Coprecipitation of Oxalates: An Easy and Reproducible Wet-Chemistry Synthesis Route for Transition-Metal Ferrites

Enhanced catalytic performance of Cu-doped MnFe2O4 magnetic ferrites: Tetracycline hydrochloride attacked by superoxide radicals efficiently in a strong alkaline environment

It is important to develop a catalyst that can maintain good activity in alkaline environment for Fenton or Fenton-like reactions. In order to achieve stable Fenton catalytic degradation in a wide pH range, this study reports Cu-doped MnFe₂O₄ heterogeneous catalysts still has excellent effect when the pH is extended to 11 for removing organic pollutants, such as tetracycline hydrochloride (TC-HCl). The synergistic effect among Fe, Mn and Cu ions has been proved to enhanced the catalytic activity in this work. When the molar ratio of Cu/Mn = 4:1, the porous Cu_0·8Mn_0·2Fe₂O₄ materials had the highest photo-Fenton catalytic activity compared with pure MnFe₂O₄, CuFe₂O₄ and other Cu_xMn_1-xFe₂O₄. The XPS showed that Cu_0·8Mn_0·2Fe₂O₄ formed oxygen vacancies, which exposed more active sites to attract more H₂O₂ for TC-HCl degradation. Results indicated 94.3% of TC-HCl was efficiently degraded by 0.1 g/L Cu_0·8Mn_0·2Fe₂O₄ with 50 mM H₂O₂ at pH = 11 under 30 min visible light irradiation, and the corresponding apparent rate constant was 0.08286 min^-1. With free radicals quenching experiment, O₂^- was responsible for the high catalytic degradation and OH was participated in the photo-Fenton reaction. To sum up, Cu_0·8Mn_0·2Fe₂O₄ exhibited high activity, great stability and easily recyclable, which eliminated the pH limitation of the Fenton reaction and provided practical application performance for water purification.

Low-temperature wet chemistry synthetic approaches towards ferrites

Solution chemistry allows the crystallisation of range of iron oxides, including MFe₂O₄ spinels, MFeO₃ perovskites and hexaferrites, such as BaFe₁₂O₁₉, with nanoscale crystallinity and properties suitable for fields such as catalysis and electronics.

Zinc-Containing Magnetic Oxides Stabilized by a Polymer: One Phase or Two?

Here we developed a new family of Zn-containing magnetic oxides of different structures by thermal decomposition of Zn(acac)2 in the reaction solution of preformed magnetite nanoparticles (NPs) stabilized by polyphenylquinoxaline. Upon an increase of the Zn(acac)2 loading from 0.15 to 0.40 mmol (vs 1 mmol of Fe(acac)3), the Zn content increases, and the Zn-containing magnetic oxide NPs preserve a spinel structure of magnetite and an initial, predominantly multicore NP morphology. X-ray photoelectron spectroscopy (XPS) of these samples revealed that the surface of iron oxide NPs is enriched with Zn, although Zn species were also found deep under the iron oxide NP surface. For all the samples, XPS also demonstrates the atom ratio of Fe(3+)/Fe(2+) = 2:1, perfectly matching Fe3O4, but not ZnFe2O4, where Fe(2+) ions are replaced with Zn(2+). The combination of XPS with other physicochemical methods allowed us to propose that ZnO forms an ultrathin amorphous layer on the surface of iron oxide NPs and also diffuses inside the magnetite crystals. At higher Zn(acac)2 loading, cubic ZnO nanocrystals coexist with magnetite NPs, indicating a homogeneous nucleation of the former. The catalytic testing in syngas conversion to methanol demonstrated outstanding catalytic properties of Zn-containing magnetic oxides, whose activities are dependent on the Zn loading. Repeat experiments carried out with the best catalyst after magnetic separation showed remarkable catalyst stability even after five consecutive catalytic runs.

Cooperative assembly synthesis of mesoporous SrTiO3with enhanced photocatalytic properties

The cooperative assembly of silica precursors and organic metal complexes leads to the synthesis of mesoporous, crystalline SrTiO₃with improved photocatalytic activity.