Treatment of Perfluorinated Chemicals by Electro-Microfiltration

Abstract

Perfluorinated compounds (PFCs) are negatively charged and have low pK(a) values in water; therefore, a laboratory-scale electro-microfiltration (EMF) unit that applies a direct-current electrical field across its membrane can greatly enhance their removal from aqueous systems. We examined the effects of an aqueous inorganic matrix (pH: 4, 7, or 10; ionic strength: 0.4-4.8 mM; ionic composition: Na(2)SO(4), NaCl, NH(4)Cl or CaCl(2)) and an organic matrix such as dissolved organic matter (DOM) on the ability of EMF to remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Decreased removal of PFOX (X = A or S) was observed when the proton concentration and the ionic strength increased. When the applied electrical field strength was less than the critical electrical field strength (E(critical, HA)), PFOX removal was lower in the presence of DOM. We hypothesize that these matrices affect PFOX rejection by altering membrane zeta potential during filtration in the presence of an electrical field. In addition, EMF was found to remove three other PFCs effectively (perfluorodecanoic acid, perfluorohexane sulfonate, and perfluorohexanoic acid), and was also able to remove 70% PFOX and 80% DOC from real industrial wastewaters.