Green Mixture Research Articles

SHS of pyrochlore-type ceramic matrices for immobilization of actinide-containing nuclear wastes

Mineral-like Y2(Ti1–x Zr x )2O7 ceramic matrices for immobilization of actinide–Zr–RE-containing high-level nuclear wastes (HLW) were prepared by SHS method. In experiments, HLW were modeled by a mixture of CeO2, La2O3, ZrO2, MnO2, and Fe2O3 powders. An increase in the HLW content of green mixture decreased the amount of Y2(Ti1–x Zr x )2O7 in combustion product and increased that of ZrO2, LaTiO3, and CaTiO3; decreased the fractional substitutionality of Zr for Ti; and increased the product porosity. An increase in combustion temperature and suppression of heat sink during SHS reaction did not diminish markedly the porosity of synthesized ceramics.

Calciothermic reduction of titanium dioxide and molybdenum trioxide under pressure of nitrogen gas

Explored was the phenomenology of calciothermic reduction in model green mixtures containing metal oxides with strong (TiO2) and weak (MoO3) Me–O bonds. In case of high affinity metal (Ti), the process occurs in two stages: (1) combustion reaction of Ca with N2 yielding calcium nitride and (2) calciothermic reduction of TiO2 to give TiN. In case of low affinity metal (Mo), the above reactions proceed in parallel, without noticeable time delay.

Hemin-utilizing G-quadruplex DNAzymes are strongly active in organic co-solvents

The widespread use of organic solvents in industrial processes has focused in recent years on the utility of “green” solvents – those with less harmful environmental, health, and safety properties – such as methanol and formamide. However, protein enzymes, regarded as green catalysts, are often incompatible with organic solvents. Herein, we have explored the oxidative properties of a Fe(III)-heme, or hemin, utilizing catalytic DNA (heme·DNAzyme) in different green solvent-water mixtures. We find that the peroxidase and peroxygenase activities of the heme·DNAzyme are strongly enhanced in 20–30% v/v methanol or formamide, relative to water alone. Protic solvent content of >30% v/v gradually diminishes heme·DNAzyme catalytic activity; however, the heme·DNAzyme is still active in as high as 80% v/v methanol. In contrast to protic solvents, aqueous dimethylformamide solutions largely inhibit heme·DNAzyme activity. In view of the strong catalytic activity of heme·DNAzyme in aqueous methanol, we were able to determine that a 60% v/v methanol-water mixture gives the most optimal yield of the dibenzothiophene sulfoxide (DBTO) oxidation product of petroleum-derived dibenzothiophene (DBT). The high product yield reflects both DNAzyme catalysis and a high substrate availability. Overall, these results emphasize the excellent promise of G-quadruplex forming DNA catalysts in application to “greener” industrial chemistry. This article is part of a Special Issue entitled “G-quadruplex” Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

Composite W–Cu powders by joint reduction of oxides in combustion mode

Composite powders W–Cu were prepared via joint reduction of WO3 and CuO oxides with Mg‒C combined reducer in a combustion mode by using the method of coupled reactions. Combustion phenomenology and the processes of phase and microstructure formation were investigated by thermocouple and copper- wedge techniques combined with XRD, SEM, and EDS analyses. Thermal conditions of combustion and phase composition and microstructure of products were found to depend on a Mg/C ratio in green mixtures. It was established that the magnesiothermic reaction was preceded by the stage of low-caloric carbothermal reduction. Slow propagation of combustion wave was found to favor the complete reduction of oxides and formation of target W–Cu composite nanopowder.

Removal of binary dyes mixtures with opposite and similar charges by adsorption, coagulation/flocculation and catalytic oxidation in the presence of CeO2/H2O2 Fenton-like system

