Effective photocatalytic degradation of dye pollution in synthetic wastewater using nanocomposites of chromium and potassium oxides

In the present work, chromium(III) oxide (Cr2O3) and potassium oxide (K2O) nanoparticles (NPs) were synthesized using the combustion method. Mixed oxides of varying concentrations in the form of (1-x)Cr2O3/xK2O (x = 0.1, 0.3, 0.5, and 0.7) were prepared. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and optical measurements were used to investigate the properties of NPs. XRD indicates that the grain size of the mixed oxides decreased as the K2O content increased. Additionally, HRTEM revealed several types of shapes, such as hexagonally shaped NPs. The optical measurements showed a blue shift, indicating that the band structure was slightly modified during the Cr2O3/xK2O mixing. The optical band gap obeys the direct allowed transition and varies from 2.29 to 2.59 eV as the K2O ratio in the compos-ites increases from x = 0.1 to 0.7. The (1-x)Cr2O3/xK2O NPs were used as catalysts in wastewater during a photocatalytic process. Orange G was chosen as an impurity in the water. The absorbance curves of Orange G in the water were measured at different times in the presence of the same quantity of Cr2O3/xK2O NPs. It was found that after 120 min, the efficiency reached 11% and 33% for (1-x)Cr2O3/xK2O NPs with x = 0.1 and 0.7, respectively. Furthermore, the experimental results were analyzed by pseudo-first-order model. A first-order kinetic model had the best fit for the (1-x)Cr2O3/xK2O NPs. The strongest relationship occurred with a composition of 0.1Cr2O3/0.7K2O. The formed composites could be used to degrade organic dyes for water purification.