PFAS removal by ozonation/advanced oxidation

GAC adsorption, ion exchange, reverse osmosis are physical removal technologies, which merely transfer PFAS from one phase to another (or collect/concentrate PFAS streams), instead of really destructing these chemicals. Oxidation by breaking the chemical bond are then presumed to be a more complete approach for PFAS elimination.

Ozone is often used in drinking water treatment plant for disinfection or organic pollutant removal purposes. However, research shows that ozone alone is unable or very insufficient to break down PFAS chemicals as the C-F bond is very strong. It has to be supplemented with catalyst or oxidizing agents (advanced oxidation process, AOP), to decompose ozone and create reactive radicals for a desirable PFAS degradation. In this case, a high dose of ozone will be needed [1]. This leads to a very high energy cost if applied in large-scale practice.

Together with an iron-oxide based catalysis and persulfate, ozone can reach an overall maximum PFAS removal of 70% in tap water. The process is especially effective towards PFAS with medium, i.e. 6-11 C-F chain length, regardless of their ‘head’ functional groups [1].

However, concerning the production of unwanted byproducts (such as bromate) and the transformation of PFAS precursor into short-chain PFAS, a robust treatment chain is yet to be defined with ozone-related AOP.

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References:

[1] Removal of per- and polyfluoroalkyl substances (PFASs) from tap water using heterogeneously catalyzed ozonation. Environ. Sci.: Water Res. Technol., 2019, 5, 1887-1896.