Preparation of sorbents derived from bamboo and bromine flame retardant for elemental mercury removal

This work showcases cost-effective elemental mercury capture strategy enabled by bamboo saw dust and bromine flame retardant (BFR) derived sorbent prepared by a novel hydrothermal-pyrolysis method. The hydrothermal treatment of bamboo and BFR blend was conducted in subcritical water resulting in a hydrothermal char. Subsequently, the hydrothermal char was pyrolyzed in nitrogen atmosphere leading to an improved pore architecture. The resulting biomaterials were proven highly effective for Hg removal. A thorough analysis of the physicochemical properties of the samples was conducted by means of BET, SEM, XRD, XPS and FT-IR. Key parameters such as bamboo/BFR ratio, hydrothermal temperatures and pyrolysis temperatures influence Hg0 removal capacity of our bio-sorbents. Overall, the optimal bamboo/BFR ratio, hydrothermal temperature and pyrolysis temperature are 2:1, 320 ?C and 800 ?C, respectively. Under these optimized conditions, a very promising elemental mercury removal efficiency of 99% is attained. The kinetics and mechanism of Hg0 removal are also proposed. The experimental data fit well with a pseudo-second-order model, indicating that Hg0 adsorption over sorbents was dominated by chemisorption. Our results indicate that the C?Br groups in sorbents provide active sites for oxidizing Hg0 into HgBr2.

Automated summary

This study demonstrates a cost-effective strategy for capturing elemental mercury using bamboo saw dust and bromine flame retardant sorbents, prepared by a novel hydrothermal-pyrolysis method. The optimal conditions of bamboo/BFR ratio, hydrothermal temperature, and pyrolysis temperature result in highly efficient removal of elemental mercury with a 99% removal efficiency. Additionally, the C-Br groups in the sorbents play a key role in oxidizing Hg0 into HgBr2.