## 4 Conclusions  
Polyacrylonitrile (PAN) fiber has been abundantly discharged from industrial textile factories, thus its recycling studies are essential. In this study, we applied PAN for preparing an excellent adsorbent for a fast and selective recovery process for precious metals (i.e., Pd(II) and Pt(IV)). For sorbent preparation with appropriate functional groups for metal binding (PAN-oxime fiber), spinning a PAN-dimethylsulfoxide mixture in water, followed by amidoxime chemical modification, was carried out. For the surface modification, it was found that as amidoxime increased, the conversion from PAN to PAN-oxime increased. However, reaction greater than 20 min led to  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Adsorbents**} & \multirow{2}{*}{**Conditions**} & \multirow{2}{*}{**Metals**} & \multicolumn{3}{c}{**Pseudo-First-Order**} & \multicolumn{3}{c}{**Pseudo-Second-Order**} \\ \cline{4-7}  & & & \(q_{1}\) **(mg/g)** & \(k_{1}\) **(min\({}^{-1}\))** & \(\mathbf{R}^{2}\) & \(q_{2}\) **(mg/g)** & \(k_{2}\times 10^{-3}\) & \(\mathbf{R}^{2}\) \\ \hline \multirow{4}{*}{PAN-oxime fiber} & \multirow{2}{*}{Single} & Pd(II) & 229.26 \(\pm\) 1.22 & 0.644 \(\pm\) 0.028 & 0.994 & 235.52 \(\pm\) 1.86 & 5.5 \(\pm\) 0.5 & 0.990 \\  & & Pt(IV) & 158.04 \(\pm\) 1.93 & 1.008 \(\pm\) 0.117 & 0.973 & 162.16 \(\pm\) 1.72 & 11.5 \(\pm\) 1.7 & 0.983 \\ \cline{2-7}  & \multirow{2}{*}{Binary} & Pd(II) & 214.09 \(\pm\) 2.74 & 0.757 \(\pm\) 0.084 & 0.972 & 221.00 \(\pm\) 1.05 & 6.0 \(\pm\) 0.3 & 0.997 \\  & & Pt(IV) & - & - & - & - & - & - \\ \hline Amberjet(tm) 4200 & Binary & Pd(II) & 126.84 \(\pm\) 3.10 & 0.053 \(\pm\) 0.006 & 0.933 & 139.48 \(\pm\) 2.11 & 0.5 \(\pm\) 0.04 & 0.984 \\  & & Pt(IV) & 149.40 \(\pm\) 3.22 & 0.041 \(\pm\) 0.004 & 0.959 & 166.82 \(\pm\) 2.19 & 0.3 \(\pm\) 0.02 & 0.991 \\ \hline \multicolumn{7}{l}{\({}^{a}\),\({}^{a}\) represents that the data cannot be estimated using the pseudo-first- and pseudo-second-order models.} \\ \end{tabular}
\end{table}
Table 2: Kinetic parameters of the pseudo-first-order and pseudo-second-order models.  
Figure 6: Adsorption kinetics of PAN–oxime fiber in single-metal system (**a**) and binary metal system (**b**); and of Amberjet(tm) 4200 in binary metal system (**c**). Standard errors are less than 5%.  
destruction of the fibrous structure. Isotherm and kinetic experiments in the single-metal systems showed that the uptakes of Pd(II) and Pt(IV) by Amberjet(tm) 4200 were approximately 1.3 and 2.4 times higher than those by the PAN-oxime fiber, respectively. However, in the binary solution, PAN-oxime fiber showed high selectivity for Pd(II), and moreover it had a much faster equilibrium time than Amberjet(tm) 4200.  
This study showed that the PAN textile can be used to prepare an excellent adsorbent. As an example, it was clearly shown that the developed PAN-oxime fiber shows great potential for recovering anionic metals. Moreover, since it has fast binding ability and selectivity, it can be applied in column systems and other separation processes.  
This work was supported by the Korean Government through KETEP (20115020100060) and KEITI (The Eco-Innovation project 20115020100060 ) grants and the Korean Government through NRF grant (2014R1A1A2008337 and 2014R1A2A1A09007378).  
[PERSON] and [PERSON] contributed to sorbent development, batch experiments, and FTIR & microscopic analyses under supervision of [PERSON] and [PERSON].  
The authors declare no conflict of interest.