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Application of O 2 Activation toward Organic Pollutant Degradation

Application of O 2 Activation toward Organic Pollutant Degradation. Derek F. Laine and I. Frank Cheng University of Idaho Chemistry Department Moscow, ID 83843-2343 lain3267@uidaho.edu ifcheng@uidaho.edu 208-885-6387. The ZEA Organic Pollutant Degradation System.

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Application of O 2 Activation toward Organic Pollutant Degradation

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  1. Application of O2 Activation toward Organic Pollutant Degradation Derek F. Laine and I. Frank Cheng University of Idaho Chemistry Department Moscow, ID 83843-2343 lain3267@uidaho.edu ifcheng@uidaho.edu 208-885-6387 The ZEA Organic Pollutant Degradation System

  2. ZEA Pollutant Degradation System • Zero valent iron (ZVI) • EDTA (Ethylenediaminetetraacetic acid) • Air Open round bottom flask Aqueous Solution of 4-chlorophenol Stir bar and ZVI particles Stir Plate

  3. The Search For Alternatives to the Bulk Destruction of Organic Pollutants • High temperature use of O2 • Incineration • Expensive • Dioxins • Public reluctance • Low temperature use of O2 • ZEA system • Operates at room temperature and pressure • Inexpensive • Common reagents • Long term storage • No specialized catalysts • Simple Reactor Design • Easily transportable • Versatile (can be applied to water treatment)

  4. Destruction of 4-Chlorophenol • Products include low molecular weight acids and CO2. Noradoun, Christina, et al. Ind. Eng. Chem. Res. 2003, 42, 5024-5030.

  5. Pollutants destroyed by the ZEA System • Halocarbons • 4-chlorophenol • Pentachlorophenol • Organophosphorus Compounds (nerve agents) • Malathion (vx surrogate) • Malaoxon • Organics • EDTA • Phenol

  6. Hypothesis-Oxygen Activation • Oxygen has a triplet ground state, while organic compounds have a singlet ground state. • How to overcome this kinetic barrier. • Add energy in the form of heat. • Addition of electrons (activation) • The ZEA system works by Reducing O2 to form reactive oxygen species • O2.-, H2O2, HO. http://www.meta-synthesis.com/webbook/39_diatomics/diatomics.html

  7. Hypothesis-Site for O2 Activation O2 FeIIIEDTA + HO∙ + HO- I Fe(0) H+ H2O2 Fe2+ + EDTA → FeIIEDTA FeIIIEDTA O2 H+ II Fe(0) Fe2+ + EDTA FeIIEDTA H2O2 FeIIIEDTA HO∙ + HO- • (I) Heterogeneous activation at the ZVI surface. • (II) Homogeneous activation by FeIIEDTA.

  8. Electrochemical Homogeneous Degradation System - Cell Design Three electrode system: • Working electrode • (RVC) • Auxiliary electrode • Graphite rod • A salt bridge keeps the auxiliary electrode separated from the bulk solution. • Reference electrode • Ag/AgCl

  9. Electrochemical Pollutant Degradation System FeIIEDTA can reduce oxygen to form the superoxide ion (O2·- ), as well as other reactive oxygen species. Degradation of EDTA is measured in this system HPLC is used to measure the degradation of EDTA. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH▪

  10. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH▪ Experimental Conditions • FeIII(NO3)3 and Na2H2EDTA were added in a 1:1 ratio to make 80 ml of a 0.5 mM FeIIIEDTA solution. • -120 mV potential is applied to the working electrode. • A high stir rate and large surface area working electrode is used to facilitate fast and efficient electrolysis. • KCl is used as the supporting electrolyte. • Oxygen is bubbled through the system.

  11. HPLC Results

  12. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH▪ Results

  13. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH▪ Comparison of FeII/IIIEDTA degradation and pH

  14. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH· Detection of Intermediate Oxidizing Agents (H2O2 and HO·) Electrochemical system ZEA system Graf, Ernst; Penniston, John T. Method for Determination of Hydrogen Peroxide, with its Application illustrated by Glucose Assay. Clin. Chem. 1980, 26/5, 658-660.

