The discharge of congo red dye into water sources by factories has been associated with a range of health concerns, such as cancer, redness, skin irritation, and allergic reactions. As a result, this research focused on the cost-effective and straightforward production of MgAl₂O₄ nanoparticles by using the Pechini sol-gel process. Subsequently, these nanoparticles were employed for the successful photocatalytic decomposition of congo red dye. Moreover, extensive characterization of the fabricated MgAl₂O₄ nanoparticles was conducted through diverse methodologies, which included Fourier-transform infrared spectroscopy, ultraviolet-visible spectrophotometry, high-resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FE-SEM), and powder X-ray diffraction (XRD). Furthermore, the XRD analysis disclosed that the average crystal size of the produced MgAl₂O₄ nanoparticles is 10.36 nm, and their optical energy gap was determined to be 3.71 eV. The FE-SEM examination unveiled a combination of spherical and disorganized structures with a 0.14 μm average grain size. HR-TEM analysis, in turn, revealed that the fabricated MgAl₂O₄ nanoparticles were composed of minuscule spherical particles with an average diameter of 8.75 nm. The maximum degradation of 50 mL of congo red dye at a concentration of 25 mg/L reached 99.27% within 80 min at a pH of 3. Additionally, the findings confirmed the consistent decomposition activity toward congo red dye even after four cycles, thereby validating the effectiveness and reusability of the MgAl₂O₄ nanoparticles that were developed in this study.

Photocatalytic degradation has been suggested to be a cheap and efficient way to dispose of organic pollutants, such as dyes. Therefore, our research team strives to produce nanophotocatalysts in a simple and inexpensive way. In this work, the Pechini sol–gel technique was employed for the facile synthesis of Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ and Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ as mixed metal oxide nanoparticles for the efficient photocatalytic degradation of Rhodamine B and Congo Red dyes. XRD, FT-IR, a N₂ adsorption/desorption analyzer, EDS, FE-SEM, and an UV–Vis diffuse reflectance spectrophotometer were used to characterize the produced samples. The XRD patterns revealed that the average crystallite size of the Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ and Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ samples is 90.25 and 80.62 nm, respectively. The FE-SEM images revealed that the Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ sample consists of cubic and irregular shapes with an average diameter of 1.71 µm. Additionally, the Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ sample consists of spherical shapes with an average diameter of 0.26 µm. The energy gaps of the Fe_0.5Mn_0.5Co₂O₄/Fe₂O₃ and Mn_0.5Zn_0.5Fe₂O₄/Fe₂O₃ samples are 3.50 and 4.3 eV and 3.52 and 4.20 eV, respectively. In the presence of hydrogen peroxide, the complete degradation of 100 mL of 20 mg/L of Rhodamine B and Congo Red dyes occurred at pH = 8 and 3, respectively, within 50 min, using 0.1 g of the synthesized samples.