**4. Conclusions**

In the current investigation, Levafix dye oxidation as an example of reactive dye molecules in aqueous media was conducted using a modified Fenton technique with Fuller's earth as the elemental catalyst source. SEM and FTIR suggested that the oxidation reaction was highly efficient due to the presence of a porous medium and elemental sources. The Levafix Dark Blue dye removal rates verified the effectiveness of the Fuller's earth-based Fenton treatment system. Response surface methodology based on a Box– Behnken factorial design was used to optimize the operating conditions, and the optimum values were 818 and 1.02 mg/L for Fuller's earth and hydrogen peroxide, respectively. This investigation found that using an optimal pH of 3.0 resulted in a 99% removal rate within 15 min of the illumination time. The kinetic rate equation for the system was best modeled by a second-order equation that well fitted the experimental results. The data of the experimental work, coupled with the calculated thermodynamic parameters, verified the significance of the system in removing azo dye. Therefore, this study demonstrates a sustainable and environmentally benign Fenton system since it is based on a naturally occurring catalyst. It is worth mentioning that the results of the current study have led to the application of such a technique in real textile wastewater effluent. However, more data are required to apply such a system to real textile effluent for both scientists and industrial operators. Additionally, much effort can be made to better design solar photocatalysis to satisfy the industrial sector and operate in a more economic flexible system to meet wastewater treatment requirements. Thus, upgrading such technology could highlight a new opportunity for the industrial sector.

**Author Contributions:** Conceptualization, M.A.T.; methodology, M.M.N. and M.A.T.; software, H.A.N.; formal analysis, H.A.N.; investigation, M.A.T.; data curation, H.A.N.; writing—original draft, M.M.N. and M.A.T.; writing—review and editing, M.A.T. and H.A.N.; project administration, M.M.N.; funding acquisition, M.M.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors extend their appreciation to Prince Sattam bin Abdulaziz University for funding this research work through project number (PSAU/2023/01/31544).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data are available upon request.

**Acknowledgments:** The authors extend their appreciation to Prince Sattam bin Abdulaziz University for funding this research work.

**Conflicts of Interest:** The authors declare no conflict of interest.
