Abstract
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•Bimetallic FeNi nanoparticles/straw-derived biochar was synthesized.•biochar reduces the aggregation of Fe0.•Ni doping promotes the formation of Fe(II) and H atoms.•BC@Fe/Ni is a promising material for controlling Cr(VI) pollution.
Nano-zero-valent iron (nZVI) can efficiently control Cr(VI) pollution in groundwater, but its application is hindered by the tendency of Fe0 to agglomerate and form a passivation layer. In this study, to increase the reactivity of Fe0, biochar (BC) -supported Fe/Ni bimetal nanoparticles (BC@Fe/Ni) were developed to promptly remove Cr(VI) from water. The results demonstrated that the mesoporous structure of BC can provide a supportive environment for Fe0 and reduce the aggregation of Fe0. The removal efficiency of BC@Fe/Ni was found to be better than that of BC and Fe/Ni. Good performance was achieved when the Ni content was approximately 5%. At pH 2.0, the removal rate of Cr(VI) reached 99.62%. A higher temperature was found to be favorable for the reaction, indicating that BC@Fe/Ni is endothermic in removing Cr(VI). The mechanism of BC@Fe/Ni and Cr(VI) is as follows. First, a part of Cr(VI) is adsorbed on BC@Fe/Ni via electrostatic attraction; then, the driving force for Cr(VI) reduction is mainly the continuous electron transfer of Fe0 and Fe(II); moreover, Ni promotes the formation of Fe(II) and H atoms. In conclusion, this work demonstrates that BC@Fe/Ni is a promising material for controlling Cr(VI) pollution. This work will serve as a reference for the improvement of bimetallic nanomaterials and the treatment of Cr(VI) contamination.