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The treatment of wastewater from arsenic compounds is an important and urgent problem. Composite nanostructures consisting of boehmite and iron compounds have a high adsorption capacity towards As(V) specie. In this work, the adsorption properties of nanostructured composites prepared by the oxidation of bimetallic Al/Fe nanoparticles with different iron contents were investigated. As a result of oxidation, boehmite AlOOH nanosheets are formed, with the resultant FeAl2 nanoparticles being distributed on the surface of boehmite nanosheets. The nanostructured composites prepared from Al/Fe nanoparticles containing 20 wt% Fe have been found to show the highest adsorption capacity towards As(V) specie, being 248 mg/g. The adsorption isotherms are most accurately described by the Freundlich model, with the arsenic adsorption process obeying pseudo second order kinetics. As a result of the study, the optimal ratio of Al and Fe in Al/Fe nanoparticles has been determined to obtain an AlOOH/FeAl2 composite adsorbent with a developed and accessible surface and a high sorption capacity towards As(V). This allows us to consider this material as a promising adsorbent for the removal of arsenic compounds from water. [ABSTRACT FROM AUTHOR]

The water oxidation of bimetallic Al/Ag nanoparticles has been shown to yield nanoscale structures whose morphology, phase composition and textural characteristics are determined by the synthesis conditions. Flower-like nanoscale structures with silver nanoparticles, with an average size of 17 nm, are formed in water at 60 °C. Under hydrothermal conditions at temperatures of 200 °C and a pressure of 16 MPa, boehmite nanoplatelets with silver nanoparticles, with an average size of 22 nm, are formed. The oxidation of Al/Ag nanoparticles using humid air at 60 °C and 80% relative humidity results in the formation of rod-shaped bayerite nanoparticles and Ag nanoparticles with an average size of 19 nm. The thermal treatment of nanoscale structures obtained at a temperature of 500 °C has been shown to lead to a phase transition into γ-Al2O3, while maintaining the original morphology, and to a decrease in the average size of the silver nanoparticles to 12 nm and their migration to the surface of nanoscale structures. The migration of silver to the nanoparticle surface influences the formation of a double electric layer of particles, and leads to a shift in the pH of the zero-charge point by approximately one, with the nanostructures acquiring pronounced antimicrobial properties. [ABSTRACT FROM AUTHOR]

The paper studies patterns of interaction of electroexplosive Co nanoparticles with air oxygen during heating. The characteristics of Co nanoparticles and composite Co/CoO/Co3O4 nanoparticles formed as a result of oxidation were studied using transmission electron microscopy, X-ray phase analysis, thermogravimetric analysis, differential scanning calorimetry, and vibrating sample magnetometry. It was established that nanoparticles with similar morphology in the form of hollow spheres with different content of Co, CoO, and Co3O4 can be produced by varying oxidation temperatures. The influence of the composition of composite nanoparticles on their magnetic characteristics is shown. [ABSTRACT FROM AUTHOR]

In this study, the modification of macroporous α-Al2O3 ceramics with AlOOH nanostructures impregnated with silver particles is carried out using bicomponent Al/Ag nanoparticles obtained by the simultaneous electrical explosion of Al and Ag wires. Nanoparticle suspension impregnation of porous ceramics followed by oxidation with water is shown to lead to the formation of a continuous AlOOH nanosheet coating on the ceramic surface, with silver releasing on the surface of nanosheets in the form of individual particles sized 5–30 nm. Modified with AlOOH/Ag nanostructures, macroporous α-Al2O3 pellets with a diameter of 11 mm and a thickness of 5 mm show 100% efficiency for water purification from bacteria with a concentration of 105 CFU/mL for 7.5 min at a flow rate of 6.7 mL/min. [ABSTRACT FROM AUTHOR]

Betulin (90–94%) was extracted from birch with a non-polar solvent and recrystallized from 2-propanol. Liquid-phase oxidation of betulin aimed at obtaining its biologically active oxo-derivatives (betulone, betulonic and betulinic aldehydes), exhibiting e.g. antitumor, anti-inflammatory, antiparasitic, anticancer and anti-HIV properties, was demonstrated for the first time over gold-based catalysts. Gold was deposited on pristine TiO2 and the same support modified with ceria and lanthana, followed by pretreatment with a H2 or O2 atmosphere. The catalysts were characterized by XRD, BET, ICP, TEM, XPS, DRIFT CO, TPD of NH3 and CO2 methods. The nature of the support, type of modification and the pretreatment atmosphere through the metal–support interactions significantly influenced the average particle size of gold, its distribution and the electronic state of gold, as well as the acid–base properties and, thereby, the catalytic performance (activity and selectivity) in betulin oxidation. Au/La2O3/TiO2 pretreated in H2 displayed the highest catalytic activity in betulin oxidation among the studied catalysts with selectivities to betulone, betulonic and betulinic aldehydes of 42, 32 and 27%, respectively, at 69% conversion. Side reactions resulting in oligomerization/polymerization products occurred on the catalyst surface with the participation of strong acid sites, diminishing the yield of the desired compounds. The latter was improved by adding hydrotalcite with the basic properties to the reaction mixture containing the catalyst. Kinetic modelling through numerical data fitting was performed to quantify the impact of such side reactions and determine the values of rate constants. [ABSTRACT FROM AUTHOR]