Removal of decabromodiphenyl ethane (DBDPE) by BC/nZVI in the soil: Kinetics, pathways and mechanisms

Decabromodiphenyl ethane (DBDPE), as a crucial novel brominated flame retardant, has been widely used in the world, of which the accumulation in soil also poses a significant threat to human health. Biochar (BC) and nano-zero-valent iron (nZVI) are environmental-friendly remediation materials for contaminants. In this study, the biochar-supported nZVI (BC/nZVI) particles were synthesized using bagasse at 600 °C under nitrogen protection and then were used to remove DBDPE in a soil system. The results indicated that BC was a good carrier for nZVI due to the decrease of agglomeration. The highest removal efficiency of BC/nZVI was up to 86.91% at 24 h at a mass ratio of 2:1 (BC:nZVI), which was much higher than BC or nZVI alone. The degradation kinetics of BC/nZVI to DBDPE followed the pseudo-first-order reaction model well. DBDPE was firstly removed by the adsorption of BC from soil via π-π interactions and hydrogen bonds, and then was oxidized by ·OH generated from BC forming DBDPE-CO (DP-1). Subsequently, the debromination of DP-1 gradually occurred by the ·H from surface hydrolysis of nZVI attacking the bromide on the benzene ring. This technology may act as a promising way for the remediation of highly DBDPE-contaminated soil.