Reusable UiO-66-NH₂ Functionalized Polyacrylonitrile Nanofiber Membrane for Effective Removal of Cr(VI) from Water

Metal–organic framework UiO-66-NH₂ powder used for effective removal of Cr(VI) from water is difficult to recover after usage. In this study, UiO-66-NH₂ was in-situ grown on polyacrylonitrile (PAN) nanofiber membrane using water as solvent and trifluoroacetic acid as structure regulator, via hydrothermal method for adsorption of Cr(VI) ions. The optimal proportion of trifluoroacetic acid, hydrothermal synthesis time and pH level were 30%, 4 h and pH = 2, respectively. Scanning electron microscopy showed that UiO-66-NH₂ was uniformly and densely coated on the PAN nanofibers. N₂ adsorption–desorption experiments and thermogravimetric analysis showed large surface area (680.99 m²/g) and good thermal stability of PAN@UiO-66-NH_2, compared to PAN nanofiber membrane. The adsorption capacity of PAN@UiO-66-NH₂ nanofiber membrane for Cr(VI) at 298 K was 312.25 mg/g. Kinetic studies revealed that the adsorption process was consistent with Langmuir isotherm and pseudo-second-order model. The composite showed good reusability in Cr(VI) removal in 5 cycles. Based on Zeta potential, the influence of pH and XPS analysis, PAN@UiO-66-NH₂ nanofiber membrane effectively adsorbs Cr(VI) through electrostatic interaction. PAN@UiO-66-NH₂ nanofiber membrane is therefore considered as an efficient and reusable adsorbent with high potential for Cr(VI) removal in industrial wastewater.