Beneficiation of borax by reverse flotation in boron saturated brine

Flotation is one of the plausible methods for recovering borax fines discharged as fine waste to the tailings dam in the Kirka borax processing plant. A literature review dealing with the flotation behavior of boron minerals reveals that clay minerals in the boron ores coat boron minerals and thus deteriorate the quality of boron concentrates produced by direct flotation. The main objective of this study is therefore to recover borax fines from the tailings of the concentrator by reverse flotation. A three-level-factor experimental design was used to determine the main and interaction effects of variables selected on the metallurgical performance of reverse flotation. An analysis of variance for experimental results indicates that interaction effects of the variables for concentrate quality and recovery of B2O3 is nonsignificant and the most important variable for grade of concentrate and recovery is the collector dosage. It is shown that a concentrate assaying 11.25% B2O3 with 89.90% B2O3 recovery could be produced by means of single-stage (rougher) reverse flotation. Additionally, in order to produce a sufficient-quality concentrate, a multistage reverse flotation scheme involving rougher, scavenger, and two cleaners was devised. A final concentrate containing 23.47% B2O3 with 81.78% B2O3 recovery was obtained from these tests. The reverse flotation method can be thus considered as an important option for the beneficiation of borax fines.     

Electrochemical fluorination of acetamide and formamide in molten KH2F3

The electrofluorination of acetamide (CH₃CONH₂) and formamide (HCONH₂) on the anode was studied in molten KH₂F₃ at 120°C. Amorphous carbon was used as the anode and Pt-rod as the reference electrode. Anodic products were analyzed by both gas chromatography and infrared spectroscopy.In the cases of both CH₃CONH₂ and HCONH₂, the anode effect occurred often in electrolysis at the current density range of 3～20 mA·cm^?2 and the anode gas was then composed 5of N₂(+O₂), NF₃, CF₄, C₂F₆, N₂O, CO₂(+COF₂) and so on. The addition of 1.0 wt% LiF into the electrolyte decreased the yield of NF₃.From these results, it is suggested that CH₃CONH₂ and HCONH₂ would react chemically with atomic fluorine produced on the (C_xF)n [x > 2] film by the discharge of fluoride ion. The mechanism of electrofluorination of CH₃CONH₂ or HCONH₂ in this melt is as follows;

     

Molecular weight determination of hypromellose phthalate (HPMCP) using size exclusion chromatography with a multi-angle laser light scattering detector

The molecular weight of hypromellose phthalate (HPMCP), a polymer used for enteric coating, was determined using size exclusion chromatography with a multi-angle laser light scattering detector. The values of weight-average molecular weight (Mw) of commercially available grades (HP-55, HP-55S, and HP-50) were 45600, 60200, and 37900, respectively. Their inter-day precisions expressed in terms of the coefficient of variation were less than 3%. A correlation curve between Mw and solution viscosity was prepared so that Mw could be easily estimated from the solution viscosity measured by the compendial method.     

Biodiesel fuel from vegetable oil by various supercritical alcohols

Biodiesel was prepared in various supercritical alcohol treatments with methanol, ethanol, 1-propanol, 1-butanol, or 1-octanol to study transesterification of rapeseed oil and alkyl esterification of fatty acid at temperatures of 300 and 350°C. The results showed that in transes terification, the reactivity was greatly correlated to the alcohol: the longer the alkyl chain of alcohol, the longer the reaction treatment. In alkyl esterification of fatty acids, the conversion did not depend on the alcohol type because they had a similar reactivity. Therefore, the selection of alcohol in biodiesel production should be based on consideration of its performance of properties and economics.     

Dynamic Thermal Deformation Measurement of Large-Scale, High-Temperature Piping in Thermal Power Plants Utilizing the Sampling Moiré Method and Grating Magnets

