Chitosan/UiO-66 composites as high-performance adsorbents for the removal of methyl orange in aqueous solution

UiO-66 and chitosan/UiO-66 composites were successfully synthesized by varying the mass addition of chitosan which were 0%, 2.5%, 5%, 10%, and 20% of the mass of UiO-66, denoted as UiO-66, Cs(2.5)/UiO-66, Cs(5)/UiO-66, Cs(10)/UiO-66, and Cs(20)/UiO-66, respectively. UiO-66 was modified with chitosan using the impregnation process. The X-ray diffraction patterns of the synthesized materials showed characteristic peaks at 2θ of 7.25° and 8.39°, which matched to that of the reported UiO-66. In addition, the Fourier transform infrared spectroscopy spectra of the materials showed absorption bands at the same wavenumber as UiO-66 and chitosan previously reported. The surface morphology of UiO-66 observed from scanning electron microscopy images was in the form of agglomerated small cube particles, where the smaller particles were observed for Cs(10)/UiO-66. From the N₂ adsorption isotherms, it was found that the Brunauer-Emmett-Teller surface areas of UiO-66, Cs(5)/UiO-66, and Cs(10)/UiO-66 materials were 825.7 m²/g, 835.4 m²/g, and 882.2 m²/g, respectively. The results of the study on adsorption of methyl orange in aqueous solutions showed that Cs(5)/UiO-66 had the highest adsorption capacity of 370.37 mg/g and followed the pseudo–second-order adsorption kinetic with a Langmuir isotherm model.     

Enhancement of catalytic activity of titanosilicalite-1 - sulfated zirconia combination towards epoxidation of 1-octene with aqueous hydrogen peroxide

Summary Titanosilicalite-1 (TS-1) in combination with sulfated zirconia efficiently catalyzes the epoxidation of 1-octene with aqueous hydrogen peroxide. The presence of both octahedral zirconium and sulfate species in the catalysts enhances the epoxidation rates.     

Influence of the degree of crystal perfection and deviation from the stoichiometric composition on the diffusion processes in samarium sulfide

The processes of diffusion of samarium and europium in nonstoichiometric samarium sulfide (SmS) at temperatures in the range 950–1600°C have been investigated by the radioactive isotope method and the method of weight loss upon evaporation of excess samarium. It has been found that there is a correlation between the diffusion coefficient D and the size of coherent X-ray scattering regions in SmS samples, as well as between the diffusion coefficient and the degree of deviation from the stoichiometric composition: the diffusion coefficient of impurities decreases as the size of coherent X-ray scattering regions increases and the stoichiometric composition is approached. The calculation of the diffusion coefficient of electrons in samarium sulfide at T = 77–300 K has demonstrated that the value of D increases with increasing temperature and increasing size of coherent scattering regions.     

Review on recent advances of carbon based adsorbent for methylene blue removal from waste water

The growth in textile and printing industries proven detrimental to the aquatic environment as the industrial waste containing dye seeped into the ecosystem. A high concentration of dye in water possess negative impacts on water ecosystem and harmful to human health. Removal of methylene blue (MB) dye from industrial waste via adsorption pathway has been widely investigated that promised high efficiency of MB removal. This review will summarize researches published from 2008 to 2019 on the removal of MB using carbon adsorbent with focus will be given on the synthesis and modification of carbon-based materials, and the structural properties influencing the performance of MB adsorption. Summary on the type of material used for the synthesis of carbon materials (activated carbon and biochar) will be included from utilization of the naturally occurring carbon sources such as polymers, biomasses and biowastes, and also sucrose and hydrocarbon gases. Modification of carbon materials such as chemical activation and physical activation; surface grafting to form functionalized surfaces; deposition with metal and magnetic nanoparticles via impregnation; and manufacturing of carbon composites will be discussed on the effects to promote MB adsorption and desorption. Another type of carbon adsorbents such as porous carbon; graphitic carbons including graphite, graphene, graphene oxide, and carbon nitride (g-C₃N₄); and finally nanocarbon in the form of nanotube, nanorod and nanofiber; will be included in the review with details on the synthesis method and the correlation between structural properties and adsorption activity. The regeneration process to increase the life cycle of carbon adsorbent will also be discussed based on two regeneration pathway i.e. a thermal degradation and desorption on MB. Finally the thermodynamics, kinetics, and the adsorption models of MB on carbon adsorbent will be discussed in this review.     

