Layered double hydroxide based composite core–shell electrospun nanofibers for lead and fluoride filtration from contaminated streams

Abstract

Coaxial electrospinning was used to synthesize polyacrylonitrile–polyethersulfone (PAN–PES) core–shell nanofibers with magnesium–aluminum layered double hydroxide (Mg–Al LDH) for filtration of lead and fluoride from contaminated streams. Fiber geometry was characterized at a 0.5 mL h−1 flow rate for the core polymer (PES/LDH) and 0.8 mL h−1 flow rate for the shell polymer (PAN), with a potential of 23 kV and a distance of 15–17 cm between the collector and the needle head. A homogeneous fiber shape was achieved using an optimal LDH concentration of 0.7%. The prepared nanofibers served as an ultrafiltration membrane with a permeability of 5 × 10−12 m s−1 Pa−1. The uptake capacity of the produced nanofibers for fluoride and lead was estimated to be 948 mg g−1 and 196 mg g−1, respectively at 298 K as per Langmuir's isotherm model. These fibers exhibited hydrophilic properties and possessed a significant level of porosity. XPS study revealed binding energies of 139.3 eV and 685.2 eV, indicating lead and fluoride uptake by the nanofibers. Ether, sulfone, hydroxyl and nitrile groups found in the nanofibers' shell and core most likely contributed to the lead and fluoride uptake. This facilitated the uptake of both ions on the surface of the nanofibers. In terms of the inhibition effect, fluoride had a stronger masking effect compared with lead in a multicomponent solution (consisting of lead and fluoride). Dynamic vacuum filtration was also investigated using the prepared nanofibers in artificial and real-life feed solutions.