## 3 Results
### Modeling Adsorption from Uranium in Solution
#### 3.2.2 Transport Modeling with Uranium UN Solutions  
Table 5 presents the results of uranium concentrations in the sediments of the lower segments of UN6 and supernatant solutions. The concentration values of Na, K, Mg, Ca, cations are shown in Appendix B.1, Table 2, and uranium in the effluent solution are shown in Appendix B.4, Table 4 from samples 1 to 5. Taken as a whole, the UN6 column was fed with 0.540 L of solution, carrying 307 mgU as uranyl. The transported uranyl replaced the pore water and was adsorbed by the sediments at the three levels of the column. The effluent solution showed negligible concentrations of uranium (Table 4); 6.39 mgU was adsorbed on the UN6 CSC segment and 1.06 mgU was adsorbed on the UN6 FSC segment. Overall, 2.42% of the uranyl was adsorbed in the lower segments of the column. The concentration values of the effluent solution samples of WUN6 show practically only the displacement of pore water. In other words, the U in the solution was adsorbed by the fine sediment as it passed through the column, which was in agreement with the values of the U concentrations in the CS and FSC samples. The filter and fiberglass that support the packed material can be absorbing uranium; however, as the study's goal is to examine sediment adsorption, no measurements were conducted on this material. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**UN6**} \\ \hline \multirow{2}{*}{**Sample Type**} & **ID** & \multirow{2}{*}{\({}^{234}\)**U (Bq kg\({}^{-1}\))**} & \multirow{2}{*}{\({}^{238}\)**U (Bq kg\({}^{-1}\))**} & **RQ (\%)** & \multirow{2}{*}{\({}^{238}\)**U mg kg\({}^{-1}\)**} \\  & **Sample** & & & & \\ \hline \multirow{8}{*}{Solid} & UN6 CSC & \(641\pm 17\) & \(1015\pm 26\) & 90 & 82 \\  & UN6 PSC & \(101\pm 1\) & \(171\pm 2\) & X & 14 \\  & UN6 CS & \(364\pm 7\) & \(796\pm 13\) & 82 & 64 \\ \cline{1-1} \cline{2-6}  & UN6 FS & \(50\pm 1\) & \(109\pm 2\) & 67 & 9 \\ \cline{1-1} \cline{2-6}  & UN6C\({}_{1}\) & \(742\pm 15\) & \(1573\pm 29\) & 94 & 127 \\ \cline{1-1} \cline{2-6}  & UN6C\({}_{2}\) & \(189\pm 3\) & \(329\pm 5\) & 93 & 27 \\ \hline \multirow{2}{*}{Superantant solution} & \multicolumn{4}{c}{\({}^{234}\)U (Bq L\({}^{-1}\))} & \({}^{238}\)U (Bq L\({}^{-1}\)) & \multicolumn{1}{c}{RQ (\%)} & \multicolumn{1}{c}{\({}^{238}\)U mg L\({}^{-1}\)} \\  & WUN6 CSC & \(0.96\pm 0.03\) & \(2.07\pm 0.05\) & 78 & 0.17 \\ \cline{1-1} \cline{2-6}  & WUN6 FSC & \(0.086\pm 0.003\) & \(0.18\pm 0.01\) & 58 & 0.014 \\ \hline \hline \end{tabular}  
* The uncertainty of the supernatant solution experiments is approximately 15%, see Appendix A.1.  
\end{table} 
Table 5: U activity concentration in solid samples and the supernatant solution * of UN6 column. Figure 6: SEM backscattered electron micrographs at 1000\(\times\) magnification showing (**A**) U(VI) adsorption (C\({}_{0}\) = 120 mg\(\cdot\)L\({}^{-1}\)) at pH = 5; and (**B**) U(VI) adsorption (C\({}_{0}\) = 120 mg\(\cdot\)L\({}^{-1}\)) at pH = 7. Table 6 presents the results of U concentrations in the sediments of the lower segments of UN**12**; WUN**12** concentration values in the effluent solution are shown in Appendix B.4, Table B5 from samples 1 to 12, and cation concentration are in Appendix B.1, Table B2. The UN**12** column was fed with 1.020 L of solution, carrying 580 mgU as uranyl. The effluent solution also showed negligible concentrations of uranium. A total of 14.35 mgU was adsorbed on the UN**12**CSC segment, and 9.46 mgU was adsorbed on the UN**12**FSC segment. Overall, 4.09% of the uranyl was adsorbed in the lower segments of the column. Considering the initial concentration of the input solution of 569 mgU kg\({}^{-1}\), the concentration values of the effluent solution samples from WUN**12** are generally very low, similar to those of the UN**6** experiment (see Tables B4 and B5). The concentration values obtained by the two methods are of the same order of magnitude, up to the effluent WUN**12**-9.