailing water to prevent migration from the pond, or clay curtains

around tailings could keep the radium inside.



Contact: A'ndrea Messer         aem1@psu.edu

-- 

.....................................................

Susan L. Gawarecki, Ph.D., Executive Director

Oak Ridge Reservation Local Oversight Committee

                       -----                       

A schedule of meetings on DOE issues is posted on our Web site

http://www.local-oversight.org/meetings.html - E-mail loc@icx.net

.....................................................











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