1H Nuclear Magnetic Relaxation Spectroscopy of Ultradispersed Diamond Hydrosols

The spin-lattice relaxation of water protons in hydrosols of ultradispersed diamonds with the volume content of the dispersed phase up to 1% is studied by the high-resolution NMR. The relaxation rate of water protons is measured as a function of the dispersed phase concentration. It is shown that hydrosols of ultradispersed diamonds can be used as model systems for studying the relaxation parameters of aqueous phases in heterogeneous media.     

丙烯酸树脂水溶胶的乳液法合成

描述了通过乳液聚合方法合成丙烯酸树脂水溶胶的合成方法，研究了分子量、亲水基团(羧基)含量对水溶胶粒径的影响，分析了在乳液转变成水溶胶的过程中，体系粘度、透光率、表面张力以及粒子形态的变化。     

Synthesis and Some Properties of Cerium Dioxide Hydrosols

Cerium dioxide hydrosols are synthesized by peptizing with nitric acid a precipitate obtained by hydrolyzing cerium(III) nitrate. The synthesized sols are stable with respect to aggregation in both acidic (pH 1.5–3.0) and alkaline media (pH 9.0–11.0). The mean hydrodynamic radius of particles is about 25 nm. The isoelectric point corresponds to pH 6.2. The phase composition of sol particles is determined by X-ray diffraction at pH of the dispersion medium ranging from 1.5 to 3.0. The sol coagulation thresholds are determined in the presence of sodium nitrate and sulfate, as well as of mixed magnesium salt at various pH values of the dispersion medium. Assumptions are made concerning the nature of the aggregative stability of sols.     

Composite Copper-Based Coatings with Ultradispersed Phase

The electrolytic deposition of composite copper-based coatings with an ultradispersed phase(TiN or Al₂O₃) was studied. Conditions for obtaining coatings with the maximum microhardness were determined.     

Rhenium-Based Hydrosols: Preparation and Properties

Transmission electron microscope (TEM), ultraviolet-visible (UV/vis), electrospray mass spectrometric (ESMS), and X-ray photoelectron spectroscopic (XPS) studies are presented on a little studied rhenium hydrosol system produced by reduction of aqueous K(2)ReCl(6) with hydrazine in the presence or absence of a gum arabic protecting agent. The studies indicate that hydrazine-generated "rhenium hydrosols" are unstable in water and slowly dissolve over time in aqueous media to form the highly stable perrhenate ion. Copyright 2001 Academic Press.     

Electrodialysis of acetate fermentation broths

Electrodialysis (ED) shows good potential for downstream processing of acetate fermentation broths, to separate acetic acid while unreacted glucose and other nutrients are partially recycled back to the fermenter. With conventional anion- and cation-exchange membranes, higher current increased acetate flux, water flux, and energy consumption. Multiple ED stacks connected in series with unequal initial volumes for a batch process maximized acetate concentration in the concentrating stream to 134g/L calcium-magnesium acetate (CMA) in the fermentation broth at pH 6.8. Back-transport of acetate from the product into the feed stream and water transport limit the maximum concentration possible. Cost of ED is about $295/ton acetate for the CMA broth.     

Adsorption of Dyes in Studying the Surface Chemistry of Ultradispersed Diamond

Russian Journal of Physical Chemistry A - The effect the surface chemistry of ultradispersed diamond (UDD) has on the adsorption of watersoluble dyes is considered. A comparison is made to...     

Chemical Purification of Ultrafine Cutting Diamonds

A procedure was developed for recovery and purification of ultrafine diamonds.     

Floating Diamonds with Nanomagnetic Particles

In the diamond industry, ferrofluids are used in ferrohydrostatic separators for the density separation of diamonds from gangue material. The size of the magnetic core of the coated particles forming the ferrofluid suspension is vital in ensuring the stability of the fluid. The particle size must be small enough such that sedimentation does not occur in a magnetic field gradient and under the influence of a gravitational field and such that magnetic agglomeration can be overcome. This paper discusses the particle size requirements for fluid stability under the influence of these effects.     

Electrodialysis Kinetics by Laser Interferometry

A new approach to studying electromembrane systems by the laser interferometry method is proposed. Problems in the electrodialysis kinetics that had been solved by this method are reviewed. These include the determination of the size of diffusion boundary layers, the measurement of concentration profiles of solutions at a concentration polarization of ion-selective membranes in solutions of one and two components in isothermal and nonisothermal conditions, the verification of mathematical models for electrodialysis, and the measurement of local Sherwood numbers. A method for measuring concentration profiles in solutions at the interface with bodies of spherical symmetry following the imposition of a gradient of an electric potential on the system is offered. The results of studying the concentration polarization of an ion exchanger granules are analyzed.     

Synthesis and Characterization of Silver Hydrosols in the Presence of Carboxyalkylated Amine Complexones

The specifics of formation of silver nanoparticles in aqueous solution in the presence of carboxyalkylated amine complexones (NTA and DTPA) have been studied for the first time. Sols with these ligands are found to be formed in alkali solutions at рН ≥ 10.0 and 80°С. Their optical spectra and the particle sizes and morphologies are determined by synthesis conditions: рН, the ratio Ag⁺/L, and the order of mixing components. A scheme has been suggested for silver nanoparticle formation in the presence of NTA and DTPA, consistent with the experimental results. The efficacy of the prepared silver sols in SERS measurements is shown.     

