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Pre- and Postapplication Thermal Treatment Strategies for Sorption Enhancement and Reactivation of Biochars for Removal of Per- and Polyfluoroalkyl Substances from Water
https://orcid.org/0000-0002-8033-3950
https://orcid.org/0000-0001-5686-6055
https://orcid.org/0000-0002-2772-5250
Exposure to per- and polyfluoroalkyl substances (PFAS) in drinking water poses a major public health threat. Commercial granular activated carbon (GAC) has been used for the sorptive removal of PFAS in practical applications. Biochar is a possible cheaper alternative to GAC for small-scale water treatment systems. Here, we report a strategy for employing biochar for PFAS removal that combines post-pyrolysis modification, which greatly improves performance, with a reactivation step that enables its reuse. Modification entails brief postpyrolysis air oxidation at 400 °C, which considerably enlarges pore size and specific surface area and thereby increases the solid-to-water distribution ratio, K D, of individual PFAS by as much as 3 orders of magnitude. In some cases (e.g., perfluorooctanoic acid) the K D was comparable to that of commercial GAC. The sorbed PFAS could be decomposed by brief thermal reactivation of the spent biochar at 500 °C in N2 or air. After thermal reactivation in air, the biochars exhibited even greater PFAS K D values in a second cycle. While thermal reactivation of a GAC in air could be achieved, as well, sorption affinity for the shorter-chain PFAS was noticeably reduced. Overall, this study points to a new strategy of using biochars for PFAS removal.
Pre- and Postapplication Thermal Treatment Strategies for Sorption Enhancement and Reactivation of Biochars for Removal of Per- and Polyfluoroalkyl Substances from Water
https://orcid.org/0000-0002-8033-3950
https://orcid.org/0000-0001-5686-6055
https://orcid.org/0000-0002-2772-5250
Exposure to per- and polyfluoroalkyl substances (PFAS) in drinking water poses a major public health threat. Commercial granular activated carbon (GAC) has been used for the sorptive removal of PFAS in practical applications. Biochar is a possible cheaper alternative to GAC for small-scale water treatment systems. Here, we report a strategy for employing biochar for PFAS removal that combines post-pyrolysis modification, which greatly improves performance, with a reactivation step that enables its reuse. Modification entails brief postpyrolysis air oxidation at 400 °C, which considerably enlarges pore size and specific surface area and thereby increases the solid-to-water distribution ratio, K D, of individual PFAS by as much as 3 orders of magnitude. In some cases (e.g., perfluorooctanoic acid) the K D was comparable to that of commercial GAC. The sorbed PFAS could be decomposed by brief thermal reactivation of the spent biochar at 500 °C in N2 or air. After thermal reactivation in air, the biochars exhibited even greater PFAS K D values in a second cycle. While thermal reactivation of a GAC in air could be achieved, as well, sorption affinity for the shorter-chain PFAS was noticeably reduced. Overall, this study points to a new strategy of using biochars for PFAS removal.
Pre- and Postapplication Thermal Treatment Strategies for Sorption Enhancement and Reactivation of Biochars for Removal of Per- and Polyfluoroalkyl Substances from Water
https://orcid.org/0000-0002-8033-3950
https://orcid.org/0000-0001-5686-6055
https://orcid.org/0000-0002-2772-5250
Exposure to per- and polyfluoroalkyl substances (PFAS) in drinking water poses a major public health threat. Commercial granular activated carbon (GAC) has been used for the sorptive removal of PFAS in practical applications. Biochar is a possible cheaper alternative to GAC for small-scale water treatment systems. Here, we report a strategy for employing biochar for PFAS removal that combines post-pyrolysis modification, which greatly improves performance, with a reactivation step that enables its reuse. Modification entails brief postpyrolysis air oxidation at 400 °C, which considerably enlarges pore size and specific surface area and thereby increases the solid-to-water distribution ratio, K D, of individual PFAS by as much as 3 orders of magnitude. In some cases (e.g., perfluorooctanoic acid) the K D was comparable to that of commercial GAC. The sorbed PFAS could be decomposed by brief thermal reactivation of the spent biochar at 500 °C in N2 or air. After thermal reactivation in air, the biochars exhibited even greater PFAS K D values in a second cycle. While thermal reactivation of a GAC in air could be achieved, as well, sorption affinity for the shorter-chain PFAS was noticeably reduced. Overall, this study points to a new strategy of using biochars for PFAS removal.
Pre- and Postapplication Thermal Treatment Strategies for Sorption Enhancement and Reactivation of Biochars for Removal of Per- and Polyfluoroalkyl Substances from Water
Wang, Zhengyang (author) / Alinezhad, Ali (author) / Sun, Runze (author) / Xiao, Feng (author) / Pignatello, Joseph J. (author)
ACS ES&T Engineering ; 3 ; 193-200
2023-02-10
Article (Journal)
Electronic Resource
English
Effects of Environmental Factors on the Sorption of Per- and Polyfluoroalkyl Substances by Biochars
| American Chemical Society | 2023