Unit Volume Of Solution Research Articles

High-efficiency separation of CO2 from CO2-CH4 gas mixtures via gas hydrates under static conditions

Hydrate technology with high gas storage capacity and excellent safety features has attracted much attention for capturing CO2 from biogas to produce purified CH4. When considering operational efficiency, it is desirable to overcome technical barriers such as slow hydrate generation and low separation efficiency. Therefore, based on the properties of surfactant-enhanced hydrate generation kinetics, this work first systematically evaluated the performance of 500 ppm SDS on the separation efficiency of 40 mol% CO2 and 60 mol% CH4 simulated biogas. The experimental results show a significant increase in gas capture at higher driving forces, with the rise being dominated by the CH4 component, indicating that larger driving forces reduce hydrate selectivity to CO2-CH4 and weaken gas separation efficiency, with a maximum CO2 recovery of 84.24 ± 1.19% at 275.15 K and 8 MPa. Interestingly, hydrate growth mainly occurred in the liquid phase, leading to the separation factor being positively correlated with the induction time with sufficient CO2 dissolution. In comparison, the gas capture per unit volume of solution could be improved by more than a factor of 2 at higher gas–liquid ratios. The best separation factor of 7.84 ± 0.73 was achieved, and separation factors in general gradually decreased with increasing gas–liquid ratio; however, there was high-pressure failure behavior. Furthermore, the impact of the defoamer on separation efficiency was deeply investigated for SDS decomposition foaming, with results showing that the defoamer would alleviate hydrate decomposition foaming behaviour while having no significant effect on hydrate generation kinetics and separation efficiency.

Removal of Copper Ions from Wastewater by Ion Exchange Resin Using Pulsation Technique

The rate of removal of heavy metal Copper ion (Cu 2+) from synthetic wastewater was studied using an ion exchange resin and pulsation technique. Variables examined were initial concentration of (Cu 2+), ratio of mass of resin to solution liquid volume, frequency, amplitude and geometry of the disc responsible for the pulsation motion. The results were presented mathematically by using the dimensionless analysis and the mass transfer correlation was obtained also Langmuir and Freundlich adsorption isotherms were examined where the date fits Freundlich adsorption isotherms more than Langmuir adsorption isotherms. It is concluded that percentage of (Cu 2+) removal decreases as initial concentration of (Cu 2+) presented increases and increases with contact time, frequency (rpm), amplitudes and mass of resin per unit volume of solution.

The kinetics of homogeneous and two‐step nucleation during protein crystal growth from solution

AbstractMany experimental reports for the kinetics of crystal nucleation and growth, from an isothermal solution, point to a sigmoidal‐like behavior for the process. Here we consider three different nucleation models from the literature and show that all lead to sigmoidal or sigmoidal‐like behavior for the kinetics of nucleation. A two‐step nucleation process is known to occur within certain supersaturated protein solutions, and it is demonstrated in this report how the sigmoidal law yields kinetic information for the two‐step and homogeneous nucleation modes. We propose here that two‐step solute‐rich associates form in the solution around seed nuclei that are already present at or near the point in time when the solution is prepared. Using this hypothesis, we are able to model the time‐dependent volume of the two‐step phase per unit volume of solution and show that this compares well with reported experimental data. A kinetic model is given for the proposed process, which leads to a sigmoidal rate law. Additionally, a relation between the initial and final nuclei densities and the induction time is derived. As a result of this study, the conclusion is that two‐step activity increases with increasing initial supersaturation or increasing salt concentration.

Effect of gold and magnetite on the decomposition kinetics of formic acid at 200 °C under hydrothermal conditions

Formic acid and formate ions are intermediate compounds in the water gas shift reaction as well as in the abiotic formation of organic molecules from dissolved CO2 and H2 under hydrothermal conditions. The decomposition kinetics of a 0.1 M formic acid solution has been investigated using PTFE-lined reactors at 200 °C on the liquid-vapour equilibrium of water for calculated in-situ pH comprised between 2.8 and 3.6. Under these conditions, formic acid is the dominant aqueous species. Formic acid aqueous decomposition follows a first-order kinetics with a constant k (s−1) such that ln(k) = −13.6 ± 0.6 at 200 °C. The addition of gold chips in the reactor is found to promote formic acid decomposition and the kinetics constant of the reaction is a linear function of the exposed gold surface by unit volume of solution (S/V). Consequently, experiments run in gold tubes as those typically used in cold-seal vessels can be by more than two orders of magnitude faster than those performed in PTFE reactors under the same conditions. The addition in the PTFE-lined reactor, of particles of magnetite (Fe3O4) with sizes centred on 300 nm or the presence of aqueous Fe at the millimolal level does not catalyse the hydrothermal decomposition of formic acid at 200 °C.

