Mutual Coagulation Research Articles

Formation, Stability, and Coagulation of Fullerene Organosols: C70 in Acetonitrile-Toluene Solutions and Related Systems.

This paper is aimed at better understanding the nature of C70 aggregates in organic solvents. As liquid media, acetonitrile-toluene mixed solvents were chosen. At a high content of CH3CN, e.g., 90 vol %, colloidal particles with a size of ca. 225 ± 10 nm are formed with a negative ζ-potential of -(55 ± 5) mV and are stable over time. The interaction with electrolytes containing single-, double-, and triple-charged cations was examined using dynamic light scattering and UV-visible spectra. Additional experiments were carried out with methanol and benzene instead of acetonitrile and toluene, respectively. For comparison, data were obtained with C60 organosols. It was found that coagulation obeys the classical Schulze-Hardy rule. The specificity of the coagulating power of various single-charged cations was explained by their different abilities to adsorb on negatively charged C70 aggregates. The overcharging effect is expressed not only for Ca2+ and La3+ ions but even for Li+ and is caused by poor solvation of such cations in a cationophobic solvent, acetonitrile. After introduction of the cryptand [2.2.2], a substantial increase in the critical concentrations of coagulation for Na+, Li+, and Ca2+ was observed owing to conversion of "bare" metal cations into their cryptates. The application of the Derjaguin-Landau-Verwey-Overbeek theory allowed for evaluation of the Hamaker constant of the C70-C70 interaction in vacuum, AFF, which lies in the interval of 5.8-16.6 × 10-20 J. Such an estimate, close to that made previously for C60 organosols, was received after withdrawing electrolytic systems where the hetero- and mutual coagulation were highly likely. However, it is impossible to completely exclude the interfering influence of the latter phenomena. Based on the obtained AFF values, two approaches to understanding the behavior of fullerenes in water were proposed.

On the Differentiation of Heterocoagulation and Coagulation Processes Processing in Binary Mixed Sol

Results of turbidimetry study of aggregate stability of binary SiO2–ZrО2 sol and its components in 10–3–10–1 M KCl solutions at рН 3.4 when ZrO2 particles have a high positive charge and SiO2 particles are slightly (close to zero) negatively charged are presented. The ratio of numerical concentrations of sol particles ZrO2 to SiO2 was 7.8 : 1. It was found that in binary SiO2–ZrО2 sol both the process of heterocoagulation (mutual coagulation) of sols and coagulation of the same oxide particles occur throughout the studied range of KCl concentrations. The way of differentiation of processes of dissimilar SiO2 and ZrO2 particles heterocoagulation and coagulation of components is proposed. It is shown that at pH 3.4 the increase in the concentration of KCl solutions in binary SiO2–ZrО2 sol leads to a decrease in the intensity of the process of ZrO2 and SiO2 particles mutual coagulation, which is explained by the decrease in the radius of action of attraction of dissimilar particles.

Characteristics according to the Amount of HAp Added in Resin for Tooth Repair

A study was conducted to investigate the possibility of a composite material containing a composite resin as a matrix and hydroxyapatite (HAp) powder as a substitute material for tooth repair. As the content of HAp increased, hardness value (111.9 HV at 9%) increased and flexural strength (73.3 MPa at 9%) decreased. Observation of the microstructure after immersion in a simulated body fluid (SBF) solution confirmed a dense structure due to mutual coagulation and curing. It was thought that fine HAp recrystals were formed with the lapse of time, and they were entangled to form a condensation structure and had a dense structure. In addition, since the activity was shown by the ion migration on the surface of a tooth, it was highly likely that a biocompatible bond occurred during tooth contact. Therefore, it could be used as a substitute material for tooth repair. Key words: Hydroxyapatite, Composite, Repair, Resin, Tooth

Peculiarities of Dyes Removing from Water with Diatomite

The peculiarities of removing methylene blue from water have been investigeted. It is established, that in the purification of water from methylene blue using diatomite, together with adsorption coagulation processes can occur. This consists in heterocoagulation of positively charged dye associates with negatively charged particles of diatomite. At low concentrations dye ions can be removed from solution by adsorption on the clay surface. Adsorption of methylene blue ions can be based on the ion exchange between silanol groups of the clay surface and dye cations. At high concentrations cleaning of water occurs due to mutual coagulation of the positively charged particles of dye and the negatively charged particles of diatomite. In this conditions dye molecules similar molecules of surfactants form associates containing tens or hundreds molecules. The highest degree of dye ions extraction from water is observed at contact time 6 hours and at medium pH ≥ 4. In acidic medium (pH <4) degree of dye removing from water decreases due to protonisation of clay’s silanol groups to SiOH2

Effect of hydrolyzable metal cations on the coagulation between hexadecane and mineral particles

Mutual coagulation tests were conducted between hexadecane droplets (with and without doping with 0.001 mol/L sodium oleate) and micrometer-sized quartz, kaolinite, and illite particles in the presence and absence of multivalent hydrolyzable metal cations. It was observed that while hexadecane did not coagulate with quartz particles in the entire pH range tested (from 3 to 11), the presence of multivalent metal ions significantly increased the mutual coagulation between the hexadecane and quartz. And this only happened when the pH was raised to the level where first-order metal hydroxyl species and/or metal hydroxides were formed. The implications of this mutual coagulation for bitumen liberation from Alberta oil sands are discussed.

