Nano-sized Zero Valence Iron Detection

1. Nano-sized Zero Valence Iron Detection Jing Zhenqing Shi Paul G. Tratnyek Division of Environmental Biomolecular Systems Oregon Health & Science University Portland, OR

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

3. RDE (rotational disk electrode) Rotating disc Potentiometer Working electrode (Pt/GC) Data acquisition Argon gas purging Reference electrode (Ag/AgCl) Background electrolyte (NaHCO3) or nZVI solution (CMC)

4. Results: RDE with CMC nZVI Figure 1 Figure 2

5. Results: RDE comparison of various nZVI Figure 3.

6. FCE (flow cell electrode) and RDE Rotating disc Data acquisition Working electrode (Pt/GC) Argon gas purging Potentiometers Reference electrode (Ag/AgCl) Flow Cell Background electrolyte (NaHCO3) or nZVI solution (M2) Waste beaker

7. Results: FCE and RDE comparison of various flow rates Figure 4.

8. Figure 4.

9. Results: FCE comparison of GC and Pt Electrodes Figure 4.

10. Future FCE (flow cell electrode) column experiment Potentiometers Data acquisition Fractional Collector Working electrode (Pt/GC) Reference electrode (Ag/AgCl) Flow Cell Rotating disc Column Argon gas purging Masterflex pump Background electrolyte (NaHCO3) or nZVI solution (M2)

11. Summary • RDE 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

12. References and Acknowledgements 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 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.