slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Yuhoon Hwang 1 , Young- Chul Lee 2,3 , Paul Mines 1 , Yun-Suk Huh 2 , Henrik Andersen 1 PowerPoint Presentation
Download Presentation
Yuhoon Hwang 1 , Young- Chul Lee 2,3 , Paul Mines 1 , Yun-Suk Huh 2 , Henrik Andersen 1

Loading in 2 Seconds...

play fullscreen
1 / 26

Yuhoon Hwang 1 , Young- Chul Lee 2,3 , Paul Mines 1 , Yun-Suk Huh 2 , Henrik Andersen 1 - PowerPoint PPT Presentation


  • 134 Views
  • Uploaded on

<8 TH Annual Meeting of DWRIP 2014, January 30 >. Highly stable and reactive nano zero- valent -iron synthesis with Mg-aminoclay and aging characteristics for practical application. Yuhoon Hwang 1 , Young- Chul Lee 2,3 , Paul Mines 1 , Yun-Suk Huh 2 , Henrik Andersen 1.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Yuhoon Hwang 1 , Young- Chul Lee 2,3 , Paul Mines 1 , Yun-Suk Huh 2 , Henrik Andersen 1' - monty


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

<8TH Annual Meeting of DWRIP 2014, January 30>

Highly stable and reactive nano zero-valent-iron synthesis with Mg-aminoclay and aging characteristics for practical application

Yuhoon Hwang1, Young-Chul Lee2,3, Paul Mines1, Yun-Suk Huh2, Henrik Andersen1

  • 1Department of Environmental Engineering, DTU, Denmark
  • 2 Department of Civil and Environmental Engineering, KAIST, Korea
  • 3 Department of Chemical Engineering, Inha University, Korea
introduction nzvi for environmental application
Introduction - nZVI for environmental application

Heavy metals

Cr(VI)

As(III)

ZVI

ClO4-

TCE

Inorganic

ions

Chlorinated organics

NO3-

PCBs

Main mechanism: Redox!

introduction nzvi injection into sub surface
Introduction - nZVI injection into sub-surface

Tratnyek and Johnson, Nanotoday 1, 44-48 (2006)

introduction nzvi aggregation
Introduction – nZVI aggregation

(Phenrat et al., 2007)

  • Tendency to agglomerate of uncoated nZVI

- Cluster size increased to 70 µm in 30 min (Phenrat et al., 2007)

  • Undeliverable to the target location for remediation

- Uncoated nZVI could migrate only few inches to feet (Li et al., 2006)

(Saleh et al., 2007)

1 min

3.75 min

9 min

30 min

25 µm

(Li et al., 2006)

introduction particle stabilization
Introduction – Particle stabilization
  • Particle stabilization has been achieved by attaching stabilizers onto the NPs.

- Surfactant, carboxymethylcellulose (CMC), starch, guar gum, etc.

- Provide strong interparticle electrostatic and/or steric repulsion

1 min

3.75 min

9 min

30 min

Tween-20 (conc.)

Starch (conc.)

(Chen et al., 2012)

(Dong and Lo, 2013)

introduction mg aminoclay
Introduction – Mg-aminoclay
  • Mg-aminoclay for stabilizing metal nanoparticles

- Stacked lamellar structure, water solubilized by protonation of amine group

- Reported as effective stabilizing agent for noble metal NPs (Au, Ag, Pt, Pd)

(Datta et al., 2013)

introduction aging effect
Introduction – Aging effect

(Kim et al., 2012)

  • Contact with air and water after nZVI synthesis

- Simultaneous oxidation of Fe(0) core to iron oxide

  • For practical application: synthesis – (transport) – application (injection)

 What is the essential step to maintain nZVI properties before application ??

overall objectives
Overall objectives
  • Stable and reactive nZVI synthesis in a Mg-aminoclay solution

- Feasibility of Mg-aminoclay as stabilizer

: stability in aqueous solution, reactivity (rate & capacity)

- Stabilization mechanism

- Optimal synthesis condition

  • Aging study of MgAC coated nZVI

- Effect of preparation (washing and storage) procedures

slide9

Stable and reactive nZVI synthesis

in a Mg-aminoclay solution

Q.

  • Mg-aminoclay (MgAC):effective stabilizer for noble metal particles
  • Is it applicable for nZVI ? (stability & reactivity)
  • Then, what is the stabilization mechanism?
materials and methods
Materials and Methods

1. Synthesis of MgAC coated nZVI (borohydride reduction of ferrous salt)

2. Stability test

- Sedimentation

- Dynamic light scattering (Aggregate size & zeta potential)

3. Reactivity test

- Reactive iron content (acid digestion followed by H2 measurement)

- Nitrate reduction batch test(100 mg NO3-N/L, 1000 mg Fe/L)

4. Characterization (KAIST)

- TEM, XRD, FTIR

nzvi stability
nZVI stability

Sedimentation test

Dynamic light scattering (DLS)

  • MgAC/Fe ↑: higher stability & smaller particle size
  •  Feasible as stabilizer for nZVI synthesis
stabilization mechanism
Stabilization mechanism

