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STABILIZATION OF PFAS-CONTAMINATED SOIL WITH SEWAGE SLUDGE- AND WOOD-BASED BIOCHAR SORBENTS
Sormo, E., C.B.M. Lade, J. Zhang, A.G. Asimakopoulos, G. Wold Asli, M. Hubert, A.I. Goranov, H.P.H. Arp, and G. Cornelissen.
Science of The Total Environment 922:170971(2024)
Filed Under: Research
Filed Under: Research
A study investigated the effects of waste-based biochars on PFAS leaching from sandy soil at a former fire-fighting facility with a low total organic carbon content (TOC, 0.57 ± 0.04%) impacted by PFAS from AFFF. Six different biochars (pyrolyzed at 700-900°C) made from clean wood chips (CWC), waste timber (WT), activated waste timber (aWT), two digested sewage sludges (DSS-1 and DSS-2), and de-watered raw sewage sludge (DWSS) were tested. Up-flow column percolation tests (15 days and 16 pore volume replacements) with 1% biochar indicated that PFOS was retained best by the aWT biochar (99.9% reduction) in the leachate, followed by sludge-based DWSS (98.9%) and DSS-2 (97.8%) and DSS-1 (91.6%). The non-activated wood-based biochars (CWC and WT) reduced leaching by < 42.4 %. Extrapolating this to field conditions, 90% leaching of PFOS would occur after 15 y for unamended soil and after 1200 y and 12,000 y, respectively, for soil amended with 1% DWSS-amended and aWT biochar. The high effectiveness of aWT and the three sludge-based biochars in reducing PFAS leaching from the soil was attributed largely to high porosity in a pore size range (>1.5 nm) that can accommodate the large PFAS molecules (>1.02-2.20 nm) combined with a high affinity to the biochar matrix. Other factors, like anionic exchange capacity, could play a contributing role. Sorbent effectiveness was better for long-chain than short-chain PFAS due to weaker apolar interactions between the biochar and the latter's shorter hydrophobic CF2-tails.
Science of The Total Environment 922:170971(2024)
Filed Under: Research
Filed Under: Research
A study investigated the effects of waste-based biochars on PFAS leaching from sandy soil at a former fire-fighting facility with a low total organic carbon content (TOC, 0.57 ± 0.04%) impacted by PFAS from AFFF. Six different biochars (pyrolyzed at 700-900°C) made from clean wood chips (CWC), waste timber (WT), activated waste timber (aWT), two digested sewage sludges (DSS-1 and DSS-2), and de-watered raw sewage sludge (DWSS) were tested. Up-flow column percolation tests (15 days and 16 pore volume replacements) with 1% biochar indicated that PFOS was retained best by the aWT biochar (99.9% reduction) in the leachate, followed by sludge-based DWSS (98.9%) and DSS-2 (97.8%) and DSS-1 (91.6%). The non-activated wood-based biochars (CWC and WT) reduced leaching by < 42.4 %. Extrapolating this to field conditions, 90% leaching of PFOS would occur after 15 y for unamended soil and after 1200 y and 12,000 y, respectively, for soil amended with 1% DWSS-amended and aWT biochar. The high effectiveness of aWT and the three sludge-based biochars in reducing PFAS leaching from the soil was attributed largely to high porosity in a pore size range (>1.5 nm) that can accommodate the large PFAS molecules (>1.02-2.20 nm) combined with a high affinity to the biochar matrix. Other factors, like anionic exchange capacity, could play a contributing role. Sorbent effectiveness was better for long-chain than short-chain PFAS due to weaker apolar interactions between the biochar and the latter's shorter hydrophobic CF2-tails.
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