Feasibility Study on the Removal of Perfluorooctanoic Acid by Using Palladium-Doped Nanoscale Zerovalent Iron

Perfluorinated chemicals (PFCs) are highly persistent organic contaminants that have become a global health concern. Few studies so far have demonstrated successful decomposition of PFCs under ambient condition. As a result, this feasibility study aimed to quickly examine whether palladium-doped nanoscale zerovalent iron (nZVI/Pd), known to dehalogenate many halogenated chemicals, can remove perfluorooctanoic acid (PFOA) in water, one of the most widely used PFCs. Batch experiments were performed to evaluate the effects of various operation parameters, including reaction pH, nZVI/Pd dose, and PFOA concentration, to find best treatment options for PFOA. Significant removal of PFOA was observed at low pH and high nZVI/Pd dosage while nZVI/Pd was superior to micron-size ZVI and nZVI without Pd. However, the decrease in total organic carbon was very similar to PFOA removal, negligible amounts of fluoride ions were detected in water, and mass spectrometry analysis indicated no significant formation of reaction intermediates. The results implied that the observed PFOA removal was more closely associated with adsorption than reaction (i.e., defluorination). Kinetic models and adsorption isotherm models were employed to explain the PFOA removal and obtain insights on the physicochemical processes around nZVI/Pd interacting with PFOA.