Preparation of Polyacrylonitrile/Iron Oxide Nanofiber Adsorbent Modified with 2-Amino-3-Methyl- 1-Hexanethiol for the Adsorption of Th4+ Ion

In this study, novel polyacrylonitrile/iron nano oxide (PAN/Fe-ONPs) nanofiber adsorbent modified with 2-Amino-3-methyl-1-hexanethiol (AMH) was synthesized by combination of hydrothermal and electrospinning method and evaluated as an adsorbent for removing thorium (IV) (Th4+) ion from aqueous solution. The PAN/Fe-ONPs/AMH was characterized by X-ray diffraction (XRD), Fourier Transform Infra-Red (FT-IR), Scanning Electron Microscopy (SEM), energy dispersive X-ray analysis (EDX) and Brunauer–Emmett–Teller (BET). Response Surface Methodology (RSM) was utilized in the optimization of Th4+ adsorption for parameters such as pH, the initial metal ion concentration (Th4+ concentration) and contact time. For this purpose, the central composite design (CCD) with a predictive quadratic model was applied with 8 cubic points, 6 pivot points and 6 replicates at the center. The statistical measures (i.e., Analysis of variance (ANOVA), R2, the lack of fit test and the P value) specify that the developed model is proper. The results of optimization showed that the adsorption percentage of PAN/Fe-ONPs/AMH for Th4+ under optimal conditions (pH=5.7, initial concentration 232 mgL-1 and contact time=67.8 min) was 98% at 25oC. In addition, the adsorption kinetics was well defined by the pseudo second-order equation, while the Langmuir model better fit the adsorption isotherms. The adsorption capacity of PAN/Fe-ONPs/AMH was 472 mg Th4+g-1 composite. The loaded Th4+ can be easily regenerated with HNO3/HCl and the PAN/Fe-ONPs/AMH could be used repeatedly without any significant reduction in its adsorption capacity. Adsorbent recovery by using 0.4M HNO3/0.2M HCl solution for adsorbent reuse indicated that the PAN/Fe-ONPs/AMH adsorption capacity for Th4+ was decreased by about 7.5%.