Nano-Scale Zero-Valent Iron State of the Technology. Lessons Learned from R&D, Production, and Global Field Implementations

Transcription

1 Nano-Scale Zero-Valent Iron State of the Technology Lessons Learned from R&D, Production, and Global Field Implementations

2 Presentation Outline 1. Timeline of Significant IP Developments 2. Production 3. Key Technical Issues nzvi Reactivity nzvi Deliverability nzvi Treatment Longevity Toxicity and Risk 4. Experience Valcartier Garrison, Canada July 20,

3 Timeline of Significant IP Developments Waterloo patent (1993) Applicable to any iron body (iron only) placed in the ground by any means (PRB, reactive zone, etc.). EnviroMetal Inc (Adventus) exclusive license. NASA (2003) EZVI = Emulsified Zero Valent Iron. Colloidal iron in oil emulsion (DNAPL application) Lehigh - Zhang (2005) Production and use of nzvi (also BNP) for groundwater remediation Golder produces and implements nzvi under nonexclusive license from Lehigh University July 20,

4 Production Stock ZVI 2-5 μm Top-down Mechanically Ground / Ball-Milling Physical size reduction Lehigh University (2005) Bottom-up Chemically Precipitated Classical l method since Atoms or 1996 molecules Borohydride reduction July 20,

5 nzvi Reactivity Surface Chemistry Fe 2+ e - RCl + H + Half Reactions Fe 0 Fe 2+ _+ +2e - C 2 HCl 3 + 2e - + H + C 2 HCl 2 + Cl - Overall Reaction (TCE to Ethene) 3Fe 0 + C 2 HCl 3 + 3H + 3Fe 2+ + C 2 H 4 + 3Cl - Fe Surface RH + Cl - July 20,

6 nzvi Reactivity Chemistry Background Fe 0 core that shrinks over time Iron oxide coating forms immediately with contact of H 2 O or air Iron oxides will interact with aquifer materials Will not travel indefinitely Agglomeration ultimately forms Fe-oxide flocs with some continued reactivity Palladium added as catalyst 0.05% wt/wt Enhances reactivity Enhances treatment longevity July 20, Image from Zhang (2005)

7 nzvi Reactivity Reaction Pathways ~ 80% to 90% ~ 10% to 20% July 20, Roberts, A. L., et. al, 1996 Reductive Elimination of Chlorinated Ethylene by ZVI Metals. Environmental Science and Tech.

8 nzvi Reactivity Size Issues Definition - nano is <100 nm and novel properties versus bulk-scale Nature Paper to come soon (accepted) for citation Truly nano iron may not occur until below 10 nm and potentially far below July 20, Graph taken from Tratnyek and Johnson (2006)

9 nzvi Deliverability - Agglomeration Issues Surface charge promotes agglomeration Fe 0 is magnetic, promotes agglomeration More dense slurry, more particle interaction Need to modify the nzvi surface to maintain suspension Fe(0) Fe(0) July 20,

10 nzvi Deliverability - Surface Modification July 20,

11 nzvi Treatment Longevity Paradigm shift from abiotic treatment of CAHs to reagent for enhanced bioremediation approach Observed transition of abiotic CAH degradation to enhanced bioremediation Transition driven by altered redox condition coupled with addition of complex source of soluble and sparring soluble carbon Continued degradation of CAHs observed for over two (2) years and achieved a groundwater concentration target of 5 ppb for TCE without build-up up of intermediate degradation products Combined remedy of nzvi injection and long-term enhanced bioremediation may be a strong candidate technology for specific CAH impacted sites July 20,

12 Toxicity and Risk 48 hour LC 50 ~ 55 ppm Same as bulk iron Classified as slightly toxic No different from PRBs Fish study shows no mortality July 20, Taken from: Oberdorster et al., Rapid Environmental Impact Screening for Engineered Nanomaterials: A Case Study Using Microarray Technology June 2006

13 Experience Valcartier Garrison, Canada Plume Characteristics 2.5 miles long 0.5 miles wide 130 ft deep TCE Multiple Source Areas July 20,

