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.