## 2 Materials and Methods
### Anode Consumption and Sludge Characterisation  
To understand the impact of different parameters on the TY dye removal efficiency during the EC process, the consumption of the anode material (determined as the difference in electrode mass before and after the EC process) and collected sludge mass (after the EC process, the solution was filtered, and the sludge was dried and weighed) were monitored. The results are compared in Table 3. It can be seen that under all conditions, there is consumption of anode material, which increases with increasing current density and does not depend significantly on the initial pH value. On the other hand, the sludge mass increases with increasing current density, but also with decreasing pH value. It should be noted that the durations of RUN1 and RUN12 (pH = 3) were about 20 min shorter. Anode consumption with increasing current density is expected and occurs through electrode kinetics (i.e., the Butler-Volmer equation), according to which the rate of metal dissolution increases exponentially with the rise in anode polarisation [72]. The dissolution of Al anodes and the formation of Al\({}^{3+}\) ions are necessary for the further conduction and progression of the EC process. However, when the anodes dissolve, the state of their surfaces changes. Microscopic examination of the electrodes after the EC process (Figure 5) reveals the nature of their dissolution and their corrosion patterns. Under all test conditions, a general pattern of corrosion attack can be observed. The current density and the solution's initial pH value have no significant influence on the corrosion form. It is known that TY belongs to the group of anionic azo dyes, which means that it is negatively charged in aqueous solutions [73; 74] and easily combines with positively charged coagulants (Al\({}^{3+}\) ions formed during the dissolution of the anode). Due to strong electrostatic attraction, their coagulation and flocculation are very effective, forming stable Al(OH)\({}_{3}\) flocs (of different surface areas) that settle quickly. A comparison of the results (Figures 1 and 3) shows that the best efficiency is achieved under neutral to slightly alkaline  
Figure 5: Microscopic images of aluminium anodes at 200\(\times\) magnification under different current densities (pH = 7.0) and initial pH values (\(i\) = 0.024 A cm\({}^{-2}\)). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Experiment** & **pH** & \begin{tabular}{c} **\(t\)** \\ **(min)** \\ \end{tabular} & \
\begin{tabular}{c} **\(i\)** \\ **(A cm\({}^{-2}\))** \\ \end{tabular} &
\begin{tabular}{c} **Anode** \\ **Consumption (g)** \\ \end{tabular} & **Sludge Mass (g)** \\ \hline RUN 1 & 7.0 & 32 & 0.008 & 0.0860 & 0.1853 \\ \hline RUN 4 & 7.0 & 50 & 0.016 & 0.2574 & 0.6047 \\ \hline RUN 5 & 7.0 & 50 & 0.024 & 0.3733 & 1.1764 \\ \hline RUN 8 & 4.8 & 50 & 0.024 & 0.3973 & 1.5023 \\ \hline RUN 12 & 3.0 & 37 & 0.024 & 0.2895 & 1.1693 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Anode material consumption and sludge mass under different process conditions. conditions (pH 6-8), where flocs are easily formed. These conditions are most effectively produced during the EC process at higher current densities and a lower initial pH. After the EC process, the settling ability of the resulting milky, gelatinous precipitate was determined, and the results are shown in Figure 6. During sedimentation, a sharp boundary forms between the clear solution and the sludge, which facilitates the determination of settling ability (Figure 6a). In all investigated cases, the \"interface height between the solid and liquid phases\" (\(h\)) decreases over time. A curve exhibiting a steeper slope, i.e., a more pronounced decline in \(h\), indicates superior settling performance and more efficient solid-liquid phase separation.