Application of Rapid, Small-Scale Column Tests to Assess Treatment of Perfluoroalkyl Acids in Groundwater Using A Novel Modified Clay Sorbent

Rapid small-scale column tests (RSSCTs) are often used to assess the efficacy of adsorption media, such as granular activated carbon (GAC) and anion exchange resin (AER) in removing perfluoroalkyl acids (PFAAs) from impacted waters. By reducing GAC and AER particle sizes via grinding, RSSCTs allow for enhanced mass transfer and simulation of long-term field or pilot testing in a much shorter time frame under controlled laboratory settings. Fluoro-Sorb (FS), a novel surface-modified organoclay sorbent, has recently been used for removal of PFAAs in drinking water applications and is receiving increased attention as an alternative to GAC or AER. However, unlike GAC and AER products, the appropriateness of employing RSSCTs for assessing PFAA removal from impacted water using ground versus unground (i.e., as-received) FS has not been assessed. Herein, bench-scale column experiments were conducted using FS to preliminarily determine the scaling relationship needed to properly design RSSCTs and to compare the PFAA removal effectiveness to GACs and AERs. With respect to scaling, results indicated that an RSSCT approach assuming constant diffusivity was appropriate for FS. In general, FS outperformed GAC and AER with respect to treatment of long-chained PFAAs. No desorption of organic carbon or quaternary amines or leaching of metals was observed from the FS. However, a slight change in chloride to sulfate mass ratio (CSMR) and high pH excursions were observed, highlighting the need for proper monitoring immediately following FS startup to avoid unwanted changes in water quality.