The spinel structure Mn3O4 and the spinel Mn3O4/ZrO2 nano-composites particles were synthesized successfully as photocatalysts by employing the co-precipitation process and ultrasonic technique, respectively. The morphology of the top mention prepared photocatalysts was distinguished using X-ray diffraction (XRD) technology and atomic force microscopy (AFM) and indicated that the mean crystal sizes and particle sizes for all studied samples were nanometric. In addition, the optical properties

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... the obtained photocatalysts were investigated using a UV-Visible spectrophotometer with Labsphere diffuse reflectance accessory to measure the bandgaps of them. Based on the Tauc equation, the bandgaps (Bg) for the studied photocatalysts were determined. The bandgaps are indirect for all samples, and it is increased in values for the nanocomposites with the increasing the ratio of ZrO2. So, the sequence of bandgaps values is: Bg spinel Mn3O4 Bg Comp.1 Bg Comp.2 Bg Comp.3 Bg ZrO2, and equal to 2.21 eV 3.15 eV 4.51 eV 4.26 eV 5.29 eV. The research revealed that the spinel Mn3O4 and the spinel Mn3O4 ZrO2 nano-composites particles were quasispherical and spherical particles respectively. Moreover, the incorporation of spinel Mn3O4 particle with ZrO2 particle was successfully carried out that was proved by XRD and AFM analyses. This work discovered that the photocatalytic reaction response via employing Fe(II)-(4,5-Diazafluoren-9-one 11) complex as model material under UV-A lamp with the use of the studied photocatalysts. The primary photo experiments for these photocatalysts found that the decolorization of Fe(II)-(4,5-Diazafluoren-9-one 11) complex is not active without addition of H2O2, that attitude is due to the very high stability of these complex with having an octahedral structure, which was proved with using mole ratio method. Whereas, after the addition of H2O2 to the aqueous solution of these complex, the activity with using the spinel Mn3O4 ZrO2 nanocomposite 3 was found to be the double active than that using the spinel Mn3O4 alone, and the sequence of phootdecolorization efficiency (E%) is being: E% composite 3 E% composite 2 E% composite 1 E% spinel Mn3O4.