Effect of gamma-irradiation on surface and catalytic properties of CuO−ZnO/Al2O3 system

Design and Development of Novel Composites Containing Nickel Ferrites Supported on Activated Carbon Derived from Agricultural Wastes and Its Application in Water Remediation

Recently, efficient decontamination of water and wastewater have attracted global attention due to the deficiency in the world's water sources. Herein, activated carbon (AC) derived from willow catkins (WCs) was successfully synthesized using chemical modification techniques and then loaded with different weight percentages of nickel ferrite nanocomposites (10, 25, 45, and 65 wt.%) via a one-step hydrothermal method. The morphology, chemical structure, and surface composition of the nickel ferrite supported on AC (NFAC) were analyzed by XRD, TEM, SEM, EDX, and FTIR spectroscopy. Textural properties (surface area) of the nanocomposites (NC) were investigated by using Brunauer-Emmett-Teller (BET) analysis. The prepared nanocomposites were tested on different dyes to form a system for water remediation and make this photocatalyst convenient to recycle. The photodegradation of rhodamine B dye was investigated by adjusting a variety of factors such as the amount of nickel in nanocomposites, the weight of photocatalyst, reaction time, and photocatalyst reusability. The 45NFAC photocatalyst exhibits excellent degradation efficiency toward rhodamine B dye, reaching 99.7% in 90 min under a simulated source of sunlight. To summarize, NFAC nanocomposites are potential photocatalysts for water environmental remediation because they are effective, reliable, and reusable.

Efficient and Eco-Friendly Perspectives for C-H Arylation of Benzothiazole Utilizing Pd Nanoparticle-Decorated Chitosan

In this contribution, an eco-friendly, sustainable, and efficient palladium nanoparticle-decorated chitosan (Pd@Chitosan) catalyst was synthesized by a simple impregnation method. The synthesized material was utilized as a heterogeneous catalyst for the C-H arylation of benzothiazole under ultrasonic irradiation. The Pd@Chitosan catalyst efficiently catalyzed the conversion of aryl iodides and bromides to 1-(4-(benzothiazol-2-yl)phenyl)ethan-1-one selectively. A single product of 83–93% yield was obtained in N,N-dimethylformamide solvent at 80 °C for 2.5h. This study reveals that Pd@Chitosan is an efficient catalyst, which catalyzes the C-H arylation with good reaction yields. The activity of the Pd@Chitosan is due to the presence of highly dispersed Pd(0) nanoparticles on the surface of the chitosan and Pd2+; a tentative mechanism was proposed based on the XPS results of the fresh catalyst and spent catalyst.

Effects of γ-Irradiation on the Surface and Catalytic Properties of Co3O4/MgO Systems Aged for One Year

The effects of γ-rays (20–160 Mrad) on the surface and catalytic properties of two Co3O4/MgO systems were investigated. The formulae of the investigated solids were 0.05Co3O4/MgO and 0.2Co3O4/MgO, respectively, both prepared by the impregnation method and calcined at 500°C. The irradiated samples were left for one year in sealed tubes before any measurements were undertaken.

γ-Irradiation of the investigated solids resulted in a progressive decrease in the particle size of the Co3O4 and MgO phases. This treatment also led to a measurable increase in the specific surface area of the treated solids to an extent proportional to the γ-ray dosage. Treatment of the Co3O4/MgO system with different doses of γ-rays brought about a significant increase in the catalytic activity expressed both as the reaction rate constant and as the reaction rate constant per unit surface area. However, the curve relating to the catalytic activity and dosage of γ-rays showed maxima located at 40 and 80 Mrad for samples having the formula 0.05Co3O4/MgO and 0.2Co3O4/MgO, respectively. Furthermore, samples exposed to 160 Mrad showed a larger catalytic activity than the unirradiated samples.

The results demonstrate the role of γ-rays in inhibiting the deterioration of the catalytic activity of the investigated systems as a function of aging time. The irradiation process did not modify the activation energy of the catalyzed reaction but altered the concentration of active centres on the surfaces of the solids without changing their energetic nature.

Catalytic Decomposition of H2O2 over a γ-Irradiated CuO–ZnO/Al2O3 System

A CuO–ZnO/Al2O3, catalyst sample was prepared by wet impregnation methods using Al(OH)3, zinc and copper nitrate solutions followed by drying at 110°C and calcination at 600°C. The nominal molar composition of the resulting material was calculated to be 0.25CuO · 0.03ZnO/Al2O3 Samples of this solid were exposed to varying dosages of γ-irradiation (20–160 Mrad) and the effect of such treatment on their surface characteristics and catalytic activity investigated using nitrogen adsorption studies at −196°C and studies of the decomposition of H2O2 at 30–50°C.

The results obtained indicate that doses of γ-rays up to 80 Mrad had no significant effect on the specific surface area. SBET, of the supported mixed oxide material although this quantity increased by 20% when the solid was exposed to γ-irradiation doses of 160 Mrad. In contrast, such treatment brought about a progressive decrease in the catalytic activity of the treated catalyst samples. Thus, the reaction rate constant (k) of the catalyzed reaction measured at 50°C diminished from 8 × 10−2 min−1 to 0.3 × 10−2 min−1 on exposure of the supported mixed oxide material to a dose of 160 Mrad. What was surprising was that the activation energy (δE) of the catalytic reaction decreased as a function of the dose employed whereas it should have been expected to increase in the light of the observed decrease in the catalytic activity. This apparent discrepancy was resolved by recalculating the values of ΔE taking into account any possible changes in the pre-exponential factor of the Arrhenius equation brought about by γ-irradiation. The observed decrease in the catalytic activity due to treatment with γ-rays was attributed, mainly, to the enhanced removal of Brönsted acid centres by the action of such irradiation.

Physicochemical Surface and Catalytic Properties of the Na2O-doped CuO–ZnO/Al2O3 System

In order to investigate the effect of Na2O doping (0.75–4.5 mol%) on metal oxide-support interactions, the surface and catalytic properties of the CuO–ZnO/Al2O3 system have been studied using XRD, nitrogen adsorption at -196°C and the catalytic oxidation of CO by O2 at 150–200°C. Pure and doped mixed oxide solid samples were prepared via the wet impregnation method using Al(OH)3, NaNO3. Zn(NO3)2 and Cu(NO3)2 solutions, followed by drying and calcination at 600°C and 700°C.The nominal composition of the solids thus prepared was 0.25CuO:0.06ZnO: Al2O3.

The results obtained showed that Na2O doping followed by heating in air at 600°C leads to enhanced crystallization of the CuO crystallites to an extent proportional to the amount of dopant present, while doping followed by heating in air at 700°C hinders the solid–solid interactions between CuO andA12O3, and leads to the production of CuAl2O4. The specific surface area was found to increase progressively as a function of the dopant concentration for the solid calcined at 700°C. The catalytic activity was also found to increase progressively on increasing the amount of dopant added. The maximum increase in the catalytic activity measured at 150, 175 and 200°C over solids calcined at 700°C was 114, 102 and 82%. respectively. The doping process did not modify the mechanism of the catalyzed reaction but rather increased the concentration of catalytically active constituents (surface CuO crystallites) involved in the chemisorption and catalysis of the CO oxidation reaction without affecting their energetic nature.