# Precipitation of Germanium from Sulphate Solutions Containing Tin and Indium Using Tannic Acid
## 3 Results
### Ge Precipitation from Detinned Solution Using Solid and Dissolved Tannic Acid  
The comparison of two ways of tannic acid addition (as a solid and dissolved in water) was investigated. Firstly, it was done using tannic acid powder and the freshly prepared 20% aqueous solution. In both cases three 20 g portions of the acid per 1 dm\({}^{3}\) of the solution were added. The results of the tests are shown in Table 4 and Figure 2A. Secondly, the time influence on the composition of the solution after tannic acid addition was determined. Changes in the compositions and precipitation yields are shown in Table 5 and Figure 2B. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Tannic Acid Form**} & \multirow{2}{*}{**Tannic Acid g/dm\({}^{3}\)**} & \multicolumn{2}{c}{**C\({}_{\text{solution}}\) g/dm\({}^{3}\)**} & \multirow{2}{*}{**pH\({}_{\text{solution}}\)**} & \multicolumn{2}{c}{**C\({}_{\text{precipitate}}\) \%**} \\ \cline{3-4} \cline{6-7}  & & **Ge** & & **In** & & **Ge** & **In** \\ \hline - & initial & 5.6 & 1.6 & 2.0 & - & - \\ \hline \multirow{3}{*}{powder} & 20 & 2.4 & 1.3 & 1.6 & 7.09 & 0.14 \\  & 40 & 0.9 & 1.2 & 1.3 & 6.57 & 0.17 \\  & 60 & 0.01 & 1.1 & 1.3 & 6.09 & 0.21 \\ \hline \multirow{3}{*}{20 wt\% solution} & 20 & 1.9 & 1.3 & 1.5 & 7.45 & 0.19 \\  & 40 & 0.9 & 1.2 & 1.3 & 6.74 & 0.23 \\ \cline{1-1}  & 60 & 0.006 & 1.1 & 1.2 & 5.96 & 0.26 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Composition of the solution and precipitate after precipitation with tannic acid powder and 20 wt% solution (90 \({}^{\circ}\)C, tannic acid added in portions, 1 h between portions). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Step**} & \multicolumn{3}{c}{**C\({}_{\text{solution}}\) g/dm\({}^{3}\)**} & \multirow{2}{*}{**pH\({}_{\text{solution}}\)**} & \multicolumn{3}{c}{**C\({}_{\text{precipitate}}\) \%**} \\ \cline{2-2} \cline{6-10}  & **Ge** & & **In** & **Sn** & **Zn** & & **Ge** & **In** & **Sn** & **Zn** \\ \hline initial & 6.3 & 1.8 & 4.6 & 5.7 & 0.1 & - & - & - & - \\ detinned & 5.6 & 1.6 & 0.024 & 5.7 & 0.0 & 7.97 & 2.74 & 43.9 & 0.53 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Composition of the solution and precipitate before and after tin removal (70 \({}^{\circ}\)C, 1 h, 6 cm\({}^{3}\)/dm\({}^{3}\) H\({}_{2}\)O\({}_{2}\)). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Time min**} & \multicolumn{3}{c}{**C\({}_{\text{solution}}\) g/dm\({}^{3}\)**} \\ \cline{2-7}  & \multicolumn{3}{c}{**Powder**} & \multicolumn{3}{c}{**20 wt\% Solution**} \\ \cline{2-7}  & **Ge** & & **In** & **Ge** & **In** \\ \hline initial & 5.6 & 1.6 & 5.6 & 1.6 \\
15 & 1.6 & 1.4 & 0.13 & 1.3 \\
30 & 0.61 & 1.3 & 0.11 & 1.3 \\
60 & 0.33 & 1.3 & 0.074 & 1.3 \\
90 & 0.12 & 1.3 & 0.066 & 1.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Composition of the solution after precipitation with tannic acid powder and 20 wt% solution (90 \({}^{\circ}\)C, 60 g/dm\({}^{3}\) active tannic added in 1 portion). There was no significant influence of the tannic acid form on the process efficiency. A small difference between Ge concentrations in the solution after the first added portion was noticed--2.4 g/dm\({}^{3}\) for the powder form and 1.9 g/dm\({}^{3}\) for the dissolved tannic acid. After the addition of the next portions, the difference became less significant--0.91 g/dm\({}^{3}\) vs. 0.89 g/dm\({}^{3}\) after the second portion and 0.010 g/dm\({}^{3}\) vs. 0.0057 g/dm\({}^{3}\) after the third portion. A slightly higher Ge precipitation yield after first (58%-50%) and second (84%-80%) portions was noticed for tannic acid solution. After the addition of the third portion, Ge precipitation yield in both cases exceeded 99%.