Improved Synthesis of Nanosized Silica in Water-in-Oil Microemulsions

Present contribution describes modified Stöber synthesis of silica nanoparticles in oil-in-water microemulsion, formulated using heptane, 2-ethylhexanol, Tween® 85 nonionic surfactant, and tetraethyl orthosilicate (TEOS). After some specified incubation time, ammonium hydroxide was added and the reaction mixture was stirred for 24 hours at room temperature. Prior to synthesis, pseudoternary diagram was created for oil-rich area and Winsor IV region was identified. These microemulsions were used for synthesis of silica particles. Resulting particles were characterized by dynamic light scattering, electrokinetic measurements, specific surface area measurements, and powder diffraction. Particles’ diameter was ranging between ca. 130 and 500 nm; usually monodisperse distribution was obtained. The specific surface area of nanoparticles was ranging between 250 and 300 m2/g. Notably, productivity per unit volume of solution was 3 to 5 times higher than for previously reported procedures. Our method can be extended, because polymeric materials can be added to dispersed aqueous phase. In our studies, β-cyclodextrin and hydroxyethylcellulose have been used, giving particles between 170 and 422 nm, with the surface area larger than 300 m2/g.

Osmotic potential calculations of inorganic and organic aqueous solutions over wide solute concentration levels and temperatures.

To demonstrate that the authors' new "aqueous solution vs pure water" equation to calculate osmotic potential may be used to calculate the osmotic potentials of inorganic and organic aqueous solutions over wide ranges of solute concentrations and temperatures. Currently, the osmotic potentials of solutions used for medical purposes are calculated from equations based on the thermodynamics of the gas laws which are only accurate at low temperature and solute concentration levels. Some solutions used in medicine may need their osmotic potentials calculated more accurately to take into account solute concentrations and temperatures. The authors experimented with their new equation for calculating the osmotic potentials of inorganic and organic aqueous solutions up to and beyond body temperatures by adjusting three of its factors; (a) the volume property of pure water, (b) the number of "free" water molecules per unit volume of solution, "Nf," and (c) the "t" factor expressing the cooperative structural relaxation time of pure water at given temperatures. Adequate information on the volume property of pure water at different temperatures is available in the literature. However, as little information on the relative densities of inorganic and organic solutions, respectively, at varying temperatures needed to calculate Nf was available, provisional equations were formulated to approximate values. Those values together with tentative t values for different temperatures chosen from values calculated by different workers were substituted into the authors' equation to demonstrate how osmotic potentials could be estimated over temperatures up to and beyond bodily temperatures. The provisional equations formulated to calculate Nf, the number of free water molecules per unit volume of inorganic and organic solute solutions, respectively, over wide concentration ranges compared well with the calculations of Nf using recorded relative density data at 20 °C. They were subsequently used to estimate Nf values at temperatures up to and excess of body temperatures. Those values, together with t values at temperatures up to and in excess of body temperatures recorded in the literature, were substituted in the authors' equation for the provisional calculation of osmotic potentials. The calculations indicated that solution temperatures and solute concentrations have a marked effect on osmotic potentials. Following work to measure the relative densities of aqueous solutions for the calculation of Nf values and the determination of definitive t values up to and beyond bodily temperatures, the authors' equation would enable the accurate estimations of the osmotic potentials of wide concentrations of aqueous solutions of inorganic and organic solutes over the temperature range. The study illustrates that not only solute concentrations but also temperatures have a marked effect on osmotic potentials, an observation of medical and biological significance.

