▎ 摘　　要

Biochar (BC)-supported graphene-encapsulated zero-valent iron nanoparticle composites (BC-G@Fe-0) are promising engineering nanocomposites that can be used to scavenge heavy metal from wastewater. However, the production of BC-G@Fe-0 through carbothermal reduction using biomass as a carbon source remains challenging because of biomass pyrolysis complications. Here, we examined two carbothermal reduction routes for preparing BC-G@Fe-0 using bamboo as the carbon source. The first route impregnated Fe ions (Fe2+/3+) into unpyrolyzed bamboo particles initially, followed by carbonization at 600-1000 ?. This process produced BC-G@Fe-0 dominated by iron carbide (Fe3C), which led to low heavy metal removal efficiency (i.e., Cu2+ capacity of < 0.3 mmol g(-1)). In the second route, bamboo particles were pyrolyzed (600 ? ) to biochar first, followed by impregnating this biochar with Fe ions, and then carbonized at 600-1000 ?. This route produces zero-valent iron nanoparticles, which resulted in high heavy metal removal capacities (i.e., 0.30, 1.58, and 1.91 mmol g(-1) for Pb2+, Cu2+, and Ag+, respectively). The effects of carbonization temperature (600-1000 ?), iron source (i.e., iron nitrates, iron sulfate, ferrous chloride, and ferric chloride), and iron loading (5-40%) on the morphology, structure, and heavy metal ion aqueous uptake performance of BC-G@Fe-0 were also investigated. This study revealed the formation mechanisms of BC-G@Fe-0 through biomass carbothermal reduction, which could guide the application-oriented design of multifunctional iron-BC composites for water remediation.