Depassivation of Ion-Exchange Membranes in Electrodialysis

Procedures were developed to prevent precipitation on the ion-exchange membrane surface in demineralization of natural hydrocarbonate water by electrodialysis.     

Preparation of Thermostable Highly Dispersed Titanium Dioxide from Stable Hydrosols

A large set of stable nanodispersed TiO₂ hydrosols differing in particle structure and dispersion medium composition was synthesized. For highly dispersed TiO₂ samples obtained by calcination of dried sols at 500°C phase compositions, sizes of primary crystallites, and specific surface areas were found. The factors affecting thermal stability of TiO₂ nanoparticles were analyzed. The sol containing the most thermostable nanoparticles was used to produce a highly efficient catalyst for cyclohexanone ammoximation.     

Ultradispersed diamond as a new carbon support for hydrodechlorination catalysts

The properties of palladium and nickel catalysts supported on ultradispersed diamond (UDD) were studied in the vapor-phase hydrodechlorination (HDC) reaction of chlorobenzene and the multiphase HDC of polychlorobenzenes. The catalysts on UDD exhibited a number of advantages: the vapor-phase HDC of chlorobenzene on Ni/UDD occurred at lower temperatures, and the multiphase HDC of chlorobenzene, 1,3,5-trichlorobenzene, and 2,4,8-trichlorodibenzofuran on Pd/UDD occurred more rapidly than that on catalysts supported on activated carbon. The structure of the catalysts and the electronic states of the active components were studied using IR spectroscopy, temperature-programmed reduction, and adsorption techniques. It was found that the properties of the catalysts depend on the electronic state of palladium, which depends on its concentration in the sample; the structural properties, which are responsible for the accessibility of the active surface to adsorption; and the presence of other metal impurities.     

Ionic Transport in Electrodialysis of Ammonium Nitrate

During the electrodialysis of ammonium nitrate solution, the fluxes of salt ions pass through the maximum, which is observed near the limiting current, with increasing current density. A decrease in the flux of ammonium ions at the overlimiting current densities is caused by the effect of competitive transport of solution ions and by the formation of weak NH₃ ? H₂O electrolyte due to the alkalization of solution layer adjacent to the cation-exchange membrane in the desalination channel. A decrease in the flux of nitrate ions in the overlimiting current modes is caused by a change in the composition and catalytic activity of the functional groups of anion-exchange membrane towards the dissociation of water molecules due to the effect of ammonium ions.     

Electrodialysis purification of 5-aminolevulinic acid hydrochloride

The possibility of using electrodialysis for purifying 5-aminolevulinic acid hydrochloride from pollutants, ammonium chloride, formed in the course of synthesis was studied. Electrodialysis conditions: current density, linear velocity of a solution in desalting chambers, concentration of ammonium chloride and 5-aminolevulinic acid hydrochloride, were optimized.     

The Stability of Detonation Nanodiamond Hydrosols in the Presence of Salts and Surfactants

The regions of stability and coagulation of hydrosols of oxidized detonation nanodiamonds in the presence of inorganic salts and surfactants of different types have been determined. Concentration C_c of inorganic salts corresponding to the onset of the growth of aggregates in a hydrosol dramatically decreases with an increase in coagulating ion charge z: C_c ~ z^?5.3. Anionic and nonionic surfactants stabilize dispersions of nanodiamonds, while additives of cationic and zwitterionic surfactants cause coagulation. The study of the coagulating effect of alkylpyridinium chlorides has shown that the coagulation threshold halves upon elongation of the hydrocarbon chain in a surfactant molecule by a СН₂ group.     

Electrodialysis: From an Idea to Realization

The historical validity demands some clarifications in the early history of electrodialysis. Early investigations with non-selective membranes are not to be recognized as electrodialysis-related although some of them have used the term electrodialysis. Only in 1950 the first synthetic ion-exchange membranes were produced (W. Juda and W.A. McRay). Preceding them membranes manufactured by T.R.E. Kressman were in fact a modified natural product—impregnated parchment membranes. Major electrodialysis" shortcomings such as membrane fouling and scaling were mostly overcome with electrodialysis reversal (EDR) commercial introduction by Ionics in 1967. Synthesis of novel sodium-selective membrane did not spark a burst in ED manufacturing. However higher demand for sodium-selective membranes can be expected in conjunction with nitrate-selective membranes for potable water denitrification—the essential step in water treatment in Europe. New break-through in ED progress was associated with development of apparatuses with ion-exchange resin beads filling desalting compartment. The analysis of energy consumption in ED process shows that the possibility of its reduction by traditional ways of membranes and spacers improvements is practically exhausted. However there is practically undeveloped option to lower the polarization resistance with help of electrodynamic instability (volumetric-charge development). Another possible improvement is creating membranes with special profile. As EDI targets higher levels of water purity the removal of weakly ionized ions becomes important issue.