Using the benzenepolycarboxylic acid (BPCA) method to assess activated biochars and their PFAS sorption abilities

Aleksandar I Goranov; Erlend Sørmo; Nikolas Hagemann; Gerard Cornelissen; Andrew R Zimmerman; Patrick G Hatcher

doi:10.1016/j.chemosphere.2024.141750

Using the benzenepolycarboxylic acid (BPCA) method to assess activated biochars and their PFAS sorption abilities

Chemosphere. 2024 May:355:141750. doi: 10.1016/j.chemosphere.2024.141750. Epub 2024 Mar 22.

Authors

Aleksandar I Goranov¹, Erlend Sørmo², Nikolas Hagemann³, Gerard Cornelissen², Andrew R Zimmerman⁴, Patrick G Hatcher⁵

Affiliations

¹ Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA, USA. Electronic address: aleksandar.i.goranov@gmail.com.
² Department of Environmental Chemistry, Norwegian Geotechnical Institute (NGI), Oslo, Norway; Faculty of Environmental Science and Natural Resource Management (MINA), University of Life Sciences (NMBU), Ås, Norway.
³ Agroscope, Reckenholz, Switzerland; Ithaka Institute for Carbon Strategies, Arbaz, Switzerland and Goldbach, Germany.
⁴ Department of Geological Sciences, University of Florida, Gainesville, FL, USA.
⁵ Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA, USA. Electronic address: phatcher@odu.edu.

PMID: 38522671
DOI: 10.1016/j.chemosphere.2024.141750

Abstract

Activated carbon (AC) has important industrial and environmental applications as it has excellent abilities to sorb contaminants such as per- and polyfluoroalkyl substances (PFAS). Current research aims to develop activated biochars (AB) from renewable biomass to replace AC that is produced from fossil feedstock. Both AC and AB are primarily comprised of condensed aromatic carbon (ConAC), the component that is the focus of this study. ConAC is characterized to determine its relationship with biochar activation conditions and PFAS sorption, which are understudied at present. Benzenepolycarboxylic acid (BPCA) markers for ConAC were quantified in steam-activated biochars (AB-Steam) and carbon dioxide-activated biochars (AB-CO₂) prepared from waste timber at different temperatures (800, 850, 900 °C) and molar ratios of feedstock-carbon:steam (0.50 - 1.25). A non-activated biochar was also included as a reference. ConAC relative to total organic carbon content was higher in AB-Steam than in AB-CO₂ (92 ± 2 % vs. 81 ± 11%). The ratio of benzenehexa- (B6CA) to benzenepentacarboxylic (B5CA) acids revealed that AB-Steam also had larger ConAC clusters than AB-CO_2. These findings provide novel evidence that steam activation is more effective than CO₂ activation in creating ConAC. To assess how ConAC impacts AB sorption abilities, AB-Steam were used to remediate PFAS from contaminated soils. The observed strong correlations between ConAC content and sorption of long-chain PFAS suggest the importance of hydrophobic interactions between PFAS tails and ConAC. Poor correlations for short-chain PFAS, on the other hand, indicated the existence of electrostatic repulsion interactions between PFAS head groups and ConAC. Collectively, these results explain the great ability of AB-Steam to sorb PFAS from contaminated soils (up to 100% remediation). More broadly, this work demonstrates that the BPCA method can be a valuable tool to assess the quality of biochars and other carbonaceous sorbents in relation to their production conditions or contaminant sorption abilities.

Keywords: Activated biochars; Activated carbon; BPCA method; Condensed aromatic carbon (ConAC); PFAS; Sorption mechanism.

MeSH terms

Adsorption
Carbon Dioxide*
Charcoal / chemistry
Fluorocarbons*
Soil
Steam

Substances

biochar
Carbon Dioxide
Steam
Charcoal
Soil
Fluorocarbons