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

Abstract

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) chloride in soil-free conditions and in the presence of soil from Tinker Air Force Base. When the total PFOS concentration in a soil system is known, knowledge of these PFOS binding characteristics permits quantitative prediction of the mobile (free) and polymer-bound fractions of PFOS as a function of the concentrations of the polyquaternium polymer. Because the technique reported here is based on the selective in situ determination of the free ionic surfactant, we expect it to be similarly useful for determining the sequestration of a variety of other ionic pollutants.

Potentiometric Sensing

“…As a result, a better reliability of the potentiometric measurements with fluorous membranes was achieved. The same group presented another advantageous application of perfluoroperhydrophenanthrene-based ISEs for the determination of the equilibrium binding constants of perfluorooctyl-1-sulfonate to poly­(dimethylamine- co -epichlorohydrin) and poly­(diallyldimethylammonium) in groundwater and in soil suspensions . Perfluorooctyl-1-sulfonate is a pollutant whose removal from the environment can be conducted by its binding to the positively charged functional groups of polyquaternium polymers, and the knowledge of the binding constant is very important for this process.…”

“…In this way, the first membrane plays the role of the solid contact material, while the second one ensures the selectivity to the ion of interest. 112 Perfluorooctyl-1-sulfonate is a pollutant whose removal from the environment can be conducted by its binding to the positively charged functional groups of polyquaternium polymers, and the knowledge of the binding constant is very important for this process. The authors proposed a method allowing one to calculate the binding constants by fitting the potentiometric response curve.…”

Indirect Potentiometric Determination of Polyquaternium Polymer Concentrations by Equilibrium Binding to 1-Dodecyl Sulfate

“…To relate K to the experimental data, the binding equilibrium can be combined with experimental observables, as previously reported, 34 resulting in the following equation:…”