*Article* **Magnetite, Hematite and Zero-Valent Iron as Co-Catalysts in Advanced Oxidation Processes Application for Cosmetic Wastewater Treatment**

**Jan Bogacki \* , Piotr Marcinowski , Dominika Bury , Monika Krupa, Dominika Scie ´ zy ´nska and ˙ Prasanth Prabhu**

> Faculty of Building Services, Hydro and Environmental Engineering, Warsaw University of Technology, 00-653 Warsaw, Poland; piotr.marcinowski@pw.edu.pl (P.M.); dominika2609@o2.pl (D.B.); monika.krupa@onet.eu (M.K.); domino233@wp.pl (D.S.); lytic.sam@gmail.com (P.P.) ´ **\*** Correspondence: jan.bogacki@pw.edu.pl

**Abstract:** Background: There is a need for more effective methods of industrial wastewater treatment. Methods: Cosmetic wastewater was collected and subjected to H2O2/Fe3O4/Fe2O3/Fe<sup>0</sup> and UV/H2O2/Fe3O4/Fe2O3/Fe<sup>0</sup> process treatment. Results: Total organic carbon (TOC) was decreased from an initial 306.3 to 134.1 mg/L, 56.2% TOC removal, after 120 min of treatment for 1:1 H2O2/COD mass ratio and 500/500/1000 mg/L Fe3O4/Fe2O3/Fe<sup>0</sup> catalyst doses. The application chromatographic analysis allowed for the detection and identification of pollutants present in the wastewater. Identified pollutants were removed during the treatment processes. Processes carried out at a pH greater than 3.0 were ineffective. The UV process was more effective than the lightless process. Conclusions: The applied processes are effective methods for wastewater treatment. Chromatographic results confirmed the effectiveness of the treatment method. The kinetics of the process were described by the modified second-order model. On the basis of ANOVA results, the hypothesis regarding the accuracy and reproducibility of the research was confirmed.

**Keywords:** industrial wastewater; advanced oxidation processes; zero valent iron; magnetite; hematite
