New compound may immobilize AIDS virus and some radionuclides

A compound that could potentially immobilize the AIDS virus or selectively extract radionuclides from nuclear wastes at various US high-level storage sites has been developed by a Sandia researcher who wasn’t even looking for it.

An article in the Aug. 9 Science describes characteristics of the newly discovered, extremely active compound, called niobium heteropolyanions (hetero-poly-an-ions) or HPAs.

"It wasn’t difficult to synthesize, it was luck," lead researcher May Nyman (6118) says of her discovery. "I wasn’t going after it intentionally, but after I found it, I realized I had something new and exciting."

May found the right conditions to synthesize the first niobium HPA, and then tweaked to create an assortment of them.

The entities became the first niobium HPAs ever reported, formed inexpensively at the relatively benign and easily achievable temperature and pressure of boiling water.

Unlike other HPAs, niobium HPAs are basic rather than acidic, which means they can survive longer and possibly even thrive in the generally basic or neutral environments of radioactive wastes and blood, respectively.

Preliminary work with the Savannah River site indicates that the new compounds do indeed selectively remove certain radionuclides from their waste solutions.

To bind viruses, researchers have tested a host of HPA compositions, says May. "In these exhaustive studies, it’s been found that HPAs with small amounts of iron or niobium have an especially strong binding effect. Now we have HPAs that are completely niobium."

HPAs in the form of oxides of vanadium, tungsten, and molybdenum have been known to researchers since the late 19th century. The compounds’ peripheries consist of voraciously active oxygen ions. These have long intrigued researchers because of their capabilities to do much useful chemistry, including bind viruses and large metal atoms such as some radionuclides.

Once such compounds bind with an AIDs virus, the virus is no longer capable of entering a cell to damage it. HPAs may also bind with radionuclides called actinides, which removes them from the mixture by phase separation for easier and safer storage.

While previously known HPAs were made cheaply and easily at room temperatures and pressures, they were known to be stable only in acid environments.

This behavior means they cannot function well in blood as antiviral agents, because blood is neither acidic nor basic but instead is neutral.

Even worse, the liquid nuclear wastes at most DOE waste sites — for example, Hanford, Savannah River, and Oak Ridge — are extremely basic. These environments attack acidic compounds and cause them to fall apart, says May.

May’s discovery of the base-stable HPA came about when Sandia was called upon by the Savannah River site to find the cause of a clogging problem at the site’s attempts to extract a dangerously radioactive isotope of cesium. The extraction called for passing nuclear waste solution through a column of pebble-sized materials called zeolites that sequester cesium into tiny pores. She found that the zeolites contained small amounts of an impurity that forms during manufacturing. The acidic manufacturing treatment of the zeolites led to column-clogging behavior of the impurity. Identifying the problem concluded her task, but scientific curiosity led her to attempt to create the compound as an independent entity.

"I was curious to see if I could synthesize it pure, rather than leave it merely as a discovered impurity," says May.

Her research on developing and utilizing HPAs will be soon be supported by two Laboratory Directed Research and Development grants, as well as the Environmental Management Science Project out of the DOE Office of Science in collaboration with the Savannah River site.

"One man’s trash is another’s treasure," May says of her experience. "What used to be clogging columns could now be taking out radionuclides, so it can be Savannah River’s and DOE’s treasure in the end, as well."

May’s co-authors include Francois Bonhomme and Jim Krumhansl (6118), Todd Alam and Brian Cherry (1811), Mark Rodriguez (1822), Tina Nenoff (6233), and Amy Sattler (former summer intern).