# Application of Modern Research Methods for the Physicochemical Characterization of Ion Exchangers
## 3 Results and Discussion
### Optical Profilometry of Ion Exchangers  
The surface texture, especially its roughness and waviness, is characterized by many parameters, among which the amplitude-height parameters are the most important. In the \begin{table}
\begin{tabular}{c c c} \hline
**Dowex M 4195** & **Amberlite IRA 743** & **Purolite Arsen X\({}^{\text{np}}\)** \\ \hline  & before the sorption of Cu(II) or As(V) & \\ \end{tabular}
\end{table} 
Table 2: SEM images of Dowex M 4195, Amberlite IRA 743 and Purolite Arsen X\({}^{\text{np}}\). case of Dowex M 4195, Amberlite IRA 743 and Purolite Arsen X\({}^{\rm mp}\), these parameters were determined before and after the sorption of metal ions. The most useful for the assessment of surface roughness of ion exchangers are the following parameters: R\({}_{\rm a}\), the arithmetic mean of the elevation profile, R\({}_{\rm q}\), the mean square elevation profile, and maximum profile height R\({}_{\rm t}\). The roughness measurement uncertainty, R\({}_{\rm a}\) was estimated taking into account repeatability, recovery, declalibration of the apparatus and pattern uncertainty. The uncertainty was estimated for the two extreme points of the R\({}_{\rm a}\) measurement range (upper and lower limits) with the assumption of a trapezoidal distribution. This kind of analysis is very useful for effective sorption characterization and can be applied in the dynamic method. The examples of the surface microgeometry analysis for the cut beads of Dowex M 4195 ion exchanger before and after the Cu(II) ion sorption are presented in Table 3 (due to the two-layer structure of Dowex M 4195, the maps were made of the middle and edge parts of the cut beads). Analogous tests were carried out for the Amberlite IRA 743 ion exchangers before and after the Cu(II) sorption (Table 4). \begin{table}
\begin{tabular}{c c c} \hline
**Ion Exchanger** & **Surface Microgeometry Maps** & **Surface Microgeometry Maps** \\  & **(Middle Part of the Cut Beads)** & **(Edge Part of the Cut Beads)** \\ \hline Dowex M4195 & & \\ Roughness parameters & R\({}_{\rm a}\)—203.86 nm \(\pm\) 27.72 nm & R\({}_{\rm a}\)—24.41 nm \(\pm\) 3.31 nm \\  & R\({}_{\rm q}\)—254.39 nm & R\({}_{\rm q}\)—31.10 nm \\  & R\({}_{\rm r}\)—2.62 um & R\({}_{\rm t}\)—0.329 um \\ \hline \end{tabular}
\end{table} 
Table 3: Surface microgeometry and roughness parameters of Dowex M 4195 before and after the sorption of Cu(II). The profilometric tests were also carried out for the cut beads using ultramicrotome for Purolite Arsen X\({}^{\rm{xp}}\) before and after the As(V) ion sorption (Table 5). The surface microgeometry maps from the edge and middle parts of the beads are shown in Tables 3-5. The tests carried out using an optical profilometer allowed the determination of the following roughness parameters: arithmetic mean of profile ordinates (R\({}_{\rm{a}}\)), square mean of profile ordinates (R\({}_{\rm{q}}\)) and maximum profile height (R\({}_{\rm{t}}\)). It was found that Amberlite IRA 743 shows the highest values of R\({}_{\rm{a}}\) and R\({}_{\rm{q}}\) compared to the other ion exchangers under discussion before and after the sorption process. After the sorption of Cu(II) ions, the R\({}_{\rm{a}}\) values increase from 203 to 550 nm for Dowex M 4195, from 771.44 to 751.34 nm for Amberlite IRA 743 and decrease from 770.49 to 627.51 nm for Purolite Arsen X\({}^{\rm{xp}}\). The analogous tendency was observed for the \(R_{\rm{q}}\) parameter. The largest differences were observed for Dowex M4195. The studies have also shown the differences in the edge middle roughness of the ion exchangers. The largest differences were observed in the Dowex M4195 ion exchanger, which is characterized by a two-layer structure. What is interesting a quite similar structure compared to Dowex M 4195 can be observed in the case of shallow shell resins (SST) or pellicular ion exchangers (IEP) with the glass or silica core. IEPs are mechanically strong and can cope with high pressures very easily.