Synthesis and photocatalytic application of TiO₂ nanoparticles immobilized on polyacrylonitrile nanofibers using EDTA chelating agents

The photocatalytic properties of TiO₂ nanoparticles (TNPs) have been widely demonstrated in the literature. Here, we report the chemical attachment of TNPs to the surface of polyacrylonitrile nanofibers (PNFs) using the ethylenediaminetetraacetic acid (EDTA) and ethylenediamine (EDA) as the chelating agents. The composite nanofibers were prepared through the chelation of Ti⁴⁺ ions with surface carboxylic and amine groups followed by self-growth of TiO₂ nanoparticles on the surface of modified PNFs during the incubation process. The fabricated composite nanofibers were stabilized at 240 °C in a tube furnace under N₂ gas. The heat treatment served to simultaneously crystallize the TNPs and enhance robustness of PNFs as cyclization reactions and the cross-linking of adjacent nitrile groups (–C[dbnd]N[sbnd]C[dbnd]N–) usually takes place at temperatures above 200 °C. Characterization techniques included X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman spectroscopy and Brunauer-Emmett-Teller (BET) technique. The chemical impregnation of EDTA-EDA on the surface of PNFs resulted in slight increase in the average nanofiber's diameter. The anatase TiO₂ nanoparticles with average 9.4 nm particle size prepared in situ were immobilized on the surface of pre-functionalized PNFs. The fabricated composite nanofibers were applied in the photocatalytic degradation of methyl orange (MO) in synthetic aqueous solutions. The as-prepared composite nanofibers were reused for five (5) cycles without considerable decline in the MO removal efficiency (i.e. >98% of initial performance).