In this study, the removal of binary mixtures of dyes with similar (Orange II/Acid Green 25) or opposite charges (Orange II/Malachite Green) was investigated either by simple adsorption on ceria or by the heterogeneous Fenton reaction in presence of H2O2. First, the CeO2 nanocatalyst with high specific surface area (269 m2/g) and small crystal size (5 nm) was characterized using XRD, Raman spectroscopy and N2 physisorption at 77 K. The adsorption of single dyes was studied either from thermodynamic and kinetic viewpoints. It is shown that the adsorption of dyes on ceria surface is highly pH-dependent and followed a pseudo-second order kinetic model. Adsorption isotherms fit well the Langmuir model with a complete monolayer coverage and higher affinity towards Orange II at pH 3, compared to other dyes. For the (Orange II/Acid Green 25) mixture, both the amounts of dyes adsorbed on ceria surface and discoloration rates measured from Fenton experiments were decreased by comparison with single dyes. This is due to the adsorption competition existing onto the same surface Cex+ sites and the reaction competition with hydroxyl radicals, respectively. The behavior of the (Orange II/Malachite Green) mixture is markedly different. Dyes with opposite charges undergo paired adsorption on ceria as well as homogeneous and heterogeneous coagulation/flocculation processes, but can also be removed by heterogeneous Fenton process.

Temperature dependence of electrical conductivity of a green porcelain mixture

AC conductivity of a green porcelain body was investigated using impedance spectroscopy over a temperature range of 100–950°C. The results showed that during the heating, conductivity at 100–200°C increased mainly arising from H+ and OH− ions generated from adsorbing physical water. The activation energy increased below the dehydroxylation of clay resulting from movement of monovalent ions. At the dehydroxylation of clay, a combination of H+, OH− and monovalent ions dominated the conductivity. The activation energy rose to 1.14eV (600–950°C) controlled by diffusion of Na+, and K+ ions. During the cooling, conductivity showed single activation energy with 0.86eV resulting from denser microstructure and change in mineralogical constituents and the heat treated porcelain sample showed higher electrical conductivity at the same temperature. Understanding conduction behaviour of the green porcelain enabled more accurate control of furnace temperature in flash sintering, a process which relies on electrical conductivity at high temperatures.

Large‐scale production of well‐dispersed submicro ZrB2 and ZrC powders

ZrB2 and ZrC powders were synthesized via metallothermic reduction route using ZrO2, B/C, and Mg as raw materials. Low packing density of the green mixture and high heating temperature of the furnace are crucial for the formation of well‐dispersed submicro powders. Optimum reaction time helped achieve good crystallization and high purity. The as‐prepared samples were characterized by XRD, FESEM, TEM, and particle size analyzer. Results showed that well‐dispersed ZrB2 powders with mean particle size of 0.534 μm and ZrC powders with mean particle size of 0.376 μm can be obtained. Oxygen content can be controlled lower than 1.0 wt%. The bench‐scale output is about 10 kg/d.

Fate and transport with material response characterization of green sorption media for copper removal via desorption process

Multiple adsorption and desorption cycles are required to achieve the reliable operation of copper removal and recovery. A green sorption media mixture composed of recycled tire chunk, expanded clay aggregate, and coconut coir was evaluated in this study for its desorptive characteristics as a companion study of the corresponding adsorption process in an earlier publication. We conducted a screening of potential desorbing agents, batch desorption equilibrium and kinetic studies, and batch tests through 3 adsorption/desorption cycles. The desorbing agent screening revealed that hydrochloric acid has good potential for copper desorption. Equilibrium data fit the Freundlich isotherm, whereas kinetic data had high correlation with the Lagergren pseudo second-order model and revealed a rapid desorption reaction. Batch equilibrium data over 3 adsorption/desorption cycles showed that the coconut coir and media mixture were the most resilient, demonstrating they could be used through 3 or more adsorption/desorption cycles. FE-SEM imaging, XRD, and EDS analyses supported the batch adsorption and desorption results showing significant surface sorption of CuO species in the media mixture and coconut coir, followed by partial desorption using 0.1 M HCl as a desorbing agent.

