## 2 Materials and Methods
### Photocatalytic Assays  
The photocatalytic activity was evaluated through the degradation of a real effluent under visible light. The effluent was sourced from an aluminum anodizing company based in Sao Carlos, Brazil, specializing in industrial applications.  
In a typical process, 50 mg of the synthesized materials were dispersed in 100 mL of the residue and subjected to ultrasonication for 10 min in an ultrasonic bath (42 kHz, model 1510). The mixture was then transferred to a 100 mL glass bottle and stirred in the dark for 30 min to ensure homogeneous dispersion of the catalyst and allow adsorption processes to occur. Subsequently, the suspensions were irradiated with six visible-light lamps (PHILIPS TL-D, Sao Paulo, Brazil, 15 W) positioned 10 cm from the reactor under vigorous stirring of \(\sim\)600 rpm throughout the photocatalytic process, while the temperature was maintained at 20 \({}^{\circ}\)C using a thermostatic bath. The estimated irradiance at the sample surface was approximately 12-24 mW cm\({}^{-2}\), and the photon flux was approximately 4.35 \(\times\) 10\({}^{-4}\) mol s\({}^{-1}\), assuming emission centered in the visible spectrum (around 550 nm). These values were used for comparison and reproducibility purposes. At predetermined intervals (0, 5, 10, 15, 20, 30, 60, 90, and 120 min), 1 mL aliquots were withdrawn from the photocatalytic system and transferred to plastic tubes. The suspensions were then centrifuged at 6000 rpm for 5 min to completely remove the catalyst particles. The resulting solutions were analyzed using UV-vis absorption spectroscopy with a V-660 spectrophotometer (JASCO, Japan) to monitor changes in the absorption band of the residue, which exhibited a maximum at \(\lambda\) = 616 nm in all photocatalytic tests. The percentage of degradation was estimated using the relationship shown in Equation (1):  
\[\% Degradation=\frac{C_{o}\ -\ C_{f}}{C_{o}}\times 100 \tag{1}\]  
where \(C_{o}\) and \(C_{f}\) are the initial and final concentrations, respectively. A photolysis control experiment, conducted without a photocatalyst, was also carried out under identical conditions. In the following, the total organic carbon (TOC) concentration was analyzed to investigate the extent of mineralization using a TOC analyzer (TOC-L CSH/CSN, Shimadzu, Kyoto, Japan). The effluent composition was monitored using a 930 Compact IC Flex system (Metrohm, Switzerland) equipped with an 863 Compact Autosampler (Switzerland), a CO\({}_{2}\) suppression system, and an IC Conductivity Detector. Anion separation and quantification were performed on a Metrosep A Supp 5 column (150 mm \(\times\) 4.0 mm) with a Metrosep A Supp 5 Guard/4.0 column, and cation separation and quantification were performed on a Metrosep C4 column (150 mm \(\times\) 4.0 mm) with a Metrosep C4 Guard/4.0 column, both at 25 \({}^{\circ}\)C. Anion analysis was performed at a flow rate of 0.7 mL min\({}^{-1}\) with an isocratic elution of 3.2 mmol L\({}^{-1}\) of Na\({}_{2}\)CO\({}_{3}\) with 1.0 mmol L\({}^{-1}\) of a NaHCO\({}_{3}\) solution prepared in ultrapure water. For cations, an isocratic elution of 100% 1.7 mmol L\({}^{-1}\) HNO\({}_{3}\) with 0.7 mmol L\({}^{-1}\) dipicolinic acid at a flow rate of 1.0 mL min\({}^{-1}\) was employed.