Reductive Degradation of PFOS in Groundwater Using Nano-Scale Zero Valent Iron

Perflurooctane sulfonate (PFOS), one of the most often detected perfluorinated chemicals, has been defined as an emerging contaminant due to its ubiquitous distribution, high persistence and strong bioaccumulation. Research on the oxidative decomposition of PFOS using persulfate shows that it is quite resistant to oxidation process compared with perfluorooctanoate (PFOA). Here we studied the reductive degradation of PFOS utilizing nano-scale zero valent iron (nZVI). The fluorination ratio and decrease of PFOS were used to evaluate the degradation efficiency of PFOS.

The effect of different environmental conditions, including nZVI dosage, temperature, pH and dissolved oxygen concentration in water, were investigated. It was found that the defluorination ratio increased significantly with the increase of nZVI dosage. At the dosage of 11.2g/L, the PFOS defluorination ratio reached nearly 100%, demonstrating a complete PFOS decomposition. The defluorination ratio increased from 60% to nearly 100% with the temperature increasing from 27 °C to 40 °C. However, the defluorination ratio decreased significantly if the solution pH was adjusted from 7.5 to 3 using hydrochloric acid. Comparative experiments showed that dissolved oxygen in water would affect the reductive defluorination of PFOS. In addition, kinetic experiments were conducted to investigate the reaction rate. To investigate the PFOS degradation mechanisms, further work to identify the degradation products are being carried out.