Nano-sized Zero Valence Iron Detection

Jing

Zhenqing Shi

Paul G. Tratnyek

Division of Environmental Biomolecular Systems

Oregon Health & Science University

Portland, OR

2Introduction

nZVI: nano-sized zero valence iron: currently used for groundwater remediation (shown right)

ORP: oxidation-reduction potential: used to assess the results of injection of nZVI for groundwater remediation

http://www.todaamerica.com/products/eco/rnip/rnip_03.html

Applications: Measuring the ORP after injection of nZVI can serve as a sensitive probe for a range of important processes, such monitoring and detecting the nanoparticles. The time dependence of the electrode response reflects the kinetics of corrosion and aggregation/settling of the nZVI. Thus, ORP measurements can prove to be a useful parameter in determining movement of the nano-particles upon injection.

3

Potentiometer

Rotating disc

Argon gas purging

Reference electrode (Ag/AgCl)

Working electrode (Pt/GC)

Background electrolyte (NaHCO3) or nZVI solution

(CMC)

RDE (rotational disk electrode)

Data acquisition

4

200 mg/L and 50 mg/L CMC nZVI in NaHCO3 Solution with 5 mm GC Electrode

-800-700-600-500-400-300-200-100

0100

0 50 100 150 200

Time (min)O

RP

(mV

)

200 mg/L

50 mg/L

200 mg/L, 50 mg/L, and 20 mg/L CMC nZVI in NaHCO3 Solution with 5 mm Platinum Electrode

-800

-700

-600

-500

-400

-300

-200

-100

0

100

0 50 100 150 200

Time (min)

OR

P (m

V)

200 mg/L

50 mg/L

20 mg/L

Figure 1 Figure 2

Results: RDE with CMC nZVI

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Figure 3.

200 mg/L BH, CMC, 10DS, and M2 nZVI in NaHCO3 Solution with 5 mm GC Electrode

-800-700-600-500-400-300-200-100

0100

0 50 100 150 200Time (min)

OR

P (

mV

)

BHCMC10DSM2

Results: RDE comparison of various nZVI

6

Potentiometers

Reference electrode (Ag/AgCl)

Working electrode (Pt/GC) Argon gas

purging

Background electrolyte (NaHCO3) or nZVI solution

(M2)

Waste beaker

Flow Cell

FCE (flow cell electrode) and RDE

Rotating disc

Data acquisition

7

Figure 4.

FCE results of 200 mg/L M2 nZVI in NaHCO3 Solution (Pt Electrode)

-800-700-600-500-400-300-200-100

0100

0 50 100 150

Time (min)

OR

P (

mV

)

0.25 mL/min

1.0 mL/min

0.5 mL/min

0.125 mL/min

Results: FCE and RDE comparison of various flow rates

8

Figure 4.

FCE results of 200 mg/L M2 nZVI in NaHCO3 Solution (GC Electrode)

-800-700-600-500-400-300-200-100

0100

0 50 100 150

Time (min)

OR

P (

mV

)

0.25 mL/min

1.0 mL/min

0.5 mL/min

0.125 mL/min

9

Figure 4.

FCE results of 200 mg/L new CMC nZVI in NaHCO3 Solution (GC and Pt Electrode, Q = 0.5 mL/min)

-800-700-600-500-400-300-200-100

0

0 50 100 150

Time (min)

OR

P (

mV

)

Pt GC

Results: FCE comparison of GC and Pt Electrodes

10

Potentiometers

Reference electrode (Ag/AgCl)

Working electrode (Pt/GC)

Argon gas purging

Background electrolyte (NaHCO3) or nZVI solution

(M2)

Flow Cell

Future FCE (flow cell electrode) column experiment

Rotating disc

Data acquisition

Masterflex pump

Column

Fractional Collector

11SummaryRDE set up• Platinum electrodes under similar conditions gave much lower ORP readings than

glass carbon electrodes

• In comparing past ORP measurements of BH, 10DS, and M2 with CMC nZVI, results have shown that the difference in preparation process and organic coating of the particles have little effect on ORP measurements

• Particles with organic coating, such as CMC and M2 nZVI, have a much higher minimum ORP value than those without organic coating (BH and 10DS)

RDE and FCE combined set up• A flow rate of 0.5 mL/min was found to be most effective, because ORP readings

stabilize at a relatively fast rate, and because there was considerably less noise in the FCE data.

• Flow rates of 1 mL/min, 0.25 mL/min, 0.125 mL/min were also used, but resulted in more unstable FCE curves. Reasons for this remain to be tested.

FCE GC and Pt electrodes set up• Similar to the RDE set up results, platinum electrodes under controlled conditions

gave much lower ORP readings than glass carbon electrodes

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Referencing:

• Standard Methods for the Examination of Water and Wastewater. 17th ed. American Public Health Association, American Water Works Association (AWWA), and Water Pollution Control Federation, 1989. pp. 3-102 – 3-106.

• Hill, A.G. et al. "Standardized General Method for the Determination of Iron with 1,10-Phenanthroline." Analyst 103 (1978): 391-96.

• Adapted from Zhenqing Shi’s RDE, FCE, FCE and RDE combined, and FCE column experiment SOPs in July, 2010. Other contributors include: Paul Tratnyek and Jim Nurmi.

• Adapted from Hach SOP book, FerroVer Total Iron method #265

• Adapted from Graham’s Total Iron Analysis SOP through Rick Johnson in August, 2010.

• Adapted from Viollier, E. et al. "The Ferrozine Method Revisited: Fe(II)/Fe(III) determination in natural waters." Pergamon 15 (2000): 785-90.

Acknowledging:

Dr. Paul G. Tratnyek for significant mentoring and contributions

Dr. Zhenqing Shi for close guidance and assistance in experiments and procedures

Dr. Antonio Baptista for generous funding and support

Ms. Karen Wegner and Ms. Elizabeth Woody for their time and efforts in making this internship a possibility

References and Acknowledgements