Zero-valent iron nanoparticles with tunable properties: synthesis, inclusive characterization and applications

Size: px

Start display at page:

Download "Zero-valent iron nanoparticles with tunable properties: synthesis, inclusive characterization and applications"

Anne Sutton
6 years ago
Views:

1 Zero-valent iron nanoparticles with tunable properties: synthesis, inclusive characterization and applications Jan Filip 1, J. Kašlík 1, V. Blechta 1, I. Medřík 1, M. Vondráček 2, O. Schneeweiss 3, Z. Marušák 1, E. Otyepková 1, J. Pechoušek 1, Jan Slunský 4, Radim Lédl 4, R. Zbořil 1 et al. 1 Regional Centre of Advanced Technologies and Materials, Palacký University, Olomouc, CZ 2 Institute of Physics, Academy of Sciences of the Czech Republic, Praha, CZ 3 Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno, CZ 4 NANO IRON, s.r.o., Rajhrad, CZ

area high reactivity Small particle size migration Tunable properties (size, surface

2 Why nanoscale zero-valent iron (nzvi) particles? Unusual properties: Low standard reduction potential high reactivity Large surface area high reactivity Small particle size migration Tunable properties (size, surface treatment) variable rates of reaction Usually simple synthesis High potential for application in environmental techniques

reduction Liquid phase reduction (borohydride reduction) Fe 3+ (H 2 O) 6 + 3BH 4- + 3H

3 Ball milling Cryogenic milling Solid-state reduction of Fe-bearing precursor at high temperature Methods of synthesis of nzvi Sonochemical Electrochemical Gas phase reduction Liquid phase reduction (borohydride reduction) Fe 3+ (H 2 O) 6 + 3BH H 2 O Fe 0 + 3B(OH) H 2 (BET surface area m 2 /g Wang et al. 2009, J Nanopart Res)

4 How to finely tune the properties of nzvi prepared by solid-state processes? Selection of the precursor Submicrocrystalline Nanocrystalline Amorphous Controlling the conditions of thermal reduction Post-synthesis (surface)modification Passivation Applying surfactants

How to in-situ monitor the process of nzvi synthesis/surface

$Variable-temperature X-ray powder diffraction (VT-XRD)$ Thermogravimetric analysis + evolved-gas analysis (TGA+EGA)

5 How to in-situ monitor the process of nzvi synthesis/surface passivation? Variable-temperature X-ray powder diffraction (VT-XRD) Temperature-programmed reduction/oxidation (TPR/O) Thermogravimetric analysis + evolved-gas analysis (TGA+EGA) VT-XRD TPR/O TGA EGA Characterization of the products: XRD, Mössbauer spectroscopy, SEM, TEM, BET, XPS, reactivity measurements, etc.

Design of high-temperature experiments Non-isothermal

under hydrogen/forming gas (10% of H 2 in N 2 )

FeOOH polymorphs Fe 2 O 3 polymorphs Magnetite Fe 3 O

6 Design of high-temperature experiments Non-isothermal and isothermal heat treatment of suitable precursor under hydrogen/forming gas (10% of H 2 in N 2 ) Precursor materials: Ferrihydrite Fe 5 HO 8 4H 2 O FeOOH polymorphs Fe 2 O 3 polymorphs Magnetite Fe 3 O 4 Variable gas pressure Variable gas flow Variable particle size

transform. growth of coherent Fe 0 domains Counts 6000 MCL: ~ 12 nm!

7 Ferrihydrite precursor 2-line and 6-line 10 % of H 2 in N 2 Correction made by using of Mössbauer spectroscopy Fh-to-Fe 0 transform. growth of coherent Fe 0 domains Counts 6000 MCL: ~ 12 nm! Surface area: >58 m 2 /g Position [ 2Theta] (Cobalt (Co))

8 Crystalline precursor FeOOH polymorphs Goethite Akaganéite Lepidocrocite

9 Goethite: the influence of particle-size and atmosphere H 2 10% of H 2 in N 2 Nanocrystaline 117 m 2 /g Microcrystalline Nanocrystaline Surface area: <50 m 2 /g

5 nm 10000 6400 311 3600 1600 Surface area: ~25 m 2 /g 40.4 40.

10 Intensity (counts) Crystalline precursor Fe 2 O 3 polymorphs a-fe 2 O 3 b-fe 2 O 3 g-fe 2 O 3 MCL = 33 nm SEM Mean: 68.5 nm Surface area: ~25 m 2 /g Theta ( ) magnetite maghemite

11 Relative abundance (wt.%) Hematite: the influence of gas flow and gas pressure atm. pressure Gas pressure: 3 bars Gas flow: 30 ml/min gas flow 30 ml/min TGA TPO

Surface passivation and/or stabilization of nzvi No

poly(ethylenglycol) polyaspartate poly(styrene)

guar gums potato starch alginate chitosan www.

12 Surface passivation and/or stabilization of nzvi No surface treatment Surface passivation via iron oxides/ carbon shell Surface modifiers: poly(acrylic) acid poly(methyl) methacrylate poly(ethylenglycol) polyaspartate poly(styrene) sulfonate triblock copolymer (PMAA48-PMMA17-PSS660) carboxymethylcellulose polyvinyl alcohol-co-vinylacetate-co-itaconic acid xanthan and guar gums potato starch alginate chitosan Tween 80 (polyoxyethylenesorbitane monooleate) Axilate 32S (disp. of sodium salt of polyacrylic acid)

13 The formation of FeO x -shell 2 % of O VT-XRD 2 in N 2 RT 150 C TGA TPO

14 The character of the shell of FeO x -stabilized nzvi Room temperature EDX TEM 150 C Fe 2p Fe 3+ Fe 2+ Fe 0 TEM XPS

15 Reactivity and stability of FeO x -stabilized nzvi TCE 35 mg/l (40 ml) 15 mg nzvi added analyzed by GC 4 nm shell TG in air XRD Bare nzvi: k SA = (L m -2 hr -1 ) nzvi with 4 nm shell: k SA = (L m -2 hr -1 ) nzvi with 7 nm shell: k SA = (L m -2 hr -1 ) k SA surface-area normalized reaction rate constant

16 Thank you for your attention!

R.M.Cornell U. Schwertmann. The Iron Oxides. Structure, Properties, Reactions, Occurrence and Uses. Weinheim New York Basel Cambridge Tokyo VCH

R.M.Cornell U. Schwertmann. The Iron Oxides. Structure, Properties, Reactions, Occurrence and Uses. Weinheim New York Basel Cambridge Tokyo VCH R.M.Cornell U. Schwertmann The Iron Oxides Structure, Properties, Reactions, Occurrence and Uses VCH Weinheim New York Basel Cambridge Tokyo Contents 1 Introduction to the iron oxides 1 2 Crystal structure