Effects of different types of biochar on the properties and reactivity of nano zero-valent iron in soil remediation

The addition of nano zero-valent iron (nZVI) is a promising technology for the in situ remediation of soil. Unfortunately, the mobility and, consequently, the reactivity of nZVI particles in contaminated areas decrease due to their rapid aggregation. In this study, we determined how nZVI particles can be stabilized using different types of biochar (BC) as a support (BC@nZVI). In addition, we investigated the transport behavior of the synthesized BC@nZVI particles in a column filled with porous media and their effectiveness in the removal of BDE209 (decabromodiphenyl ether) from soil. The characterization results of N-2 Brunauer-Emmett-Teller (BET) surface area analyses, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) indicated that nZVI was successfully loaded into the BC. The sedimentation test results and the experimental breakthrough curves indicated that all of the BC@nZVI composites manifested better stability and mobility than did the bare-nZVI particles, and the transport capacity of the particles increased with increasing flow velocity and porous medium size. Furthermore, the maximum concentrations of the column effluent for bagasse-BC@nZVI (B-BC@nZVI) were 19%, 37% and 48% higher than those for rice straw-BC@nZVI (R-BC@nZVI), wood chips-BC@nZVI (W-BC@nZVI) and corn stalks-BC@nZVI (C-BC@nZVI), respectively. A similar order was found for the removal and debromination efficiency of decabromodiphenyl ether (BDE209) by the aforementioned particles. Overall, the attachment of nZVI particles to BC significantly increased the reactivity, stability and mobility of B-BC@nZVI yielded, and nZVI the best performance. (C) Higher Education Press 2021

Automated summary

The study demonstrated that stabilizing nZVI particles with different types of biochar (BC) can enhance their stability and mobility, leading to improved removal of BDE209 from contaminated soil. The transport behavior of BC@nZVI composites in porous media showed better performance compared to bare nZVI particles, with potential for increased efficiency at higher flow velocities and in larger porous media.