Optimizing operational parameters for improved photocatalytic activity of hematite–rGO nanocomposites in methylene blue dye degradation

The α-Fe2O3/rGO nanocomposites with varying GO concentrations were successfully synthesized utilizing the co-precipitation method followed by annealing. FESEM investigation revealed that the nanocomposites were composed of quasi-spherical α-Fe2O3 nanoparticles with an average particle size of 32.77 nm which were distributed on the wrinkled rGO sheets. Further, the elemental mapping of FESEM confirms that carbon is the dominant component with 66.26 at.%. The nanocomposites were studied for degrading methylene blue dye under varying conditions like photocatalyst load, dye concentration, light intensity, and pH. The photocatalyst load of 0.4 g/L gives the best results at the dye concentration of 5.34 µM. On the other hand, as load and dye concentrations increased further, the nanocomposite’s photocatalytic activity reduced. The nanocomposites were also found to be effective in degrading MB dye molecules under high light intensity and alkaline pH. The impact of operational parameters on nanocomposite’s degrading efficiency was examined in depth by contrasting their deterioration rate constant values, which were derived from the Langmuir–Hinshelwood model. Additionally, a suitable mechanism has been mentioned to explain the outcomes of photocatalytic activity. The highest doped nanocomposite with 0.4 g/L load at 5.34 μM initial dye concentration, high light intensity, and pH 12 had the maximum degradation efficiency of 94%. Graphical abstract