## 2 Materials and Methods  
### Chemicals and Reagents  
A synthetic ALSEP feed simulant was prepared with a target composition that would be expected for the raffinate from a U/Pu co-decontamination process [31]. The simulant was based on a light water reactor fuel burned at 50 gigawatt days per metric ton initial heavy metal, 5 years cooled, after processing with the PUREX process [9]. It was prepared by dissolving the appropriate metal nitrates in HNO\({}_{3}\) solution. The exceptions were tin (Sn) and tellurium (Te). In the former case, Sn metal was dissolved in HNO\({}_{3}\) and the resulting solution was added to the simulant. In the latter case, Te was added in the form of Na\({}_{2}\)TeO\({}_{4}\)-2H\({}_{2}\)O. Table 1 presents the composition of the feed simulant used.  
A solvent composed of 0.5 mol L\({}^{-1}\) HEH[EHP] and 0.05 mol L\({}^{-1}\) T2 EHDGA dissolved in \(n\)-dodecane was used. HEH[EHP] was obtained from Marshallton Research Laboratories, USA, and purified by a literature procedure [32]. The final purity of the HEH[EHP] was greater than  
\begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Element**} & \multicolumn{2}{c}{**Concentration ALSEP**} & \multirow{2}{*}{**Element**} & \multicolumn{2}{c}{**Concentration ALSEP**} \\  & **Feed [mg L\({}^{-1}\)] \({}^{*}\)** & & **Feed [mg L\({}^{-1}\)] \({}^{*}\)** \\ \hline Fe & 7 & Cs & 665 \\ Rb & 90 & La & 309 \\ Sr & 207 & Ce & 591 \\ Y & 119 & Pr & 267 \\ Zr & 718 & Nd & 1003 \\ Mo & 425 & Sm & 213 \\ Ru & 296 & Eu & 44 \\ Rh & 1 & Gd & 45 \\ Pd & 6 & \({}^{241}\)Am & 3.1 MB\({}_{4}\) L\({}^{-1}\) \\ Sn & 14 & \({}^{244}\)Cm & 3.0 MB\({}_{4}\) L\({}^{-1}\) \\ Te & 69 & \({}^{152}\)Eu & 5.6 MB\({}_{4}\) L\({}^{-1}\) \\ HNO\({}_{3}\) & 2.9 mol L\({}^{-1}\) & & \\ \hline \end{tabular} \({}^{*}\) or as shown.  
\end{table}
Table 1: Composition of the synthetic Actinide Lanthanide Separation Process (ALSEP) feed solution.  
Figure 1: Chemical structures of molecules used in this study.  
99% based on \({}^{31}\)P NMR analysis. The neutral extractant, T2 EHDGA, was obtained from Eichrom Technologies LLC (Lisle, IL, USA) and used as received. Anhydrous \(n\)-dodecane was purchased from Sigma-Aldrich, Saint Louis, MO, USA.  
CDTA (purity \(\geq\) 99.0%) and ammonium citrate (purity \(\geq\) 99.0%) were purchased from Sigma-Aldrich, Munich, Germany. AHA (purity 98%) and DTPA (purity \(\geq\) 98.0%) were purchased from Alfa Aesar, Karlsruhe, Germany. Nitric acid solutions (Merck AG, Germany) were prepared by dilution from a 65% HNO\({}_{3}\) solution EMSURE(r) for analysis using ultrapure water (18.2 M\(\Omega\) cm), which was obtained using an ELGA PURELAB Ultra water purification system. All chemicals were used as received and only ultrapure water was used for the experiments unless otherwise specified.  
CDTA was dissolved in the feed solution to a final concentration of 0.05 mol L\({}^{-1}\). The \"Scrub 1\" solution was prepared by dilution of 65% HNO\({}_{3}\) solution to a concentration of 6.3 mol L\({}^{-1}\) HNO\({}_{3}\). The \"Scrub 2\" solution was prepared by dissolving AHA and ammonium citrate in water and adjusting the pH of the solution with HNO\({}_{3}\) to yield 0.75 mol L\({}^{-1}\) AHA and 0.175 mol L\({}^{-1}\) ammonium citrate at pH 3.4. The \"Strip 1\" solution was prepared by dissolving DTPA and ammonium citrate in water and adjusting the pH of the solution with HNO\({}_{3}\) to yield 0.015 mol L\({}^{-1}\) DTPA and 0.2 mol L\({}^{-1}\) ammonium citrate at pH 2.0.  
The radiotracers \({}^{241}\)Am, \({}^{244}\)Cm, and \({}^{152}\)Eu were purchased from Isotopendienst M. Blaseg GmbH, Waldburg, Germany, Oak Ridge National Laboratory, Oak Ridge, USA, and Eckert & Ziegler Nuclitec GmbH, Braunschweig, Germany, respectively.