## 3 Results and Discussion
### Results of the Two-Stage Counter-Current Acid Leaching with the Addition of Hydrogen Peroxide  
The use of two-stage counter-current leaching resulted in obtaining high, stable, repeatable leaching efficiencies of cobalt, nickel, lithium and copper from battery masses--as shown in Table 5. In the case of Material I, the metal leaching efficiencies were above 96%, and those for Material II were slightly lower but, on average, were significantly above 90%. A similar trend was observed for Material III as for Material II. The remaining components, i.e., manganese, iron, phosphorus and fluorine, were leached at a high, stable level. Only in the case of Material III was a low fluorine efficiency observed, which did not exceed 60%. It should also be noted that in the case of cobalt, for Materials II and III, high, targeted concentrations of this metal were obtained in the solutions after leaching, ranging from 19.40 g/dm\({}^{3}\) to 47.90 g/dm\({}^{3}\). In the case of Material I, the concentrations of cobalt and nickel in the leaching solutions were at a similar level and amounted to about 15 g/dm\({}^{3}\) of each of these metals. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{**Solid to Liquid** **Phase Ratio**} & \multicolumn{3}{c}{**Volume of the Solution after**} & \multirow{2}{*}{**pH**} & \multicolumn{3}{c}{**Free Acid**} & \multicolumn{3}{c}{**Concentration of the Element in the Solution after Leaching (g/dm\({}^{3}\))**} \\ \cline{3-14}  & & & **Co** & & & & & & & & & \\ \cline{3-14}  & & & **Co** & & & & & & & & & \\ \hline \multirow{3}{*}{I} & 1:5 & 5700 & 0.45 & 48.5 & 14.90 & 15.70 & 5.67 & 3.98 & 13.20 & 0.50 & 1.06 & 4.30 \\ \cline{2-14}  & 1:4 & 1885 & 0.60 & 40.2 & 24.30 & 26.00 & 9.58 & 5.54 & 19.00 & 0.70 & 1.51 & 5.85 \\ \hline \multirow{3}{*}{II} & 1:5 & 5960 & 0.60 & 62.7 & 43.90 & 3.28 & 6.04 & 2.56 & 1.43 & 0.42 & 0.33 & 2.60 \\ \cline{2-14}  & 1:4 & 1980 & 0.60 & 65.1 & 63.90 & 4.63 & 8.89 & 3.62 & 1.85 & 0.57 & 0.82 & 3.55 \\ \cline{2-14}  & 1:5 & 5520 & 0.39 & 85.8 & 36.40 & 4.21 & 5.50 & 2.00 & 2.26 & 0.64 & 0.69 & 2.00 \\ \cline{2-14}  & 1:4 & 2150 & 0.50 & 49.0 & 51.50 & 5.24 & 7.92 & 2.75 & 3.07 & 0.67 & 1.03 & 2.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of the single-stage acid leaching with the addition of hydrogen peroxide—selection of the phase ratio. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{**Cycle**} & \multicolumn{3}{c}{**Volume of the Solution after**} & \multirow{2}{*}{**pH**} & \multicolumn{3}{c}{**Concentration of the Element in the Solution after Leaching (g/dm\({}^{3}\))**} \\ \cline{3-14}  & & & **I Stage** & & & & & & & & & \\ \cline{3-14}  & & 4900 & - & 0.2 & 11.10 & 13.20 & 6.51 & 4.74 & 8.89 & 0.42 & 1.05 & 4.80 \\ \hline \multirow{3}{*}{I} & 1 & - & 6800 & 0.2 & 5.73 & 5.09 & 0.84 & 0.55 & 5.23 & 0.09 & 0.18 & 0.33 \\ \cline{2-14}  & & 6100 & - & 0.4 & 14.70 & 15.50 & 5.68 & 3.65 & 12.60 & 0.41 & 0.99 & 4.40 \\ \cline{2-14}  & 2 & - & 6300 & 0.1 & 6.44 & 5.69 & 0.98 & 0.99 & 5.63 & 0.13 & 0.17 & 0.33 \\ \cline{2-14}  & 3 & 5840 & - & 0.3 & 16.60 & 17.40 & 6.39 & 4.50 & 13.70 & 0.63 & 1.01 & 4.40 \\ \cline{2-14}  & 3 & - & 6380 & 0.1 & 6.61 & 5.52 & 1.15 & 1.04 & 5.12 & 0.29 & 0.24 & 0.43 \\ \hline \multirow{3}{*}{II} & 4700 & - & 0.1 & 30.00 & 2.73 & 6.32 & 3.00 & 1.26 & 0.50 & 0.50 & 3.14 \\ \cline{2-14}  & 1 & - & 6000 & 0.1 & 24.00 & 0.55 & 1.32 & 0.23 & 0.41 & 0.12 & 0.15 & 0.20 \\ \cline{2-14}  & 2 & 5510 & - & 0.4 & 47.90 & 2.52 & 5.63 & 1.84 & 1.33 & 0.49 & 0.58 & 2.98 \\ \clAfter the analysis of the carried-out tests, it can be stated with certainty that for each tested material, in subsequent cycles of the leaching process, an increase in the amount of leached components such as cobalt, nickel, copper, lithium and manganese was observed.