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September 22nd, 2008

QUT’s Zhu has ceramic filter for radioactive waste

Published on September 22nd, 2008 | By: pwray@ceramics.org

(Graphic: Zhu)

Water contaminated in nuclear power applications and other situations where radiactive elements used can be a significant problems, especially because of the volume compared to the actual amount of radiactive particles. What if there was a fairly simple way to run the water through a filter and remove those materials? Queensland University of Technology’s Zhu Huai Yong says he has just such a filter. Regular readers might remember Zhu’s name. We had a post about him recently pondering the possibility that medieval stained glass makers who used gold were early nano technologists. But Zhu’s forté is ceramic filters. Zhu thinks there has to be a better way of storing contaminated fluids like water other than to put them in barrels or lakes. His idea involves ceramic fibers that will capture and “outlive” the decaying material.

“We have created ceramic nanofibres which attract and trap radioactive cations (positively charged ions), possibly forever,” Zhu said. “The ceramic material can last a very long time, much longer than the radioactivity of a radioactive ion. The fibres are in very thin layers, less than one nanometre in width, and the radioactive ions are attracted into the space between the layers. Once the ceramic material absorbs a certain amount, the layers collapse to lock the radioactive ions inside.”

Zhu’s fibers are made from titanium dioxide, and are about 40 microns in length. In an interview with Nanowerk, Zhu explained some of the details behind his filter:

“Natural inorganic cation exchange materials, such as clays and zeolites, have been extensively studied and used in the removal of radioactive ions from water via ion exchange and are subsequently disposed of in a safe way. However, synthetic inorganic cation exchange materials – such as synthetic micas, g-zirconium phosphate, niobate molecular sieves, and titanate – have been found to be far superior to natural materials in terms of selectivity for the removal of radioactive cations from water. Radioactive cations are preferentially exchanged with sodium ions or protons in the synthetic material. More importantly, a structural collapse of the exchange materials occurs after the ion exchange proceeds to a certain extent, thereby forming a stable solid with the radioactive cations being permanently trapped inside. Hence, the immobilized radioactive cations can be disposed safely. Generally, ion exchange materials exhibiting a layered structure are less stable than those with 3D crystal structures and the collapse of the layers can take place under moderate conditions” says Zhu. “Then again, it has also been found that nanoparticles of inorganic solids readily react with other species or are quickly converted to other crystal phases under moderate conditions, and thus are substantially less stable than the corresponding bulk material.”

Zhu has been active in looking for other filter applications. In 2007, he suggested a method for using ceramics to filter HIV from bloodstreams.

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