Combustion synthesis of mesoporous CoAl2O4 for peroxymonosulfate activation to degrade organic pollutants

A mesoporous cobalt aluminate (CoAl₂O₄) spinel is synthesized through a combustion method and adopted for the activation of peroxymonosulfate (PMS) to degrade organic pollutants. Multiple characterization procedures are conducted to investigate the morphology and physicochemical properties of the CoAl₂O₄ spinel. Due to its mesoporous structure, large surface area, and high electrical conductivity, the obtained CoAl₂O₄ exhibits remarkable catalytic activity for Rhodamine B (RhB) degradation. Its RhB degradation rate is 89.0 and 10.5 times greater than those of Co₃O₄ and CoAl₂O₄ spinel prepared by a precipitation method, respectively. Moreover, the mesoporous CoAl₂O₄ spinel demonstrates a broad operating pH range and excellent recyclability. The influence of several parameters (catalyst amount, PMS concentration, initial pH, and coexisting inorganic anions) on the oxidation of RhB is evaluated. Through quenching tests and electron paramagnetic resonance experiments, sulfate radicals are identified as the predominant reactive species in RhB degradation. This paper provides new insights for the development of efficient, stable, and reusable cobalt-based heterogeneous catalysts and promotes the application of persulfate activation technology for the treatment of refractory organic wastewater.     

Synthesis of high surface area CoAl2O4 and NiAl2O4 spinels by an alkoxide route

The mixed metal oxides CoAl₂O₄ and NiAl₂O₄ were prepared in a high surface area form by using a sol-gel method which involves hydrolysis of cobalt-aluminium and nickel-aluminium isopropoxides. The resulting gels were calcined at 673 K to yield the corresponding spinel-type metal oxides. Powder X-ray diffraction was used to confirm spinel formation. Nitrogen adsorption-desorption measurements have shown the materials obtained to be highly porous. The BET surface area was found to be 240 m²g⁻¹ for CoAl₂O₄ and 255 m²g⁻¹ for NiAl₂O₄. Both materials showed a unimodal distribution of pore radii, where the most frequent pore radius is 5 nm for cobalt aluminate and 3 nm for nickel aluminate.     

Preparation and Spectroscopic Characterization of Blue CoAl2O4 Coatings

Optically selective thin films of CoAl₂O₄ with a spinel structure were produced for an automotive lamps application by the sol-gel process using aluminum sec-butoxide, ethylacetoacetate chelating agent and cobalt nitrate hexahydrate. The use of two metal-oxide precursors is advantageous over the single bimetallic alkoxide precursor (aluminum cobalt isopropoxide), because it allows us to vary the Co/Al ratio in the precursor solution. We found that the Co/Al ratio should not exceed 0.3 if we are to achieve films with the characteristic blue colour at 700°C. The structural characteristics of the oxide powders were determined from infrared (IR) spectra and X-ray diffraction (XRD) analysis, while the optical properties of the films were investigated with UV-VIS spectroscopy.     

Gasification reaction of organic compounds catalyzed by RuO2 in supercritical water

Nearly complete gasification of organic compounds has been achieved by stoichiometrically insufficient amounts of RuO2 in supercritical water (SCW) to provide CH4, CO2 and H2, all the hydrogen atoms of which originate from water, and the catalytic effect of RuO2 results from a redox couple of Ru(IV)/Ru(II) induced by SCW.     

CoAl2O4/Al2O3载体对钴基费托催化剂反应性能影响的研究

通过浸渍和高温焙烧,制得表面附着CoAl₂O₄微晶颗粒的改性Al₂O₃载体,并采用等体积浸渍法制备负载型Co基催化剂。结合 N₂物理吸附、XRD、H₂-TPR、XPS及H₂化学吸附等表征手段,研究改性载体及其负载钴基催化剂的织构特征;采用费托合成反应评价其催化性能。结果表明,Al₂O₃改性后,表面CoAl₂O₄的存在有效减少了载体与活性组分Co的相互作用,显著提高了催化剂的还原度和催化活性。载体的改性量在20%左右达到最佳值,继续增加,催化剂还原度和活性基本不再升高。载体改性促使催化剂CH₄选择性有所降低,C₅₊选择性略有提高。     

CoAl2O4包覆LiNi1/3Co1/3Mn1/3O2的电化学性能

通过共沉淀法制得类球形锂离子电池正极材料LiNi_1/3Co_1/3Mn_1/3O₂,并用非水相共沉法对其进行CoAl₂O₄包覆得到LNCMO(x). 采用X射线衍射（XRD）、扫描电子显微术（SEM）和透射电子显微术（TEM）测试材料的结构和观察材料形貌. 结果表明,CoAl₂O₄在材料表面形成8 nm均匀包覆层,未改变主体材料的结构. 电化学性能测试表明,1%（by mass）CoAl₂O₄包覆量的LiNi1/3Co1/3Mn1/3O2材料（LNCMO(1)）高充电电压（3.0 ~ 4.6 V,150 mA·g^-1）100周期循环放电容量保持率为93.7%（无包覆LNCMO(0)保持率为74.4%）;55 °C高温100周期循环容量保持率为77%（无包覆LNCMO(0)保持率17%）. XRD和电感耦合等离子体原子发射光谱（ICP-AES）测试表明,CoAl₂O₄包覆的LNCMO(x)材料可有效地减缓材料中Mn离子在电解液的溶解,提高材料结构稳定性和热稳定性.     

