Soon Il Higashino ’20, Civil and Environmental Engineering

Per- and polyfluoroalkyl substances (PFAS) are man-made compounds capable of persisting in the environment long after introduction. Adsorption onto minerals, such as montmorillonite clay, may potentially serve as an effective way to remove PFAS from water. I examined how cations and salinity influence the adsorption of perfluorobutanesulfonic acid onto montmorillonite clay. Three batch adsorption experiments tested NaCl solutions of .01 M and 1M, and a KCl solution of .1 M, at five concentrations (80 μL, 60μL, 40 μL, 20 μL, 10 μL), including blanks and standards, to determine the adsorption coefficient Kd. The Na-montmorillonite with .01 M salinity yielded a Kd value of 270 ± 73 L solution/kg (log Kd = 2.43 ± 1.86); Na-montmorillonite with 1 M salinity gave a Kd value of 156 ± 40 L solution/kg (log Kd = 2.19 ± 1.60); and K-montmorillonite with .1 M salinity gave a Kd value of 1016 ± 55 L solution/kg (log Kd = 3.01 ± 1.73). This suggests that increasing salinity leads to a decrease in adsorption of PFBS onto Na-saturated smectite, and of the cations Na, Ca, and K, the presence of K led to an increase in adsorption.