Fast and accurate deformation measuring techniques show promising potential for monitoring high-temperature piping and other machinery in the energy sector, such as in thermal, steam, or nuclear power plants. Optics-based, nonintrusive, and real-time monitoring systems are critical for preventing high-temperature steam leaks, unexpected accidents, explosions, and other failures that can have catastrophic consequences for the power supply, the workers, and the public. In this study, a dynamic thermal deformation measurement technique utilizing the sampling Moiré method and grating magnets is developed for large-scale, high-temperature piping in a thermal power plant. Because of the high temperature of the piping of nearly 300 °C several 100 mm by 100 mm ferrite magnets were placed to select locations of the high-temperature piping. In each ferrite magnet, a regular, two-dimensional binary grating pattern with a pitch of 15 mm was painted on the surface, and the grating magnets were used as the reference grating to analyze the small in-plane displacement distribution using the sampling Moiré method. A compensation method of misalignment angle is also proposed to improve the measurement accuracy. The effect on vibration remove, mirage due to conversion in air, wide angle of camera lens, and compensation of misalignment angle, are discussed. The experimental results showed that our measurement technique is suitable for evaluation of high-temperature, large-scale infrastructure.     

Thermoelastic damping in micro-scale circular plate resonators

The governing equations of coupled thermoelastic problems are established for out-of-plane vibration of a circular plate. The analytical expression for thermoelastic damping is obtained. Then the thermoelastic damping is studied under different environmental temperature, plate dimensions and boundary conditions.     

X-ray structural analysis, antioxidant and cytotoxic activity of newly synthesized salicylic acid derivatives

New salicylic (2-hydroxybenzoic) acid derivatives 1–6 were prepared by conventional heating or microwave irradiation of a mixture consisting of methyl salicylate and the corresponding amino alcohol (2,2′-dihydroxydiethylamine, 2,2′,2″-trihydroxytriethylamine or N-phenyl-2,2′-dihydroxydiethylamine) and metallic sodium as catalyst. For compounds 1, 3, and 5 X-ray structure analysis was performed, as well as molecular mechanics calculations (MMC), to define their conformation in terms of their energy minima. Comparison of crystal and MMC structures for these three compounds (1, 3, and 5) revealed that the intramolecular hydrogen bonds play an important role, stabilizing conformation of the most part of the molecule. The antioxidant activity and cytotoxicity of the synthesized derivatives were evaluated in a series of in vitro tests. The newly synthesized compounds exhibited strong activity against hydroxyl radical, as well as promising lipid peroxidation inhibition. The study showed that the electronic effects of the groups at the N atom are responsible for neutralization of the OH radical, i.e., antioxidant activity. Compounds 1–3 exhibited sub-micromolar cytotoxicity against HeLa S3, whereas compounds 1, 3 and 5 efficiently inhibited the growth of PC3 cells.     

Development of a micro-total analysis system (μ-TAS) for the determination of catecholamines

In this study, the first micro-total analysis system (μ-TAS) for catecholamines (dopamine, epinephrine, and norepinephrine) analysis in which preconcentration, separation, and determination steps were integrated on a microchip was developed. Electrophoresis microchips in a variety of channel lengths and designs were produced in borofloat glass for the μ-TAS studies. Chambers for the preparation of monolithic disks were formed in the microchips at the intersection of the injection and separation channels. Vinyl phenylboronic acid–ethylene glycol dimethacrylate polymers were prepared as monolithic disks in these chambers with a depth of 0.05 mm and a diameter of 2.1 mm. The microchips could be used more than 50 times if mechanical problems such as plugging or fracturing did not occur. Adsorption and elution of catecholamines were realized electrokinetically, with catecholamines determined via laser-induced native fluorescence detection following elution and electrophoretic separation. The most promising results were obtained with 100 mM phosphate buffer (pH 2) for elution with 25% propanol added to the separation buffer (100 mM phosphate, pH 3).     

Constrained CVT meshes and a comparison of triangular mesh generators

Mesh generation in regions in Euclidean space is a central task in computational science, and especially for commonly used numerical methods for the solution of partial differential equations, e.g., finite element and finite volume methods. We focus on the uniform Delaunay triangulation of planar regions and, in particular, on how one selects the positions of the vertices of the triangulation. We discuss a recently developed method, based on the centroidal Voronoi tessellation (CVT) concept, for effecting such triangulations and present two algorithms, including one new one, for CVT-based grid generation. We also compare several methods, including CVT-based methods, for triangulating planar domains. To this end, we define several quantitative measures of the quality of uniform grids. We then generate triangulations of several planar regions, including some having complexities that are representative of what one may encounter in practice. We subject the resulting grids to visual and quantitative comparisons and conclude that all the methods considered produce high-quality uniform grids and that the CVT-based grids are at least as good as any of the others.