Strength and Stiffness Properties of Green Lightweight Fill Mixtures

Approximately 250 million tires are discarded each year in the United States and 20 million in Canada. Finding sustainable ways to dispose these tires continues to be a problem throughout the world not only in North America. Disposal issues along with a continuing increase in tire production have resulted in an increase in tire stockpiles, 30 % of these tires end up occupying valuable landfill space. Tire Derived Aggregates (TDA) made from scrap tires have a compacted dry unit weight of 6.9 kN/m3 and a specific gravity of 1.06 making their use as lightweight fill material especially for highway embankments over soft soils very advantageous. Using TDA as fill material not only provide a new construction material but also help to provide sustainable solution for several environmental and economic problems. Previous studies have shown that the addition of Tire Derived Aggregates (TDA) to sand results in a fill material which is characterized by its higher shear strength compared to that of 100 % sand. While there have been several studies investigating various properties and situations involving TDA’s, there remain areas that still require exploration. The effect of soil/aggregate gradation on shear strength is one of particular interest. All of the research conducted to date investigated only the sand gradation mixed with uniform TDA gradation. None of the conducted research investigated the interaction between the gradation of the two materials and its effect on the performance of the fill mixture. The main goal of this paper is to gain an understanding of this interaction in aim of producing better fill mixtures with enhanced characteristics.

Optimization of a Three-Component Green Corrosion Inhibitor Mixture for Using in Cooling Water by Experimental Design

Factors such as inhibitor concentration, solution hydrodynamics, and temperature influence the performance of corrosion inhibitor mixtures. The simultaneous studying of the impact of different factors is a time- and cost-consuming process. The use of experimental design methods can be useful in minimizing the number of experiments and finding local optimized conditions for factors under the investigation. In the present work, the inhibition performance of a three-component inhibitor mixture against corrosion of St37 steel rotating disk electrode, RDE, was studied. The mixture was composed of citric acid, lanthanum(III) nitrate, and tetrabutylammonium perchlorate. In order to decrease the number of experiments, the L16 Taguchi orthogonal array was used. The “control factors” were the concentration of each component and the rotation rate of RDE and the “response factor” was the inhibition efficiency. The scanning electron microscopy and energy dispersive x-ray spectroscopy techniques verified the formation of islands of adsorbed citrate complexes with lanthanum ions and insoluble lanthanum(III) hydroxide. From the Taguchi analysis results the mixture of 0.50 mM lanthanum(III) nitrate, 0.50 mM citric acid, and 2.0 mM tetrabutylammonium perchlorate under the electrode rotation rate of 1000 rpm was found as optimum conditions.

β-SiAlON–BN composites by infiltration-mediated SHS under high pressure of nitrogen gas

Infiltration-mediated SHS of β-Si6–zAlzOzN8–z–TiN/TiB2–BN composites was explored upon variation in applied nitrogen pressure, amount of combustible and inert components in green mixture, sample size, and BN content of resultant composites. Synthesized ceramics of different density and phase composition were characterized by their strength parameters, tribological behavior, electrical resistance, and thermal shock resistance.

Accumulation of Biopesticide-Based Rotenone from an Optimized [BMIM][OTf] Green Binary Solvent Mixture in Different Parts of Terong Plant (Solanum Melongena)

Infestation of pests on the field crops has resulted losses on its productivity yearly. Moreover, over usage of pesticides has also affected consumer's health as pesticides residues are detected inside the post-harvested crops. Therefore, the aim of this study is to determine the accumulation of rotenone Derris sp. in leaves, stem and fruit of terong plant (Solanum melongena) through the degradation rate (k) and half-life (t1/2) of sprayed rotenone extract. The sprayed rotenone was prepared by using an optimized binary solvent mixture of 95% (v/v) acetone and ionic liquid (1-butyl-3-methylimidazolium trifluoromethansulfonate [BMIM] [OTf] via normal soaking extraction method. The same extraction method was used on the plant parts by using only 95% (v/v) of acetone. Reverse-phase high performance liquid chromatography (RP-HPLC) was used in analysing rotenone and [BMIM][OTf] traces. The results indicate that the degradation rates of 20ppm were (1.35 ± 0.02 day-1 for leaves; 1.89 ± 0.07 day-1 for fruit) faster than 1000ppm of rotenone extract (0.24 ± 0.00 day-1 for leaves; 0.21 ± 0.01 day-1 for stem; 0.31 ± 0.01 day-1 for fruit) (p<0.05) within 6 days of observation. Rotenone was identified to possess the half-life (t1/2) in the range of 0.37 ± 0.01 day to 0.51 ± 0.01 day in the study of 20ppm rotenone extract. In contrast, the half-life (t1/2) for rotenone on 1000ppm extract was in the range of 2.23 ± 0.05 days to 3.38 ± 0.10 days which was longer than 20ppm extract (p<0.05). In conclusion, rotenone extract is still considered safe and has the potential to be used as a bio-pesticide due to its shorter half-life (t1/2) (less than 7 days at the highest concentration of 1000ppm) than other commercial pesticides.

