Premium ZVI Amendments for the Remediation Industry
Provectus Environmental Products, Inc. (PEP) has teamed with GMA Industries, Inc. to offer our superior Zero Valent Iron (ZVI) amendments to the remediation industry.
The GMA production process for reclaiming cast steel abrasive is a controlled series of scalping, magnetic separation, cleaning via air wash separation and/or heat kiln decontamination followed by screening to size specification. Spiral separation can further separate round from non-round particles. All material recycled through our process meets or exceeds industry specifications for metallurgy, hardness and screening. Benefits of our product offerings include:
- Guaranteed Quality and Purity
- Demonstrated Reactivity
- Proven Effectiveness / Longevity
- Custom Formulations Available
- >35 Years Industry Experience
- >15% Lower Cost (on average)
- Recycled / Reuse Credits
- Made in the USA (FAR 52.225-11)
The potential effectiveness of ZVI for remediation of groundwater impacted by chlorinated solvents has been documented since the early 1990s (Gillham, 1993). As described by Arnold and Roberts (2000), chemical transformation via ZVI occurs on particle surfaces and therefore involves at least three steps: (a) adsorption of the substrate to reactive sites on the ZVI particle surface, (b) reaction at the surface, and (c) desorption of the transformation product. In the absence of interspecies competition by catabolites, the kinetics of PCE transformation via α- and/or β-elimination reactions (and, to a lesser degree, hydrogenolysis and hydrogenation reactions) is therefore directly related to reactive surface area.
Intuitively, smaller particle sizes would promote more rapid degradation of target contaminants. However, when normalized for surface area, Liu et al. (2005) demonstrated that TCE degradation rates achieved with various nanoscale metals and bimetallic particles were similar to those measured with granular iron (Nurmi et al., 2005). Leaders in the field of ZVI technologies subsequently noted that sub-micron ZVI particles would have to remain at least 20 times as reactive as conventional sources over their lifetime to be cost-competitive (ETI, 2006).
Table 1. Physical Parameters and General Characteristics for ZVI reagents.Notes: *Ferox ZVI materials presented for comparative analysis (based on data available from references as noted, not reviewed by vendor). **BET analyses performed by MicroMetrics and Cathay Industries. ***Geometric mean calculated using spherical geometry, which yields values with recognized limitations+.
Results: Over the first 72 hr incubation period there was a clear correlation between ZVI surface area and PCE transformation rates, with the smallest ZVI particles (PEP Micro ca. 3 micron ZVI) exhibiting the fastest PCE removal rate of 10.58 µg/L per g ZVI/hr (Table 2). The relationship between reactive surface area and kinetics of PCE transformation has been previously established (Gillham and O’Hannesin, 1994), but other factors have been identified that may influence these responses (Horiba, 2016; Reinsch et al., 2010; Tratnyek et al., 2014). For example, ZVI degradation kinetics can reflect declining rate patterns over time resulting from interspecies competition from catabolites and occlusion of the reactive surfaces via ferrous iron and oxyhydroxide passivation. Indeed, during the short course of these studies, the smaller ZVI particles lost more of their reactivity than larger ones as measured in terms of PCE transformation kinetics. Notably, the sponge- or flake-type ZVI materials, with higher “internal” surface area, quickly lost up to >36% of their reactivity.
The PCE removal rates (i.e., slopes of lines for PCE removal) for both of the Ferox® sponge-type ZVI products were notably slower following re-spike after an initial 72 hours reaction time, with both the blue and green lines “flattening” over time (Figures 1a/b). However, reaction rates for the GMA ZVI materials (i.e., slopes of red, gray and black lines for PCE removal) were essentially the same for the first 72 hours and the second 96 hours following a PCE re-spike. Presumably, the more substantial loss of reactivity for the Ferox® ZVI is a result of deeply embedded internal surfaces of the “sponges” being rapidly occluded/obscured by surface encrustation et cetera thus rendering them physically unavailable hence, inert. Particles that are more spheroidal or angular geometries are less susceptible to such blockage (Horiba, 2016).
- In general, ZVI particles that lose reactivity over a short period of time in the subsurface are usually not strong candidates for remedial applications.
- High ZVI surface area alone does not always equate to high reactivity, especially not over a period of time that is required for remedial applications (need for reactivity can range from months to many years).
- Independent, third-party tests demonstrated that all Provectus/GMA ZVI products had high reactivity that was better sustained over time.
- PEP Micro ZVI demonstrated the fastest, sustained rate of PCE removal
- Ferox® ZVI lost >36% of its reactivity over a short period of time (ca. 200 hours).
- GMA-ZVI materials maintained their performance over the same period of time.
- GMA offers multiple types of highly reactive ZVI that can be specially selected for your project needs:
- PEP ZVI – Micro (average 3 microns, or 4,800 mesh)
- GMA ZVI – Fine (average 45 microns, or 400 mesh
- GMA ZVI – Medium (average 100 microns, or 150 mesh)
- GMA ZVI – Coarse (average 297 microns, or 50 mesh)
- Custom Formulations
Please contact Customer Service at 800 869-9946 or email (Sales@gmaind.com) for pricing and logistics support.
- Arnold, W.A. and A. L. Roberts. (1998). Pathways and Kinetics of Chlorinated Ethylene and Chlorinate Acetylene Reaction with Fe(0) Particles. Environ. Sci. Technol. 1998.
- ETI. (2006). EnviroMetal Technologies, Inc.’s Perspective on Nanoscale Iron. Technical Note 5.10
- Gillham, R. (1993). Cleaning Halogenated Contaminants from Groundwater. US PTO 5,266,213, November 30, 1993.
- Gillham, R.W. and S.F. O’Hannesin. (1994). Enhanced Degradation of Halogenated Aliphatics by Zero-Valent Iron. Ground Water, Vol 32., No. 6 pages 958 - 967.
- Hepure Technologies “1”. (date unknown). Technical Specification Sheet Ferox-Flow™ ZVI Reactive Powder.
- Hepure Technologies “2”. (date unknown). Technical Specification Sheet Ferox-PRB™ ZVI Reactive Powder.
- Horiba Scientific. (2016). “A Guide to Particle Size Analysis”.
- Kim, E-J., J-H Kim, Y-S-Chang, D. Ortega and P.G. Tratnyek. (2014) Effects of Metal Ions on the Reactivity and Corrosion Electrochemistry of Fe/FeS Nanoparticles. Environ. Sci. Technol.
- M. Velimirovic, P. Larssonc, Q. Simons, L. Bastiaens. (2012) Reactivity screening of microscale zerovalent irons and iron sulfides towards different CAHs under standardized experimental conditions. Journal of Hazardous Materials. Elsevier B.V.
- R. MIEHR, P. TRATNYEK, J. BANDSTRA, M. SCHERER, M. ALOWITZ, E. BYLASKA. (2004) Diversity of Contaminant Reduction Reactions by Zerovalent Iron: Role of the Reductate. Environ. Sci. Technol.