# Application of Modern Research Methods for the Physicochemical Characterization of Ion Exchangers
## 3 Results and Discussion
### X-ray Photoelectron Spectroscopy (XPS) of Ion Exchangers  
There are many research techniques used to obtain information about the physicochemical properties of ion exchangers and sorbents after the sorption process. The photoelectron spectroscopy can be one of them. This method measures distribution of the electrons energy emitted from the sample which absorbed ultraviolet photons (ultraviolet photoelectron spectroscopy, UPS) or X-rays radiation (X-ray photoelectron spectroscopy, XPS). The literature reports numerous data resulting from the analysis of different types of ion exchangers using the XPS method. In the paper, the photoelectrons were recorded by the hemispherical analyser Scienta R4000. The measurements were made based on the following basic parameters: operating mode--sweeping, pass energy 200 eV, measured range of the binding energy of photoelectrons 0-1200 eV, measuring step 0.5 eV, collection time in a single step 0.2 s and the number of iterations was 5. There were applied the following parameters of the analyser for the high resolution spectra: operating mode sweeping, pass energy 50 eV, measuring step 0.1 eV and collection time in a single step 0.667 s. The CasaXPS software was used to process the XPS spectra and calculate the quantitative surface composition of the tested materials. The review spectra were used to calculate the quantitative surface composition of the tested materials. For the purposes of chemical analysis, i.e., the assessment of functional groups, the XPS spectra recorded in a narrow range of energy were used. Due to the fact that the XPS bands are characterized by small resolution, they were \"decomposed\" (deconvolution method) using the Gauss/Lorentz asymmetric function. To normalize the spectroscopic measurements, the X axis of the spectra (binding energy) was calibrated to a C1s aliphatic carbon peak, EB = 285 eV. The exemplary results are presented in Tables 6-9 and Figures 7-9. Analogous results can be obtained for Amberlite IRA 743 and Purolite Arsen X\({}^{\rm mp}\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name** & **Position [eV]** & **Area** & **\% Atom Concentration** & **Phase** \\ \hline O 1s & 531.4 & 812.25 & 68.9 & SO42\({}^{-}\), C=O \\ O 1s & 532.9 & 365.79 & 31.1 & O-H \\ C 1s & 284.7 & 2322.86 & 66.6 & C=C, C-C, C-H \\ C 1s & 286.0 & 868.44 & 24.9 & C-N \\ C 1s & 287.5 & 82.66 & 2.4 & C=O, C-N \\ C 1s & 289.0 & 35.96 & 1.0 & Shake-up \\ C 1s & 290.8 & 52.84 & 1.5 & \(\pi\)-\(\pi\) \\ C 1s & 292.3 & 127.03 & 3.6 & \(\pi\)-\(\pi\) \\ N 1s & 399.3 & 349.52 & 70.5 & N-pyridine \\ N 1s  
Figure 8: XPS spectrum obtained in a wide range of binding energy made for the Dowex M 4195 after the Cu(II) sorption. Figure 7: XPS spectrum obtained in a wide range of binding energy made for the Dowex M 4195 before the sorption process. The XPS tests showed the presence of the following elements: 82.2% carbon 7.9% oxygen, 7.5% nitrogen and 2.4% sulphur (Table 6). Of the total number of carbon atoms, 66.6% is in the form of C = C, C-C, C-H. 68.9% of oxygen present on the surface in is in the form of SO4\({}^{2-}\), the remaining oxygen is in the form of O-H groups (Table 7) [79]. The study showed the presence of two forms of nitrogen [80; 81; 82]. All nitrates present on the ion exchangers surface come from the functional groups. The ratio of nitrogen from the pyridine rings to the amine nitrogen is 2:1, which is consistent with the theoretical data provided by the ion exchanger manufacturer because in the bis-(2-pyridylmethyl)amino function group, one nitrogen in the form of an aliphatic amine accounts for two pyridine nitrogen atoms [83]. The XPS tests showed the presence of sulphur as SO4\({}^{2-}\) (Table 7), which is also consistent with the data of the ion exchangers manufacturer [84]. The percentage of individual elements is given in atomic%. The XPS study of Dowex M4195 ion exchanger was also carried out after the Cu(II) ion sorption process (Tables 8 and 9, Figures 8 and 9).