Optical and Color Properties of Green and Red Phosphor Mixtures Doped into Hybrid Sol-Gel Matrix to Generate White Light

Eu (tta)3phen and Tb (4DBBA)3TPPO were synthesized as red and green phosphor for generating white light under the excitation of UV LED. The phosphor materials were doped into hybrid sol-gel (VTES:TEOS) matrix with different ratio of 1:8, 1:16, 1:25, 1:30, 1:40 and 1:50. The samples were fabricated as thick films by drop-casting and heat treated at 60°C overnight. Photoluminescence spectra were measured using spectrafluorometer system. Measurement of color properties such as color rendering index (CRI), color temperature and Commission Internationale de L’Eclairge coordinates were recorded by exciting the samples using a 380nm UV LED and focused the generated light into an integrating sphere. Based on the results, the mix ratio of 1:40 produce the nearest coordinate within the white color region with color temperature around 4100K to 4200K.

To SHS Aspects other than those of Distributed Electrochemical Systems: From Current-Voltage Generators, Bio-cells, Batteries and Accumulators to Emission and Radiation Effects during SHS, etc

Recent Experimental and numerical studies on Combustion Synthesis of sulfides (CSS) in combination with the current Electronic Theory of a Solid Body (ETSB) lead us to the conclusion that the CSS chemical reactions are accompanied by electron transitions inside the sulfide valence zone, i.e., by transitions between the energy states of electrons localized in the valence zone. Such a conclusion only can explain the huge difference of energy of sulfur clusters affinity to an electron from the sulfur ionization potential which is available in literature. In addition to the interrelated aspects of CSS and ETSB We have presented also a small review of the existing literature on electrochemical sources of current and voltage (cells, accumulators).This review is devoted to distributed electrochemical systems and to a certain extent supplements some of the earlier reviews written (with the participation of the author) for the sources of electricity based on SHS solely. As the result, it has been made the conclusion about the advantage of the combustion based sources of electric current (pyrotechnic sources of electric current, PSEC) in comparison with the modern accumulators and bio-cells. The conditions of PSEC stable work are discussed. Incidentally we have also considered a few works concerning materials synthesis and nanoparticles. Nanoparticles are extremely popular now. The authors of the articles concerning such exotic objects use often in their publications unreasonable approximations or/and unchecked facts. In our opinion, the readers have to realize, where and what conclusions of similar authors deviate from the reality or from the classical results received earlier. To prove a solvency and a coherence of new results and representations is the business of innovators themselves, not of others or us. We just reveal some of their frequent shortcomings here. The comparison of the SHS systems on the specific electric energies generated during the synthesis has been also carried out. The energies appear to depend strongly on the composition, green density and the sample electric resistance. We have shown that in the SHS semiconductive systems of a loosed density (SLD) the generated specific electric energy is comparably less than that of a fish slope. Therefore, We have suggested new non-system units based on the specific electric energy generated by a fish slope as a useful measure for the SLD generated electric energies. It has appeared that the greatest quantity of specific electric energy is emitted by the loosed mixture of titanium with its nitride. Nevertheless, We have calculated that even the titanium nitride mixtures contain the overwhelming part of their energy in that of a chemical type (as the enthalpy of the green mixture formation). Both in compact and in SLD systems the specific standard enthalpies of formation of green components or products exceed significantly the electric energy released. Any source of electric voltage or electric current based on the combustion synthesis cannot be compared by the efficiency to electrolytic accumulators (their efficiency is close to unit by the definition). Therefore, We have also considered the general principles of association of such sources into batteries. It is well known that exoemission of electrons (EE) is an inevitable condition of any solid body existence in Nature. Nevertheless, there is still no clear understanding of high energetic EE caused by some of SHS processes. We have given the estimate confirming the possibility of high energetic electrons to be emitted during SHS, reveal the most perspective SHS systems in this relation, and simultaneously discuss the problems of chemically stimulated exoemission of electrons (CSEE) existing now in our opinion.

