Removal of micropollutants by ozone based processes

• Ozonation and nZVI processes showed significant selectivity toward removal of organochlorine pesticides.
• Combined O3/GAC and O3/ZEO processes provided high removal rates and efficiencies of studied compounds, except for γ-HCH.
• The highest potential to intensify degradation and removal of organochlorine pollutants has integrated O3/nZVI process.
• The nZVI and O3/nZVI reductive/oxidative processes are potentially complementary.

Discharging various micropollutants into aquatic environment, in particular substances classified as priority and hazardous ones, leads to serious concerns due to their potential adverse effects on human health and living organisms. Their effective removal requires novel processes. Ozone based processes are considered to be very promising. Results on ozonation, adsorptive ozonation and combined process of ozone with zero-valent iron nanoparticles are presented. Five selected organochlorine pesticides were used as organic contaminants in model water. High removal efficiencies of ozonation, except for lindane and hexachlorobutadiene, were observed. Even higher removal rates and efficiencies were measured using the O3/UV process. However, the low removal efficiencies obtained for lindane and hexachlorbutadiene have not been explained. Adsorptive O3/GAC and O3/ZEO ozonation processes also provided high removal rates and efficiencies, but again, except for lindane. Significant reduction of the reaction time resulted from these processes. Very low removal efficiencies measured for hexachlorobenzene and hexachlorbutadiene with nZVI, were solved using the O3/nZVI process. Moreover, the O3/nZVI process is characterized by a significant reduction of the reaction time when compared with the ozonation processes. The results suggest that nZVI and O3/nZVI processes have the highest potential to intensify the degradation and removal of organochlorine pollutants.

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