Due to the extreme toxicity of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), the remediation of PCDD/F aquifer source zones is greatly needed; however, it is very difficult due to their persistence and recalcitrance. The potential degradability of PCDD/F bound to a real matrix was studied in five systems: iron in a high oxidation state (ferrate), zero-valent iron nanoparticles (nZVI), palladium nanopowder (Pd), a combination of nZVI and Pd, and persulfate (PSF). The results were expressed by comparing the total toxicity of treated and untreated samples. This was done by weighting the concentrations of congeners (determined using a standardized GC/HRMS technique) by their defined toxicity equivalent factors (TEF). The results indicated that only PSF was able to significantly degrade PCDD/F. Toxicity in the system decreased by 65% after PSF treatment. Thus, we conclude that PSF may be a potential solution for in-situ remediation of soil and groundwater at PCDD/F contaminated sites.
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Polycyclic aromatic hydrocarbons (PAHs) are a common part of the environment where they come from burning fossil fuels (through an incomplete combustion process). From a toxicological point of view, PAHs are considered to be carcinogens with a mutagenic and teratogenic effect. On the other hand, ferrates are generally believed to be the ideal chemical agent for water treatment due to their strong oxidation potential. Herein, the efficiency of degradation of PAHs (with the special emphasis on B[a]P) by ferrates under laboratory conditions was studied. The formation of degradation products was also considered. For this, two types of ferrates were used and both of them efficiently degraded B[a]P. When comparing ferrates that were bought from a Czech and USA company, no significant changes in terms of B[a]P degradability were observed. It was determined that the degradation efficiency of PAHs by ferrates was dependent on their molecular weight. Two and three cyclic PAHs have been completely degraded within 30 minutes, whereas five (and more) cyclic PAHs, only partially. The results obtained with ferrates were compared to the ones obtained with a classical oxidizing agent - KMnO4. In a qualitative test to detect degradation products of PAHs, two were identified, namely fluoren-9-one derived from fluorene and acentaphthylene, formed from acenaphthene.
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