Synthesis of a Co/Ni-MOF-74@PDI Z-scheme photocatalyst as a highly efficient photo-assisted Fenton-like catalyst for the removal of chlortetracycline hydrochloride

In this paper, ultra-thin nanofiber PDI was obtained by self-assembly dispersion of commercial PDINH. A novel Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material was constructed by a simple solvothermal method. XRD, SEM, TEM, FT-IR and other characterization techniques proved the successful preparation of the Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material. By degrading chlortetracycline hydrochloride, it was found that the photocatalytic activity of Co/Ni-MOF-74@PDI was much higher than that of pure Co/Ni-MOF-74 and PDI. Subsequently, Co/Ni-MOF-74@PDI was used to activate H2O2 to further improve the degradation efficiency of chlortetracycline hydrochloride. It was found that the photocatalytic performance was greatly improved after the addition of 19.6 mM H2O2 to the system, and the degradation rate of chlortetracycline hydrochloride was 87% within 90 min. The electron transfer pathway and H2O2 activation mechanism of the Co/Ni-MOF-74@PDI composite photocatalyst were proved by free radical quenching experiments, electron paramagnetic resonance analysis and X-ray electron spectroscopy. Finally, the easy exfoliation point and degradation pathway of chlortetracycline hydrochloride were studied using density functional theory, UPLC-MS and toxicity evaluation software. It was found that the main active substances were h+, ˙O2, 1O2 and ˙OH, and the toxicity of chlortetracycline hydrochloride and its intermediates was evaluated.

Double activating peroxymonosulfate with g-C3N4/Fe2(MoO4)3 to enhance photocatalytic activity under visible light irradiation

The peroxymonosulfate was double activated by photogenerated e−/h+ and Fe(iii).

Crystal morphology control of synthetic giniite for enhanced photo-Fenton activity against the emerging pollutant metronidazole

Metronidazole (MNZ) is a recalcitrant antibiotic with toxic and carcinogenic effects in aquatic environments. In this work, Fe₅(PO₄)₄(OH)₃·2H₂O (giniite) particles were synthesised with three different alkaline cations (Li⁺, Na⁺ and K⁺) and used as Fenton catalysts for MNZ removal. It is shown that the addition of different cations during the hydrothermal synthesis process promote different morphologies from asterisk-like to flower-like and branches-like, maintaining the crystalline structure of pure giniite. The photo-Fenton activity of these particles was then evaluated through the degradation of MNZ under sunlight radiation for 9 h. The results indicate that the alkaline cation has a predominant role in the photo-Fenton efficiency, as demonstrated by the superior degradation efficiencies of Na@giniite particles (91.2% and 72.5% with giniite concentration of 0.2 g L^-1 and 0.07 g L^-1, respectively), related with its high surface area (10.7 m² g^-1). Thus, it is demonstrated the suitability of Na@giniite particles as Fenton catalyst for MNZ removal from water.

Hollow single-crystalline octahedra of hydrated/dehydrated hydroxyl ferric phosphate and crystal-water-enhanced electrochemical properties of the hydrated sample for reversible lithiation–delithiation

Crystal water could modify lattice cell parameters and improve the lithium intercalation capability of Fe₅(PO₄)₄(OH)₃·2H₂O hollow single-crystalline octahedra.

Partial-Redox-Promoted Mn Cycling of Mn(II)-Doped Heterogeneous Catalyst for Efficient H2O2-Mediated Oxidation

The development of a heterogeneous catalyst with high catalytic activity and durability for H₂O₂-mediated oxidation is one of the most important industrial and environmental issues. In this study, a Mn(II)-doped TiO₂ heterogeneous catalyst was developed for H₂O₂-mediated oxidation. The TiO₂ substrate-dependent partial-redox behavior of Mn was identified on the basis of our density functional theory simulations. This unique redox cycle was induced by a moderate electron transfer from Ti to Mn, which compensated for the electron loss of Mn and finally resulted in a high-efficiency cycling of Mn between its oxidized and reduced forms. In light of the theoretical results, a Mn(II)-doped TiO₂ composite with well-defined morphology and large surface area (153.3 m² g^-1) was elaborately fabricated through incorporating Mn(II) ions into a TiO₂ nanoflower, and further tested as the catalyst for oxidative degradation of organic pollutants in the presence of H₂O₂. Benefiting from the remarkable textural features and excellent Mn cycling property, this composite exhibited superior catalytic performance for organic pollutant degradation. Moreover, it could retain 98.40% of its initial activity even in the fifth cycle. Our study provides an effective strategy for designing heterogeneous catalytic systems for H₂O₂-mediated oxidations.

Ferric Phosphate Hydroxide Microstructures Affect Their Magnetic Properties

Uniformly sized and shape-controlled nanoparticles are important due to their applications in catalysis, electrochemistry, ion exchange, molecular adsorption, and electronics. Several ferric phosphate hydroxide (Fe4(OH)3(PO4)3) microstructures were successfully prepared under hydrothermal conditions. Using controlled variations in the reaction conditions, such as reaction time, temperature, and amount of hexadecyltrimethylammonium bromide (CTAB), the crystals can be grown as almost perfect hyperbranched microcrystals at 180 °C (without CTAB) or relatively monodisperse particles at 220 °C (with CTAB). The large hyperbranched structure of Fe4(OH)3(PO4)3 with a size of ∼19 μm forms with the "fractal growth rule" and shows many branches. More importantly, the magnetic properties of these materials are directly correlated to their size and micro/nanostructure morphology. Interestingly, the blocking temperature (T B) shows a dependence on size and shape, and a smaller size resulted in a lower T B. These crystals are good examples that prove that physical and chemical properties of nano/microstructured materials are related to their structures, and the precise control of the morphology of such functional materials could allow for the control of their performance.

A review of BiPO4, a highly efficient oxyacid-type photocatalyst, used for environmental applications

This review presents the recent progress on the oxyacid-type photocatalyst, BiPO₄, which possesses excellent UV-activity for environmental applications.

Synthesis of Fe2(MoO4)3 microspheres by self-assembly and photocatalytic performances

The difference in photocatalytic activities for Fe₂(MoO₄)₃ microspheres is mainly attributed to defects.