Coagulation Stage Research Articles

Transport and Mechanical Properties of Polyurethane Film Treated by Ultrasonic Energy

The properties of microporous polyurethane film are mainly determined by the size and distribution of the pores which are microscopic spaces within the polyurethane layer. It is very important for the manufacturer to be able to control the size and shape of the pores. In this study, the probability of controlling the pores was tested by treatment with ultrasonic energy during the coagulation stage. The mechanical and transport properties of film treated by ultrasonic energy were significantly different from those of film made by the normal process. This was due to the subdivision of very large pores within the polyurethane by the ultrasonic treatment and the consequent increase in the number of pores.

Influence of structural properties of alum and ferric flocs on sludge dewaterability

Sludges are made of flocs produced during the coagulation stage. Their dewatering not only depends on the equipment used but also on the chemical, structural and physical characteristics of flocs. In this study, the relation between floc structure and sludge dewaterability is investigated beside the influence of the operating conditions during coagulation. Eight synthetic clay flocs families are produced using clay suspensions with four initial solids concentrations ranging from 0.5 to 5 g L −1 and two coagulants (Al 2(SO 4) 3 and FeCl 3). Flocs structure is characterised by their fractal dimension and by the size of the basic units (clusters, aggregates) they are made from. Fractal dimension values about 2.5 are indicative of rather compact structures with slightly looser flocs obtained when using FeCl 3. Except for clusters, larger in ferric flocs, the basic units sizes are similar whatever the coagulant used and they decrease when the solids concentration during coagulation is increased. Sludge dewaterability is estimated from the bound water content and the capillary suction time (CST) giving respectively information on the extent and on the rate of water removal. Ferric flocs contain about 20% less bound water but exhibit higher CST values and therefore higher resistance to water removal than alum ones. Flocs structure and sludge dewaterability are found linked. The sludge bound water content is found to decrease with the floc fractal dimension: less compact flocs contain more water but less bound water. And the capillary suction time is lower when sludges are made of smaller flocs.

Effect of coagulation conditions on the microfibrillar network of a rigid polymer

AbstractAn important element in the microstructure of high performance fibers and films fabricated from rigid polymers is an interconnected network of oriented microfibrils, the lateral size of which is about 10 nm. This study is an attempt to elucidate the mechanism by which the microfibrils are formed so that larger lateral dimensions can be achieved by suitable processing. Because this morphology emerges in the coagulation stage of the spinning process, we compared the microfibrillar network formed by drastically different coagulation conditions. Ribbons, spun from solution of poly(p‐phenylene benzobisthiazole) in polyphosphoric acid through a slit die, were coagulated either in the ordinary rapid process with water (timescale of seconds) or in a slow process with phosphoric acid (timescale of hours). The coagulated microfibrillar network was dried with supercritical CO2 for X‐ray scattering measurements and impregnated with epoxy resin for sectioning and imaging by TEM. Slow coagulation yields better‐aligned microfibrils of enhanced chain packing, but the lateral size of the microfibrils formed in both cases is similar, about 10 nm. Heat treatment increases the width of water‐coagulated microfibrils but not the acid‐coagulated ones. The observations do not support spinodal decomposition as the mechanism of microfibril formation during coagulation, as was previously suggested. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1087–1094, 2002

Termination of Planetary Accretion Due to Gap Formation

The process of gap formation by a growing planetary embryo embedded in a planetesimal disk is considered. It is shown that there exists a single parameter characterizing this process, which represents the competition between the gravitational influence of the embryo and planetesimal-planetesimal scattering. For realistic assumptions about the properties of the planetesimal disk and the planetary embryo, a gap is opened long before the embryo can accrete all the bodies within its region of influence. The implication of this result is that the embryo stops growing and, thus, large bodies formed during the coagulation stage should be less massive than is usually assumed. For conditions expected at 1 AU in the solar protoplanetary disk, gap formation is expected to occur around bodies of mass < 10^24 g. The effect of protoplanetary radial migration is also discussed.

