Facile synthesis of ZIF-8 incorporated electrospun PAN/PEI nanofibrous composite membrane for efficient Cr(VI) adsorption from water

Abstract

Hexavalent chromium Cr(VI) is one of the most toxic heavy metal ions. Therefore, the removal of this contaminant from wastewater is of particular importance. Herein, a novel zeolitic imidazolate framework (ZIF-8) nanoparticles based electrospun polyacrylonitrile (PAN)/polyethylenimine (PEI) nanofibrous composite membranes (NCMs) were prepared and characterized by SEM, XRD, FTIR, TGA and other characterization techniques. The NCMs were tested for the adsorption of Cr(VI) from water. Results showed that the inclusion of PEI tailored the surface of the NCM to be superhydrophilic. The prepared electrospun NCM showed a high adsorption capacity for Cr(VI) (up to 403.5 mg·g−1) under ZIF-8 concentration of 5 wt%. More importantly, introducing ZIF-8 up to 5 % did not only increase the adsorption capacity but also enhanced the thermal stability, mechanical strength, and structure of the NCM. The experimental analysis of co-existing ions and the reusability of up to ten cycles showed that the optimized PAN/PEI@ZIF-8 NCM exhibited good selectivity and excellent stability for wastewater treatment. The adsorption kinetics followed the pseudo-second-order model and the adsorption isotherm could be fitted well by the Langmuir model. Thermodynamics revealed that the adsorption process was spontaneous and endothermic. The adsorption mechanism was found to be mainly electrostatic attraction and reduction. This study demonstrated the potential of ZIF-8-incorporated PAN/PEI NCMs for the removal of Cr(VI) from water.