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Chemist wins EPA grant to develop nanoreactor

By : Susan Barker

Binghamton University chemistOmowunmi Sadik has been awarded a three-year, $351,000 grant from the Environmental Protection Agency to develop advanced nanosensors for continuous monitoring of heavy metals in drinking water and industrial effluent.

While conventional approaches for detection of heavy metals in water are expensive and not suited for use in the field, Sadik and her research collaborators have already developed a prototype nanosensor that can concentrate and trap lead particles 10 times smaller than a human hair. No existing technology is able to filter such small metal particles from water, Sadik said.

The lead prototype was enough to secure EPA funding to go after some of the other “most wanted” metals in the EPA’s priority list of metals that are of major environmental concern. The list includes lead, cadmium (industrial), arsenic (natural decomposition and industrial), chromium 6 (nuclear reactors) and copper, among others. Cadmium and copper are industrial wastes, arsenic is produced by natural decomposition and as an industrial waste, and chromium 6 is a nuclear waste product, Sadik said.

Working with Joseph Wang from New Mexico State University, who will focus on nanofabrication of the small electrodes required by the nanoreactor, and chemical engineer Ashok Muchandani of the University of California at Riverside, who will work on the remediation or metal reclamation phase of the project, Sadik intends to develop a one-square-centimeter prototype nanoreactor capable of detection and remediation of all of the above mentioned heavy metals.

In order to do that, she will first have to develop specific colloidal-metal nanoparticles that can be incorporated into a bed of electrically conducting polymers. In analogy to integrated circuits used in semiconductors, in which millions of microcircuits are located on a small silicon chip, this nanoreactor can be viewed as comprising millions of identical, elementary, molecular active sites 10 times smaller than a human hair. These molecular active sites will be generated through electromechanical synthesis and tailored to meet specific environmental or industrial needs. It is basically an elementary, molecular, heavy metal reactor which can generate a field of molecular interactions, secure the recognition of the desired metal and decide on the specificity of the reaction. The nanoreactor may be coupled with other components and additives in order to achieve the desired remediation or to meet industrial needs.

“With additives that ensure a very specific reaction, each of the monomers is sensitized to the particular metal so that in the making of the polymer, it creates colloids that will do the sensing and trapping,” Sadik said.

Once Sadik has worked out the required chemistry from temperature and pH to the novel nanostructured materials that will be used in the nanoreactor, she is hoping the team can produce a simple device that could be used much like the paint-matching systems common to most home improvement stores.

“For example, if we come up with a set of conditions for the chemicals, pH and temperature for removal of lead in water, by changing the chemistry inside the reactor we can make it applicable for industrial effluent,” she said. “And we should be able to provide a template for each of the metals in water or in industrial effluent.”

The idea is that after all the metals have been trapped, they can then be stripped out into another medium, making reclamation possible in the case of valuable metals, such as silver. As for toxic metals, such as arsenic and chromium 6, the EPA would likely oversee safe disposal, Sadik said.

Although the tiny size of the proposed prototype nanoreactor will limit the quantity of water it can treat, at this point in the research, that is not an issue, Sadik said.

“What matters is we must be capable of removing 100 percent of the metal in a volume of water. So if I have only a cup of water, I must be able to remove all the metal,” she said. “If we can do this so that it will give us 100 percent trapping of the metal, then the engineers can come in and scale the system up to the size that would be required to treat larger volumes. What matters to us as chemists is to make sure the chemistry works for the metals of interest.”
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Last Updated: 10/14/08