# Optimization of Organic Content Removal from Aqueous Solutions by Fenton-Ozonation
## 3 Results
### Fenton Process
#### 3.1.1 Initial State of ANOVA Analysis
Therefore, closer attention has been paid to the influence of this main parameter and its evolution during the Fenton treatment in terms of TOC. First, it can be noted that all three main factors increase in statistical significance up to 60 min of treatment duration. The catalyst dose term has a \(p\)-value lower than 0.05 in the first 40 min, and at 60 min, it decreases below 0.01, thus strengthening its confidence interval up to 99%. The solution pH term presents the highest confidence interval from the beginning of the Fenton process, and even then, the positive evolution is still valid, with a lower and lower \(p\)-value until reaching values lower than 0.0001. The issues in terms of statistical significance within the chosen experimental ranges were recorded in the case of the H\({}_{2}\)O\({}_{2}\) dose. In the first 30 min of treatment, it seems this parameter has a low influence over the process performance; its term gets significant at 90% confidence interval after 40 min, and becomes stronger (relevant at 95% confidence interval) after 60 min. Among the many aspects considered in choosing the experimental design, special attention was given to the ratio of Fe ions and H\({}_{2}\)O\({}_{2}\) dose, with its optimality standing around 1:10 [30]. Nevertheless, in the present study, the amount of AC support is quite high with respect to the aforementioned ratio. Consequently, at the beginning of each  
\begin{table} \begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Source**} & \multicolumn{5}{c}{**Sum of Square; Degrees of Freedom; F-Value; \(p\)-Value \(\times\) 10\({}^{2}\)**} \\ \cline{2-7}  & \(\chi^{\text{domain}}_{\text{TOC}}\) & \(\chi^{\text{domain}}_{\text{TOC}}\) & \% & \(\chi^{\text{domain}}_{\text{TOC}}\) & \% & \(\chi^{\text{domain}}_{\text{TOC}}\) & \% \\ x\({}_{1}\)x\({}_{3}\) & 32.6; 1; 0.71; 42.6 & 34; 1; 0.726; 42.2 & 65; 1; 0.61; 45.9 & 44.4; 1; 2; 0.03; 19.7 & 45.7; 1.2; 49; 15.9 \\ x\({}_{2}\)x\({}_{3}\) & 216; 1; 4.74; 6.58 & 61.4; 1.1; 31; 29 & 50.7; 1; 0.48; 51.1 & 27.4; 1; 1.25; 30 & 8.34; 1; 0.46; 52.2 \\ x\({}_{1}\)\({}^{2}\) & 49.2; 1; 1.08; 33.4 & 2.25; 1; 0.05; 83.3 & 44.3; 1; 0.42; 53.8 & 5.34; 1; 0.24; 63.7 & 70.9; 1; 3.86; 9.01 \\ x\({}_{2}\)\({}^{2}\) & 13.3; 1; 0.29; 60.6 & 0.92; 1; 0.02; 89.3 & 84.6; 1; 0.8; 40.1 & 4.97; 1; 0.23; 64.8 & 11.7; 1; 0.64; 45.1 \\ x\({}_{3}\)\({}^{2}\) & 894; 1; 19.6; 0.31 * & 614; 1; 13.1; 0.85 * & 2440; 1; 23; 0.2 * & 818; 1; 37.4; 0.05 * & 861; 1; 46.9; 0.02 * \\ Residual & 319; 7 & 328; 7 & 741; 7 & 153; 7 & 129; 7 \\ Lack of Fit & 302; 5; 6.9; 13.1 & 226; 5; 0.89; 60.6 & 612; 5; 1.9; 38 & 45.6; 5; 0.17; 95.2 & 47.8; 5; 0.24; 91.6 \\ Pure Error & 17.5; 2 & 102; 2 & 129; 2 & 108; 2 & 80.7; 2 \\ \hline \hline \end{tabular}   
experimental run, the concurrent adsorptions of 2,4-D and H\({}_{2}\)O\({}_{2}\) are very strong, shadowing the influence of H\({}_{2}\)O\({}_{2}\) dose on the overall treatment process. Quasi-similar findings are also valid in the case of \(Y_{HPLC}\) responses, as shown in Table 10.