## 3 Results and Discussion
### Photocatalytic Degradation  
In this study, the photocatalytic activity of the synthesized materials was evaluated by monitoring the degradation of a real industrial effluent from aluminum anodizing processes under visible light irradiation. The effluent exhibited a dark blue color, with a maximum absorbance peak at 616 nm. Additional information regarding the effluent composition is summarized in Table 3.  
In polluted environments such as industrial effluents or contaminated soils, a wide variety of chemical compounds can poison or deactivate catalysts, including heavy metals, sulfur, chlorine, and particulate matter. These contaminants tend to bind to the active sites of the catalysts, thereby blocking catalytic activity and significantly reducing overall efficiency. Moreover, the presence of color or high turbidity in the effluent can hinder light penetration, limiting the interaction between the catalyst and the irradiation source, and consequently reducing both process efficiency and the photogeneration of reactive species [33]. The synthesized Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\) and FeWO\({}_{4}\) samples were applied for the photocatalytic degradation of a real effluent from aluminum anodizing industries (Figure 4). Both iron-based oxides demonstrated the ability to remove the effluent's color under the tested conditions (Figure 4A). A control experiment, performed in the absence of a photocatalyst (photolysis), confirmed that light irradiation alone did not degrade the effluent, highlighting the essential role of the catalysts in the process. Specifically, Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\) achieved an average color removal efficiency of 35.6%, while FeWO\({}_{4}\) reached 44.6%. \begin{table}
\begin{tabular}{c c} \hline \hline
**TOC removal** & **\%** \\ \hline
**Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\)** & 60.6 \(\pm\) 0.01 \\
**FeWO\({}_{4}\)** & 66.7 \(\pm\) 0.07 \\ \hline
**Parameters** & Result \\ \hline Total organic carbon (mg L\({}^{-1}\)) & 14.2 \\ pH & 6.0 \\ Conductivity (mS cm\({}^{-1}\)) & 126 \\ Fluoride (mg L\({}^{-1}\)) & 1.18 \\ Chloride (mg L\({}^{-1}\)) & 1.14 \\ Nitrite (mg L\({}^{-1}\)) & \textless{}0.04 \\ Bromide (mg L\({}^{-1}\)) & \textless{}0.01 \\ Chlorate (mg L\({}^{-1}\)) & \textless{}0.04 \\ Chlorite (mg L\({}^{-1}\)) & 0.71 \\ Nitrate (mg L\({}^{-1}\)) & 2.48 \\ Phosphate (mg L\({}^{-1}\)) & \textless{}0.01 \\ Sulfate (mg L\({}^{-1}\)) & 30.69 \\ Sulfite (mg L\({}^{-1}\)) & \textless{}0.04 \\ Lithium (mg L\({}^{-1}\)) & \textless{}0.04 \\ Sodium (mg L\({}^{-1}\)) & 12.36 \\ Ammonium (mg L\({}^{-1}\)) & 0.36 \\ Potassium (mg L\({}^{-1}\)) & 2.10 \\ Calcium (mg L\({}^{-1}\)) & 5.84 \\ Magnesium (mg L\({}^{-1}\)) & 1.16 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: TOC removal efficiency and wastewater initial composition characterization. Several factors may account for the difference in photocatalytic performance between the two materials, particularly their morphology. Although Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\) exhibited a more defined morphology with exposed (001) and (110) surfaces, FeWO\({}_{4}\) showed a more irregular morphology with smaller particle sizes, which is likely to enhance surface area and catalytic activity. These structural differences may directly influence the materials' ability to generate reactive species and interact with pollutants during photocatalysis. [PERSON] et al. [34] investigated the synthesis of FeWO\({}_{4}\) with different morphologies (nanoparticles, nanorods, and nanofibers) via the hydrothermal method and evaluated their influence on ciprofloxacin degradation using various Fenton-based processes. While all morphologies exhibited photocatalytic activity, the nanoparticles demonstrated superior performance, achieving complete antibiotic removal at neutral pH within 40 min using 100 mg L\({}^{-1}\) of the catalyst and 2.0 mmol L\({}^{-1}\) of H\({}_{2}\)O\({}_{2}\). Reusability tests demonstrated that both materials maintained their photocatalytic performance after two consecutive cycles (Figure 4B).