Determination of Minimal Required Doses of Nanoirons for Relevant Degradation of TCE, PCE and cDCE in Liquid Medium

摘要

The use of granular zero-valent iron (>50 urn) for the degradation of chlorinated solvents through reductive dehalogenation has been studied and applied successfully in permeable barrier systems for more than ten years. More recently, microscale and also nano-sized (bi)metallic particles (NBPs) are gaining increasing interest as these materials have been found to be more reactive towards a higher,diversity of pollutants,, In addition, in contrast with granular and microscale iron particles, NBPs ( ~ 100 nm) are more mobile in aquifer materials. NBPs can be injected in the subsurface without excavation, creating a reactive zone as such. Lab scale experiments have been set up to quantify the reactivity of different nano-scale irons towards Volatile Organic Chlorinated compounds (VOCls) in liquid media. Based on mass normalised data, the test confirmed that NBPs were more reactive than granular or fine powder irons. With specific surface area normalised data tha advantage of nano-iron decreased. The reactivity varied considerable between different NBPs,, With trichloroethylene (TCE) as target compound, it was shown that a minimum dose of at least 2 g/1 of NBP was required to obtain significant degradation in liquid medium within a time period of several weeks. With real groundwater, gasanalyses indicated degradation of tetrachoroethylene (PCE) and TCE via acethylene, and cis-dichloroethylene (cDCE) was found to be degraded only very slowly. Determination of the granulometric distribution and the specific surface area (BET-analyses) indicated that aggregates of NBPs were present.