Granular activated carbon adsorption of perfluoroalkyl acids from ground and surface water

Abstract

Adsorption of perfluoroalkyl acids (PFAAs) by granular activated carbon (GAC) was evaluated in bench‐, pilot‐, and full‐scale studies to determine effects of PFAA characteristics and background organic matter on carbon use rates. Rapid small‐scale column tests (RSSCTs) were conducted according to the proportional diffusivity (PD) design to assess their suitability to predict full‐ or pilot‐scale GAC performance. PFAA removal from groundwater (GW) and coagulated surface water (SW) was studied with two sub‐bituminous coal‐based GACs. In batch tests conducted with pulverized GAC, the GACs performed similarly in GW, but the GAC with the larger mesopore volume was more effective for PFAA removal from SW. In column tests, carbon use rates decreased with increasing PFAA chain length and were lower for GW (total organic carbon [TOC] = 0.7 mg/L) than for SW (TOC = 2.0–2.7 mg/L). The volume of SW that could be treated to 10% or 50% PFAA breakthrough was about 50–60% of the volume of GW that could be treated when comparing pilot‐scale data for SW with full‐scale data for GW. Consistent differences in PFAA adsorption capacity were not observed for empty bed contact times of 13 and 26 min in full‐scale adsorbers treating GW. The PD‐RSSCT simulating PFAA removal from GW consistently overpredicted full‐scale adsorption capacity, on average by ~70%. Using a carbon use rate of <25 mgGAC/Lwater treated) as a criterion for the feasibility of GAC treatment, full‐ and pilot‐scale GAC adsorber data suggest that GAC is a viable treatment option (carbon use rate < 25 mgGAC/Lwater treated) for perfluoroalkylcarboxylic acids with six or more carbon atoms in SW and five or more carbon atoms in GW. For perfluoroalkyl sulfonic acids, GAC treatment is viable for compounds containing four or more carbons based on results obtained with both SW and GW.

Comparing PFAS removal across multiple groundwaters for eight GACs and alternative adsorbent

“…Many previous studies (Belkouteb et al, 2020;Kempisty et al, 2022;Liu et al, 2019;Najm et al, 2021;Park et al, 2020;Wu et al, 2020;Yan et al, 2020;Yuan et al, 2022) have investigated PFAS removal by GAC, and less frequently by AA (Najm et al, 2021), either at bench-or pilotscale or full-scale but have used either a single water source and/or studied only a few adsorbents. Different GAC products can vary widely in their adsorption capacity, and their performance for the particular target organic contaminant depends on empty bed contact time (EBCT), hydraulic loading rate, influent quality as well as flow rate of water flowing through the bed (Rahman et al, 2014).…”

PFAS are forever? The state of the science and research needs for analyzing and treating PFAS‐laden water

“…Similarly, Kempisty et al (2022) evaluate adsorption of 10 PFAAs onto two sub-bituminous, coal-based GACs at the bench-, pilot-, and full-scales to evaluate GAC scale-up procedures and to determine the effects of PFAA characteristics and background organic matter on carbon use rates. Batch tests with pulverized GAC show the GACs perform similarly in groundwater, but the GAC with the larger mesopore volume is more effective for PFAA removal in surface water.…”

Modification of activated carbon for enhanced treatment of per‐ and polyfluoroalkyl substances: A focused review

“…Granular activated carbon (GAC) and powdered activated carbon (PAC) are both porous carbon materials with well-defined pore structures and a substantial surface area (Cantoni et al, 2021;Emenike, Adeleke, et al, 2022), making them suitable for efficiently removing longer-chain PFAS compounds (Kempisty et al, 2022).…”