This work reports
the fabrication of nanomagnetite- and nanotitania-incorporated
polyacrylonitrile nanofibers (MTPANs) by an electrospinning process,
which has the potential to be used as a membrane material for the
selective removal of Cd(II) and As(V) in water. The fiber morphology
was characterized by scanning electron microscopy (SEM). The incorporation
of nanomagnetite and nanotitania in the composite fiber matrix was
confirmed by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction
(XRD), and Fourier transform infrared (FT-IR) spectroscopy. The fibers
doped with nanomagnetite and nanotitania (MPAN and TPAN fibers, respectively),
as well as MTPAN and neat polycrylonitrile (PAN) fibers, after thermally
stabilizing at 275 °C in air, were assessed for their comparative
As(V)- and Cd(II)-ion removal capacities. The isotherm studies indicated
that the highest adsorption of Cd(II) was shown by MTPAN, following
the Langmuir model with a q
m of 51.5 mg/m2. On the other hand, MPAN showed the highest As(V)adsorption
capacity, following the Freundlich model with a K
F of 0.49. The mechanism of adsorption of both Cd(II)
and As(V) by fibers was found to be electrostatically driven, which
was confirmed by correlating the point of zero charges (PZC) exhibited
by fibers with the pH of maximum ion adsorptions. The As(V) adsorption
on MPAN occurs by an inner-sphere mechanism, whereas Cd(II) adsorption
on MTPAN is via both surface complexation and an As(V)-assisted inner-sphere
mechanism. Even though the presence of coexistent cations, Ca(II)
and Mg(II), has been shown to affect the Cd(II) removal by MTPAN,
the MTPAN structure shows >50% removal efficiency even for minute
concentrations (0.5 ppm) of Cd(II) in the presence of high common
ion concentrations (10 ppm). Therefore, the novel polyacrylonitrile-based
nanofiber material has the potential to be used in polymeric filter
materials used in water purification to remove As(V) and Cd(II) simultaneously.