Tandem cyclization/arylation of diaryliodoniums via in situ constructed benzoxazole as a directing group for atom-economical transformation

Linear diaryliodoniums often undergo only single arylation and leave equivalent aryliodide as waste. Herein, we demonstrate that linear unsymmetrical diaryliodoniums could be tuned by dual nickel/palladium metal system to accomplish...

The Fractal Geometry of TiAlNiAu Thin Film Metal System and Its Sheet Resistance (Lateral Size Effect)

This paper investigates the relation between the geometry of metric space of a TiAlNiAu thin film metal system and the geometry of normed functional space of its sheet resistances (functionals), which are elements of the functional space. The investigation provides a means to describe a lateral size effect that involves a dependency in local approximation of sheet resistance Rsq of TiAlNiAu metal film on its lateral linear dimensions (in (x,y) plane). This dependency is defined by fractal geometry of dendrites, or, more specifically, it is a power-law dependency on fractal dimension Df value. The revealed relation has not only fundamental but also a great practical importance both for a precise calculation of thin film metal system Rsq values in designing discreet devices and ICs, and for controlling results at micro- and nanoscale in producing workflow for thin metal films and systems based on them.

Single and Binary Adsorption Behaviour and Mechanisms of Cd2+, Cu2+ and Ni2+ onto Modified Biochar in Aqueous Solutions

The chitosan–EDTA modified magnetic biochar (E–CMBC) was successfully used as a novel adsorbent to remove heavy metals. The adsorption behaviour and mechanisms of E–CMBC to Cd2+, Cu2+ and Ni2+ were performed in single and binary system in aqueous solutions. In single–metal system, the adsorption process of Cd2+, Cu2+ and Ni2+ on E–CMBC fitted well with the Avrami fractional–order kinetics model and the Langmuir isotherm model. The measured maximum adsorption capacities were 61.08 mg g−1, 48.36 mg g−1 and 41.17 mg g−1 for Cd2+, Cu2+ and Ni2+, respectively. In binary–metal system, coexisting ions have obvious competitive adsorption behaviour on E–CMBC when the concentration of heavy meal beyond 20 mg L−1. The maximum adsorption capacities of the heavy metals were found to be lower than that in single–metal system. The order of the competitive adsorption ability was Cu2+ > Ni2+ > Cd2+. Interestingly, in Cd2+–Cu2+ system the earlier adsorbed Cd2+ could be completely replaced by Cu2+ from the solution. Different competitive adsorption ability of those heavy metal were due to the characteristics of heavy metal and resultant affinity of the adsorption sites on E–CMBC. The adsorption mechanism indicated that chemical adsorption played a dominating role. Therefore, E–CMBC could be a potential adsorbent for wastewater treatment.

Competitive adsorption and mechanism of hexahydroxy metallic system by aminated solution-blown polyacrylonitrile micro/nanofibers

Adsorptive properties for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) onto an amidoxime-functionalized polyacrylonitrile (APAN) micro/nanofibers were systematically investigated in hexahydroxy metallic solution system using batch experiments. The interactive effect of multi-metal ions in multi- metal systems was antagonistic in nature, and the adsorption capacity in multi-metal system was lower than that in single-metal system. The Langmuir isotherm model could explain respectively the isotherm and kinetic experimental data for hexahydroxy metallic system with much satisfaction. The maximum adsorption capacity in hexahydroxy metallic for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) was calculated to be 98 mg/L, 158 mg/L, 80 mg/L, 76, 312 and 58 mg/L individually. The APAN micro/nanofibers possessed good selectivity toward Pb(II) and Cr(III), over Cd(II), Cu(II), Ni(II), and Zn(II), having the highest selectivity coefficients at 17.52 and 6.07 in the test range. The five adsorption-desorption cycle experiments exhibited that APAN micro/nanofibers adsorbent are readily reusable, and have potential for heavy metal removal from wastewater. The adsorption behavior in multi-metal systems was shown to be complex, including surface complexation, antagonistic competition and displacement reactions. The diversity and selectivity in metal ion adsorption onto the micro/nanofibers relate mainly to the stability constants, and the microscopic coupling mechanism between the heavy metal ions and the functional groups on the fiber surface. This interaction mechanism between the favorable component and other metal ions could contribute significantly to the direct displacement impact illustrated schematically.

Metal Hydride Technologies for Separation of Hydrogen Isotopes

The paper considers the issue of theoretical prediction of characteristics at which separation of hydrogen isotopes occurs in the “gas-metal” system. Mathematical modeling of sorption is based on the use of the lattice gas model often used for metal hydrides. In contrast to the Leicher ideal solution model, it is taken into account that the dissolution of hydrogen in the metal increases the volume of the crystal lattice. This leads to additional contributions to potential energy. The model also takes into account the interaction between the atoms of the incorporated (absorbed) hydrogen isotopes. These phenomena are described by the methods of thermodynamic perturbation theory. The different composition of the gas (protium and deuterium) in contact with the metal leads to the fact that sorption, accompanied by the formation of hydride, proceeds for the same temperature at different equilibrium pressures. This phenomenon characterizes the isotope effect. The temperature dependences of the pressure on the "plateau" for palladium hydride and deuteride are obtained. The differences in these pressures can be used for the practical use of metal hydrides in the separation of hydrogen isotopes.

