NanoFASE Case Study: Groundwater remediation with zerovalent iron

Zerovalent iron nanoparticles (nZVI) are being used for remediation of groundwater polluted with chlorinated ethenes, hexavalent chromium and arsenic. Remediation using nZVI shows several advantages compared to other methods:

  • nZVI remediation is fast because it is abiotic (by contrast, microbes need time to process pollutants in soils for remediation and that increases monitoring cost)
  • nZVI enhances biodegradation (by opening niches for halorespiring microbes)
  • nZVI is efficient (it works at high concentrations and for recalcitrant compounds)
  • nZVI is safe by design (it is designed to react with pollutants and then oxidize into rust).

Nanoparticles injected into the borehole aggregate, deposit and react with both the pollutants and electron acceptors in the groundwater. Finally, the particles oxidize and produce secondary minerals and dissolved iron non-distinguishable from natural iron. As such, nZVI application at subsurface could be considered both safe and beneficial to the environment. However, in some countries, regulators hesitate to use nZVI for groundwater remediation. The NanoFASE case study takes a ‘worst case’ approach in order to test safety.

Study aim
 

This study explores the fate of nZVI particles escaping the application zone that could be transported towards receiving water. nZVI fate is modelled using the fate descriptors (parameters) gained from the NanoFASE column experiments.
 

Experimental approach

Overview
 
  1. Column experiments are performed in the lab at low nZVI concentrations (representing conditions far from the injection borehole) to determine the fate descriptors. Inlet particles are prepared in the combined reactor with anode- and cathode-volume separated by ion membrane. 
  2. Field application: Injected nZVI is monitored in the observatory boreholes. nZVI can migrate up to about 50 m (usually still within the contaminated site being remediated). The concentration is predicted by the model based on the fate descriptors.

Environmental medium: 

Soil

NP type/size:

Fe0, 100nm

Results

 
 
 
The focus on experiments under realistic conditions (electric field, nZVI concentration, pH) makes predictions of nZVI transport out of the polluted zone more realistic. This is an ongoing study.

Modelling parameter ouputs

Emitted to
 
  • Retardation (the ratio of water pore flow velocity to nano-iron pore flow velocity)
  • First order removal rate
  • Pore flow velocity of groundwater

 

 

  Soil                            Water

Read more

Read also
 

 

Visit the NanoFASE Libraryto read summaries of these reports:

NanoFASE Report D7.3 Differences in framework for assessment of intentional versus unintentional terrestrial NM exposures

http://nanoiron.cz

Nathanail CP et al., 2016. A preliminary risk assessment procedure for renegade nanoparticles deployed during nanoremediation. Remediation Journal. 26(3), 95–108. doi:10.1002/rem.21471 

 

 

Contact

 

Jaroslav Nosek

Technical University of Liberec (TUL)

jaroslav.nosek1@tul.cz