Development of surface-modified polyacrylonitrile fibers and their selective sorption behavior of precious metals

The purpose of this study was to design a powerful fibrous sorbent for recovering precious metals such as Pd(II) and Pt(IV), and moreover for identifying its selectivity toward Pd(II) or Pt(IV) from a binary metal solution. For the development of the sorbent, polyacrylonitrile (PAN) was selected as a model textile because its morphological property (i.e., thin fiber form) is suitable for fast adsorption processes, and a high amount of PAN has been discharged from industrial textile factories. The PAN fiber was prepared by spinning a PAN-dimethylsulfoxide mixture into distilled water, and then its surface was activated through amidoximation so that the fiber surface could possess binding sites for Pd(II) and Pt(IV). Afterwards, by Fourier-transform infrared (FT-IR) and scanning electron microscopy (SEM) analyses, it was confirmed that the amidoximation reaction successfully occurred. The surface-activated fiber, designated as PAN-oxime fiber, was used to adsorb and recover precious metals. In the experiment results, it was clearly observed that adsorption capacity of PAN-oxime fiber was significantly enhanced compared to the raw material form. Actually, the raw material does not have sorption capacity for the metals. In a comparison study with commercial sorbent (Amberjet™ 4200), it was found that adsorption capacity of PAN-oxime was rather lower than that of Amberjet™ 4200, however, in the aspects of sorption kinetics and metal selectivity, the new sorbent has much faster and better selectivity.