## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Samples** & \multicolumn{4}{c}{**FA + BA Line 1**} & \multicolumn{4}{c}{**FA + BA Line 2**} & \multicolumn{4}{c}{**FA + BA Line 3**} \\ \hline
**Time** & **1 M** & **2 M** & **3 M** & **1 M** & **2 M** & **3 M** & **1 M** & **2 M** & **3 M** \\ \hline
**pH** & **13.6** & **8.7** & **7.7** & **13.7** & **12.2** & **8.0** & **13.6** & **12.1** & **8.4** \\ \hline
**Elements** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** \\ \hline P \({}^{*}\) & \(65.4\pm 23.1\) & \(30.2\pm 1.9\) & \(28.2\pm 14.6\) & \(40.4\pm 17.7\) & \(57.7\pm 2.8\) & \(27.9\pm 2.8\) & \(39.5\pm 1.8\) & \(49.2\pm 2.3\) & \(32.5\pm 18.9\) \\ S \({}^{*}\) & \(640\pm 180\) & \(422\pm 219\) & \(604\pm 244\) & \(330\pm 121\) & \(363\pm 50\) & \(469\pm 177\) & \(244\pm 24\) & \(378\pm 54\) & \(562\pm 172\) \\ Cl & \(3740\pm 484\) & \(3038\pm 1181\) & \(2185\pm 677\) & \(2327\pm 159\) & \(5123\pm 106\) & \(1953\pm 835\) & \(3677\pm 281\) & \(5381\pm 1266\) & \(2287\pm 640\) \\ K & \(474\pm 105\) & \(311\pm 8\) & \(257\pm 83\) & \(242\pm 126\) & \(636\pm 13\) & \(202\pm 136\) & \(369\pm 24\) & \(606\pm 201\) & \(215\pm 61\) \\ Ca & \(3156.4\pm 474\) & \(2190\pm 722\) & \(1643\pm 443\) & \(1400\pm 925\) & \(3810\pm 79\) & \(1290\pm 642\) & \(2553\pm 416\) & \(4248\pm 1396\) & \(1857\pm 524\) \\ Cr & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(0.110\pm 0.002\) & \(0.2\pm 0.1\) & \(<\) LOD \\ Mn & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(0.11\pm 0.004\) & \(<\) LOD \\ Fe & \(0.2\pm 0.1\) & \(0.3\pm 0.1\) & \(0.5\pm 0.1\) & \(0.5\pm 0.1\) & \(0.17\pm 0.01\) & \(0.3\pm 0.2\) & \(0.3\pm 0.2\) & \(<\) LOD & \(0.28\pm 0.02\) \\ Cu & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD & \(<\) LOD \\ Zn & \(0.2\pm 0.1\) & \(0.3\pm 0.1\) & \(1.0\pm 0.1\) & \(0.9\pm 0.2\) & \(0.9\pm 0.1\) & \(0.3\pm 0.1\) & \(1.7\pm 0.5\) & \(2.0\pm 1.1\) & \(0.07\pm 0.04\) \\ Br & \(649\pm 11.4\) & \(82.2\pm 13.1\) & \(75.3\pm 3.4\) & \(102.3\pm 27.6\) & \(85.8\pm 7.4\) & \(90\pm 32\) & \(94.1\pm 7.4\) & \(921\pm 6.5\) & \(107.3\pm 2.3\) \\ Rb & \(2.7\pm 0.2\) & \(4.6\pm 1.5\) & \(3.4\pm 0.5\) & \(4.3\pm 2.1\) & \(3.5\pm 0.3\) & \(4.5\pm 2.5\) & \(3.1\pm 0.2\) & \(3.3\pm 0.4\) & \(4.5\pm 0.6\) \\ Sr & \(9.7\pm 0.6\) & \(10.9\pm 1.8\) & \(9.0\pm 1.6\) & \(12.9\pm 4.0\) & \(10.4\pm 0.3\) & \(9.5\pm 4.3\) & \(17.4\pm 0.5\) & \(15.9\pm 1.4\) & \(19.0\pm 1.2\) \\ Pb & \(2.4\pm 0.4\) & \(<\) LOD & \(<\) LOD & \(7.1\pm 1.9\) & \(7.6\pm 1.3\) & \(<\) LOD & \(8.3\pm 2.8\) & \(10.7\pm 5.7\) & \(<\) LOD \\ \hline \hline \end{tabular} Values are expressed as the average \(\pm\) standard deviation of three measurements. Relative sensitivities for elements with \({}^{*}\) were calculated based on a calibration curve. LOD lower detection limit  
\end{table} 
Table 4: Results of the TXRF analysis and pH values of samples stabilized following the b) procedure with Sewage-MSWI FA from different lines after (1), (2) and (3) months. Both pozzolanic and carbonation reactions have been demonstrated to be effective in heavy metal mobilization [31], but the comparison between procedures a) and b) highlights the fundamental contribution of carbonation. As explained in the introduction part, the difference in the amount of SS in the co-combustion with MSW is considered to evaluate if the addition of this waste plays a role in the stabilization mechanism. For this aim, the procedure not involving the use of BA (procedure b) is considered. Moreover, this procedure allows for the reaching of lower pH values of the obtained eco-materials (see Table 4), increasing the efficacy of stabilization. Figure 2 reports the concentration of Pb and Zn in the leaching solutions of stabilized samples, considered after different times, versus the pH of the solution (for both procedures a) and b)).