Preparation of biotic and abiotic iron oxide nanoparticles (IOnPs) and their properties and applications in heterogeneous catalytic oxidation

Abstract

Iron oxide nanoparticles (IOnPs) as solid catalyst were prepared using a biotic method, i.e., biomineralization, and abiotic methods, i.e., thermal decomposition and electrochemical methods, for use as solid catalysts in the heterogeneous catalytic ozonation of para-Chlorobenzoic acid (pCBA). It was determined that characteristics of IOnPs, including particle size, morphology, surface area, electrokinetic mobility, basic group content, and chemical composition were significantly influenced by the preparation methods. TEM and FE-SEM analyses showed that the thermal decomposition method produced monodispersed and regularly spherical particles. The smallest iron oxide was also prepared by the thermal decomposition method, whereas the electrochemical method produced the largest iron oxide in terms of mean particle size. The specific surface area was found to be inversely proportional to the mean particle size. In catalytic ozonation at acidic pH levels, it was clearly observed that IOnPs enhanced the degradation of pCBA by the production of circle OH radicals resulting from the catalytic decomposition of ozone. Additionally, functional groups and surface area were found to play an important role in the catalytic activity of IOnPs. To this extend, in a comparison of particle types, IOnPs prepared by the thermal decomposition method (IOTD) showed the greatest catalytic activity in terms of R-ct value representing the ratio of hydroxyl radicals and ozone. This result may be due to the relatively higher surface area and basic group content of IOTD than other IOnPs.