Treatment of a mixture of pharmaceuticals, herbicides and perfluorinated compounds by powdered activated carbon and ozone: Synergy, catalysis and insights into non-free •OH contingent mechanisms

Powdered activated carbon (PAC) is a strong adsorbent also capable of catalyzing ozonation processes. Ozone (O-3) and PAC were simultaneously applied to treat a mixture of 17 micropollutants (MPs) at low concentrations, including 13 compounds that were studied for the first time by simultaneous addition of O-3 and PAC system. Synergy and catalysis improved the removals and specific degradation rates of MPs in the first minute of the treatment. Radical probing experiments showed that scavenging hydroxyl radicals ((OH)-O-center dot) did not have a significant impact on the removals, while scavenging other reactive oxygen species was more influential. A detailed study by electron paramagnetic resonance spectroscopy ascertained that the decomposition of ozone in presence of PAC at neutral pH did not boost the generation of free (OH)-O-center dot. Instead, adsorbed (OH)-O-center dot was likely produced as PAC(center dot)-HO along with other oxidizing species resulting from adsorbed singlet oxygen and superoxide radicals. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Powdered activated carbon (PAC) acts as a strong adsorbent and catalyst for ozonation processes in treating micropollutants. The simultaneous addition of ozone (O-3) and PAC enhances the removal and degradation rates of micropollutants, with scavenging actions of hydroxyl radicals ((OH)-O-center dot) and other reactive oxygen species. Detailed studies show that the presence of PAC does not boost the generation of free hydroxyl radicals in the decomposition of ozone at neutral pH, but rather produces adsorbed hydroxyl radicals and other oxidizing species.