A brief study on the kinetic aspect of the photodegradation and mineralization of BiOI-Ag3PO4 towards sodium diclofenac

Bismuth oxyiodide and silver phosphate nanoparticles (NPs) were synthesized in-situ and mechanically mixed to obtain BiOI-Ag3PO4 nano-composite (NC). A body-centered cubic structure of Ag3PO4 and the tetragonal BiOI were detected in the XRD pattern of NC with a crystallite size of 37 nm (obtained by Scherrer equation). The absorption edge wavelengths (lambda(AE)) of 571, 665, and 745 nm were respectively obtained for the Ag3PO4, BiOI, and the NC samples, corresponding to the bandgap energies of 2.17, 1.86 and 1.66 eV, respectively. BiOI, Ag3PO4, and the NC catalysts degraded about 37, 48, and 61% of diclofenac (DCF) molecules, respectively. The composites with the Ag3PO4: BiOI mole ratios of 1:4 and 2:1 showed the highest photocatalytic activities, and the apparent first-order rate constants of 0.0187 and 0.0224 min(-1), respectively. The photodegradation of DCF molecules showed an apparent rate constant of 0.024 min(-1) corresponds to t(1/2) value of 28.9 min. The DCF mineralization also showed an apparent rate constant of 0.029 min(-1) which corresponds to t(1/2) value of 23.9 min obtained by applying the Hinshelwood model on the results obtained by COD results of the photodegraded DCF solutions.