Abstract
The performance of nano-zero-valent iron for heavy metal remediation can be enhanced via incorporation into bimetallic carbon composites. However, few economical and green approaches are available for preparing bimetallic composite materials. In this study, novel Co/Fe bimetallic biochar composites (BC@Co/Fe-X, where X = 5 or 10 represents the CoCl(2) concentration of 0.05 or 0.1 mol L(-1)) were prepared for the adsorption of Pb(2+). The effect of the concentration of cross-linked metal ions on Pb(2+) adsorption was investigated, with the composite prepared using 0.05 mol L(-1) Co(2+) (BC@Co/Fe-5) exhibiting the highest adsorption performance. Various factors, including the adsorption period, Pb(2+) concentration, and pH, affected the adsorption of Pb(2+) by BC@Co/Fe-5. Further characterisation of BC@Co/Fe-5 before and after Pb(2+) adsorption using methods such as X-ray diffraction and X-ray photoelectron spectroscopy suggested that the Pb(2+) adsorption mechanism involved (i) Pb(2+) reduction to Pb(0) by Co/Fe, (ii) Co/Fe corrosion to generate Fe(2+) and fix Pb(2+) in the form of PbO, and (iii) Pb(2+) adsorption by Co/Fe biochar. Notably, BC@Co/Fe-5 exhibited excellent remediation performance in simulated Pb(2+)-contaminated water and soil with good recyclability.