# Precipitation of Germanium from Sulphate Solutions Containing Tin and Indium Using Tannic Acid
## 3 Results  
### Ge Precipitation from Solutions Containing Sn  
Firstly, the precipitation of Ge-tannin complex from the original solutions obtained after leaching of GeIn dross was investigated. Table 1 and Figure 1A present the temperature influence on composition of solutions and precipitates as well as precipitation yields of Ge, In, and Sn. During these tests 100 g pure tannic acid was added to 1 dm\({}^{3}\) of the solution. Results of pure tannic acid addition in 20 g portions to 1 dm\({}^{3}\) of the solutions are shown in Table 2 and Figure 1B. It was noticed that after the addition of solid tannic acid it was not dissolved in the solution, but formed a suspension. Ge concentration in solution after addition of tannic acid decreased from 6.0 g/dm\({}^{3}\) down to 0.03 g/dm\({}^{3}\). The lowest concentration was noticed for the highest applied temperature. Moreover, the concentration of Ge in the precipitate increased from 3.67% for 20 \({}^{\circ}\)C to 5.48% at 90 \({}^{\circ}\)C. It corresponded to a change in Ge precipitation yield from 64% at 20 \({}^{\circ}\)C to \(>\)99% at 90 \({}^{\circ}\)C. The concentration of Sn also significantly decreased from 4.4 g/dm\({}^{3}\) in the original solution down to 3.0 g/dm\({}^{3}\). Sn precipitation yield changed from 16% at 20 \({}^{\circ}\)C to 33% at 90 \({}^{\circ}\)C. It was accompanied by the increase of tin content in the precipitate--from 0.77% at 20\({}^{\circ}\)C to 1.96% at 90\({}^{\circ}\). The change in In concentration was small--it decreased from 1.7 to 1.4 g/dm\({}^{3}\). In concentration in the precipitate was also low--between 0.03% at 20 \({}^{\circ}\)C and 0.13% at 90 \({}^{\circ}\)C. The precipitation yield of In varied from 4% at 20 \({}^{\circ}\)C to 19% at 90 \({}^{\circ}\)C.  
In the case of tannic acid addition in portions, it was observed that Ge concentration in the solution declined during the process. The decrease was highest for first portion added--from 7.8 g/dm\({}^{3}\) in the initial solution to 5.2 g/dm\({}^{3}\) (32% precipitation yield). For the last added portion, the decrease was the lowest--from 0.15 g/dm\({}^{3}\) to 0.04 g/dm\({}^{3}\)--total Ge precipitation yield increased from ca. 98% to \(>\)99%. The concentration of Sn also significantly decreased during the course of the process--from 5.4 g/dm\({}^{3}\) in the initial solution to 2.8 g/dm\({}^{3}\) after the fifth portion of tannic acid was added. Sn precipitation yield after the last portion was found at the level of 45%. A small decrease of In concentration was also noticeable--from 2.1 gm/dm\({}^{3}\) to 1.6 g/dm\({}^{3}\) (22% precipitation yield). A change of Ge content in the precipitate was also observed. After the first added portion it contained 9.37% Ge, while after the fifth \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Temperature**\({}^{\circ}\)C} & \multicolumn{2}{c}{**C\({}_{\text{solution}}\) g/dm\({}^{3}\)**} & \multirow{2}{*}{**pH\({}_{\text{solution}}\)**} & \multicolumn{2}{c}{**C\({}_{\text{precipitate}}\) \%**} \\ \cline{3-3} \cline{5-8}  & **Ge** & **In** & **Sn** & & **Ge** & **In** & **Sn** \\ \hline initial & 6.0 & 1.7 & 4.4 & 2.0 & - & - & - \\
20 & 2.1 & 1.6 & 3.6 & 1.6 & 3.67 & 0.03 & 0.77 \\
60 & 0.1 & 1.5 & 3.3 & 1.4 & 5.48 & 0.07 & 1.04 \\
90 & 0.03 & 1.4 & 3.0 & 1.3 & 5.34 & 0.13 & 1.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of the solution and precipitate after precipitation with tannic acid (2 h, 100 g/dm\({}^{3}\) pure tannic acid, 1 portion).