Preparation of hydrazine-modified polyacrylonitrile nanofibers for the extraction of metal ions from aqueous media

Polyacrylonitrile (PAN) nanofibers (prepared by an electrospinning technique) were chemically modified with hydrazine. The Fourier transform infrared spectrum of the hydrazine-modified polyacrylonitrile (HM-PAN) showed that the intensity of the nitrile peak (2250 cm^-1) of the PAN nanofibers decreased significantly after treatment with hydrazine. New peaks at about 3400-3100 cm^-1 (N-H stretching vibration) also appeared, which showed that the hydrazine was chemically attached to the PAN nanofibers. HM-PAN had a smooth surface (as confirmed by a scanning electron microscopy) and was a suitable material for the adsorption of metal ions from aqueous solutions. The adsorption capacity of HM-PAN increased as the adsorption time increased and became constant at 114 and 217 mg/g for Cu(II) and Pb(II) ions, respectively, after 24 h. In addition, more than 90% of the adsorbed Cu(II) and Pb(II) ions were recovered in a 1M HNO₃ solution after 1 h.