tailieunhanh - Synthesis and Application of Nanosize Semiconductors for Photoxidation of Toxic Organic Chemicals

At the open burning sites, some metals were present at concentrations over one hundred times typical background levels for soils, including lead, a highly toxic metal. High levels of other toxic metals, including cadmium and antimony, were also present. Numerous classes of organic chemicals were also present in one or more of the samples, including many halogenated (chlorinated or brominated) chemicals. Many of the compounds identified are intentionally used in electronic devices. These included phthalates, widely used as plasticisers in flexible plastics such as PVC, polybrominated diphenyl ethers (PBDEs) and triphenyl phosphate (TPP) both used as flame retardants, and polychlorinated biphenyls (PCBs) , long banned from. | Synthesis and Application of Nanosize Semiconductors for Photoxidation of Toxic Organic Chemicals . Wilcoxon Nanostructures and Advanced Materials Chemistry Sandia National Laboratories Albuquerque . 87185-1421 jpwilco@ Colloborators . Thurston P. Provencio . Samara Talk Outline Industrial Solvents in the Environment Impregnated Sediments Water Table Brief History of the problem and possible remediation approaches Bioremediation Soil Washing Adsorption Photooxidation Photocatalysis using UV light and nanosize TiO2 and SnO2. Photocatalysis using visible light and MoS2 nanoclusters. Acknowledgement Div. Of Materials Science and Engineering Office of Science US Dept. of Energy under contract DE-AC-04-AL8500. Sandia is a multiprogram laboratory operated by Sandia Corporation a Lockheed-Martin Company for the US Dept. of Energy. This work performed under the aupices of the DOE Environmental Science Environmental Research ER ES Program. tsnl Typical Scenario-Dense Non-Aqueous Solvent Pools Rain Organic Pool in Soil _ Slow Leaching Water Table Examples- Cleaning Solvents- Tri-Chloroethylene TCE Herbicides Fungacides Pesticides Pentachlorophenol PCP DDT Explosives . TNT Major Remediation Issues- 1 Low Solubility 1-10 ppm in water provides continuous leaching with time 2 Treatment of large volumes of highly diluted toxins 3 Cost of treatment tsnl Possible Treatment Approaches- Step 1 Excavation Soil Washing Conventional Treatment Options 1 Filtration and or Adsorption of toxic chemicals in aqueous supernatant from Step 1 2 Chemical Oxidation or Total Mineralization of the the Organics 3 Deep UV Photooxidation of the Organics 4 Photocatalytic oxidation of the Organics . colloidal titania slurries Cost and large volumes involved are the principal practical concerns. .