Fabrication of Yolk/Shell Partially Inverse Spinel Cobalt Ferrite/Mesoporous Silica Nanostructured Catalysts for Organic Pollutants Degradation by Peroxymonosulfate Activation

Fabrication, functionalization and advanced applications of magnetic hollow materials in confined catalysis and environmental remediation

Magnetic hollow-structured functional hybrid materials with unique architectures and preeminent properties have always been an area of extensive research. They represent a subtle collaboration of hollow architecture, mesoporous nanostructure and magnetic character. Owing to the merits of a large void space, low density, high specific surface area, well-defined active sites and facile magnetic recovery, these materials present promising application projections in numerous fields, such as drug delivery, adsorption, storage, catalysis and many others. In this review, recent progress in the design, synthesis, functionalization and applications of magnetic hollow-meso/nanostructured materials are discussed. The first part of the review has been dedicated to the preparation and functionalization of the materials. The synthetic protocols have been broadly classified into template-assisted and template-free methods and major trends in their synthesis have been elaborated in detail. Furthermore, the benefits and drawbacks of each method are compared. The later part summarizes the application aspects of confined catalysis in organic transformations and environmental remediation such as degradation of organic pollutants, dyes and antibiotics and adsorption of heavy metal ions. Finally, an outlook of future directions in this research field is highlighted.

Synergistic activation of peroxymonosulfate via in situ growth FeCo2O4 nanoparticles on natural rectorite: Role of transition metal ions and hydroxyl groups

Developing low-cost, high-efficiency catalysts for advanced oxidation processes remain a key issue for the degradation of organic pollutants. In this study, a novel FeCo₂O₄/rectorite composite was synthesized via a facile combustion process and employed to activate peroxymonosulfate (PMS) for dealing with atrazine (ATZ). The addition of rectorite could result in higher specific surface area, smaller pore size and more hydroxyl groups, which were beneficial to enrich pollutants to the adsorption sites and provide sufficient reactive sites. After meticulous evaluation, the degradation efficiency of FeCo₂O₄/rectorite composite towards ATZ exhibited improved PMS activation efficiency which was about 2.6 times than that of pure FeCo₂O₄. Based on the characterization results, the sulfate radicals and hydroxyl radicals were considered to be the main free radicals which were involved into the circulation of Co(II)-Co(III)-Co(II) as well as the oxidation of ≡Fe(II), which was responsible for the remarkable catalytic efficiency. In addition, the chemical stability and superior catalytic performance of FeCo₂O₄/rectorite should also be attributed to the chemical combination between metal ions and the surface hydroxyl groups of rectorite. Overall, these findings are beneficial for understanding the mechanism of PMS activation by natural mineral-based catalysts and contributing to the practical application of sulfate-based technology for organic wastewater treatment.

Enhanced catalytic peroxymonosulfate activation over carbon shells encapsulating cobalt ferrite via radical and nonradical routes

Well-defined carbon shells encapsulating CoFe2O4 deliver superior performance in catalytic PMS activation for organics degradation with a reaction rate constant of 0.269 min-1, 4.7 times the hollow CoFe2O4 and 2.7 times the solid carbon sphere encapsulated one. This is attributed to the comprehensive effects of the Co2+ and C[double bond, length as m-dash]O active sites for free radical and nonradical mechanisms. The nanostructured materials outperformed most of the carbon- or cobalt-iron-based catalysts.