A review of application mechanism and research progress of Fe/ montmorillonite-based catalysts in heterogeneous Fenton reactions

To mitigate the problem of excessive iron sludge production inherent in homogeneous Fenton reactions, heterogeneous Fenton processes have been developed, replacing dissolved iron with solid catalysts containing iron. The advancement of Fe -based catalysts, which synergize iron oxide with porous supports (e. g. montmorillonite, molecular sieves, ion exchange resins, carbon materials, activated alumina, silica, and graphite oxide) has garnered significant interest in the scientific community. Among these supports, montmorillonite stands out as a naturally occurring, environment-friendly material, characterized by its high specific surface area and good cation exchange capacity. Iron-based heterogeneous Fenton catalysts employing montmorillonite as a support have demonstrated notable catalytic activity in both decomposing hydrogen peroxide and the removing organic pollutants. However, there is few comprehensive reviews systematically reporting the synthesis, characterization, and applications of Fe/montmorillonite-based heterogeneous Fenton catalysts. Therefore, it is crucial to thoroughly summarize the performances of various Fe/montmorillonite-based catalysts in heterogeneous Fenton systems and elucidate the activation mechanisms that these catalysts employ for different oxidants. On the basis, this article reviews the research status of Fe/montmorillonite, Fe/Al/montmorillonite, and Fe/Cu/montmorillonite heterogeneous Fenton catalysts, which are the focus of current research. Moreover, this paper delves into recent advancements in the application of Fe/montmorillonite within photo-assisted heterogeneous Fenton processes, especially for degrading organic pollutants in aqueous solutions. The aim of this review is to offer a more comprehensive understanding of the various preparation methods for Fe/montmorillonite-based catalysts and the underlying mechanisms of pollutant degradation in heterogeneous Fenton processes. Furthermore, it analyzes the future development directions of Fe/montmorillonite-based Fenton catalysts.