Photoelectrocatalytic advanced oxidation of perfluoroalkyl substances in groundwaters of the Veneto Region, Italy

Photoelectrocatalysis (PEC) was applied for the degradation of PFASs in natural groundwater collected from two wells located in the Veneto Region (Italy) where a massive contamination of the aquifer was discovered. Out of 48 monitored species, up to 9 PFASs were detected. On average, the degradation rate followed the order: PFOA>PFHpA>PFHxA≈PFPeA>PFBA and PFOS>PFHpS; the concentration of PFBS and PFHxS did not change during the tests. The overall PFASs concentration decreased by 63 % in well 1 and by 65 % in well 2. PEC tests of PFOA solutions ([PFOA] = 2 μg/l; [K2SO4] = 4 mM] induced the transient formation of PFHpA, followed by PFHxA, PFPeA and PFBA, confirming the reaction pathway consisting of decarboxylation followed by a stepwise losing of CF2 units, transiently forming shorter chain intermediates. PEC efficiency was compared to photolysis. According to electrical energy per order of magnitude, PEC outperforms conventional photolysis and most of the other advanced oxidation processes reported in literature.