New Ion Exchange Technology Shows Potential for Trapping Pollutants

September 08, 2011

Effective substrate could be used to prevent groundwater contamination

Chemists at the University of California, Santa Cruz (UCSC) have developed a new type of material that can soak up negatively charged pollutants from water. The new material, which they call SLUG-26, could be used to treat polluted water through an ion exchange process similar to water softening.

In a water softener, sodium ions weakly attached to a negatively charged resin are exchanged for the hard-water minerals, which are held more tightly by the resin. SLUG-26 provides a positively charged substrate that can exchange a nontoxic negative ion for the negatively charged pollutants.

Water softening techniques are very effective for removing minerals such as calcium and magnesium, which occur as positively charged ions in hard water. But many heavy metals and other inorganic pollutants form negatively charged ions, and existing water treatment processes to remove them are inefficient and expensive.

"Our goal for the past 12 years has been to make materials that can trap pollutants, and we finally got what we wanted. The data show that the exchange process works," said Scott Oliver, associate professor of chemistry at UCSC.

The chemical name for SLUG-26 is copper hydroxide ethanedisulfonate. It has a layered structure of positively charged two-dimensional sheets with a high capacity for holding onto negative ions. Oliver and UCSC graduate student Honghan Fei describe the compound in a paper that will be published in the journal Angewandte Chemie and is currently available online.

The researchers are currently focusing on the use of SLUG-26 to trap the radioactive metal technetium, which is a major concern for long-term disposal of radioactive waste. Technetium is produced in nuclear reactors and has a long half-life of 212,000 years. It forms the negative ion pertechnetate in water and can leach out of solid waste, making groundwater contamination a serious concern.

"It's a problem because of its environmental mobility, so they need new ways to trap it," Oliver said.

Source:

University of California, Santa Cruz

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