Effects of biochar–BDE-47 interactions on BDE-47 bioaccessibility and biodegradation by Pseudomonas putida TZ-1

•The presence of biochars dramatically decreased the biodegradation rate of BDE-47.•Hysteretic desorption played a rate-limiting role for biodegradation.•Molecules sorbed onto external surfaces can be completely desorbed and bioaccessible.•Molecules in micropores were more persistent and resulted in lower bioaccessibility.

With biochar amendments widely accepted as efficient POPs contamination remediation methods, the post-remediation risk assessment and effectiveness evaluation were urgently needed. So in the study, the effects of biochar –2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) interactions on the bioaccessibility and biodegradation of BDE-47 were systematically examined. Biodegradation was monitored over 7 day incubation time with strain Pseudomonas putida TZ-1 and it was revealed that the presence of three model biochars dramatically decreased the biodegradation rate by 87.50–92.19%. The desorption rate gradually decreased to eventually make it a rate-limiting process for BDE-47 biodegradation. To further explore the impact of biochar–BDE-47 sorption on its bioaccessibility, chemical extraction and biosurfactant facilitated desorption experiments were conducted. Both results suggested that almost all the molecules sorbed onto non-porous biochars could be completely desorbed, whereas BDE-47 molecules sequestered within deep micropores were more persistent on the solid phase, and resulted in lower bioaccessibility.