This work explores the use of granular activated carbon (GAC) as a sorbent to remove a suite of 10 perfluoroalkyl acids (PFAAs) from impacted groundwater at environmentally relevant concentrations. To allow these measurements to be performed, solid phase extraction (SPE) methods were developed to allow detection of concentrations of PFAAs in water in the ng/L range. Following method development, two types of sorption experiments were completed. Kinetics experiments were performed to determine the time required to achieve sorption equilibrium. Then, five-point batch sorption isotherms were completed using Calgon, F400 GAC and PFAA concentrations ranging from 70 – 50,000 ng/L. The background-corrected SPE spike recoveries were between 70 and 130% except for PFHxA (174%), PFOS (64%), and PFUnA (143%). The method yields detection limits of 70ng/L or lower for all PFAAs studied. Kinetics experiments suggest sorption batch reactors equilibrate within 36 hours or fewer. Batch isotherm results revealed that the use of too much GAC (5 grams) in batch reactors lead to poor recovery of aqueous PFAA concentrations, especially for longer chained perfluoroalkyl carboxylic acids (PFCAS) and for all perfluoroalkyl sulfonic acids (PFASs). Additionally, extraction of the PFAAs off of the GAC after equilibrium was reached proved difficult when using techniques previously established for soils and sediments, when 5 grams of GAC was used in the reactors. A new method for determining batch isotherms was explored, using less GAC (5 – 25 mg) and holding initial aqueous concentration of PFAAs in the reactors constant (500 ng/L) while varying the amount of GAC in the reactors instead. Preliminary results indicate that this method is an improvement over the earlier one, but additional method development is required.
MacInnis, Allyson Elizabeth,
"Adsorption of Perfluoroalkyl Acids onto Granular Activated Carbon and Other Materials"
(2017).
Engineering Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z05719HV