金ナノ粒子濃厚ペーストの調製と塗料用色材としての応用

A novel preparation method of concentrated gold nanoparticle pastes was developed. A comb-shaped block copolymer was used to prevent the mutual coagulation of gold particles. Certain kinds of amines were found to reduce Au 3 + ion at an industrially preferable and controllable rate. The maximum metal concentration in the paste was 20% and the paste also contained 10% of the protective polymer. Gold nanoparticles having diameter of a few tens nanometer were known to exhibit red color due to plasmon light absorption. The gold nanoparticle paste obtained in this study was applied as a paint colorant and proved to show an aesthetic color and high weather durability.

Upper tropospheric SO2 conversion into sulfuric acid aerosols and cloud condensation nuclei

We have investigated the potential of upper tropospheric cloud condensation nuclei (CCN) formation from sulfur dioxide. This process involves three steps including SO2 conversion to gaseous sulfuric acid (GSA), homogeneous bimolecular nucleation of GSA and water vapor leading to new aerosol particles, and new aerosol particle growth via mutual coagulation and GSA‐H2O condensation. Our investigation includes both measurements of SO2 and GSA as well as model calculations of SO2 conversion to new aerosol particles in the presence of preexisting aerosols which act as a competing sink for GSA. The model reproduces the measured abundance ratio GSA‐SO2 reasonably well. Furthermore, the model predicts that efficient upper tropospheric CCN formation from SO2 may, in fact, occur under certain plausible conditions. These conditions are explored utilizing the factor FCCN, defined as a ratio of the source and sink terms of gaseous sulfuric acid. In particular, a threshold FCCN value for efficient CCN formation is calculated with the model.

Quantifying interspecific coagulation efficiency of phytoplankton

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 159:75-79 (1997) - doi:10.3354/meps159075 Quantifying interspecific coagulation efficiency of phytoplankton Jørgen L. S. Hansen1, Thomas Kiørboe2,* 1Marine Biological Laboratory, Strandpromenaden 5, DK-3000 Helsingør, Denmark 2Danish Institute for Fisheries Research, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark *Addressee for correspondence. E-mail: tk@dfu.min.dk Non-sticky latex beads and sticky diatoms were used as models to describe mutual coagulation between sticky and non-sticky particles. In mixed suspensions of beads and Thalassiosira nordenskjoeldii, both types of particles coagulated into mixed aggregates at specific rates, from which the interspecific coagulation efficiency could be calculated. Stickiness between beads and T. nordenskjoeldii was 50% of that of T. nordenskjoeldii in monospecific suspensions, and this ratio remained constant throughout 12 experiments covering 1 order of magnitude variation in the stickiness level of T. nordenskjoeldii. Mutual coagulation between Skeletonema costatum and the non-sticky cells of Ditylum brightwellii also proceeded with half the efficiency of S. costatum alone. The latex beads were suitable to be used as 'standard particles' to quantify the ability of phytoplankton to prime aggregation of suspended particles. Phytoplankton stickiness · Interspecific coagulation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 159. Publication date: November 29, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Adaptive significance of phytoplankton stickiness with emphasis on the diatom Skeletonema costatum

Diatom aggregate formation was analyzed using coagulation theory. Population dynamics models show that coagulation has an important impact on species succession during diatom blooms. When different species collide and form mixed aggregates this process causes interspecific interference competition within the diatom community. The outcome can be predicted by a set of simple differential equations. For a twospecies system the equations reduce to the Lotka-Volterra two-species competition model. The outcome of this interference competition depends on species-specific growth rates, cell sizes, stickiness and on the species composition of the seeding populations of a bloom. Due to mutual flocculation some species may disappear from the environment. Small and fast growing diatoms are favoured by high stickiness coefficients. The impact of stickiness on species succession was found to be most pronounced in eutrophic and hydrographically isolated environments. The sticking properties of the diatom Skeletonema costatum are discussed in an evolutionary context; we suggest that mutual coagulation increases the abundance of S. costatum relative to other diatom species in coastal areas. The model was tested on field data, and the predicted dynamics of a spring bloom was very similar to that observed.

