A new nFe@ZIF-8 for the removal of Pb(II) from wastewater by selective adsorption and reduction

A nFe@ZIF-8 composite, which combined the tailorable porosity of ZIF-8 with the versatile functionality of Fe nanoparticles (nFe), was synthesized for Pb(II) removal. Batch adsorption experiments showed that more than 95.3% of Pb(II) was removed from aqueous solution at an initial concentration of 50 mg L-1 when using nFe@ZIF-8 within 60 min at pH value of 5. The mechanism of Pb(II) removal was studied via characterization of changes the morphology, size and composition of in nFe@ZIF-8 before and after exposure the solutions containing Pb(II). Specifically, Fourier transform infrared (FTIR) and X-ray powder diffraction (XRD) indicated that nFe@ZIF-8 was successfully synthesized and also remained stable after Pb(II) removal. Transmission Electron Microscope (TEM) and Scanning electron microscopy-X-ray energy dispersive spectrometer (SEM-EDS) both confirmed that Pb(II) was partially adhered onto the surface of nFe@ZIF-8, where X-ray photoelectron spectroscopy (XPS) specifically revealed the existence of Pb(0) on the surface. This indicated that Pb(II) was initially adsorbed onto the surface of nFe@ZIF-8 and subsequently reduced to Pb(0). Moreover, Pb(II) removal fit well to kinetics of absorption and reduction. Finally, in practice, nFe@ZIF-8 could remove 96.3% of Pb(II) from an electroplating wastewater. (C) 2020 Elsevier Inc. All rights reserved.