Statistical Modeling of Water Structure in a Near-Electrode Layer

The structure of water near the electrode surface is studied by a molecular dynamics method, the electrode is assumed to be a structureless conducting surface, a cell of 216 water molecules is used. It is shown that the structure of water in a near-electrode area formed under the electric field influence differs greatly from that in the bulk. The effect of anisotropy of water structure normally to the surface is found. The effect consists of a lower diffusion mobility of molecules in this direction, quantitatively depends on the surface charge density, and decays with increasing distance from the surface. The main role in forming the water structure in the near-electrode layer is played by electrostatic interaction.     

Europium diffusion in SmS

Europium diffusion in samarium sulfide was studied in the temperature range from 780 to 1100°C. Data on the diffusion coefficient and activation energies for the diffusion of europium in single-crystal and polycrystalline SmS samples were obtained. In single-crystal samarium sulfide, europium was shown to migrate predominantly over lattice sites (D ? 10^?12?10^?9 cm²/s). In SmS polycrystals, diffusion was found to exhibit a complex pattern and have both a slow (D ? 10^?10?10^?9 cm²/s) and a fast (D ? 10^?8?10^?7 cm²/s) component. Europium diffusion in a polycrystal is primarily due to europium migration over the boundaries of single-crystal grains in the polycrystal, whose characteristic size is assumed to be that of x-ray coherent-scattering regions.     

Distribution of the isotopes produced in the YBa2Cu3O7−x superconductor and PbZr0.54Ti0.46O3 ferroelectric by energetic charged particles

A study has been made of the concentration profiles of radioactive isotopes produced by transmutation in the YBa₂Cu₃O_7−x superconductor and PbZr_0.54Ti_0.46O₃ ferroelectric by energetic protons (10 and 15 MeV), deuterons (4 MeV), and ³He and ⁴He nuclei (20 MeV). Profiles of two types have been observed: monotonic and with a maximum. It is shown that the type of isotope concentration profile is determined by the nature of the cross-section energy dependence of the nuclear reaction producing a given isotope. Fiz. Tverd. Tela (St. Petersburg) 40, 2189–2191 (December 1998)     

A review on synthesis of kaolin-based zeolite and the effect of impurities

Zeolite is extensively synthesized for the application in a large variety of catalysis processes such as ion exchange, hydrocarbon cracking, and organic synthesis. In order to satisfy the serious terms of sustainability that denotes to the reduction of costs and chemical waste, kaolinite-based zeolites were produced from cheap natural resources as against to the conventional process that employs pure sodium silicate and sodium aluminate. This review paper is to highlight the current trends in the synthesis of zeolite. Prior to previous reviews, great concern is focused on the impurities effect on the catalytic performance of kaolinite-based zeolites. This study reveals that the impact of impurities in a catalytic reaction was in fact, underestimated or neglected. For instance, it was found that Fe ion concentration as small as 60 ppm gives significant catalytic output. Hence, a new practice to report the concentration of impurities in the research publication is suggested. This undoubtedly will generate a better interpretation of the catalytic activity from the zeolite framework.     

Profiles of transmutation-produced isotopes in proton-and helium-irradiated germanium

Profiles of radioactive isotopes produced in nuclear reactions in germanium irradiated by protons or ⁴He nuclei were studied. The profiles were used to determine the energy dependence of the cross sections of nuclear reactions producing transmutation isotopes.     

Pulsed generation of an electrical voltage at the thermovoltaic effect in SmS

The thermovoltaic effect in SmS is measured at elevated frequencies near 1000 Hz. Pulsed generation of an electrical voltage at this effect is discovered and explained. The maximal value of the generated voltage and the power of the generated signal are measured to be 6.3 V and about 1 W, respectively. These values are attained at about 130°C.