# Sorption of \({}^{137}\)Cs and \({}^{90}\)Sr on Organic Sorbents
## 3 Results
### Chemical Composition and Acid-Base Properties of the Sorbents  
The chemical composition of the sorbents corresponds well with their mineral composition. The largest amounts of aluminum were found in brown and hard coals, which can be explained by the high content of aluminosilicates in these samples. The increased Si content in these samples is also associated with the highest content of clay minerals (Tables 1 and 2). The increased content of Mg in the composition of brown coal and Si in high-moor peat, most likely, can be explained by the presence of smectite and quartz in the samples, respectively (Tables 1 and 2).  
The ignition residue content of the studied samples increases in the following order: shungite (0.93%) < hard coal (9.6%) < high-moor peat (13%) < brown coal (22%), which is in good agreement with the data on the elemental composition of organic matter (Table 3).  
The largest amount of C, in the composition of the organic matter, was found in shungite; the smallest in high-moor peat (Table 3). Based on the sum of N, C, S and H, expressed in mass percent, it can be concluded that the minimum number of oxygen atoms in the composition of organic matter is contained in the shungite material, and the maximum is in high-moor peat (Table 3).  
The atomic ratio HC in the studied samples decreases in the following order: high-moor peat > brown coal > hard coal > shungite (Table 3). A decrease in the H:C atomic ratio indicates an increase in the degree of aromaticity of high molecular weight organic compounds [20,21]. It follows from the above that high-moor peat and brown coal should contain more aliphatic functional groups in comparison with hard coal and shungite.  
This assumption is confirmed by the data from the determination of the buffer properties of the sorbents with respect to acid and base. Buffering to both acid and base was higher in the high-moor peat sample and in brown coal compared to the other two sorbents (Table 4).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**pH\({}_{\text{ITP}}\)**} & \multicolumn{2}{c}{**Total Buffering, mmol/m\({}^{2}\)**} \\ \cline{3-4}  & & **To Acid (pH\({}_{\text{ITP}}\)-pH 3.25)** & **To Base (pH\({}_{\text{ITP}}\)-pH 10)** \\ \hline Hard coal & 7.08 & 1.34 & 17.35 \\ \hline Brown coal & 4.76 & 94.93 & 320.95 \\ \hline Peat & 3.17 & - & 489.54 \\ \hline Shungite & 6.12 & 1.04 & 1.99 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Total buffering of the samples in relation to acid and base.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Sample Name** & **LOI** & **Na\({}_{\text{2}}\)O** & **MgO** & **Al\({}_{\text{2}}\)O\({}_{\text{3}}\)** & **SiO\({}_{\text{2}}\)** & **K\({}_{\text{2}}\)O** & **CaO** & **TiO\({}_{\text{2}}\)** & **MnO** & **Fe\({}_{\text{2}}\)O\({}_{\text{3}}\)** & **P\({}_{\text{2}}\)O\({}_{\text{5}}\)** & **SO\({}_{\text{3}}\)** \\ \hline Hard coal & 90.40 & 0.09 & 0.09 & 3.10 & 5.01 & 0.08 & 0.14 & 0.17 & 0.01 & 0.61 & 0.04 & 0.61 \\ \hline Brown coal & 78.00 & 0.06 & 0.26 & 6.44 & 11.59 & 0.34 & 1.10 & 0.19 & 0.05 & 1.70 & 0.01 & 0.52 \\ \hline Peat & 87.00 & 0.09 & 0.08 & 1.99 & 8.89 & 0.25 & 0.12 & 0.09 & 0.01 & 1.19 & 0.23 & 0.07 \\ \hline Shungite & 99.07 & 0.07 & 0.01 & 0.05 & 0.27 & 0.04 & 0.01 & 0.00 & \textless{}0.005 & 0.06 & 0.01 & 0.24 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical composition of the sorbents, %.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **N** & **C** & **S** & **H** & **Sum** & **H\({}_{\text{C}}\)** \\ \hline Hard coal & 2.19 & 70.20 & 0.82 & 4.17 & 77.37 & 0.71 \\ \hline Brown coal & 0.54 & 52.36 & 0.66 & 4.81 & 58.38 & 1.09 \\ \hline Peat & 1.29 & 45.35 & 0.45 & 5.01 & 52.09 & 1.31 \\ \hline Shungite & 0.74 & 90.54 & 0.64 & 2.83 & 94.75 & 0.34 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Elemental composition of the organic matter in the sorbents, %.