Nano-crystallite bones of Oreochromis niloticus and Katsuwonus pelamis for the photocatalytic degradation of Congo red dye

The bones of two fish species, Oreochromis niloticus and Katsuwonus pelamis, were chosen in this research for evaluating their photocatalytic efficacy under solar radiation. The fish bones were isolated and conditioned before analyzing crystallographic parameters. The samples were characterized by using different instrumental techniques such as Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), Field Emission Scanning Electronic Microscopy (FESEM), and optical bandgap. From the XRD data, various types of crystallographic information such as crystallite size, microstrain, lattice parameters, dislocation density, degree of crystallinity, crystallinity index, Hydroxylapatite (HAp), the volume fraction of β-TCP, β-Tricalcium phosphate (β-TCP) percentage, and specific surface area were evaluated. Different model equations such as the Sahadat-Scherrer model, Linear Straight-line model, Monshi–Scherrer's method, and Williamson–Hall plot were employed to justify the nano-crystallite size. The photocatalytic efficacy of the two types of samples was explored by changing the catalyst concentration, dye concentration, interaction time, pH of the solution, etc. under solar irradiation.