Iron filings (ZVI)
What is it?[edit]
Iron filings or zero-valent iron (ZVI) is the elemental form of iron with a zero charge carried by each atom – a result of the outer valence level being filled. ZVI is able to remove dissolved phosphorus (phosphate) from solution through precipitation. [1] Zero-valent iron nanoparticles (nZVI) are also used for phosphorus removal.
How is it being used?[edit]
- A Maplewood, Minnesota field study used an iron-enhanced (5% iron filings) ditch check sand filter for installation in swales to provide treatment of dissolved heavy metals and dissolved phosphorous in stormwater runoff from highways (Ahmed at el., 2014) [2].
- No projects that use ZVI were found in Ontario.
Benefits[edit]
A study was done that compared the phosphorus reduction capabilities of ZVI, biochar, biochar-supported ZVI (ZVI/BC), and biochar-supported nZVI (nZVI/BC). [1] It was found that nZVI/BC had the highest phosphorus reduction. Using biochar-supported ZVI or nZVI improves the dispersion and stability of the iron filings. Biochar is fine-grained and highly porous, providing a large surface area to support nZVI. Another paper reports that ZVI can remove up to 98% of influent phosphorus at low input concentrations, and at high concentrations is shown to remove up to 36% of incoming phosphorus. The phosphorus retained in the soil is mostly iron-bound, which will not be easily leached out of the system because it is very stable.[3]
Back to additives.
- ↑ 1.0 1.1 Rossetti M. Evaluation of phosphorous removals by biochar supported nano-scale zero-valent iron. 2017. Chemical Engineering Undergraduate Honors Thesis.
- ↑ Ahmed, F., Natarajan, P., Gulliver, J., Weiss, P., Nieber, J. 2014. Assessing and Improving Pollution Prevention by Swales. https://www.lrrb.org/pdf/201430.pdf
- ↑ 3.0 3.1 Lechner L. Phosphorus Removal From Stormwater Using Zero-Valent Iron. 2016. Applied Science Masters Thesis.