Interface engineering of MIL-88 derived MnFe-LDH and MnFe2O3 on three-dimensional carbon nanofibers for the efficient adsorption of Cr(VI), Pb(II), and As(III) ions

On account of their high adsorption capacity towards toxic oxyanions/cations, metal oxides and hydroxides have received considerable attention. Herein, an iron-manganese layered double hydroxide (MnFe-LDH) was developed on the surface of MnFe2O3 anchored three-dimensional porous carbon nanofibers (MnFe-LDH/ MnFe2O3@3DNF) by a subsequent hydrothermal process. The MnFe-LDH was derived from MIL-88. The prepared MnFe-LDH/MnFe2O3@3DNF effectively reduces the concentration of Cr(VI), Pb(II), and As(III) in an aqueous solution, meeting the drinking water standards prescribed by the World Health Organization. The adsorption isotherms of Cr(VI), Pb(II), and As(III) ions onto MnFe-LDH/MnFe2O3@3DNF were described by the Langmuir, Freundlich, and Sips models. The Sips adsorption isotherm model indicates the maximum sorption capacities of the MnFe-LDH/MnFe2O3@3DNF toward Cr(VI), Pb(II), and As(III) adsorptions are 564.88 mg g(-1), 591.80 mg g(-1), and 504.54 mg g(-1), respectively, at room temperature. Kinetic studies revealed that the adsorption process is pseudo-second-order. The XPS, FESEM EDX, and FTIR studies indicated that the adsorption mechanism was mainly dominated by isomorphic substitution, precipitation, surface complexation, and electrostatic attraction. Importantly, the as-prepared MnFe-LDH/MnFe2O3@3DNF can be repeatedly used several times without significant degradation of the adsorption performance or the generation of secondary pollutants. The findings highlight the potential application of MnFe-LDH/MnFe2O3@3DNF for the decontamination of heavy metals by the virtue of its admirable adsorption performances.