## 4 Results and Discussion  
### Stepwise Dosing  
The results of the stepwise dosing trials are shown in Table 3. Duplicate trials were carried out for the materials that were able to successfully reach a pH of 9 in the first trials. This category includes all the materials listed, but O2 and S2 did not reach the pH target value. In their case, the trials were stopped after several iterations, because the pH value plateaued despite the addition of more slag. The remaining four materials demonstrated that, given the experimental setup, they were able to raise the pH of the acidic wastewater to the desired values. The duplicates also guarantee replicability of the results, showing similar quantities and final pH levels between trials.  
The EQ trials showed that different quantities of slag and lime are needed to successfully reach a pH of 9. This can be attributed to two different factors, namely the particle size distribution and  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Trial Name** & **Material** & **Mass (g)** & **OTK Flocculant (mL)** \\ \hline OL-1 & OL & 5.5 & 3.0 \\ OL-2 & OL & 5.4 & 3.0 \\ OL-3 & OL & 5.5 & 3.0 \\ O1-1 & O1 & 43.9 & 0.5 \\ O1-2 & O1 & 43.8 & 1.0 \\ O1-3 & O1 & 43.8 & 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mass of material and volume of flocculant used during the water purity all in one (AIO) trials.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Trial Name** & **Material** & **Final pH** & **Total Mass (g)** \\ \hline OL-1 & OL & 10.68 & 4.79 \\ OL-2 & OL & 11.35 & 4.83 \\ SL-1 & SL & 9.35 & 6.33 \\ SL-2 & SL & 9.36 & 6.47 \\ S1-1 & O1 & 9.09 & 22.80 \\ S1-2 & O1 & 9.40 & 28.56 \\ O11-1 & S1 & 9.  
mineral composition (which is believed to be different, considering the different origins of the samples). Regarding the first, it is noticeable how a coarser PSD led to a higher amount of reactant needed for the neutralization. This can easily be explained by considering that a coarser particle has a lower surface/volume ratio. Hence, considering that the reactant does not completely dissolve, not all the Ca present in the material is able to react with the wastewater, leading to a higher amount of material needed. Moreover, the mineral composition, despite unknown, is believed to play an important role. If Ca is the element that drives the neutralization process [13], it is also clear that a different w% of said element and how it reacts with the wastewater based on the mineral structure are key factors. These two factors combined explain why both lime samples, which present a higher Ca content compared to slag and a finer PSD, neutralize one liter of wastewater with approximately four to six times less the amount of O1 and S1 sample.  
Regarding the behavior of O2 and S2, the authors believe that the data collected is not enough to rule them out as suitable reactants. Both slag samples have a higher PSD compared to the remaining materials, and that could impede the neutralization. Moreover, the trials were stopped after several iterations because the pH increases were not substantial enough. However, that does not mean that a successful neutralization could not have been obtained with higher amounts and more time. More experiments with a reduced PSD are needed to test the material again, possibly homogenizing the particle size to the one of O1 and S1 samples or even the lime samples.