LAUSR

Abstract In this study, biogenic iron (Fe) NPs (B-Fe) were synthesized using Terminalia Bellirica plant extracts and used to activate persulfate (PS) and peroxymonosulfate (PMS) oxidants for degradation of Congo red (CR) dye. Chemogenic Fe-NPs (C-Fe) were also synthesized using borohydride reduction method for comparison. The synthesized Fe NPs were characterized for their surface morphology using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS)-based particle size analysis. Biogenic B-Fe NPs were more uniform in size and smaller (67–125 nm), compared to chemogenic C-Fe (59–277 nm), due to the capping effect of the biomolecules in plant extracts. Degradation efficiencies using the nanoparticle – oxidant system followed the order: C-Fe-PMS (86%) ∼ B-Fe-PMS (83%) > C-Fe-PS (75%) > B-Fe-PS (63%). Post-degradation UV–Vis absorbance spectra indicated the absence of intermediates in the PS/PMS systems, suggesting complete mineralization of the dye. The kinetics of the process is best described by shifting order rate kinetics. Alkaline pH conditions, low oxidant loading and high initial dye concentration hindered degradation kinetics, while catalyst loading had minimal impact on the oxidation process. The data strongly suggested that biogenic Fe NPs activated oxidant system is an effective alternative to existing hydroxyl – radical based advanced oxidation processes.