## 3 Results and Discussion  
### Characterization of the Prepared Fuller's Earth Material  
Scanning electron microscopy (SEM) was used to explain the treated and calculated morphologies of the [PERSON]'s earth material; an image is displayed in Figure 2. The surface was observed to have an irregular shape, and the clay possessed lots of asymmetric, open pores. The voids aid adsorption, as well as catalytic oxidation activity, a source of various metals. Moreover, elemental analysis techniques of the [PERSON]'s earth material using an energy-dispersive X-ray analyzer (EDX) revealed its chemical composition, which constituted different oxides. The predominant oxide in the [PERSON]'s earth was SiO\({}_{2}\), as well as Al\({}_{2}\)O\({}_{3}\) and Fe\({}_{2}\)O\({}_{3}\). The presence of Al\({}_{2}\)O\({}_{3}\) and Fe\({}_{2}\)O\({}_{3}\) leads to the occurrence of the Fenton reaction. Furthermore, trace amounts of CaO, MgO, K\({}_{2}\)O, SO\({}_{3}\), and Na\({}_{2}\)O were present in the clay. A previous study [15] confirmed that the presence of Al\({}_{2}\)O\({}_{3}\) leads to the Fenton reaction [18]. Moreover, various studies [15; 16; 17; 18] verified that such oxides improve the adsorption tendency of [PERSON]'s earth clay. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Experimental Variables**} & \multicolumn{3}{c}{**Symbols**} & \multicolumn{3}{c}{**Range and Levels**} \\ \cline{2-6}  & **Uncoded** & **Coded** & \(\mathbf{-1}\) & **0** & **1** \\ \hline H\({}_{2}\)O\({}_{2}\) (mg/L) & \(\varepsilon_{1}\) & \(\zeta_{1}\) & 700 & 800 & 900 \\ [PERSON]’s earth (mg/L) & \(\varepsilon_{2}\) & \(\zeta_{2}\) & 0.75 & 1.0 & 1.25 \\ pH & \(\varepsilon_{3}\) & \(\zeta_{3}\) & 2.5 & 3.0 & 3.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Boundaries of the uncoded and coded experimental domains of the Box–Behnken factorial design with respect to their level spacing. An oxide material analysis of the [PERSON]'s earth clay data obtained via an EDX analysis is displayed in Table 2. The main oxide of the chemically treated and then calcined modified [PERSON]'s earth powder was SiO\({}_{2}\), along with Al\({}_{2}\)O\({}_{3}\) and Fe\({}_{2}\)O\({}_{3}\), with the presence of small amounts of the oxides Ca, Mg, K, and Na. The use of [PERSON]'s earth, which is considered a clay, is due to its composition. Although previous data [19] have indicated the importance of the oxides SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), and Fe\({}_{2}\)O\({}_{3}\) in enhancing the adsorption capacity of pollutants, Al\({}_{2}\)O\({}_{3}\) and Fe\({}_{2}\)O\({}_{3}\) are sources of the Fenton reaction [15; 16; 17; 18]. Such oxides might be initiated through hydrogen peroxide to generate hydroxyl radicals, which are categorized as highly reactive intermediates and possess the ability to oxidize pollutant species [13]. A Fourier transform infrared (FTIR) transmittance spectrum analysis was applied as a suggestive technique. FTIR was applied to identify the different forms of minerals present in the [PERSON]'s earth that were introduced as a source for the Fenton oxidation test. Moreover, FTIR provided information on the chemical nature of the [PERSON]'s earth substance, as well as some details about the interactions. As illustrated in Figure 3, the FTIR performances of the [PERSON]'s earth clay exhibited coupled vibrations that are mainly due to the existence of numerous elements. Additionally, the main absorption-intensive bands of [PERSON]'s earth clay appeared. Silanol, which is characterized by Si-O stretching vibrations, is located at the 1034 cm\({}^{-1}\) wavenumber. The occurrence of silanol represents the existence of quartz. Moreover, the bands at 528.4 cm\({}^{-1}\) and 779 cm\({}^{-1}\) are associated with the presence of illite, which is reflected by the Si-O-Al group. Moreover, the interlayer hydrogen bonding illustrates the possibility of hydroxyl linkage. Al-Mg-OH and Si-O-Fe bonding are reflected by the bands at 779 and 820 cm\({}^{-1}\), respectively.