# Nanofiltration of Simulated Acid Mine Drainage: Effect of pH and Membrane Charge
## 2 Materials and Methods
### Model AMD Solution Design  
The model AMD solution used in this study was designed as an average of the compositions of different mine waters as detailed in Table 3 with reference to 6 mine water solutions. They included 3 real mine water (MW) solutions (MW A: Australian Copper MW, Chilean Copper MW, and Brazilian Uranium MW) and 3 model compositions (MW B, MW C, and MW D) recreated from MW A by [PERSON] et al. (2014). The final target ion concentration was calculated from the salts used in single salt and mixed salt experiments. Table 4 shows the model AMD solution feed composition investigated in this study. Na\({}_{2}\)SiO\({}_{3}\) was omitted from the model AMD solution composition as it causes other salts in the solution to precipitate. Mn and Cu were chosen as the representative heavy metal ions in the model AMD solution.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Salt** & **Concentration** & **pH** \\ \hline MgSO\({}_{4}\) & 4000 \(\pm\) 100 mg/L MgSO\({}_{4}\) & 2.0–7.0 \(\pm\) 0.1 \\ CuSO\({}_{4}\) & 100 \(\pm\) 10 mg/L Cu & 2.0–5.4 \(\pm\) 0.1 \\ Mn(NO\({}_{3}\))\({}_{2}\) & 165 \(\pm\) 5 mg/L Mn & 2.0–5.1 \(\pm\) 0.1 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Single salt solution feed compositions.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Salt** & **Concentration** & **pH** \\ \hline NaSO\({}_{4}\) and NaCl & 2000 \(\pm\) 200 mg/L Na\({}_{2}\)SO\({}_{4}\) and 700 \(\pm\) 50 mg/L NaCl & 2.0–7.0 \(\pm\) 0.1 \\ \hline NaSO\({}_{4}\) and NaCl & 0.001 \(\pm\) 0.0001 mol/L Na\({}_{2}\)SO\({}_{4}\) and 0.001 \(\pm\) 0.0005 mol/L NaCl & \\ NaSO\({}_{4}\) and NaCl & 0.005 \(\pm\) 0.0002 mol/L Na\({}_{2}\)SO\({}_{4}\) and 0.005 \(\pm\) 0.0017 mol/L NaCl & \\  & 0.010 \(\pm\) 0.0013 mol/L Na\({}_{2}\)SO\({}_{4}\) and 0.010 \(\pm\) 0.003 mol/L NaCl & \\  & 0.015 \(\pm\) 0.0004 mol/L Na\({}_{2}\)SO\({}_{4}\) and 0.015 \(\pm\) 0.0037 mol/L NaCl & \\ \hline Na\({}_{2}\)SiO\({}_{3}\) and MgSO\({}_{4}\) & 15 \(\pm\) 1 mg/L Si and 2000 mg/L MgSO\({}_{4}\) & 7.0 \(\pm\) 0.1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mixed salt solution feed compositions.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multicolumn{3}{c}{**[PERSON] et al. [14]**} & \multicolumn{3}{c}{**[PERSON] et al. [8]**} & **Target** \\ \cline{2-7}  & **Australian MW (mg/L)** & **MW B (mg/L)** & **MW C (mg/L)** & **MW D (mg/L)** & **Chilean Copper** & **Brazilian Uranium** & **Model AMD** \\  & & & & & & **MW (mg/L)** & **MW (mg/L)** & **(mg/L)** \\ \hline pH & 4.56 & 5.50 & 4.10 & 2.60 & \textless{}2.50 & NA & 2.0–5.0 \\ Calcium, Ca\({}^{2+}\) & 480 & 260 & 280 & 270 & 325.9 & 89.9 & 270 \\ Copper, Cu & 410 & 410 & 610 & 590 & 2298 & NA & 390 \\ Magnesium, Mg\({}^{2+}\) & 770 & 870 & 900 & 900 & 630.6 & 8.84 & 2300 \\ Manganese, Mn & 440 & 420 & 530 & 500 & 224.5 & 115 & 500 \\ Sodium, Na\({}^{+}\) & 2000 & 3000 & 3800 & 3600 & 6.89 & 1.7 & 3600 \\ Sulfate, SO\({}_{2}\)- & 6900 & 8700 & 10,500 & 10,200 & 14.337 & 1508 & 10,327 \\ Chloride, Cl\({}^{+}\) & 2300 & 2300 & 3000 & 2900 & NA & 0.21 & 5599 \\ Nitrate, NO\({}_{3}\)- & NA & NA & NA & NA & NA & 1129 \\ \hline \multicolumn{7}{c}{NA–Not available.} \\ \hline \end{tabular}
\end{table}
Table 3: Composition of mine water (MW) samples from other works and target composition for model acid mine drainage (AMD).