## 3 Results and Discussion
### Influence of Initial Dose of TA  
To study the effect of this parameter, four TA concentrations of 0.05, 0.1, 0.2, and 0.4 mM were tested at optimum conditions determined in previous steps (UV/PS: [K\({}_{2}\)S\({}_{2}\)O\({}_{8}\)]/[TA] = 531, pH = 9 and T = 25 \({}^{\circ}\)C; UV/H\({}_{2}\)O\({}_{2}\)/Fe\({}^{2+}\): [H\({}_{2}\)O\({}_{2}\)]/[Fe\({}^{2+}\)] = 164, [H\({}_{2}\)O\({}_{2}\)]/[TA] = 294, pH = 3, and T = 25 \({}^{\circ}\)C). Results presenting final percentage of absorbance and TOC removals for 120 min treatment are illustrated in Figure 8. As shown in Figure 8a, the initial concentration of TA has no significant effect on either the rate or the percentage of aromatics removal during the treatment by UV/persulfate and photo-Fenton processes. In both processes, there is more than 90% of absorbance removal for the different initial concentration of TA in the range 0.05-0.4 mM. However, TOC removal was strongly influenced by the initial concentration of TA, as seen in Figure 8b. An increase in TA concentration from 0.05 to 0.1 mM resulted in an increase in removal efficiency from 42.95 to 54.41% and from 85.44 to 94.27% for the UV/persulfate and photo-Fenton processes, respectively, at 120 min of treatment. Increasing initial concentration of TA from 0.1 to 0.4 mM decreases TOC removal efficiency. The results obtained can be interpreted as follows: (i) A higher TA dose requires a big amount of oxidants, and thus, the process efficiency decreased with a constant amount of oxidant. The greater of amount in the reaction medium decreases the quantum yield of production of sulfates radicals SO\({}_{4}\)\({}^{\bullet-}\) from K\({}_{2}\)S\({}_{2}\)O\({}_{8}\) and hydroxyl radicals OH\({}^{\bullet}\) from H\({}_{2}\)O\({}_{2}\). This is mainly due to the absorption of a significant amount of UV radiation by the organic molecules, besides, by the coloring of the solution and the formation of a precipitate layer of the jacket of the reactor, which makes difficult the passage of  
Figure 7: Effect of H\({}_{2}\)O\({}_{2}\) dose on (**a**) Aromatics removal and (**b**) TOC removal by photo-Fenton process (UV/H\({}_{2}\)O\({}_{2}\)/Fe\({}^{2+}\)). Experimental conditions: [TA] = 0.1 mM; [H\({}_{2}\)O\({}_{2}\)] = 14.7–58.8 mM; [H\({}_{2}\)O\({}_{2}\)]/[Fe\({}^{2+}\)] = 164; T = 25 \({}^{\circ}\)C; and pH = 3. UV light in organic molecules. It is also due to competition between TA molecules and intermediates compounds generated during the reaction. (ii) A low concentrations of TA and oxidants (K\({}_{2}\)S\({}_{2}\)O\({}_{8}\), Fe\({}^{2+}\), and H\({}_{2}\)O\({}_{2}\)) decrease the probability of collusion between sulfates or hydroxyl radicals and aliphatic intermediates, which makes difficult their mineralization into CO\({}_{2}\) and H\({}_{2}\)O. Several authors have found similar observation in their study [44; 75; 76; 77]. From these results, it is concluded that the best performance for the mineralization and degradation of TA by UV/persulfate and photo-Fenton processes is obtained for an initial dose of TA equal to 0.1 mM. This corresponds to a ratio weight equal to 531 and 294 successively for [K\({}_{2}\)S\({}_{2}\)O\({}_{8}\)]/[TA] and [H\({}_{2}\)O\({}_{2}\)]/[TA]. The two ratios are relative to the degradation and the mineralization of TA. It is also clear that aromatics were decomposed into aliphatic intermediates by the photo-Fenton process, but it is more difficult to mineralize TA by the UV/persulfate process. Therefore, the mineralization and degradation of TA by the photo-Fenton process are more effective than by UV/persulfate process. Figure 8: Effect of TA initial concentration on (**a**) aromatics removal and (**b**) TOC removal by UV/persulfate (UV-PS) and photo-Fenton (UV/H\({}_{2}\)O\({}_{2}\)/Fe\({}^{2+}\)) processes under optimal conditions.