Mutual Coagulation of Polymer Particles and Quartz or Polyvinylidene Chloride Plates in Liquids

Mutual coagulation of substrates and particles has been investigated in various liquids. Spherical polyethylene or nylon 12 particles and polyvinylidene chloride or quartz substrates were used. The number of particles adhering to a substrate as a measure of mutual coagulation was small in n-alcohols, whereas large in n-alkanes, carbon tetrachloride and water. Mutual coagulation decreased with increasing ethanol concentration in ethanol/water mixtures. The experimental results were not explained on the basis of the heterocoagulation theory, suggesting that the polar interaction affected mutual coagulation. The results are discussed from the standpoint of liquid dielectric constants as a measure of polarity. Mutual coagulation in the present systems was found to occur hardly in the liquids whose relative dielectric constants ranged from 20 to 60.

Hetero- and homocoagulation of colloidal gold and iron oxides

The mutual coagulation of colloidal gold and iron oxides (goethite and hematite) was studied. The behavior of the mixed systems was observed by TEM. In 0.1 M sodium nitrate solution homocoagulation of the gold particles is observed, instead of the heterocoagulation observed in diluted electrolyte solutions. Peptization experiments with the colloidal gold/goethite heterocoagulated system show that electrostatic forces are dominant. The behavior of the mixed system at different temperatures is used to estimate the heat of adhesion. The HHF potentials of both systems are also calculated; both HHF and the Langmuir heat obtained are consistent.

Adsorption of colloidal gold on colloidal iron oxides

Lateritic gold enrichment can be associated with the formation of colloidal gold and its interaction with the iron-oxide-rich medium. Adsorption of colloidal gold on synthetic goethite and hematite was measured at 25°C. The observed high affinity between the oppositely charged particles depends on the medium composition. The presence of citrate anions can inhibit mutual coagulation, while inert electrolytes enhance this effect.

The effect of coagulation on the diffusive spread of aerosol particles

It is pointed out that the Brownian diffusive spread of a gaseous suspension of particles ('aerosol') will be decreased due to the mutual coagulation of the particles, which gives rise to a continually decreasing effective particle diffusion coefficient. This leads to a modified mean-square particle displacement which in general increases less rapidly with time than the linear variation characteristic of non-interacting particles. Analytic results are obtained for this displacement in the regimes Kn >1 for diffusion in one, two and three dimensions. The effects of coagulation, both on particle displacement and particle growth become less important as the number of dimensions increases, and in the 3D case it is shown that despite coagulational growth, particle sizes cannot exceed a certain maximum. Calculation of numerical values suggests that measurements of the modified spread could provide useful experimental data on coagulation effects.

A comprehensive equation for the rate of adsorption of colloidal particles and for stability ratios

A general correlating equation which can be used for predicting adsorption rates of colloidal particles on substrates of various geometry under a wide range of double layer interactions is presented. This equation is applicable as long as the depth of the secondary minimum in the surface interaction energy profile is low (⪷0.5 k B T) and can be used in the case of constant-potential or constant-charge-density double layer interactions or when a suitable combination is appropriate. The following parameters are needed for using the equation: the height of the potential barrier, V max; the magnitude of the London-van der Waals attraction, A/6 k B T (where A is the Hamaker constant); the Peclet number, Pe (which represents the influence of convection); and the ratio or radii of the two interacting surfaces. Four special cases, for adsorption on spherical and cylindrical substrates and on rotating discs, and for mutual coagulation, are derived from the general equation as illustrative examples. The extensions of the equation for adsorption in porous media and fibrous mats (useful in the theory of physical separation processes) are also presented. Since the correlating equation is a closed-form expression, it offers a convenient method for determining the effective potential barrier (the activation energy for adsorption) from experimentally determined adsorption rates.

Adsorption of brownian particles in the presence of potential barriers: effect of different modes of double-layer interaction

Adsorption of colloidal particles on charged substrates critically influences numerous industrial operations and natural systems. Such adsorption is very sensitive to the type of interaction between the electrostatic double layers surrounding the particles and the substrates, and this sensitivity depends, in addition, on the convective field that carries the particles. We present here an extensive quantitative analysis of adsorption rates under the influence of various modes of double-layer interaction (such as constant-potential, constant-charge-density, and combinations of these) for a wide range of Peclet numbers. The interaction profiles are classified under three general classes of shapes that determine whether convection will increase or decrease the adsorption rate. The adsorption rate is shown to be uniquely given (within experimental accuracy) by three parameters [ A/6 k B T, the dimensionless Hamaker constant; V max, the dimensionless interaction energy maximum; and Pe, the Peclet number] when the energy profile has shallow secondary minimum (Type-I profile). A convenient correlating equation for the adsorption rate (in terms of the Sherwood number) is presented. This equation eliminates the need for extensive computer calculations and applies for any type of double-layer interaction as long as the energy profile is Type I. Although the numerical calculations presented are based on a particular choice for the substrate (rotating disks), the correlating equation given can be extended to arbitrary geometries (as shown for the case of mutual coagulation).

