Synthesis and characteristics of chelating fibers containing imidazoline group or thioamide group

Two types of chelating fibers containing an imidazoline or thioamide group were prepared through the functionalization of hydrazine-modified polyacrylonitrile fiber by ethylenediamine and through the amination and sulfurization reaction of the hydrazine-modified polyacrylonitrile fiber under appropriate conditions, respectively. It is shown that the reaction temperature, time, and agent concentration are the dominant factors in the synthesis of fibrous sorbents. The increase of the ethylenediamine concentration from 33 to 45% (v/v) at 95-98 degreesC results in a twofold higher increase of the fibrous sorbent with the imidazoline group, and a doubling of the reaction time from 2 to 4 h leads to a weight increase of the fibrous sorbent from 10 to 25% (w/w). Raising the temperature by about 5 degreesC significantly accelerates the amination reaction of the hydrazine-modified fiber, but the temperature is an insensitive factor in the thioamide-functionalized reaction of the aminated fiber. The introduction of a thioamide or imidazoline group is further verified by IR spectroscopy analysis. X-ray diffraction spectroscopy indicates the absolute disappearance of crystalline peaks for the fibers containing an imidazoline or thioamide group. However, the crosslinking reaction of the polyacrylonitrile fiber by hydrazine may make up for the effect of the crystallinity on the mechanical strength of the fibers, and the surface crackles of fibrous sorbents are not found by SEM photographs. The adsorption experiment results show that the newly prepared sorbents have high sorption capacities for noble metals in a high acidity, and it is also proved that Au(III) loaded on the chelating fibers may be reduced to Au(0). (C) 2002 John Wiley & Sons, Inc. J Appl Polym Sci 83: 1608-1616, 2002.