# The Experimental Study of Innovative Methods Regarding the Removal of Sm(III)
## 3 Results and Discussion
### Solvent Sublation Results  
The Sm\({}^{+3}\) ions' content in the organic phase was determined from the concentration difference between the initial solution and aqueous phase [26]. The samarium ions' distribution coefficient during solvent sublimation was calculated by the formula: \(\mathbf{K_{p}}\) = C\({}_{\text{org}}\)/C\({}_{\text{aq}}\)[1]. The results of the experimental study of the diluted aqueous solutions containing Sm(NO\({}_{3}\))\({}_{3}\) and a surfactant are shown in Tables 3 and 4. From the obtained data, it is evident that when the process time lies between 5 and 10 min, the Sm\({}^{+3}\) removal is more intense than by further floating. As a result, one can find an optimal solvent sublimation process time in the REE nitrate solutions with the initial concentration of 0.001 mol/L. Depending on the solution pH, it is 10 min and higher. In time, the concentration of the studied REE ions asymptotically approaches some finite value, which is typical for the system moving into the stationary state, in which the equilibrium between the processes of lanthanide adsorption and desorption is established. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**pH** & **C\({}_{\text{org}}\)\(\cdot\)10\({}^{2}\)** & **C\({}_{\text{aq}}\)\(\cdot\)10\({}^{4}\)** & **K\({}_{\text{p}}\)** & **\(\alpha\)\%** \\ \hline
5.1 & 1.35 & 6.60 & 20.5 & 33.9 \\
6.1 & 1.41 & 6.30 & 21.9 & 35.4 \\
6.9 & 3.14 & 2.10 & 146.3 & 78.5 \\
8.0 & 3.92 & 0.17 & 2222.3 & 98.2 \\
9.9 & 3.74 & 0.65 & 576.9 & 93.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Recovery ratio \(\alpha\) and distribution coefficient of samarium (III) (process duration was 120 min and C\({}_{0}\) = 0.001 mol/L). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compound** & **\(\Delta\)/G\({}_{298}^{0}\), kJ\(\cdot\)mol\({}^{-1}\)** & **\(\Delta_{\text{compI}}\)G\({}_{298}^{0}\), kJ\(\cdot\)mol\({}^{-1}\)** & **L (Kn)** & **pHhydr** \\  & & **kJ\(\cdot\)mol\({}^{-1}\)** & **kJ\(\cdot\)mol\({}^{-1}\)** & **(pHcompl)** \\ \hline Sm(OH)\({}_{3}\) & \(-1280.16\)\(\pm\) 3.63 & \(146.33\)\(\pm\) 1.31 & \((2.3\)\(\pm\) 1.6) 10\({}^{-26}\) & 6.49 \\ \hline Sm(OH)\({}^{2+}\) & \(-866.49\)\(\pm\) 3.60 & \(-47.36\)\(\pm\) 1.21 & \((5.0\)\(\pm\) 3.1) 10\({}^{-9}\) & 5.31 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Thermodynamic characteristics of Sm (3+) hydroxo compounds. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**t, min.** & **pH = 5.1** & **pH = 6.1** & **pH = 6.9** & **pH = 8.0** & **pH = 9.9** \\ \cline{2-5}  & & **C\({}_{\text{aq}}\), mol/L (Sm\({}^{+3}\) Initial Concentration)** & & \\ \hline
0 & 0.001 & 0.001 & 0.001 & 0.001 & 0.001 \\  & & & C\(\cdot\)10\({}^{4}\) mol/L & & \\
5 & 7.81 & 7.39 & 6.49 & 0.79 & 7.25 \\
15 & 7.53 & 6.65 & 4.30 & 0.61 & 5.83 \\
30 & 7.06 & 6.48 & 2.53 & 0.19 & 3.85 \\
120 & 6.61 & 6.46 & 2.14 & 0.18 & 0.65 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Sm\({}^{3+}\) concentration change in the aqueous phase during solvent sublimation. At pH = 5.0-6.0, the process of solvent sublation removal moves into a stationary mode with high equilibrium concentrations. The maximum recovery ratio was approximately 25%. In this pH range, the formation of monohydroxyo-complexes begins. At pH = 6.8-8.0, the equilibrium concentration lowers and the recovery ratio increases, and an upward trend in the process rate was observed. The K\({}_{\text{p}}\) value and \(\alpha\) reach maximum values. An explanation of the observed patterns is possible based on the consideration of diffusing particle forms at different pH values. In the aqueous solution at the pH range from 4.8 to 6.1, the formation of lanthanide monohydroxo-complexes occurs; at pH = 6.1-6.5, dihydroxy-complexes are formed; and at the pH range from 6.5 to 7.5, the formation of hydroxides occurs. At a pH exceeding 7.4, lanthanides in the aqueous phase are in the form of Ln(OH)\({}_{2}\)(C\({}_{12}\)H\({}_{25}\)OSO\({}_{3}\)) organic complexes because otherwise the settling of the hydroxide sediment would occur, which was not observed.