## 3 Results and Discussion
### Reactive Azo Dye Oxidation
#### 3.2.8 Validation of Reclaimed Water  
A physicochemical characterization of the water was carried out to determine its potential application. Both dyed wastewater effluents, as well as the water sample treated with the modified Fenton system were characterized. The median values of the wastewater properties, before and after treatment, were determined, and they are listed in Table 6. The performance of the modified Fenton system is clear from the data displayed in Table 6. The results demonstrate that, under UV illumination conditions using the Fenton catalyst, the Chemical Oxygen Demand (COD) reduced from 420 to 38 mg/L. The non-treated dye-containing wastewater presented a high concentration of COD. This resulted from effluent oxidation. Thus, the Fenton reagent treatment was able to oxidize and degrade most of the organics in the wastewater (90% COD removal). Moreover, when compared to the non-treated water, the reclaimed water, that is, the modified-Fenton-treated wastewater, exhibited lower dissolved oxygen (DO), turbidity, and suspended solids. However, the pH declined due to the Fenton reaction being carried out in the acidic range. It is worth mentioning that this acidic range might be altered prior to reuse. Such technology suggests that wastewater might be reused without severe toxicity accumulation. The quality of the dye wastewater treated using the modified Fenton treatment system is good enough for reuse in textile dyeing processes [38; 39; 40]. Hence, to verify the possibility of reusing reclaimed water, it is important to perform reuse tests.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter (Unit)** & **Suspended Solids (mg/L)** & **Turbidity (NTU)** & **pH** & **DO (mg/L)** & **COD (mg-COD/L)** \\ \hline Wastewater & 120 & 34 & 5.0 & 2.4 & 420 \\ Treated water & 38 & 2.5 & 3.0 & 2.3 & 28 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Wastewater characteristics, including physicochemical properties.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Fenton System** & **Target Dye Pollutant** & **Initiation Source** & **Operating Conditions** & **Oxidation Time** & **Efficiency** & **Ref.** \\ \hline H2O2/Fullers’ earth & Levafix blue & Ultraviolet illumination & Catalyst 1.02 g/L; H2O2 & & \\ H2O2/Fullers’ earth & Levafix blue & Ultraviolet illumination & 818 mg/L; pH 3.0; Temperature 298 K & 20 min & 99\% & Current work \\ \hline H2O2/Clay-Fe2O4 & Levafix blue & Ultraviolet illumination & Catalyst 1 g/L; H2O2 & & \\ H2O2/Fe-laponite & Acid Black 1 & Ultraviolet illumination & 400 mg/L; pH 3.0; Temperature 300 K & 30 min & 100\% & [13] \\ \hline H2O2/Fe-laponite & Acid Black 1 & Ultraviolet illumination & Catalyst 1 g/L; H2O2 & & \\ H2O2/Fe-laponite & Acid Black 1 & illumination & 218 mg/L; pH 3.0; Temperature 298 K & 120 min & 100\% & [34] \\ \hline H2O2/Fe-zeolite & Acid Blue 74 & Ultraviolet illumination & 400.3 g/L; H2O2 & & \\ H2O2/Fe-zeolite & Acid Blue 74 & Ultraviolet illumination & 228 mg/L; pH 5.0; Temperature 298 K & 120 min & 55\% & [35] \\ \hline H2O2/Fe2.46 Ni0.54O4 & Methylene blue & Dark Fenton & Catalyst 1.0 g/L; H2O2 & & \\ H2O2/Fe2.46 Ni0.54O4 & Methylene blue & Dark Fenton & 340 mg/L; pH 7.0; Temperature 298 K & 50 min & 10\% & [36] \\ \hline H2O2/Co-Fe2O4 & Methylene blue & Natural solar radiation & Catalyst 0.2 g/L; H2O2 & & \\ H2O2/Co-Fe2O4 & Methylene blue & solar radiation & 0.68 mg/L; pH 5.0; Temperature 298 K & 150 min & 79\% & [35] \\ \hline H2O2/Mn-Fe2O4 & Methylene blue & Natural solar radiation & 40.