In-situ reduction technology for groundwater remediation industry - Soil and Groundwater
Nanoremediation represents a modern method of treatment of environment polluted by chlorinated hydrocarbons, heavy metals, radionuclides and other contaminants. This technology started to be used tentatively in USA and it already takes place on various sites around the world at present.
The technology is based on injection of Fe0 nanoparticles into the groundwater through application wells. This technology is environmentally friendly and cost-effective compared to methods like conventional permeable reactive barriers (PRB), pump&treat and others. NZVI slurry is applied through small injection wells with minimal negative environmental impact. Due to the nanodimensional character and suitable surface stabilization, the injected nanoparticles migrate through the rock environment, where they induce oxidation-reduction (redox) reactions with pollutants dissolved in the groundwater.
From a wide range of pollutants that can be successfully removed by the use of Fe(0) nanoparticles, we can mention chlorinated hydrocarbons (PCE, TCE, DDT etc.) that have been used as solvents or pesticides, and other organic substances that are decomposed into simpler non-toxic phases. As a consequence of reduction and coprecipitation processes, which occur after application of nZVI, it is possible to transform a wide variety of metals (including highly toxic arsenic) into an insoluble form, which remains tightly bounded to the rock environment. Thus, these pollutants can not migrate anymore, which leads to a significant reduction of their ecological impact.
Reducing potential of zero-valent iron nanoparticles is very high, therefore nZVI can reduce another matters contained in the water like dissolved oxygen, sulphates, nitrates, etc. NZVI reacts with oxygen dissolved in water:
Fe0 + 1/2 O2 + 2 H+ ↔ Fe2+ + H2O
Oxygen present in the environment is reduced which leads to decrease of redox potential and reduction of monitored contaminants proceeds.
The oxidation of Fe(0) nanoparticles stored in water is another important process: zero-valent iron nanoparticles tend to significantly affect the redox potential, reduce water to hydrogen and hydroxide and increase pH.
Fe0 + 2 H+ ↔ Fe2+ + H2
Oxidation (corrosion) of nanoparticles and decrease of reactivity is an undesirable phenomenon in the time since slurry production untill its application. This side effect can be suppressed by manufacturing of a fresh slurry from a dry nanopowder on site or by a just in-time delivery. Please see details of nZVI slurry ageing.
We recommend to use stabilized product NANOFER 25S (organic) or NANOFER 25DS (inorganic) for in-situ groundwater remediation. For large-scale pilot projects and full-scale applications we recommend on-site manufacturing of fresh slurry from the dry nanopowder by industrial dispersion units – please see the Equipment section or contact us directly for more details.