# Effect of Pore Size Distribution and Amination on Adsorption Capacities of Polymeric Adsorbents
## 3 Results and Discussion
### Adsorption Properties of the Modified Resins  
The adsorption properties of the three amino-modified resins (NDA-1801, NDA-1802, and NDA-1803) for phenol, ABS acid and RBB4 were investigated at 288 K, 303 K, and 318 K and were compared with NDA-1800. The results are presented in Figure 7 and Table S2 summarizes the corresponding parameters.  
The phenol adsorption capacities of the four resins were similar at the three temperatures. The order of adsorption capacity was NDA-1800 > NDA-1801 \(\approx\) NDA-1803 \(\approx\) NDA-1802. The adsorption of micromolecules such as phenol is mainly achieved through \(\pi\)-\(\pi\)and dipole-dipole interactions. The resin adsorption capacity was greatly affected by the surface of the resin, and no ion exchange occurred. Compared with NDA-1800, the specific surface areas of the three amine-modified resins were decreased; thus, the adsorption capacities were lower. However, the specific surface area of the three amino-modified resins were similar, and their adsorption capacities were not significantly different.  
The ABS acid adsorption capacity of the four resins was in the order of NDA-1801 \(\approx\) NDA-1803 > NDA-1800 > NDA-1802 at all three temperatures. Compared with NDA-1800, the adsorption capacities of NDA-1801 and NDA-1803 were increased because of the increased polarity of the resins and the enhanced dipole-dipole and ion exchange interactions that occurred between the resin and the adsorbate, even though the specific  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Resins**} & \multicolumn{4}{c}{**ABS Acid**} & \multicolumn{4}{c}{**RBB4**} \\ \cline{2-9}  & \(\mathbf{Q_{m}}\) & \(\mathbf{K_{1}}\) & \(\mathbf{K_{2}}\) & \(\mathbf{Q_{m}}\) & \(\mathbf{K_{1}}\) & \(\mathbf{K_{2}}\) & \multirow{2}{*}{\(\mathbf{R^{2}}\)} \\  & **(mmol\(\cdot\)g\({}^{-1}\))** & **(L\(\cdot\)mmol\({}^{-1}\))** & **(L\(\cdot\)mmol\({}^{-1}\))** & **(L\(\cdot\)mmol\({}^{-1}\))** & **(L\(\cdot\)mmol\({}^{-1}\))** & **(L\(\cdot\)mmol\({}^{-1}\))** & **R\({}^{2}\)** \\ \hline NDA-1 & 0.407 & 6.239 & 0.040 & 0.971 & 0.066 & 6.727 & 0.252 & 0.971 \\ NDA-2 & 0.683 & 7.862 & 0.038 & 0.995 & 0.113 & 4.054 & 0.200 & 0.995 \\ NDA-3 & 0.576 & 10.830 & 0.050 & 0.994 & 0.239 & 6.015 & 0.154 & 0.999 \\ NDA-4 & 0.493 & 10.080 & 0.047 & 0.985 & 0.166 & 5.884 & 0.212 & 0.995 \\ \hline \hline \end{tabular}
\end{table}
Table 4: The corresponding parameters of three-parameter multilayer adsorption model.  
surface areas were reduced after amination. The pore diameter distribution was slightly reduced, which was suitable for the adsorption of ABS acid molecules and increased the adsorption capacity. The adsorption capacity of the resin modified with secondary amines decreased slightly owing to the increased pore size distribution and the decreased specific surface area.  
The RBB4 adsorption capacity of the four resins at all three temperatures was in the order of NDA-1802 > NDA-1803 \(\approx\) ND-1801 > NDA-1800. Compared with NDA-1800, the adsorption capacities of the amine-modified resins markedly improved. The adsorption capacity of the secondary amine resin (NDA-1802) increased the most. This was because the presence of the polar functional group could be used for ion exchange and because the resin pore size remained large. The adsorption capacities of NDA-1801 and NDA-1803 increased owing to the presence of polar functional groups.