Biochar supported nanoscale zero-valent iron for the kinetics removal and mechanism of decabromodiphenyl ethane in the sediment.

Abstract

The extensive applications of decabromodiphenyl ethane (DBDPE), a novel brominated flame retardant, have induced its accumulation in sediment, which may have a great negative impact on the ecological environment. In this work, the biochar/nano-zero-valent iron materials (BC/nZVI) were synthesized to remove DBDPE in the sediment. Batch experiments were carried out to investigate the influencing factors of the removal efficiency, and kinetic model simulation and thermodynamic parameter calculation were performed. The degradation products and mechanisms were probed. The results indicated that the addition of 0.10g·g-1 BC/nZVI to the sediment with an initial concentration of 10mg·kg-1 DBDPE could remove 43.73% of DBDPE during 24h. The water content of the sediment was a critical factor in the removal of DBDPE, which was optimal at 1:2 of sediment to water. The removal efficiency and reaction rate were enhanced by increasing dosage, water content, and reaction temperature or decreasing initial concentration of DBDPE based on the fitting results of the quasi-first-order kinetic model. Additionally, the calculated thermodynamic parameters suggested that the removal process was a spontaneously and reversibly endothermic reaction. The degradation products were further determined by GC-MS, and the mechanisms were presumed that DBDPE was debrominated to produce octabromodiphenyl ethane (octa-BDPE). This study provides a potential remediation method for highly DBDPE-contaminated sediment by using BC/nZVI.