(186f) Assessing Factors to Consider When Assaying for per- and Polyfluoroalkyl Substances (PFAS) and the Viability of Microalgae for PFAS Bioremediation

Per- and poly-fluoroalkyl substances (PFAS) are a large class of synthetic chemicals of emerging concern that do not degrade naturally. They are persistent in the environment, bioaccumulating in organisms, and toxic at low (ppt) levels. Current PFAS removal methods are energy-intensive and require significant amounts of maintenance. Chlorella sorokiniana are small freshwater green single-celled microalga species. The cell walls of Chlorella are composed of hydrophobic chitin-like fibers.

This presentation aims to demonstrate adherence levels of two prevalent PFAS molecules through a biosorption approach using Chlorella sorokiniana cells as an adsorbent. The effect of different pH levels on the biosorption of PFAS will be evaluated as well as how the growth media, its components, and similar compounds affect the PFAS removal process as control experiments. We hypothesize that the hydrophobic-to-hydrophobic interactions play a role in PFAS adsorption and that at lower pH levels PFAS adsorption is expected to increase due to enhanced electrostatic interactions of the positively charged fibrils of the cell wall and the negatively charged PFAS.

Five different concentrations of PFOA and PFOS from 50 to 1 ppb in HPLC-grade water were analyzed on the LC-Triple Quad to obtain a calibration curve. Chlorella sorokiniana was added to the PFAS solutions and titrated to pH values of 3, 6, and 12 for PFAS analysis. Controls without algae were run to compare the target concentration to the true concentration.

Concentration profiles of each PFAS molecule will be illustrated and discussed, with additional findings highlighting apparent surface chemistry interactions. Using LC-MS Triple Quad analysis, a correlation between interfacial physicochemical properties of PFAS and associated growth media ions will be established. A possible correlation between pH and PFAS adherence to algal cells will also be presented. Future experiments include determining isotherms and investigating the ionic strength effects on PFAS removal using algae.