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The carcinogenic and hard-to-dispose Cr(VI) in high-salinity industrial wastewater has caused severe environmental problems. Herein, a novel hollow spherical CuFe2O4 spinel oxide with concentrated confined oxygen vacancies (HS/CuFe2O4-OVs) was developed for Cr(VI) decontamination. Such a fancy material delivers a remarkable removal rate of 0.041 min−1, approximately-one order of magnitude higher than the commonly reported iron-based materials. The OVs in the confined space could exert dual effects on Cr(VI) removal from the aspects of enhanced stabilization via local electronic structure regulation and strengthened immobilization via electron conductivity modulation. Importantly, due to the highly sensitive response of Cr(VI) to the changed confined OVs content, the HS/CuFe2O4-OVs showed higher selectivity for Cr(VI) removal in the interference of high concentration salts than its nonhollow-structured counterpart and can successfully treat Cr(VI)-contaminated industrial wastewater with high salinity. This work opens up a new concept for rational design of robust spatial confined architectures for Cr(VI) treatment. © 2022 Elsevier B.V.

Manganese cobalt spinel oxides are promising coating materials for the protection of ferritic stainless steel interconnects in solid oxide fuel cell (SOFC) stacks. The interaction between such coatings and the steel is here studied using diffusion couples as a model system. The interaction between MnCo2O4, MnCo1.7Fe0.3O4 and MnCo1.7Cu0.3O4 spinels and Cr2O3 was studied in air at 900 °C. In allcases, a reaction layer rich in Co and Cr formed at the interfaces. Using Pt-particles to mark the original interface reveals that the reaction layers grow by diffusion of Co (and Mn) from the spinel oxides to the Cr2O3/reaction layer interface. The growth of the reaction layers followed parabolic kinetics with rate constants of 1.3×10−5 μm2 s−1 for the MnCo2O4/Cr2O3 couple, 8.6×10−6 μm2 s−1 for the MnCo1.7Fe0.3O4/Cr2O3 couple, and finally 1.2×10−4 μm2 s−1 for the MnCo1.7Cu0.3O4/Cr2O3 couple.

A ZnxCu1-xAl2O4 catalyst was prepared via the microwave-assisted solution combustion method (MSC). This method presents a fast procedure for industrial scale catalyst preparation. The physicochemical properties of the fabricated catalyst were characterized using XRD, FTIR, BET, SEM and TEM analyses. The catalytic performance through the esterification reaction was examined under the following conditions: reaction temperature = 180 degrees C, catalyst concentration = 3% (w/w), molar ratio of oleic acid to methanol = 9 and reaction time = 6 h. XRD results showed that loading both zinc and copper oxides on alumina at a ratio of amounts that were nearly the same resulted in decreased crystalline size and well-dispersed copper-alumina and zinc-alumina crystals. Moreover, the mean pore diameter of the sample was increased by simultaneous loading of zinc and copper oxides on alumina that enhanced permeation of the reactants within pores and increased the interaction of the reactant with the catalyst active sites. The catalyst showed minimum tendency towards adsorbing moisture from air, which was attributed to it having less atoms on the surface through which binding with H2O molecules takes place. The highest level of activity in the esterification reaction (96.9%) was obtained at the optimum ratio of the Zn:Cu molar ratio, identified to be 2:3. The sample particles ranged from 10 to 30 nm in size, without agglomeration. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

The effect of co-infiltration of Co2MnO4 (CM) spinel oxides and Pd on the electrochemical activity and microstructure stability of La0.7Ca0.3Cr0.5Mn0.5O3-i (LCCM) cathodes for the O2 reduction reaction of intermediate temperature solid oxide fuel cells (IT-SOFCs) has been investigated in detail. The microstructure, thermal stability, electrochemical activity and stability of the Co2MnO4–Pd/PdO owdersand Co2MnO4–Pd/PdO co-impregnated LCCM cathode were measured using thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy and electrochemical impedance spectroscopy. The results indicate that the addition of spinel oxides effectively inhibits the growth and coalescence of the Pd/PdO nanoparticles and stabilizes the microstructure of the Pd/PdO at high temperatures. The best electrochemical activity and stability of LCCM cathodes were obtained on the cathode co-infiltrated with 50 wt% PdO/50 wt% Co2MnO4. The enhancement is due to the significantly improved stability of the microstructure as a result of the inhibited grain growth and agglomeration of Pd/PdO nanoparticles by the co-infiltrated Co2MnO4 spinel phase.

Magnetic properties of the spinel system MnGaxFe1-xCrO4 have been investigated using neutron diffraction (ND) technique in the temperature range 600K >= T >= 10 K. The distribution of the magnetic moments in the tetrahedral (A) and octahedral (B) sublattices and their ordering as a function of temperature and composition has been determined. Ferrimagnetic transition temperatures and spin compensation temperatures have been determined for all the specimens. The features observed in the ND results are explained in the light of competing inter and intra-sublattice exchange interactions. A diffuse signal was found to exist below the innermost Bragg reflection with a general increase with increasing compositions indicating the formation of short-range spin clusters.