# Sorption of Organic Electrolytes and Surfactants from Natural Waters by Heterogeneous Membranes
## 3 Results and Discussion
### Exchange Capacity and Sorption of Organic Ions
These values are in accordance with the size of the organic radical and the sorption ability of these ions. From the initial sections of the kinetic curves \(g\)-\(\surd\), according to the approximate equation:  
Figure 12:0  
where:  
1. (\(\tau\)) is the share of filling the ionic with an organic ion;
2. d is the thickness of the membrane;
3. \(\tau\) is the filling time;
4. membrane diffusion coefficients (D) were estimated for these ions. The results were \(D\) (BS\({}^{-}\)) = 2.8 \(\times\) 10\({}^{-10}\) mg-equivv/g, \(D\) (NS\({}^{-}\)) = 3.0 \(\times\) 10\({}^{-12}\) mg-equiv/g, \(D\) (CP\({}^{+}\)) = 1.0 \(\times\) 10\({}^{-13}\) mg-equiv/g. In the order of values they are consistent with the literature data. Figure 12:1 Dependence of the sorption of organic ions on the MA-40 membrane on the pH of the solution. Next, the moisture capacity of the membranes (\(W\)) was determined and its dependence on pH and the concentration of solutions was investigated. It was found that the moisture capacity of the MK-40 and MA-40 membranes, within the limits of error, does not depend on pH (in the range of pH = 3-10) nor on the concentration of solutions. Thus, for the MK-40 membrane in NaCl and MgCl\({}_{2}\) solutions, it is 37%, and for the MA-40 in NaCl and Na\({}_{2}\)SO\({}_{4}\) solutions it is 40%, which corresponds to the data presented in the literature. To verify the assumption that sorption of organic ions by membranes will change the water content in them, the moisture content of the membranes (\(W\)) was measured after sorption of organic ions by them and compared with the initial water content in them. The data obtained are presented in Table 1 which compares the moisture content, \"porosity\" and the degree of swelling of the membranes in the initial forms (MA-40-Cl and MK-40-Na) and membranes saturated with organic ions. The data obtained indicate a decrease in the water content in the membranes as the content and size of organic radicals increase, which confirms the specificity of the interaction of organic counterions with each other and with the ion exchanger matrix, due to which the membrane with the organic counterion becomes like a solid. This pattern was observed for the MK-40 in CPCI, where the membrane completely lost its elasticity. Such a specific interaction is called \"freezing\" of the units of the ion exchanger matrix. To assess the selectivity of ion-exchange membranes in the study solutions, the ion transport numbers were determined in membranes \(n_{i}\), in solutions of simple and organic electrolytes. The data obtained (Figure 22), presented in the form of the dependence of the ion transport numbers in the membranes on the logarithm of the solution concentration in Figure 21, show that the Na\({}^{+}\) ion transport numbers in the MK-40 and MA-40 membranes turned out to be almost equal to one in the entire investigated concentration range; for MgCl\({}_{2}\) in the MK-40, a decrease in ideal electrochemical activity is observed upon transition to a 0.1 N solution. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**System** & **Total Porosity** & **Degree of Swelling** & **Moisture Content** \\ \hline MK-40- NaCl & 0.56 & 0.88 & 0.40 \\ MK-40- NaBS & 0.47 & 0.41 & 0.32 \\ MK-40- NaNS & 0.32 & 0.19 & 0.20 \\ MA-40- NaCl & 0.34 & 0.50 & 0.41 \\ MA-40- CPCI & 0.21 & 0.32 & 0.26 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Water content in the membranes. Figure 22: The dependence of ion transport numbers in ion-exchange membranesMK-40 and MA-40 on the concentration. An even stronger decrease in the counterion transport numbers is observed in the MA-40 membrane in Na\({}_{2}\)SO\({}_{4}\) solutions (0.93 for a 0.001 N solution and 0.81 for a 0.1 N solution), which is apparently due to the lower mobility of the SO\({}_{4}\)\({}^{-2}\) ion in the membrane compared to the Cl\({}^{-}\) ion. As expected, an organic counterion, when adsorbed on a membrane, strongly changes its electrochemical properties (Table 2).