The difference in the adsorption mechanisms of magnetic ferrites modified carbon nanotubes

摘要

Various ferrites modified carbon nanotubes (MFe2O4/CNTs; M = Co, Cu, Mn) were synthesized and characterized using TEM-EDS, FTIR, BET, TG-DTA, VSM, and XRD. MFe2O4/CNTs were used as adsorbents for removing ciprofloxacin (CIP), and the adsorption mechanism was revealed in a comparative manner based on the experimental results and & nbsp;density functional theory & nbsp;calculations. The adsorption capacities of CIP on MFe2O4/CNTs were 63.32 (Co), 61.60 (Cu), and 46.35 (Mn) mg/g, respectively. Different M components of MFe2O4 & nbsp;affected the adsorption behavior of CIP on them, while the specific surface area and total pore volume showed no significant impact. The investigation on the adsorption energy and the bond formation indicated that CIP was more favorably captured by CoFe2O4/CuFe2O4 & nbsp;than MnFe2O4. The local density of states of metal atoms and O atoms (from the ketone or & nbsp;carboxyl groups & nbsp;of CIP) showed that the & nbsp;d-band centers of Co and Cu atoms were above the Fermi level, while that of Mn was below the Fermi level, providing the fundamental understanding of the promoted O adsorption on CoFe2O4 & nbsp;and CuFe2O4 & nbsp;and restrained adsorption on MnFe2O4. This observation was supported by the electron localization function in terms of the stronger charge density overlap between Co-O/Cu-O than that of Mn-O.