Pyrolytic synthesis of graphene-encapsulated zero-valent iron nanoparticles supported on biochar for heavy metal removal
Tharindu N. Karunaratne , R. M. Oshani Nayanathara , Chanaka M. Navarathna , Prashan M. Rodrigo , Rooban V. K. G. Thirumalai , Charles U. Pittman , Yunsang Kim , Todd Mlsna , Jilei Zhang , Xuefeng Zhang
Biochar ›› 2022, Vol. 4 ›› Issue (1)
Pyrolytic synthesis of graphene-encapsulated zero-valent iron nanoparticles supported on biochar for heavy metal removal
Biochar (BC)-supported graphene-encapsulated zero-valent iron nanoparticle composites (BC-G@Fe0) are promising engineering nanocomposites that can be used to scavenge heavy metal from wastewater. However, the production of BC-G@Fe0 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@Fe0 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 °C. This process produced BC-G@Fe0 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 °C) to biochar first, followed by impregnating this biochar with Fe ions, and then carbonized at 600–1000 °C. 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 °C), 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@Fe0 were also investigated. This study revealed the formation mechanisms of BC-G@Fe0 through biomass carbothermal reduction, which could guide the application-oriented design of multifunctional iron-BC composites for water remediation.
| • | BC-G@Fe0 nanocomposite was produced through two carbothermal reduction routes. |
| • | The biomass impregnating-carbonizing route produced graphene-encapsulated iron carbide (Fe3C) nanoparticles. |
| • | The pyrolyzing-biochar-impregnating-carbonizing route produced graphene-encapsulated nanoscale zero-valent iron particles. |
| • | BC-G@Fe0 nanocomposites exhibited good heavy metal ion removal performance. |
National Institute of Food and Agriculture(2020-65210-30763)
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