The Effect of Mediating Plant Extract on the Photocatalytic Activity of Different Eco-Friendly Synthesized Magnetite Nanoparticles Against Cresol Red Photodegradation

This study investigates the effect of mediating plant extract on the photocatalytic activities of four eco-friendly synthesized magnetite (Fe3O4) nanoparticles (NPs) against the photodegradation of cresol red (CR). For this purpose, the adsorption of CR has been carried out in dark ambient conditions at first to eliminate the impact of adsorption, followed by the recovery of Fe3O4 NPs by a centrifuge. Second, photocatalytic reactions of CR have been conducted on recovered magnetite NPs, under UV-Vis irradiation (365 nm) in ambient conditions. This study presents a novel investigation of the effect of mediating plant extract on the densities of surfacic photoactivated Brönsted and Lewis acid sites on Fe3O4 NPs against photocatalytic reactions of CR. To do so, free auxochromes and chromophores that are not reacted with photoactivated Brönsted and Lewis acid sites have been analyzed using FTIR spectroscopy. This analysis provides insights into the densities of photoactivated Brönsted and Lewis acid sites during CR photodegradation reactions on the four Fe3O4 surfaces and permits their comparison. Found results showed that, during CR photodegradation, the band gap energy is not the single parameter responsible herein for the photoactivation of acid sites and hence photocatalytic activity, but also mediating plant extract plays a crucial role. Where, a decrease in plant extract’s acidity guides to more photoactivate Lewis acid sites, and an increase in the acidity guides to more photoactivate Brönsted acid sites. Because most functional groups of CR are auxochromes that favor reacting with photoactivated Lewis acid sites, the Fe3O4 synthesized using less acidic plant extract showed the highest photocatalytic activity. These results are in accord with the calculated photodegradation capacities, yields, and kinetic rates.