1 / 13

Synthesis and characterization of poorly-crystaline Fe-Al nano-hydroxides

Synthesis and characterization of poorly-crystaline Fe-Al nano-hydroxides. Katya Bazilevskaya, Douglas Archibald, Carmen Enid Martínez. Crop and Soil Sciences Department & Center of Environmental Kinetics Analysis The Pennsylvania State University.

norris
Télécharger la présentation

Synthesis and characterization of poorly-crystaline Fe-Al nano-hydroxides

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Synthesis and characterization of poorly-crystaline Fe-Al nano-hydroxides Katya Bazilevskaya, Douglas Archibald, Carmen Enid Martínez Crop and Soil Sciences Department & Center of Environmental Kinetics Analysis The Pennsylvania State University 18th World Congress of Soil Science July 11, 2006

  2. Why we study hydroxide nano-particles? • Have large reactive surface area • Create pH-dependent charge Form coatings: meta-stable mixtures of Fe-, Al- and Si oxides and organics, which: • Affect mobility of nutrients and contaminants • Reflect soil-forming processes • Affect mineral dissolution rates

  3. Experimental conditions: [Fe+Al] = 10 mM; %Al: 0, 10, 25, 30, 50, 75, 100; pH = 5 0.1 M KOH Fe (+Al) nitrate sol-n, pH ~2 • Slow titration rate (0.1 ml/min) • Dyalisis to remove salts and excess Al

  4. Measured by light scattering (ZetaPALS, Brookhaven Instruments) AFM images of Fe-Al particles 0% Al 30% Al

  5. What methods to use? X-ray diffraction (XRD): • long range order information • synchrotron XRD for poorly crystalline hydroxides • only crystalline phase Extended X-ray Absorption Fine structure spectroscopy (EXAFS) • short range order (atom’s second neighbor information – bond distance, type of bond)) • both crystalline and amorphous • Can only probe for Fe, not Al Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR FTIR) • short range order (bonding and reactivity of protons) • both crystalline and amorphous • distinct iron and Al hydroxide OH-vibrations • ATR technique provide precise technique: measures nano-particles coatings on the sensor (do not need to separate nano-particles by centrifugation and freeze-drying)

  6. Structure of end-members Goethite Gibbsite Goethite 3450, 3206 1687, 1643 888, 798 Gibbsite 3620, 3525 3455, 3390 1024, 975 -

  7. %Al increases %Al increases Infrared spectra of Fe-Al hydroxides with different %Al 0% Al 100% Al

  8. Change of infrared spectra of Fe-Al hydroxides with time 0%Al 25%Al Time = 0 days Time = 2 days @ 50 C

  9. Fe-only Fe-O Fe-Fe Fourier Transformed XAFS, χ (R) Fe:Al=1:1 Fe-Al Distance to neighboring atom R, Å Preliminary Fe-EXAFS data(aged for 2 weeks) From the Literature • Fe-Fe distances for • goethite • 3.0 – 3.4 Å • (2.5-2.9 in R) • Fe-Al distances for • Fe3+-gibbsite • 2.9 Å (2.4 in R) • Epidote • 2.95 Å (2.5 in R) • LiAlO2with 1wt.%Fe3+ • 3.15 Å (2.6 in R) Radial distribution functions for oxide suspensions of various Fe:Al ratios

  10. Connection with real life….Spodosols Profile-view Top-view • To monitor formation of iron coatings on quartz in situ: • placed quartz in the soil profile • recovered after 1 year

  11. Acknowledgments • Funding: Center of Environmental Kinetics analysis (CEKA) • XRD and EXAFS: beamlines X-16C, X-18B, X-10C, National Synchrotron Light Source, Brookhaven National Laboratory • ….

More Related