Grain growth by radiation pressure induced coagulation

A theoretical treatment is given of the growth of grains as a consequence of their mutual coagulation brought about by relative motions induced by radiation pressure. Analytical and numerical techniques are employed to tackle the relevant coagulation equation. The results are of particular astrophysical significance in the context of forming very small grains following a nucleation process, in the production of grains large enough to allow condensation of volatiles onto their surface, and in any situation where the supply of volatiles has been exhausted. It was found that in interstellar clouds, grains composed of iron, graphite and glassy carbon, being typical examples of three basic types of material, could grow to a size where condensation of the volatiles was possible. On the other hand, olivine, a typical silicate, could not. If a source of radiation existed at the centre of the cloud, then growth could occur if the cloud was turbulent or if the density was high enough; otherwise the grains were driven out of the regions of interest at high velocity. In the latter case, with a high cloud density, re-radiation has to be taken into account.

ChemInform Abstract: APPLICATION OF A COAGULATED MIXTURE PREPARED FROM FINELY DIVIDED CATION AND ANION EXCHANGE RESINS TO THE ENRICHMENT OF COPPER(II)

AbstractDurch gegenseitige Ausflockung von Kationen‐ und Anionenaustauschersuspensionen (Amberlyst 15 und A‐26 in RSO3Na‐ bzw. RNMe3Cl‐Form) gewonnene Mischharze eignen sich in Gegenwart von 8‐Chinolinol‐5‐sulfonsäure (H2qs) zur schnellen und selektiven Anreicherung von Cu(II)‐Spuren auf dem Harz in Form des Komplexes [Cu(qs)2]2−.

Deposition of cationic styrene and styrene—butadiene latex particles on cellulose fibers

Deposition of cationic latex, stabilized with tertiary amino groups, on anionic pulp fibers in a stirred system shows a distinct difference in the behavior of hard, nonfilming (polystyrene) and soft, film-forming (polystyrene—butadiene) latexes despite their similar surface characteristics. The hard latex deposits as individual particles at a rate that is apparently diffusion controlled. The behavior expected in mutual coagulation of unlike particles is generally observed except that homocoagulating hard latex does not deposit. The deposition of soft latex indicates two concurrent mechanisms. Initial deposition of individual particles is accompanied by aggregation of the depositing latex. The rate is likely affected by the latex's tendency to coagulate and full deposition of the homocoagulating latex is observed. The response of deposited latex to the addition of neutral salt is also different. The hard latex, in apparent contradiction to expectation, is redispersed by a salt addition to the stirred system. The soft latex, after deposition, is not removed and further deposition of unattached latex takes place when enough salt is added to cause its homocoagulation. An explanation is sought in an interplay of attraction forces between latex and fiber, the distance of their closest approach and the hydrodynamic forces acting on deposited latexes. The hard latex is apparently not in intimate contact with the fiber surface and when the attractive double layer interaction is diminished due to the salt effect the attraction is outbalanced by thermal motion and fluid shear. The soft latex can establish a better contact with fibers and the attraction force over a shorter separation distance resists the hydrodynamic forces.

A Simplified Aerosol Coagulation Model

A simplified aerosol coagulation model has been developed, to determine the mutual coagulation of many discrete size classes. The model has been applied to computation of the growth of light scattering particles from a small monodisperse aerosol, and prediction of aerosol size and concentration downwind of sources. These computations are in good agreement with field observations. This model is sufficiently simplified to allow programming In contemporary desk calculators and is an extremely practical tool for application of aerosol technology to air pollution problems.

The zeta-potentials of natural and synthetic chrysotiles

Different specimens of the asbestos mineral chrysotile show widely different zeta-potentials. Strongly positive values are found with samples containing an excess of magnesia in the form of brucite, Mg(OH) 2. Synthetic chrysotile and natural samples containing little or no brucite give moderately positive ζ-values over the pH range 3–11. Feebly positive or weakly negative natural chrysotiles are materials which have suffered weathering; and deliberate acid-leaching of any chrysotile ultimately leaves a strongly negative pseudomorph of silica gel. Since the pH and the ambient concentration of Mg 2+ ions near the surface are the main factors controlling ζ, and since chrysotile is readily susceptible to leaching in practically all aqueous media and does not come to a true ionic equilibrium in any practical time, the zeta-potential of an ideal chrysotile surface is a hypothetical concept. The results also explain the temporary colloidal stability of very dilute suspensions of chrysotile in weakly acidic media and the mutual coagulation of chrysotile and amosite slurries.