APPLICATION OF NANOSCALE ZERO-VALENT IRON FOR GROUNDWATER REMEDIATION: LABORATORY AND PILOT EXPERIMENTS

It is known that the reductive effects of zero-valent iron (Fe(0)) and the sorptive capability of iron and its oxides can be used for both the dehalogenation of chlorinated hydrocarbons (CHC), especially of chlorinated ethenes (PCE -> TCE -> DCE -> VC -> ethene, ethane), and the removing of heavy metals from groundwater by turning them into a less-soluble form through changes of their oxidation state, or by adsorption. These consequences are being exploited in the construction of iron filling permeable reactive barriers for a longer time. (1) The advantages of nanoscale zero-valent iron (nanoFe(0)) over the macroscopic one consist not only in the better reactivity implicit in their greater specific surface area but also in their mobility in rock environment. (2,3) Numerous laboratory experiments, especially the batch-agitated experiments, with samples from seven various contaminated localities in Europe have been carried out with the aim to discover the measurement of the reductive effect of the nanoFe(0) on selected contaminants. It was found that the nanoFe(0) can be reliably usable as a reductive reactant for in-situ chemical decontamination of sites polluted by chlorinated ethenes (CEs), or hexa-valent chromium (Cr(VI)). The rate of reductive reaction and the optimal concentrations for the real remediation action were determined. On the basis of these laboratory experiments, the methods for pilot application of nanoFe(0) have been specified. Subsequently the pilot experiments were accomplished in surveyed localities.