Adsorption of perfluoroalkyl substances (PFAS) in groundwater by granular activated carbons: Roles of hydrophobicity of PFAS and carbon characteristics. (1st March 2020)

• Record Type: Journal Article
• Authors: Park, Minkyu; Wu, Shimin; Lopez, Israel J.; Chang, Joseph Y.; Karanfil, Tanju; Snyder, Shane A.
• Is Part Of: Water research. Volume 170(2020)
• Publication Date: 2020-03-01
• Subjects: PFAS -- Granular activated carbon -- Groundwater -- RSSCT -- Breakthrough -- Hydrophobicity; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2019.115364
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: The adsorption breakthrough behavior of nine perfluoroalkyl substances (PFAS) in groundwaters by four bituminous coal-based granular activated carbons (F400, Carbsorb 40, HPC and CMR400) was studied using rapid small-scale column tests (RSSCTs). The half breakthrough bed volume (BV50 ), an indicator of apparent adsorption capacity, correlated with the hydrophobicity of PFAS at a given pH (i.e., Log D ow ) for F400, indicating that hydrophobic interaction is important for apparent adsorption capacity of PFAS in groundwater with low dissolved organic concentrations (DOC < 1 mg C/L) and low specific UV absorbances at 254 nm (SUVA254 < 2 L mg −1 m −1 ). Higher empty bed contact time (EBCT) caused steeper PFAS breakthrough curves with respect to throughput, but did not affect apparent adsorption capacity. Three different sizes of F400 (0.13, 0.17, and 0.20 mm) exhibited similar breakthrough profiles of PFAS, indicating that the intraparticle diffusivity was independent of adsorbent diameter in the given conditions. Among the tested carbons, the positively charged adsorbents (F400, HPC, and CMR400) showed higher apparent adsorption capacities for hydrophilic (Log D ow at pH 7 < 0) and marginally hydrophobic PFAS (Log D ow at pH 7 between 0 and 1) than the negatively charged adsorbent (Carbsorb 40). In addition, activated carbons with higher micropore surface areas exhibited higher apparent adsorption capacities of hydrophilic and marginally hydrophobic PFAS among the positively-charged activated carbons, whereas the mesoporous carbon (HPC) exhibited an increasingly larger adsorption capacity for more hydrophobic PFAS compared to the microporous carbon (F400) at a later breakthrough possibly due to less pore blockage. Graphical abstract: Image 1 Highlights: Apparent adsorption capacity of PFAS was proportional to their hydrophobicity. Overshoot concentrations were observed for hydrophilic short-chain PFBA and PFPeA. Similar breakthrough profiles were observed among the tested adsorbent sizes. Micropore surface area was important to determine apparent adsorption capacity. Mesopores played increasingly important roles for hydrophobic PFAS adsorption.