## 3 Results and Discussion  
### Results of the Single-Stage Acid Leaching Method with the Addition of Hydrogen Peroxide  
_Selection of the Leaching Agent_  
The results of the tests of single-stage acid leaching with the addition of hydrogen peroxide--the selection of the leaching agent--are presented in Table 3 and described in Sections 3.1.1 and 3.1.2. 1.1 Results of the Single-Stage Acid Leaching with the Addition of 1 dm\({}^{3}\) of Hydrogen Peroxide--Selection of the Leaching Agent  
The analysis of the leaching results showed that with the increase in H\({}_{2}\)SO\({}_{4}\) concentration, the leaching efficiency of both nickel and cobalt clearly increased for all the tested battery masses. The obtained leaching efficiencies also depended to a large extent on the type and composition of the material fed into the leaching process. Thus, the leaching efficiencies obtained for cobalt ranged from 61.05% to 91.03%, and that for nickel ranged from 75.71% to 99.74%. The content of free acid in the solution after leaching was very diverse, but high enough to prove that an appropriate, excessive amount of leaching agent was used in all studies. The average free acid concentration was 42 g/dm\({}^{3}\). Obtaining high concentrations of cobalt and nickel was an important element of this research due to the aspect of its implementation in industrial conditions. The highest cobalt concentrations were obtained for Materials II and III (materials with high initial Co content). These concentrations ranged from 31.10 g/dm\({}^{3}\) to 45.90 g/dm\({}^{3}\) of Co. In the case of nickel, the highest concentrations were obtained for Material I (material with high initial Ni content),  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{ \begin{tabular}{c} **H\({}_{2}\)SO\({}_{4}\)** \\ **Concentra-** \\ **tion (\%)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Volume of the Solution after** \\ **Leading (cm\({}^{3}\))** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Volume of** \\ **30\%** \\ **(dm\({}^{3}\))** \\ \end{tabular}  } & \multirow{2}{*}{\ \begin{tabular}{c} **pH** \\ **Concentration** \\ **(g/dm\({}^{3}\))** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Free Acid** \\ **Concentration** \\ **(g/dm\({}^{3}\))** \\ \end{tabular}  } & \multicolumn{6}{c}{**Concentration of the Element in the Solution**} \\ \cline{6-13}  & & & & & & & & & & **after Leaching (g/dm\({}^{3}\))** & \\ \hline \multirow{2}{*}{1} & 15 & 4840 & \multirow{2}{*}{\(1.0\)} & 1.7 & 5.9 & 14.70 & 15.60 & 5.59 & 3.45 & 12.90 & 0.57 & 1.13 & 4.80 \\ \cline{2-13}  & 20 & 5700 & & 0.5 & 48.5 & 14.90 & 15.70 & 5.67 & 3.  
which was about 16 g/dm\({}^{3}\) of Ni. Also, for lithium, copper and manganese, the leaching efficiencies increased unequivocally with the increase in H\({}_{2}\)SO\({}_{4}\) concentration. In the case of lithium, the concentrations in the solutions after leaching ranged from 5 g/dm\({}^{3}\) to 6 g/dm\({}^{3}\). The leaching efficiency of manganese varied from 72% to 100% and that of copper ranged from 61% to 100%. It should be emphasized that the lithium content was similar in each of the tested battery masses, while both the copper and manganese contents differed significantly. In the case of iron, phosphorus and fluorine, the leaching efficiencies of these components increased with increasing H\({}_{2}\)SO\({}_{4}\) concentration. In the case of iron, the concentration in solutions formed after leaching ranged from 0.35 g/dm\({}^{3}\) to 0.61 g/dm\({}^{3}\). The leaching efficiency of phosphorus ranged from 40% to 81% and that of fluorine ranged from 43% to 84%. It should be noted that the iron content was similar in each of the tested materials, while both fluorine and phosphorus contents differed. Summing up, the applied leaching conditions resulted in the leaching of significant amounts of each of the tested components.