14 Injection Layout PO PO PO PO-06-9 PO-06-8 PO m PFD-23 PFD-13 PFD-21 PO PFD-2 PFD-4 PFD-10 PFD-5 PFD-6 PFD-7 PFD-9 CPT-10 PO PFD-16 PFD-18 PFD-20 PFD-15 PFD-3 PFD-8 PFD-12 PFD-19 PO PFD-17 PFD-11 CPT-11 CPT-7 PI-06-8 CPT-5 PI-06-7 CPT-8 PI-06-6 PI-06-5 CPT-9 PI-06-4 PO PI-06-3 PI-06-2 PI-06-1 CPT-4 PFD-24 PFD-22 PFD-1 PO-06-6 PO-06-5 PO-06-4 CPT-1 40 m PFD-14 PO-06-3 CPT-6 PO-06-2 PO-06-1 Groundwater flow Treatment zone 4,500 kg of Golder nzvi 0.1% Pd Slurry density of 10 g/l to 40 g/l 80,000 L soy protein dispersant July 20,

15 Geochemistry Mean Geochemical Values Across the Treatment Area O 2 (9.5 mg/l) O 2 (0.7 mg/l) O 2 (2.0 mg/l) ph (6.3) ORP (200 mv) ph (6.1) ORP (-450 mv) ph (7.0) ORP (-100 mv) TOC (1,5 mg/l) BOD (<4 mg/l) TOC TOC (250 mg/l) (25 mg/l) BOD (15 mg/l) Before NZVI injection 1 month 12 month after after Values measured in the treatment area Values measured at the injection wells July 20,

16 TCE Progress Monitoring 350 Injection #1 Injection #2 Injection # Concentration TCE (ug/l) Performance criteria 0 02-juil août oct nov janv mars avr juin août sept nov janv-08 Date (JJ-MM-AA) PI-06-1 PI-06-2 PI-06-3 PI-06-4 PI-06-5 PI PI-06-7 PI-06-8 July 20,

17 Cis-1,2-DCE Progress Monitoring 200 Injection #1 Injection #2 Injection # Concentration DCE (ug/l) Performance criteria juil août oct nov janv mars avr juin août sept nov janv-08 Date (JJ-MM-AA) PI-06-1 PI-06-2 PI-06-3 PI-06-4 PI-06-5 PI-06-6 PI-06-7 PI-06-8 July 20,

18 Treatment performance Plan view 8 months following last injection Treatment zone 0-15 ppb ppb ppb ppb ppb Groundwater flow direction Observation wells Injection wells

19 Interpretation Zone of middly reducing conditions Zone of high h reducing conditions Zone where Hydrogenolysis is supported Zone where Beta-elimination is supported

20 Delivery 0-5 ppb 5-50 ppb ppb > 150 ppb July 20,

21 Recirculation and Hydrogen injection H 2 Medium sand Coarse sand Silty clay Coarse sand Rock 30 gpm

22 Performance Goal Attainment (TCE) 1000 Recirculation + H2 Concentratio on en TCE (ug/l) Date (AAAA-MM-JJ) PFD-2 (aval) PFD-5 (aval) PFD-6 (aval) PFD-3 (aval-centre) PFD-23 (aval-centre) Critère de performance Départ du système de recirculation SUD July 20,

23 Performance Goal Attainment (cis-1,2-dce) 1000 Recirculation + H2 Concentration n en DCE (ug/l) Date (AAAA-MM-JJ) PFD-2 (aval) PFD-5 (aval) PFD-6 (aval) PFD-3 (aval-centre) PFD-23 (aval-centre) Critère de performance MDN Départ système recirculation SUD July 20,

24 Summary nzvi is an effective remediation approach Transition from abiotic CAH degradation to enhanced bioremediation occurs typically within several months (as TOC drops to ~20 mg/l) Long-term treatment can be achieved (~ 2 years) and can be continued using more traditional enhanced bioremediation approaches Technology is not a panacea must be carefully evaluated! Delivery issues can be overcome with good CSM and advanced injection techniques July 20,

25 Questions? July 20,