Remediation of Perfluorooctylsulfonate Contamination by in Situ Sequestration:Direct Monitoring of PFOS Binding to Polyquaternium Polymers

摘要

In situ methods for the sequestration of perfluorooctyl-1-sulfonate (PFOS) that are based on PFOS binding to polyquaternium polymers were reported previously, providing an approach to immobilize and concentrate PFOS in situ. To apply these methods in real life, the concentrations of polymers that permit efficient sequestration must be determined. This is only possible if the stoichiometry and strength of PFOS binding to polyquaternium polymers are known. Here, we report on the use of fluorous-phase ion-selective electrodes (ISEs) to determine the equilibrium constants characterizing binding of PFOS to poly(dimethylamine-co-epichlorohydrin) and poly(diallyldimethylammonium) in simulated groundwater and in soil suspensions. We introduce a new method to interpret potentiometric data for surfactant binding to the charged repeat unit of these polyions by combining a 1:1 binding model with the ISE response model. This allows for straightforward prediction and fitting of experimental potentiometric data in one step. Data fit the binding model for poly(diallyldimethylammonium) and poly(dimethylamine-co-epichlorohydrin) chloridein soil-free conditions and in the presence of soil from Tinker AirForce Base. When the total PFOS concentration in a soil system isknown, knowledge of these PFOS binding characteristics permits quantitativeprediction of the mobile (free) and polymer-bound fractions of PFOSas a function of the concentrations of the polyquaternium polymer.Because the technique reported here is based on the selective in situdetermination of the free ionic surfactant, we expect it to be similarlyuseful for determining the sequestration of a variety of other ionicpollutants.