  15. Formation of H2O2 • Starch reagents • concentrated starch • 40 mM HCl • 0.077 mM ammonium molybdate • 80 mM KI. • Add an aliquot of reaction mixture to starch reagents and analyze with UV-VIS after a 20 minute color formation period. • Any suitable oxidizing agent (such as H2O2) will oxidize the iodide to iodine. • Iodine combines with iodide to form triiodide which will then complex with starch to form a blue color. H2O2(aq) + 3I-(aq) + 2 H+(aq) → I3-(aq) + 2 H2O(aq) E. Graf, J.T. Penniston, Clin. Chem. 26/5 (1980) 658-660.

  16. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH· Formation of H2O2

  17. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA · 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH· Formation of HO· • Accomplished using the spin trapping abilities of 5,5-dimethylpyrroline-N-oxide (DMPO) and electron spin resonance spectroscopy (ESR). • The DMPO-HO· adduct has a well characterized 1:2:2:1 quartet. Das, Kumuda C.; Misra, Hara P. Mol. Cell. Biol. 2004, 262, 127-133. Yamazaki, Isao; Piette, Lawrence H. J. Am. Chem. Soc. 1991, 113, 7588-7593.

  18. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH· Formation of HO· • Before electrolysis, the same signal is obtained from a simple solution of FeIIIEDTA, KCl, and O2

  19. · Formation of HO· • The two processes can be distinguished by adding methanol as a scavenger.

  20. Formation of HO· · · ·

  21. Formation of HO· · A B Growth of the quartet when adding the reaction mixture to DMPO after electrolysis. Growth of the quartet when adding the reaction mixutre to DMPO before electrolysis A) Reaction dominates after electrolysis. K = 109 M-1 S-1 B) Reaction dominates before electrolysis Yamazaki, Isao; Piette, Lawrence H. J. Biol. Chem.1990, 265, 13589-13594

  22. Formation of HO·

  23. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH· Formation of HO·

  24. FeIIEDTA 2O2°- + 2H+ → H2O2 + O2 + FeIIEDTA 2O2 FeIIIEDTA FeIIIEDTA + OH- + OH· Cyclic voltammetry can be used to show the catalytic mechanism. FeIIIEDTA + e- → FeIIEDTA FeIIEDTA + O2 → FeIIIEDTA + O2·-

  25. Cyclic Voltammetry 5 mV/s FeIIIEDTA + O2 O2 only FeIIIEDTA only Niether FeIIIEDTA or O2

  26. pH Dependency Zang, V; van Eldik, R. Inorg. Chem.1990, 29, 1705-1711.

  27. Free Fe(II) FeIIEDTA(OH) FeIIEDTA FeIIEDTA(H2) FeIIEDTA(H)

  28. Geometrical Considerations [FeII(EDTA)(H2O)]2- + H+ = [FeII(EDTAH)(H2O)]1- Mizuta, T.; Wang, J.; Miyoshi, K. Bull. Chem. Soc. Jpn.1993, 66, 2547-2551. Mizuta, T.; Wang, J.; Miyoshi, K. Inorg. Chimica Acta.1993, 230, 119-125.

  29. Summary and Conclusion • The ZEA system can destroy organic pollutants non-selectively. • How does the ZEA system destroy pollutants? • The ZEA system has a homogeneous reaction mechanism with activation of oxygen by FeIIEDTA followed by the Fenton reaction. • The ZEA system produces H2O2 as an intermediate. • The ZEA system produces HO· which can non-selectively destroy organic pollutants. • How can the ZEA system be made to work better? • Bubble air or oxygen through the system. • Optimize for pH = 3 conditions.

  30. Acknowledgments • Dr. I. Frank Cheng • Simon McAllister • University of Idaho Dept. of Chemistry • ACS • Funding • NSF award number BES-0328827 • NIH Grant No. 1 R15 GM062777-01

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