A Study
on the Degree of Amidoximation of Polyacrylonitrile
Fibers and Its Effect on Their Capacity to Adsorb Uranyl Ions
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Abstract
Amidoximation
of polyacrylonitrile (PAN) fibers was studied by
reacting them with hydroxylamine. The chemical structure, mechanical
intensity, and morphologies of PAN and amidoximated PAN (AO-PAN) fibers
were evaluated by Fourier transform infrared spectroscopy, tensile
tests, dynamic mechanical analysis, and scanning electron microscopy,
respectively. A higher degree of amidoximation resulted in a higher
conversion ratio (CR) of the nitrile group and a higher density of
the amidoxime group, while also reducing the mechanical intensity
of the fibers. During amidoximation, a hydrogel layer formed on the
fiber surface by bonding with H<sub>2</sub>O molecules, increasing
the diameter of the AO-PAN fibers. The layer thickness increased as
the CR of the AO-PAN fibers’ nitrile group was increased. The
hydrogel layer decreased the adsorption capability by hindering the
diffusion of uranyl ions to the interior of the AO-PAN fibers. Therefore,
a CR of about 10.8% would provide an appropriate balance between the
mechanical properties and the adsorption capability