## 2 Materials and Methods
### Materials
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multirow{2}{*}{**Oxide/Metal**} & \multicolumn{6}{c}{**Slag Source**} \\ \cline{3-8}  & & **S1** & **S2** & **S3** & **TS1** & **TS2** & **TS3** \\  & & **(Raw)** & **(Raw)** & **(Synthetic)** & **(Treated)** & **(Treated)** & **(Treated)** \\ \hline \multirow{8}{*}{**S1**} & FeO & 13.5 & 21.9 & 35.3 & 16.9 & 21.6 & 31.0 \\  & SiO\({}_{2}\) & 18.5 & 17.3 & 20.6 & 50.6 & 39.0 & 21.3 \\  & CaO & 5.64 & 7.28 & 9.66 & 9.45 & 15.8 & 9.93 \\  & Al\({}_{2}\)O\({}_{3}\) & 4.25 & 2.15 & 2.68 & 11.0 & 11.8 & 5.67 \\  & Na\({}_{2}\)O & 7.04 & 2.72 & 0.67 & 9.32 & 5.76 & 3.06 \\  & K\({}_{2}\)O & 2.10 & 0.55 & 0.51 & 2.54 & 0.42 & 0.73 \\  & MgO & 4.21 & 0.28 & 2.82 & 5.84 & 7.96 & 0.65 \\  & ZnO & 7.19 & 10.7 & 12.9 & 0.18 & 0.03 & 1.45 \\  & CuO & 0.72 & 0.05 & 0.23 & 0.18 & 0.08 & 0.01 \\  & SO\({}_{3}\) & 17.3 & \(<\)0.05 & 0.77 & 0.49 & 0.29 & 0.32 \\ \hline \multirow{8}{*}{**S1**} & Pb & 3.48 & 3.86 & 4.45 & 0.001 & 0.001 & 0.075 \\  & As & 0.409 & 0.505 & 0.14 & \(<\)0.001 & \(<\)0.001 & 0.006 \\ \cline{1-1}  & Sn & 0.179 & 0.304 & 0.93 & 0.001 & 0.004 & 0.214 \\ \cline{1-1}  & Sb & 0.037 & 0.628 & 0.54 & \(<\)0.001 & 0.001 & 0.027 \\ \cline{1-1}  & Co & 0.008 & 0.011 & NA & \(<\)0.001 & \(<\)0.001 & 0.005 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The oxide and elemental composition of raw and treated slags. with TS1 (also high in alumina) and TS3 (particularly low alumina content). Nonetheless, all three slags are lean in calcium oxide, which is probably not favourable in terms of reactivity [16; 17; 27]. It is evident that there are substantial differences in the composition of such slags with typical blast furnace slags (BFS). According to EN 15167-1, the composition of BFS shall be such that two-thirds of its mass is composed of SiO\({}_{2}\), CaO and MgO and that (CaO + MgO)/SiO\({}_{2}\) exceeds 1.0. Such criteria are not met in any of the three slags investigated in this research. Moreover, all slags contain exceeding amounts of alkalis (equivalent alkali contents are, respectively, 11.0%, 6.0% and 3.5% for TS1, TS2 and TS3; EN 15167-1 limit on Na\({}_{2}\)O\({}_{\text{eq. }}\): 1.2%), which are added as flux to decrease the liquidus temperature of the slags and thus decrease the potential operating temperature of the metallurgical process. This is especially the case in lead metallurgy, where the melting temperature of the metal phase is low. This could further increase the pH of the cement pore solution, which can, in turn, exacerbate the leaching of lead [24; 25; 26]. However, if the alkalis are in the glassy phases of the slags, they would then not necessarily dissolve into the pore solution and contribute to its alkalinity [28]. The phase composition of the slags was analysed via X-ray diffractometry. Figure 1 shows the X-ray diffraction patterns of TS1, TS2 and TS3. The XRD data were collected using an Empyrean diffractometer (Panalytical) equipped with a CoK\(\alpha\) tube. The tube operating conditions were 40 kV and 45 mA. Diffraction scans were recorded from 5 to 110 \(\lx@math@degree\)20, with a step size 0.013 \(\lx@math@degree\)20 and a measurement time per step of 50 s.  
Rietveld analysis was performed using HighScore Plus software (version 4.6a), and the external standard approach was used to determine the amorphous phase content (rutile; Kronos 2300 TiO\({}_{2}\) external standard calibrated against NIST SRM 676a \(\alpha\)-Al\({}_{2}\)O\({}_{3}\)). The mass attenuation coefficients needed for the absorption correction were calculated using the chemical composition results listed in Table 1. The crystalline phases were identified for each slag and listed with their respective mass fractions and the mass fraction of the XRD amorphous phase(s) on each diffractogram (see Figure 1). TS1 is an amorphous material (99.2% amorphous content) with trace amounts of magnesium iron aluminium oxide and metallic iron.