SHS in the Nb–Si system: Influence of mechanical alloying

Influence of mechanical alloying (MA) on SHS in low-caloric Nb–2Si mixtures was explored as a function of MA time and Si content of green mixtures. The use of MA was found to extend the concentration limits for combustion synthesis in the Nb–Si system to the following range: between 43 wt % Si–57 wt % Nb and 10 wt % Si–90 wt % Nb. Due to MA, SHS in Nb–Si blends can be carried out in a mode of solid–solid or liquid–solid reaction.

English

Camellia sinensis extracts have been documented to have antibacterial activity but little knowledge on their antifungal activity. The aqueous extracts of C. sinensis (tea) both green and black, mixed with milk in equal ratio parts, referred as mixture were investigated for their antifungal activity and minimum inhibitory concentrations (MICs) against seven fungal species; Green and black tea crude extracts (100 mgmL-1) were evaluated for antifungal activities. Quantitative bioassay was done using disc diffusion method and MIC done using broth dilution methods. The fungal isolates used for bioactivity testing were yeasts. Green tea crude extract mixture showed stronger inhibitory effect against the fungal strains tested than black tea crude extract mixture. There was a significant difference in zone of inhibitions (T=4.09, P<0.05). Zone of inhibition exhibited by green tea crude extracts (8.33±0.87 mm) were higher than black tea crude extracts (6.75±0.66 mm). The pattern of activity by tea crude extracts mixture against ATCC standard fungal strains and clinical isolates strains were similar. Candida tropicalis, Candida lusitaniae, Candida parapsilosis ATCC 22019, Cryptococcus neoformans ATCC 66031 and Candida famata were inhibited by green tea crude extracts mixture (IZD≥15±0.50 mm). Clinical isolates of Candida albicans (strain 5) showed susceptibility to C. sinensis green crude extracts mixture. The MIC of C. sinensis crude extracts mixture against fungal isolates tested ranged from 50 to 1.6 mg mL-1, with green tea crude extract mixture showing highest MIC on clinical fungal isolates. The studies on C. sinensis have shown remarkable antifungal activity and highlighted its significance as potential health products. Key words: Camellia sinensis, crude tea extracts, fungal species.

Fate and transport with material response characterization of green sorption media for copper removal via adsorption process.

Green adsorption media with the inclusion of renewable and recycled materials can be applied as a stormwater best management practice for copper removal. A green adsorption media mixture composed of recycled tire chunk, expanded clay aggregate, and coconut coir was physicochemically evaluated for its potential use in an upflow media filter. A suite of tests were conducted on the media mixture and the individual media components including studies of particle size distribution, isotherms, column adsorption and reaction kinetics. Isotherm test results revealed that the coconut coir had the highest affinity for copper (q(max) = 71.1 mg g(-1)), and that adsorption was maximized at a pH of 7.0. The coconut coir also performed the best under dynamic conditions, having an equilibrium uptake of 1.63 mg g(-1). FE-SEM imaging found a strong correlation between the porosity of the micro pore structure and the adsorptive capacity. The use of the green adsorption media mixture in isolation or the coconut coir with an expanded clay filtration chamber could be an effective and reliable stormwater best management practice for copper removal.

Effect of consumption of dehydrated green leaf mixture on the hemoglobin levels of the anemic adolescent girls

Effect of consumption of dehydrated green leaf mixture on the hemoglobin levels of the anemic adolescent girls

Magnesiothermic SHS of boron carbide in conditions of temperature gradients

Magnesiothermic SHS from reactive mixtures containing energy-producing additive, Mg(ClO4)2, in green mixtures was used to explore crystallization of boron carbide and its derivatives in a large SHS reactor in conditions of strong temperature gradients within the sample bulk. The addition of Mg(ClO4)2 increased a maximum combustion temperature (Tc) up to 2500°C (instead of 2000°C without the additive). The presence of gasifying agent resulted in a non-uniform distribution of combustion products. Except for the central sample area with a maximum value of Tc, the product exhibited the cell parameters corresponding to stoichiometric B4C. A two-phase material formed in the central zone was found to contain B13C2 and B25C4Mg1.42. This was explained by different temperature conditions in different areas of the sample bulk.

Assessment of oral acute toxicity “Green Health herbal mixture” in Wistar albino rats

Assessment of oral acute toxicity “Green Health herbal mixture” in Wistar albino rats