Investigating the parameters affecting the adsorption of amino acids onto AgCl nanoparticles with different surface charges

In this paper, adsorption behaviors of typical neutral (alanine), acidic (glutamic acid) and basic (lysine) amino acids onto the surfaces of neutral as well as positively and negatively charged silver chloride nanoparticles were examined. Silver chloride nanoparticles with different charges and different water content were synthesized by reverse micelle method. The adsorptions of the above mentioned amino acids onto the surfaces of differently charged silver chloride nanoparticles were found to depend strongly on various parameters including pH of the aqueous solution, type of amino acid, water to surfactant mole ratio, and type of charges on the surfaces of silver chloride nanoparticles. It was found that the interaction of -NH(3) (+) groups of the amino acids with silver ion could be a driving force for adsorption of amino acids. Alanine and Glutamic acid showed almost similar trend for being adsorbed on the surface of silver chloride nanoparticles. Electrostatic interaction, hydrophobicity of both nanoparticle and amino acid, complex formation between amine group and silver ion, interaction between protonated amine and silver ion as well as the number of nanoparticles per unit volume of solution were considered for interpreting the observed results.

Estimating Of Etchant Copper Concentration in The Electrolytic Cell using Artificial Neural Networks

In this paper, Artificial Neural Networks (ANN), which are known for their ability to model nonlinear systems, provide accurate approximations of system behavior and are typically much more computationally efficient than phenomenological models are used to predict the etchant copper concentration in the electrolytic cell in terms of electric potential, operating time, temperature of the electrolytic cell , ratio of surface area of poles per unit volume of solution and the distance between poles. In this paper 350 sets of data are used to trained and test the network.. The best results were achieved using a model based on a feedforword Artificial Neural Network (ANN) with one hidden layer and fifteen neurons in the hidden layer gives a very close prediction of the copper concentration in the electrolytic cell.

Thermodynamic characterization of the water + methanol system, at 298.15K

Thermodynamic characterization of the water + methanol system, at 298.15 K, has been achieved through study of the composition dependence of excess differential coefficients, related to the pVT dependence of free energies and free enthalpies. For this purpose, density, heat capacity per unit volume of solution, and ultrasonic velocity were measured over the whole composition range. Results suggest that weak hydrophobic effects might develop in the water-rich region; then, the organic molecules are incorporated into the aqueous network by a substitutional association.

Kinetics of inhibited crystal growth: Precipitation of CuS from solutions containing chelated copper(II)

Precipitation of crystalline CuS (covellite) is kinetically inhibited in the presence of aminocarboxylate chelating agents, EDTA and DCTA, even in highly supersaturated solutions. At millimolar concentrations at pH 8.1, these chelating agents adsorb strongly enough to CuS surfaces to approach monolayer coverage, reaching a density of about one molecule per 80 Å 2. Bisulfide competes with the chelators for surface sites. Growth of CuS was studied turbidimetrically by mixing solutions of chelated copper with bisulfide solutions in a stopped-flow spectrophotometer. The data were well fit by a rate law d[ CuS] dt = kaθ HS[ CuY] , where k = rate constant, A = particle surface area per unit volume of solution, θ HS = fractional coverage of surface sites by sulfide, rather than chelator, and [Cu Y] = concentration of copper chelate in solution. This rate law suggests that growth is controlled by encounters between HS − bound to the surface and chelated copper from the solution. Growth is diffusion limited. Differences in k obtained when Y = EDTA and DCTA suggest that only forms of the chelated copper with coordination number less than 6 are kinetically active.

Interaction of Aqueous Mg2+ with Growing Calcite Crystals and its Effect on the Aragonite ^rarr Calcite Transformation Between 25 and 90 Degrees Celsius: ABSTRACT

The interaction of aqueous Mg2+ ions with growing calcite crystals was studied by closed system recrystallization of aragonite to calcite in the presence of aqueous CaCl2-MgCl2 solutions at 25-90°C. The measured heterogeneous coefficients for Mg2+ between calcite and solution (^lgr CMg2+) are independent of the solution's composition and rate of recrystallization. They are strongly dependent on temperature, being 0.0573 ± 0.0017 at 25°C, 0.0681 ± 0.0019 at 35°C, 0.0778 ± 0.0022 at 50°C, 0.0973 ± 0.0021 at 70°C, and 0.1163 ± 0.0034 at 90°C. If, as reported in literature, calcite containing 12-16 mole % magnesium has the same solubility as that of aragoni e, the new ^lgrCMg values exclude its formation directly from sea water. However, in closed systems isolated from seawater, the transformation of aragonite to calcite should start spontaneously once the magnesium-calcium ratio of the interstitial fluids drops from 5 to 2 or less, no freshwater intervention in this process being necessary. The kinetics of recrystallization in the absence of Mg2+ at 25 and 35°C are strictly diffusion controlled and are, thus, markedly affected by the mass of aragonite per unit-volume of solution taking part in the process. The kinetic effect of Mg2+ is still under study. End_of_Article - Last_Page 787------------

