Tuesday, February 22, 2011, 10:30 am — Room 300, Chemistry Bldg. 555
Lead is one of the most toxic and ubiquitous contaminants present in drinking water. Recent studies have shown that halogens species such as chlorine and chloramine are intimately involved in controls of lead release due to their effects on the formation of lead dioxide. When stable, PbO2 tends to suppress plumbosolvency but its destabilization by environmentally-relevant reductants can cause very high rates of lead release. Examination of the fundamental mechanisms of lead dioxide deposition and reduction shows that the electrochemical oxidation of Pb(II) proceeds via two distinct intermediates that correspond to a hydrodynamically mobile Pb(III)* species and a mixed Pb(II)/Pb(IV) complex that undergoes incorporation into growing nano-size PbO2 nuclei. Pb(II)/Pb(IV) intermediate is also formed upon the reduction of lead dioxide. The electrochemical oxidation of Pb(II) appears to be critically affected by OH• radicals whose generation at the electrode surface is catalyzed by PbO2 itself. Similar processes were in chlorine oxidations of Pb(II) hydroxide and (hydroxo)carbonates typical for environmental conditions. Further details and implications of these results will be discussed at the seminar.
Hosted by: Kotaro Sasaki
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