Reductive degradation of perfluorinated compounds in water using Mg-aminoclay coated nanoscale zero valent iron

Perfluorinated compounds (PFCs) are extremely persistent micropollutants that are detected worldwide. We studied the removal of PFCs (perfluorooctanoic acid; PFOA, perfluorononanoic acid; PFNA, perfluorodecanoic acid; PFDA and perfluorooctane sulfonate; PFOS) from water by different types of nanoscale zero-valent iron (nZVI). Batch experiments showed that an iron dose of 1 g L-1 in the form of Mg-aminoclay (MgAC) coated nZVI, at an initial pH of 3.0 effectively removed 38-96% of individual PFCs. An increasing order of removal efficiency was observed of PFOA < PFNA < PFOS approximate to PFDA. Compared to this, PFCs removal was less than 27% using a commercial air stabilized nZVI or freshly synthesized uncoated nZVI, under the same experimental conditions. The effectiveness of PFCs removal by MgAC coated nZVI was further investigated at various initial pH, nZVI dosage, temperature and age of the nZVI. A maximum removal was observed for all PFCs with high nZVI concentration, freshly synthesized nZVI, low pH and low temperature. A mass balance experiment with PFOS in a higher concentration of nZVI revealed that the removal was due to both sorption and degradation. Fluoride production partially matched the observed degradation, while no organic byproducts were detected using LC-QTOF-MS. (C) 2014 Elsevier B.V. All rights reserved.