zero valent iron powder (ZVI) is the workhorse reductant of environmental remediation. Elemental iron releases electrons that reduce, adsorb or co-precipitate contaminants such as chlorinated solvents and hexavalent chromium. Smaller particles mean more surface area and faster reaction — and at roughly 2.5 µm, 5000-mesh ultrafine iron powder sits in the range that emulsion zero-valent iron (EZVI) systems are designed around.
What zero-valent iron does underground
It starts with Fe⁰ → Fe²⁺ + 2e⁻. Those electrons strip chlorine from TCE and PCE step by step, reduce Cr(VI) to Cr(III) so it precipitates as hydroxide, and the corrosion products on the iron surface adsorb and co-precipitate heavy metals. Column studies by Gillham and O'Hannesin in Ground Water (1994) confirmed the pathway; ZVI became the default medium for direct-push injection and permeable reactive barriers.
Why particle size cuts both ways
Reactions happen at the surface, so specific surface area sets the rate: micron-scale powder carries far more reactive sites per kilogram than millimetre-scale iron chips. Push below a few microns, though, and particles agglomerate, settle out and resist forming a stable suspension. EZVI solves that by holding the iron inside a water-in-oil emulsion that travels with groundwater.
UIF: a 5000-mesh grade built for EZVI
Sagwell's ultrafine iron powder UIF runs 0.5–5 µm with D50 at 2.55 µm (about 5000 mesh), ≥98.55% Fe and ≤0.80% oxygen. Its low apparent density — 0.9 g/cm³ — makes suspension easy and helps hold the emulsion together, while the near-spherical shape reduces inter-particle friction so the emulsion spreads further into the plume. In service in the US remediation market since 2004, it is a proven grade rather than a lab sample.
Coarse iron reacts slowly; very fine iron migrates poorly. UIF's 2.55 µm median and rounded morphology land on a workable balance between reactivity and injectability. Tell Sagwell your site conditions, and the team will match particle size, purity and morphology to the job.
Please feel free to consult for more details.
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