Fe3O4@HAP-enhanced photocatalytic degradation of Acid Red73 in aqueous suspension: Optimization, kinetic, and mechanism studies

This study investigated the photocatalytic activity of synthesized magnetite hydroxyapatite nanoparticles (Fe3O4@HAP) for the removal of an acid dye. Results of Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD) pattern and scanning electron microscope (SEM) analysis revealed clearly the characteristic bands of HAP groups and Fe3O4, the crystalline structure, and the surface morphology of this nanostructured catalyst, respectively. According to the batch experiments, increasing the Fe3O4@HAP dose could successfully develop the photocatalytic activity of Acid Red73 (AR73). Accordingly, the degradation efficiency of AR73 was achieved around 97% under the optimal conditions of UV irradation for 1 h, a good photocatalytic activity. However, this performance was not high in real environment (64% removal of AR73). The results obtained from the chemical oxygen demand (COD) also illustrated that Fe3O4@HAP had a good performance in decomposing acid dye (93.3% removal of AR73). The pseudo-first-order Langmuir-Hinshelwood model could best describe degradation kinetics in equilibrium conditions which can be used for predicting the degradation rate at different initial concentrations of AR73. The high recoverability of catalyst on AR73 degradation efficiency in sequential cycles indicates the use of the proposed catalyst without any significant effect on the capability of degradation.