Nanostructured composite powders for producing protective coatings of machinebuilding parts and units

The paper studies a method for producing nanostructured composite powders of the metal – non-metal system. Powders preparation by universal disintegrator-activator technology, processing in planetary ball mills and bowl grinders is shown on the Al–Zn–Sn composition and titanium nitride nanoparticles. Judging by engineering-and-economical performance, the most promising method for obtaining nanostructured composite powders is the method of processing in a bowl grinder.

The effect of heavy metal composition on the performance of sugarcane bagasse as an adsorbant in water treatment

Wastewater produced by the industries is potentially harmful to the ecosystem because of various contaminants like heavy metals that find their way into soil and water supplies. Industrial waste constitutes different kinds of metal which contaminate natural water. Heavy metals can build up in the environment and enter living organisms through chain elements such as the food chain and therefore, pose a major health risk to living organisms. The situation has been worsened by the absence of broadly accepted heavy metal treatment techniques, thus this challenge continues to receive considerable attention from stakeholders including scientists and researchers. While many technologies have been proposed such as reverse osmosis, flocculation, ion exchange and so on and so forth, they continue to suffer from a number of drawbacks including generation of secondary wastes and cost ineffectiveness. Thus, in the present study, adsorption was chosen as a cost effective, efficient, and environmentally friendly treatment process. Sugar cane milling production produces a lot of sugar cane bagasse which is considered as environmental waste if not disposed properly. It is imperative to remove heavy metals from polluted water before discharging it into the environment, rivers and lakes using sustainable techniques. Heavy metal removal from wastewater using low-cost adsorbents like sugarcane bagasse addresses two problems: removal of pollutants from water and utilization of agricultural waste. This study evaluated the performance of sugarcane bagasse in the removal of heavy metals. Sugarcane bagasse was characterized to determine the functional groups, the porosity and surface area, crystallinity and morphology using FTIR, SEM and XRD. One factor at a time (OFAT) approach was used to evaluate the effect of operating parameters on the removal of heavy metal ions. A 3-system component of the stock solution of synthesized wastewater namely single, binary and ternary were studied. The 3 metal ions evaluated were Copper, Chromium and Cadmium. The factors considered in the OFAT design of experiments were contact time (30-240 mins), adsorbent dosage (5-30g/L), initial concentration (50-500 mg/L), pH(2-9), and particle size (75-600 μm). It was observed that all adsorption parameters had an effect on the adsorption rate. However, an adsorption dosage had a greater impact on the adsorption rate. An increase in the adsorption dosage from (5-20 g) showed that the percentage removal efficiency for chromium, copper and cadmium increased from (40-72%, 44-75% and 39-59%) in a single metal system. In addition, the percentage removal increased from (34-62% for chromium, 47- 78% for copper, and 34-62% for cadmium) in a binary metal system. Furthermore, the percentage removal increased from (38-52%, 40-59% and 24-43%) for chromium, copper, and cadmium in a ternary metal system. Adsorption capacity of the adsorbent was determined using the optimal operating parameters obtained from the OFAT design of experiments. Langmuir and Freundlich isotherms were used to analyze the adsorption data. The OFAT design of experiments resulted in producing the optimum conditions for adsorption. The optimum conditions for maximum adsorption were, contact time (180 mins), initial concentration (50 mg/L), pH (7), dosage (20 g), particle size (340-450 μm) and a mixing speed of 150 rpm. Adsorption capacities differed between the 3 system components. Maximum adsorption capacities of 38.41 mg/L were registered for copper ions and was recorded for the single component system. Stock solutions containing copper ions registered the highest adsorption capacity. There was a significant decrease in the maximum adsorption capacities for copper ions of the binary and ternary system components which were 21.45 mg/L and 1.237 mg/L respectively. This was attributed to the co-metal ion dependence in both the binary and ternary system components. In conclusion, the study showed that sugarcane bagasse can be used as an adsorbent in the efficient removal of heavy metal ions present in wastewater.

Application of Low Melting Metals for Separation of Uranium and Zirconium in a “Fused Chloride—Liquid Alloy” System

Closeness of electrochemical properties of uranium and zirconium makes separation of these metals in pyroelectrochemical reprocessing of spent nuclear fuels a challenging task. Varying electrode material can change metals’ deposition potentials. The study was aimed at assessing the effect of the cathode material on deposition potentials of zirconium and uranium from 3LiCl–2KCl based melts. Solid (tungsten) and liquid (gallium, zinc, Ga–Zn, Ga–Sn and Ga–In alloy) working electrodes were tested at 532–637 °C. Galvanostatic cathodic polarization was employed and the applied cathodic current varied from 0.0001 to 1 A. Gallium–zinc eutectic alloy demonstrated the largest difference of zirconium and uranium deposition potentials. Zirconium/uranium separation factors were experimentally determined in a “molten salt—liquid metal” system for gallium and Ga–Zn eutectic based alloys.