Algae-derived metal-free boron-doped biochar as an efficient bioremediation pretreatment for persistent organic pollutants in marine sediments

Aquatic systems are important sinks of persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs). In this study, boron-doped biochar (B-BAB) was prepared from pristine brown algae (Sargassum duplicatum) and boric acid using a facile pyrolysis method. The B-BAB was then used as catalyst for the activation of peroxymonosulfate (PMS) for bioremediation-based sediment decontamination. The effect of catalyst dosage and initial pH of the B-BAB/PMS system on PAH removal were studied. At an initial pH of 3.0, 93% of the PAH was degraded within 12 h in the presence of 1.0 g/L of B-BAB and 1 x 10(-4) M of PMS, while the removal of 2-, 3-, 4-, 5-, and 6-ring PAHs was 53, 86, 81, 83, and 91%, respectively. Results demonstrated that BBAB has superior catalytic capacity for PMS activation and significantly improved the efficacy of PAH removal. Interaction between boric and nitrogen species on the graphitized carbon framework, through the primary radical (SO4 center dot- and HO center dot) and nonradical (O-1(2)) reactions in the B-BAB/PMS system was key to efficient PAHs removal. High PAH removal capability and favorable changes in benthic bacterial communities of the B-BAB/PMS process suggested that PMS-advanced oxidation process (AOP) treatment enhanced the biological richness and microbiota diversity of the sediments, which were initially dominated by Proteobacteria and Epsilonbacter-aeota, including genera related to Woeseia and Sulfurovum. Overall, the present study significantly expanded knowledge on the metal-free nature of carbocatalysis-boosting B-BAB/PMS removal of POPs. The B-BAB/PMS system may be useful to realizing the application of green technologies for future water environment bioremediation campaigns.