Interface hydrogen bonding dominated perfluorooctanoic acid (PFOA) accumulation by iron particles in drinking water pipes

Iron particle is one of the key factors inducing discoloration in drinking water distribution system (DWDS), but the mechanism of iron particles on the accumulation of trace organic pollutants in DWDS is not clear. Here, iron -based pipes from real DWDS were used to investigate the perfluorooctanoic acid (PFOA) accumulation mecha-nisms in DWDS. Results showed that old unlined pipes had a much higher accumulation capacity for PFOA than new pipes. Among the corrosion products in old pipes, Fe2O3 and Fe3O4 did not have obvious accumulation for PFOA, while FeOOH exhibited a strong accumulation effect for PFOA. Furthermore, the in-situ formed iron particles contributed more to PFOA accumulation than pre-formed iron particles. Interestingly, PFOA caused an increase in turbidity and particle size of in-situ formed iron particles. Mulliken charge of F-bonded Fe increased from +1.28 e to +1.30 e, which indicated that the oxidation state of Fe-center was strengthened by PFOA. When dissolved oxygen existed, a PFOA-FeOOH-O2 linkage could form through COO-Fe coordination and O2 interface adsorption, which enhanced cytotoxicity due to the generation of center dot OH radicals. These findings implied that interface hydrogen bonding dominated PFOA accumulation by iron particles in DWDS, which would increase the risks of discoloration.

Automated summary

Iron particles are a key factor in the discoloration of drinking water distribution systems (DWDS), but their mechanism in the accumulation of trace organic pollutants in DWDS is unclear. This study investigated the accumulation mechanisms of perfluorooctanoic acid (PFOA) using iron-based pipes from a real DWDS. Results showed that old unlined pipes had a higher capacity for PFOA accumulation than new pipes. Among the corrosion products in old pipes, Fe2O3 and Fe3O4 showed no significant accumulation, while FeOOH had a strong accumulation effect for PFOA. In-situ formed iron particles contributed more to PFOA accumulation, and PFOA caused an increase in turbidity and particle size of in-situ formed iron particles.