Umeå University's logo

Biochar has recently been identified as a potential solution for the remediation of organic micropollutants from contaminated water. Herein, we have assessed the potential mitigation of per- and polyfluoroalkyl substances (PFAS) by means of biochar adsorption as a green alternative to coal-based sorbents for PFAS-polluted stormwater systems. For this purpose, 13 biochar materials (originating from diverse feedstocks as well as intended for both commercial and research purposes) were initially screened for PFAS remediation capabilities in static flow systems. These experiments pointed to biochar sorption as a promising strategy for PFAS remediation, with some materials showing removal efficiencies of around 99% after 7 days of exposure. Though not all of the biochar materials tested performed equally, differences could be observed. As a next step, five biochar materials were studied under constant-flow column experiments for a duration of 69 days using real stormwater spiked with PFAS. Results showed that vast differences could be observed for the retention rates of the tested PFAS contaminants, with estimated bed volumes for an 80% breakthrough ranging from, for example, 13–60 for perfluorobutanesulfonic acid and from 4 to 53 for perfluoropentanoic acid. In terms of the PFAS backbone, both the static and dynamic flow experiments highlighted that long-chain PFAS showed stronger sorption onto the biochar surface than short-chain PFAS; however, no relevant impact could be identified in terms of the PFAS functional group. Overall, biochar is emerging as a promising and environmentally friendly approach for removing PFAS from contaminated stormwater.