Efficient removal of perfluorooctanoic acid in aqueous solution via water flow-driven piezocatalytic degradation and a cavitation-impinging stream reactor

• A novel Fe 3 O 4 –MoS 2 /ceramsite piezoelectric pipe with ultrahigh piezocatalytic performance was prepared. • The Fe 3 O 4 –MoS 2 /ceramsite pipe can efficiently defluorinate PFOA by natural water flow via piezoreduction. • The CIS reactor showed high performance of advanced treatment of PFOA degradation intermediates. In this work, a novel hybrid system was developed to degrade recalcitrant perfluorooctanoic acid (PFOA) in aqueous solution. This system consisted of a Fe 3 O 4 –MoS 2 /ceramsite (FMC) pipe and a cavitation-impinging stream (CIS) reactor. The FMC pipe served as a hydraulic-driven piezocatalytic reactor by the water flow for highly efficient defluorination of PFOA. The FMC pipe effluent was further treated in the CIS reactor to accomplish effective decomposition of PFOA degradation intermediates and total organic carbon (TOC). Under the optimum conditions, the hybrid system achieved complete PFOA removal and higher than 99% of defluorination and TOC removal. The main active species in the piezocatalytic process were h + , e – , • OH, • O 2 – and 1 O 2 , of which e – dominated the PFOA degradation process. The removal ratio of PFOA was 92.5% after 8 cycles by the FMC pipe, indicating excellent reusability of the FMC pipe. Overall, this work not only offers a deep insight on PFOA process, but also provides an efficient and reliable approach for decontamination of recalcitrant wastewater.