Periodic DFT study of the structural and electronic properties of bulk CoAl2O4 spinel

In this study, structural and electronic properties of CoAl2O4 spinel are investigated for the first time by means of quantum chemical computational tools. Coupling supercell periodic calculations under the density functional theory formalism with a nonempirical quasi-harmonic Debye model, we examine the influence of temperature on the relative stability of several cation distributions of Co2+ and Al3+ over tetrahedral and octahedral interstices of the oxygen sublattice. Our simulations are able to reproduce the experimentally observed trend: (i) the normal spinel is calculated to be the stable structure at static and low-temperature conditions, and (ii) as the temperature increases, the preference of structures with Al3+ at tetrahedral sites (and Co2+ at octahedral sites) is found to progress following an asymptotic conduct. The effects of the cation distributions on geometrical variations of electronic and magnetic properties of CoAl2O4 can be interpreted as dominated by the local behavior of Co2+ at octahedral sites.     

The heat capacities and thermodynamic properties of NiAl2O4 and CoAl2O4 measured by adiabatic calorimetry from T = (4 to 400) K

The low-temperature heat capacity of NiAl₂O₄ and CoAl₂O₄ was measured between T = (4 and 400) K and thermodynamic functions were derived from the results. The measured heat-capacity curves show sharp anomalies peaking at around T = 7.5 K for NiAl₂O₄ and at T = 9 K for CoAl₂O₄. The exact cause of these anomalies is unknown. From our results, we suggest a standard entropy for NiAl₂O₄ at T = 298.15 K of (97.1 ± 0.2) J · mol^?1 · K^?1 and for CoAl₂O₄ of (100.3 ± 0.2) J · mol^?1 · K^?1.     

超(近)临界水中的有机合成反应

作为一种环境友好的化学工艺过程,以超(近)临界水作有机合成反应介质越来越受到人们的关注。人们考察了在超(近)临界水中的许多有机反应,并获得了预期的结果。综述了近年来超(近)临界水中的有机合成反应的研究进展。     

Reactions of N2O4 with organic compounds

The previously described method for the one-step synthesis of aryltrinitromethanes from araldoximes may be utilized for the preparation of trinitromethyl derivatives of pyridine and thiophene. In the latter case, in addition to the conversion of the oxime group into the trinitromethyl group, nitration of the thiophene ring also occurs.For part VII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 590–591, May, 1970.     

Surface modification of hollow microsphere Li1.2Ni1/3Co1/3Mn1/3O2 cathode by coating with CoAl2O4

Journal of Solid State Electrochemistry - Li1.2Ni1/3Co1/3Mn1/3O2 was synthesized as a cathode material for lithium-ion batteries and coated with various amounts of CoAl2O4 (0–5 wt%)...     

Synthesis of organic monolayer-stabilized copper nanocrystals in supercritical water

When water is heated and pressurized above the critical point, it becomes a suitable solvent to employ organic capping ligands to control and stabilize the synthesis of nanocrystals. Without alkanethiol ligands, Cu(NO(3))(2) hydrolyzes to form polydisperse copper(II) oxide particles with diameters from 10 to 35 nm. However, in the presence of 1-hexanethiol, X-ray photoelectron spectroscopy, selected area electron diffraction, and transmission electron microscopy reveal the formation of copper nanocrystals approximately 7 nm in diameter. The use of a different precursor, Cu(CH(3)COO)(2), leads to particles with significantly different morphologies. A mechanism is proposed for sterically stabilized nanocrystal growth in supercritical water that describes competing pathways of hydrolysis to large oxidized copper particles versus ligand exchange and arrested growth by thiols to produce small monodisperse Cu nanoparticles.     

Enhanced photocatalytic removal of hexavalent chromium and organic dye from aqueous solution by hybrid bismuth titanate Bi4Ti3O12/Bi2Ti2O7

Research on Chemical Intermediates - A hybrid bismuth titanate Bi4Ti3O12/Bi2Ti2O7 obtained via a one-step annealing procedure was employed as photocatalyst to oxidize rhodamine B dyes (RhB) and...     

Synthesis of pyrazol-quinazolinones and 2,3-dihydroquinazolin-4(1H)-ones using CoAl2O4 nanoparticles as heterogeneous catalyst

Journal of the Iranian Chemical Society - The preparation and characterization of cobalt aluminate (CoAl2O4) magnetic nanoparticles and its application as a catalyst for the synthesis of a novel...     

The reaction of N2O4 with organic compounds

The reaction of N₂O₄ with oximes of formylimidazoles is examined. It is shown that, in addition to the conversion of the oxime group to trinitromethyl, nitration of the imidazole ring occurs including nitration in the 2-position, which is not activated towards electrophilic substitution in acid media.For part VIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 669–673, May, 1970.     

Technique for complete oxidation of organic compounds in supercritical water

Results are presented of tests of a pilot stationary installation for supercritical water oxidation of organic compounds, first created in Russia. A high oxidation efficiency of nitro compounds formed as waste in manufacture of explosives is demonstrated.