Diffuse Double-Layer Interactions in One-, Two-, and Three-Dimensional Particle Swarms

The theory of diffuse double-layer interactions in homogeneous isotropic swarms of particles is developed by means of a cell model. Energies of interaction are conveniently treated in terms of the partial volumetric Gibbs free energy. Calculations use (in part) a simple “matched Debye–Hückel approximation” to exact solutions of the nonlinear Poisson–Boltzmann equation. Geometrical effects exert a dominant influence on the variation of partial Gibbs free energy with particle area per unit volume of solution. Evaluation of the relative importance of double-layer interactions and particle Brownian motion provides a check on the cell model. Results for the three-dimensional swarm are found to be consistent with available estimates of the repulsive force between two spherical particles. Application of the approach to heterogeneous swarms is discussed.

CRENATED RED CELLS IN CSF

To the Editor : On Feb 1, 1965, I sent you a letter taking issue with some of Dr. Mauer's comments concerning Crenated Red Cells in Spinal Fluid which appeared editorially in theJournal, 108: 451, 1964. It included copies of correspondence I had with Dr. Mauer as well as an alternative explanation for this phenomenon. In essence Dr. Mauer's explanation depends on the idea that Cerebrospinal fluid is 3.5% hypertonic with respect to blood plasma, and water loss from the red cell with crenation would be expected to occur promptly in this fluid. The concept that CSF is hypertonic compared to blood plasma is correct on the basis of osmolarity, ie, osmolar concentration per unit volume of solution (plasma); but it is incorrect on the basis of osmolarity, which is applied to osmolar concentration per unit weight of solvent (water). It is a biologically significant point that all body cells

Solubility Product of Iron Phosphate

AbstractThe solubility product of iron phosphate was determined by both dissolution and precipitation methods in dilute salt solutions. Solution pH values slightly below the determined isoelectric pH of 2.75 for iron phosphate were employed to get determinable amounts of iron in the solution. The pKsp value was calculated from the ionic activities of Fe3+ and H2PO4‐ in the equilibrium solution by the following equation, pKsp = pFe3+ + pH2PO4‐ + 2pOH‐ which was found to coordinate the data most satisfactorily. The pKsp value of iron phosphate increased with a 1000‐fold decrease of the solid‐to‐solution ratio from 33.6 to 35.1. It increased from 33.0 to 33.2 over a 50‐fold decrease of the concentration of the precipitation reagents. A medial value of 33.5 was approached by the two procedures; however, for low iron phosphate‐solution ratios, such as those commonly employed for soil extraction, the applicable pKsp value agrees with the most dilute solid‐solution value of 35 or more. Similarly for aluminum phosphate, the applicable pKsp value extends as high as 32 for dilute suspensions. The variation in apparent solubility product with amount of solid per unit volume of solution is negligible compared to the magnitude of the pKsp which is the reciprocal of a billion trillion trillion. The calculations from solubility products show that aluminum phosphate and iron phosphate should precipitate and accumulate even in neutral soils, as observed experimentally.

Irradiation of Ferrous Ammonium Sulfate Solutions: Energy Absorption and Ionization Calculations for Cobalt 60 and Betatron Radiation

Solutions of ferrous ammonium sulfate in 0.8N H2SO4 have been irradiated with Co60 gamma rays and with x-rays from a 25-Mev betatron. The energy absorbed per unit volume of solution has been calculated from a modification of the Bragg-Gray formula, Ev=JvWρ in which the factor ρ was determined according to a calculated distribution of primary electron energies. The chemical yield was then calculated in terms of G, the number of ferrous ions oxidized per 100 ev absorbed.