## 4 Conclusions  
In this study, iron-based oxides Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\) and FeWO\({}_{4}\) were successfully synthesized via co-precipitation followed by microwave-assisted hydrothermal treatment. Structural and morphological analyses confirmed the formation of well-crystallized phases with distinct morphologies, which directly influenced their photocatalytic behavior. Optical characterization revealed band gap values consistent with visible light absorption, while PL analysis indicated the presence of different types of lattice defects contributing to the charge carrier dynamics. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Photocatalyst** & **Effluent** & **Degradation** & \begin{tabular}{c} **Exposure** \\ **Time** \\ \end{tabular} & **Light Source** & **Conditions** & **Ref.** \\ \hline Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\) & Aluminum & 32.2 & 120 & Visible & 50 mg catalyst, 100 mL & This work \\ \hline FeWO\({}_{4}\) & anodizing & 45.3 & 120 & Visible & 140 mg/L catalyst, 100 & \\ \hline Cu\({}_{2}\)O/ZnO/Ag\({}_{3}\)PO\({}_{4}\) & \begin{tabular}{c} Sewage (textile \\ company) \\ \end{tabular} & 78.2 & 180 & Tungsten & 140 mg/L catalyst, 100 mL effluent, pH = 6.0 & [40] \\ \hline ZnO/Fe\({}_{2}\)O\({}_{3}\)/MnO\({}_{2}\) & \begin{tabular}{c} Sewage (textile \\ company) \\ \end{tabular} & 63 & 120 & Tungsten & 125 mg/L catalyst, 100 mL effluent, pH = 6.0 & [41] \\ \hline ZnO & & 50 & 77 & UV-A & 0.2 g catalyst, 150 mL & \\ \hline ZnO-iron oxide & Textile effluent & 85 & 120 & \begin{tabular}{c} Natural solar \\ radiation \\ (sunny days) \\ \end{tabular} & 120 & \begin{tabular}{c} 0.2 g catalyst, 150 mL \\ effluent, pH = 12.4 \\ \end{tabular} & [42] \\ \hline ZnO-iron oxide & & 98.6 & \
\begin{tabular}{c} Natural solar \\ radiation \\ (sunny days) \\ \end{tabular} &
\begin{tabular}{c} 0.2 g catalyst, 150 mL \\ effluent, pH = 12.4, 1 mL \\ \end{tabular} & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Photocatalytic degradation efficiencies (%) of different materials applied to a real effluent. The corresponding exposure times are reported in minutes. Figure 5: Schematic representation of the photodegradation process of real effluents mediated by iron oxides. Photocatalytic tests using a real effluent from the aluminum anodizing industry demonstrated degradation efficiencies of 32.2% and 45.3% for Fe\({}_{2}\)(MoO\({}_{4}\))\({}_{3}\) and FeWO\({}_{4}\), respectively, under visible light irradiation. FeWO\({}_{4}\) exhibited superior performance, likely due to its porous morphology and higher surface area, which enhanced light absorption and charge separation. Although the degradation of real effluents remains a significant challenge due to their complex composition, this study demonstrates that single-phase iron oxides can offer competitive photocatalytic performance without the need for complex heterostructures. These findings highlight the potential of iron-based oxides for sustainable and cost-effective wastewater treatment and reinforce the importance of tailoring morphological and electronic properties to improve photocatalytic efficiency. Conceptualization, L.K.R., M.G.G., L.H.M., M.C., and A.F.G. ; methodology, L.K.R., M.G.G., and A.F.G. ; formal analysis, L.K.R., M.G.G., and A.F.G. ; investigation, L.K.R., M.G.G., and A.F.G. ; resources, L.H.M. and M.C. ; data curation, L.K.R., M.G.G., and A.F.G. ; writing--original draft preparation, L.K.R., M.G.G., and A.F.G. ; writing--review and editing, L.H.M. and M.C. ; visualization, L.K.R., M.G.G., and A.F.G. ; supervision, L.H.M. and M.C. ; project administration, L.H.M. and M.C. ; funding acquisition, L.H.M. and M.C. All authors have read and agreed to the published version of the manuscript. This study was financed, in part, by the Sao Paulo Research Foundation (FAPESP), Brazil (process Nos. 2023/12399-7, 2023/01415-1, 2013/07296-2, 2023/11548-9, and 2024/07586-5), the Sao Paulo Research Foundation's National Council for Scientific and Technological Development (CNPq, grant Nos.