Mg-aminoclay

++

++

++

++

++

++

++

++

++

++

++

++

++

nZVI

nZVI

nZVI

nZVI

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

++

  • MgAC/Fe ↑
  • : Higher zeta potential (positively charged MgAC)
  • Stabilization mechanism
  • : Surface coating by MgAC by charge neutralization
  • : Inhibition of nuclei growth by steric hindrance of MgAC
reactivity no 3 reduction
Reactivity (NO3- reduction)
  • The low reaction rate of uncoated nZVI: Aggregation during preparation
  • Increase of Fe(0) normalized reaction rate
  • : Discrete distribution of individual nZVI particles
slide14

2. Aging study of MgAC coated nZVI

: Effect of washing & storage

Residual species from synthesis

(SO42-, Na+, H2BO3-)

<nZVI synthesis in lab>

MgAC

nZVI

Solid phase

: MgAC-nZVI

Reduction

Separation

MgAC +

FeSO4

+ NaBH4

Liquid phase

: Extra stabilizer

: Residual impurities from precursors

2Fe2++BH4−+3H2O → 2Fe0+H2BO3−+4H++2H2

Q.

  • Is washing step required for stability and reactivity?
  • Then, what is the reason?
experiment aging strategies
Experiment – aging strategies
  • Aging strategies

Set 1

Set 3

Set 2

nZVI

MgAC

Residual species from synthesis

(SO42-, Na+, H2BO3-)

effect of mgac on stability of nzvi
Effect of MgAC on stability of nZVI
  • Particle size: set 1 >> set 2, 3
  • Zeta potential: set 1 < set 2, 3

 Lower stability in set 1 (pre-washing)

 nZVI stability was influenced by excess MgAC in solution

effect of mgac on stability of nzvi1
Effect of MgAC on stability of nZVI

Fresh nZVI washed with NaHCO3 (set 1)

  • MgAC on the surface of nZVI
  • Not perfectly coated
  •  break down and loss

MgAC particles

Fresh nZVI washed with MgAC (set 3)

  • MgAC particles in solution
effect of mgac on stability of nzvi2
Effect of MgAC on stability of nZVI

1d aged sample

  • Iron oxide plate and needle like structure
  •  oxidation
  • Loosen structure

Set 1

Washing

Set 2

  • Existence of surface coating

Set 3

effect of washing on reactivity of nzvi
Effect of washing on reactivity of nZVI
  • Tendency to decrease: treatment 2 (post) >> treatment 1,3 (Pre)
  • Difference: existence of residual impurities increase of oxidation rate
  • No significant effect of excess MgAC on prevention of oxidation

NO3- reduction capacity

Fe(0) content

increase of nzvi reactivity by electrolyte
Increase of nZVI reactivity by electrolyte

Antibiotic removal (Ghauch et al., 2009)

  • Reductant: ZVI powder, NZVI
  • Electrolyte: 355 mg Cl-/L
  • Reactivity: Increase! (kobs = 0.025/min  0.041/min)

Explosives removal (Kim et al., 2007)

  • Reductant: ZVI
  • Electrolyte: 0.5 ~ 50 mM Cl-/L (29 ~ 2900 mg/L NaCl)
  • Reactivity: Increase! (kobs = 0.0037/min  0.17/min)

(Kim et al., 2007)

Due to pitting corrosion

summary
Summary
  • Stable and reactive nZVI synthesis with Mg-aminoclay as stabilizer

: Thin sheathed grape-like nZVI with high degree of crystallinity

: Electrostatic repulsion offered by positively charged MgAC

  • Aging study of MgAC coated nZVI

- Stability: w/ MgAC > w/o MgAC (pre-washing)

 Loss of stability by washing of MgAC (surface coating)

- Reactivity: Pre-washing > post-washing

 The fast oxidation of nZVI due to residual impurities

 Importance to consider estimated time frame of application

slide22

Thank you for attention

Any questions & comments?

experiment analysis
Experiment - analysis
  • Stability (treatment 1 vs. treatment 2,3)

- Particle size & zeta potential (dynamic light scattering)

- Morphology (TEM)

 Effect of excess MgAC in solution

  • Reactivity (treatment 2 vs. treatment 1,3)

- Aging time: 0, 1, 3, 7 d

- Three reactivity assays

: (1) Optical density, (2) Reactive iron content, (3) Nitrate reduction capacity

: Assumption: relationship between iron content and contaminant reduction

- Confirmation by XRD

 Effect of residual species from synthesis

aging test reactivity correlation
Aging test – Reactivity (correlation)
  • 3 factors to show reactivity: initial absorbance, reduced nitrate, Fe(0)
  • All 3 factors show high linear correlation (R2 > 0.95, P < 0.05)
  • - Especially, the initial absorbance and Fe(0) content show highest correlation
  • - Prediction of reactivity change during aging time by more simple analysis !!
slide25
XRD
  • Fresh sample showed sharp peaks of cubic α-Fe(0)
  • Set 2 (Post-storage washing): Fe(0) peaks were totally disappeared
  • Set 3 (Pre-storage washing w/ MgAC): Fe(0) peaks with co-existed iron oxides

 Effect of residual impurities on aging of nZVI

algae harvesting
Algae harvesting

Lee et al. (2014) RSC Adv., 4, 4122-4127