Nanotechnology for the Environment: Challenges, Risks and Research Directions Slawo Lomnicki Louisiana State University, Chemistry Department LSU Superfund Research Center
Catalysis Nanotechnology Pioneer catalyst design - dispersion of the active phase on the surface of the support monolayer coverage ultimate goal Usually a polydispersed systems are synthesized
Nanostructure of the Catalysts by HREM
Zeolites Nanotunnels Timeline Late 40 s and 50 s First synthetic Zeolites 1960 s High Al/Si ratio zeolites 1970 s Silica molecular sieves 1980 s ALPO, SAPO Large Pore Zeolites 1990 c MCM 2000 nonozeolites
Zeolites for Remediation Both natural and synthetic Zeolites are used as adsorber materials to remove pollutants such as cations from contaminated waters (cations Cu, Pb, Cd, As) Gas phase adsorbers (nitrozamines) Ion exchanges zeolites are used for ammonia removal Nanocrystalline zeolites - new materials
Sorbents - clays
MCM Mesoporous Materials Adsorbents Membranes Functional groups depend on the target: thiol, amino or chelating agents RSC Adv., 2012, 2, 1088 1095
SAMMS Self Assembled Monolayers on Mesoporous Supports Adsorbers for: Arsenate Chrome Copper Gold Lead Mercury
Carbon Nanotubes A novel version of activated carbon Graphic: Patrick Gillooly, MIT
Polymeric nanoparticles polyurethane acrylate anionomer (UAA) poly(ethylene glycol)-modified urethane acrylate (PMUA) Particles have hydrophilic exterior and hydrophobic interior trap hydrophobic contaminants such as PAHs aqueous soil Environ. Sci. Technol. 2004, 38, 1605-1610
Titanium Dioxide Photocatalyst Water Decontamination Halogenated Organics NOx SOx and VOC controll TiO 2 Antibacterial and Antifungal Odors Control
Other AOP Catalysts (Advanced Oxidation Processes) ZnO WO3 O 2 Fe 2 O 3 hn e - O 2.- P h + TiO 2 H 2 O P+ H + +. OH
nzvi nano Zero Valent Iron Environ. Sci. Technol. 2012, 46, 12913 12920
Nanomaterials Advantages Increased reactivity due to the quantum effects Increased mobility in the media (molecule like behavior) High surface to volume ratio Nanomaterials disadvantages Increased reactivity due to the quantum effects Increased mobility in the media (molecule like behavior) High surface to volume ratio
Biggest Challenge of Nanomaterials for Remediation LONG DISTANCE TRANSPORT SEPARATION FROM MEDIA Mädler and Friedlander, Aerosol and Air Quality Research, Vol. 7, No. 3, pp. 304-342, 2007 ZVI transport
Nanoparticle Exposure Most common exposure to nanomaterials is by inhalation Some exposure by digestion is possible some evidence of transport through intestinal and stomach epithelium Contact exposure are of less concern
Particulates Deposition in Respiratory System Particles larger than 10 microns are filtered out by nose. Particles smaller than 100nm (PM0.1) are believed to be transported through the blood system to internal organs.
Particle Deposition and Uptake W. G Kreyling, S. Hirn, C. Schleh, Nature Biotechnology, 12, 1275-1276, 2010 H. AfesehNgwa et al. / Toxicology and Applied Pharmacology 256 (2011) 227 240
Oxide Nanoparticles and Persistent Radicals O OH X O O O O M n O OH -HX M n O OH O M n-1 OH Upon chemisorption of organic molecule transition metal cation undergoes a reduction process through the electron transfer from adsorbate to the metal forming a surface bound radical.
Oxide Nanoparticles and Persistent Radicals Epinephrine adsorbed on CuO clusters
Radical Cycle Experimental data show that from 1 particle associated radical 8 OH radicals are formed 250x10 3 DMPO-OH Intensity 200 150 100 50 2%CuO/CaB-O-sil 2%CuO/CaB-O-sil-EPFRs 2%CuO/CaB-O-sil-EPFRs- 24 hours later 0 0 200 400 600 800 1000 Time from intial DMPO addition, mins 1200
Inhalation Risks - SAMMS Research is needed Leaching of adsorbate in physiological media ph effect Is desorption possible competitive reactions Effect of thiols -complexation constants Redox reactions presence of superoxide and hydroxyl radicals
Control of Nanomaterials
Supported Nano Metals and Oxides Comparison of supported metal oxide catalysts made by dendrimer template method and traditional incipient wetness method.
Supported Metal Oxide Nanoclusters d m (nm) s 190 10.0 5.64 2.52 4.09 1.59 3.27 0.24 3.17 0.71 2.37 0.34 2.05 0.23 1.86 0.17 1.68 0.19 1.55 0.19 < 1 NA Recent development of preparative methods allow for a precise control of cluster sizes
Frequency 80 60 40 Ni16 3.03+/-0.40nm Ni8 2.58+/-0.29nm Ni4 1.75+/-0.27 Bound Metal Oxide Nanoclusters NiO clusters 20 0 0 1 2 3 Diameter (nm) 4 5 Fe 2 O 3 clusters
Carbon Nanotubes - Sponges Cleaning up toxic spills has always been a problem. It s hard, and it s expensive, and you have to be thorough. It is made of carbon nanotubes regular carbon atoms arranged in a specific cylindrical shape and can absorb organic pollutants from the surface of water (such as oil and solvents) up to 180x its weight without absorbing water. And once its full of toxic liquids, the best part is that you can just wring it and start again
Polymeric Nanoparticles Comprises branched macromolecules with chemically or physically tunable sites that are combined to form globular microparticles.
Important Conclusions Nanomaterials -Expect unexpected Transport control of nanomaterials is very important New technologies can develop a non-nano nano materials Toxicological studies are urgently needed Special focus should be on the sorptive nanomaterials in physiological media do they release absorbed pollutants.
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