Rapid degradation and efficient defluorination of perfluorooctanoic acid(PFOA) by microwave discharge plasma in liquid combined with catalytic ions Fe2+

Abstract

Perfluorooctanoic acid (PFOA) is a kind of persistent and refractory organic pollutants with high concern in recent years. In this work, a new treatment method-microwave discharge plasma in liquid (MDPL) is used to study the defluorination and degradation characteristics of PFOA. The effects of discharge parameters and solution conditions on the defluorination of PFOA are investigated in detail. The results show that the degradation and defluorination of PFOA by MDPL are excellent, with a removal of 98.6 % and a defluorination of 58.0 % in 100 min. And MDPL is innovatively combined with catalytic ions. The efficient degradation of PFOA by MDPL is attributed to its high mass transfer efficiency. The catalytic ion (Fe2+) is introduced to MDPL for synergistic degradation of PFOA. Under the synergistic catalysis of Fe2+, PFOA is almost completely removed and the defluorination is 82.9 %. The defluorination increased by 24.9 %, the synergistic factor reaches 2.41. In addition, the characteristics of intermediates and free radicals in the process of defluorination are discussed. It is confirmed that eaq- is the key reactive species that initiates the decomposition of PFOA, and hydroxyl radical (·OH) also plays an important role in the subsequent decomposition of PFOA. Finally, the decomposition mechanism of PFOA is analyzed, the degradation pathway of the reaction processes is given. This work proves that MDPL is efficient for the defluorination of PFOA, which also provides a new insight for the control of PFOA pollution.