**5. Conclusions**

Due to the increasing consumption of cosmetics, an effective and inexpensive method of CW treatment is needed. The effective treatment of CW in accordance with applicable legal standards is difficult. The results of this research confirmed the effectiveness of the pretreatment of wastewater currently used by most industrial plants with the use of C/DAF.

CW can be effectively treated with both the UV/H2O2/Fe3O4/Fe2O3/Fe<sup>0</sup> and the H2O2/Fe3O4/Fe2O3/Fe<sup>0</sup> process. The condition for the application of an effective CW treatment by catalytic oxidation is the use of an appropriate dose of hydrogen peroxide as a catalyst.

The best match of the results to kinetic models was obtained by second-order equations with a modification, taking into account the amount of undegraded compounds during the treatment process.

On the basis of the ANOVA results, the hypothesis regarding the accuracy and reproducibility of the research was confirmed.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/2073-4 344/11/1/9/s1, Table S1: Experimental setup, Table S2: One-way analysis of variance for mean values of TOC for 1:1 H2O2/COD ratio, Table S3: One-way analysis of variance for mean values of TOC for 2:1 H2O2/COD ratio. Figure S1: GC-MS chromatogram: Raw wastewater, Figure S2: GC-MS chromatogram: Treated wastewater, 500/500/1000 mg/L Fe3O4/Fe2O3/Fe<sup>0</sup> catalyst doses, 1:1 H2O2/COD ratio, pH = 3.0, 120 min, Figure S3: The emission spectrum of the lamp, Figure S4: Anova plots of the UV/H2O2/Fe3O4/Fe2O3/Fe<sup>0</sup> process, Figure S5: Anova plots of the H2O2/Fe3O4/Fe2O3/Fe<sup>0</sup> process.

**Author Contributions:** Conceptualization, methodology, writing—original draft preparation, review and editing, supervision: J.B. and P.M.; laboratory work and data processing: J.B., P.M., D.B., M.K., D.S. and P.P. All authors have read and agreed to the published version of the manuscript. ´

**Funding:** This research received no external funding.

**Acknowledgments:** The authors thank Hepure for providing ZVI Ferox Target samples as research material.

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