Nano-sized diamond obtained from explosive detonation and its application

Nano-sized diamond crystallites synthesized by explosive detonation have a very spherical shape 4–6 nm in size, and a very high microstrain. The diamond crystallites are shown to experience a coagulation stage of the carbon droplets during the detonation reaction. This paper also introduces applications of this material in improving the nucleation of chemical deposition diamond film, in low field emission materials, and in wearing and antiattrition materials.

The Treatment of a High Strength Pulp and Paper Mill Effluent for Wastewater Reuse

A treatment process to polish the biologically treated, secondary effluent from a newsprint mill in order to achieve wastewater recycle, has been investigated at pilot-scale. The polishing process included chemical coagulation and solids separation as the tertiary treatment for residual organic removal, and applied electrodialysis reversal (EDR) as the deep treatment stage for desalination. The chemical coagulation stage reduced total oxygen consumption (TOC), colour, and lignins by 81%, 81%, and 78% respectively. Those organics which were inert to biodegradation and resisted chemical coagulation, were reduced by half in the EDR plant. EDR reduced conductivity by 73% from 1800 uS cm−1 to 500 uS cm−1. TOC was reduced by 90% to a level of 8 mg l−1 in this polishing process. The trial demonstrated a satisfactory plant performance and the EDR ion-exchange membrane showed a good fouling resistance. The quality of the final product was as good as, or better than, that of the fresh water supply on site. The running costs of the process were estimated at £ 0.23 m−3, which makes it an economical and viable solution to further reduce mill water consumption, especially for those modern mills which already achieve a low water usage.

Influence de trois haplotypes des caséines αsl, β et Κ fréquents en race bovine Normande sur la composition du lait et l'aptitude à la fabrication fromagère

Summary - Effect of the three most frequent casein haplotypes occurring in the Norman breed used for cheesemaking. In the Norman cow breed, the influence of three casein haplotypes, us1-Cn B, Il-Cn B et K-Cn B (BBB), us1-Cn B, Il-Cn A2 et K-Cn A (BA2A) and us1-Cn C, Il-Cn A2 et K-Cn B (CA 2B), was compared on the composition of milk and its aptitude for cheese production. The physico-chemical composition of 89 samples (40 BBB, 30 BA 2A et 19 CA 2B) selected on the basis of genotype, filiation and lactation stage, as weil as their behaviour during coagulation with rennet were determined. The same samples were used to make Saint-Paulin type cheese from 6 kg of milk (one milking). The x-casein proportion was greater in BBB and CA2B milks than in BA2A milk. The micelle size varied conversely with the proportion of x-casein in total casein and was mu ch greater for milk BA2A (15% more as compared to CA2B milk) than for milk BBB and CA2B. The coagulation ability was higher for milk CA2B than for milk BA2A. The homozygote variant B of x-casein had a higher coagulation ability than variant A. In manufacture ofmicro-cheeses with individual milk of same composition, the association K-Cn Band Il-Cn B variants led to an increase in the cheese yield mainly due to a better retention of the amount of fat in the curd of chee se BBB. The microstructure of BBB curd was doser than these of curd BA2A. At the end of the ripening period (45 days), BBB cheeses were firmer, less elastic and more breakable th an the other two haplotypes. Neither the chee se composition, nor the degree of proteolysis, nor the pH of the ripened cheeses appeared to be responsible for these texture differences which existed since the coagulation stage.

Elimination of microcystis cyanobacteria (blue-green algae) by an ozoflotation process: a pilot plant study

It is now known that since cyanobacteria (blue-green algae) occur in both swimming and drinking water supplies, and lakes and rivers, they represent an increasing hazard to animal life and human population. Moreover, high algal contents pose also a number of operation problems for water purification plants. The objective of the work is to study the elimination of a Microcystis strain of cyanobacateria by the use of an ozoflotation process which associates the oxidizing properties of ozone and the physical aspects of flotation. The functioning and the efficiency of a pilot unit is presented according to such parameters as: ozone dose, flow rate, coagulants and raw water quality. The use of ozone in pretreatment leads to an inactivation of the algal cells. Experiments let us calculate the specific ozone utilisation rate of Microcystis and the [C.t] (ozone concentration, contact time) curve is determined versus algal removal. Under real conditions, a previous coagulation stage is necessary; best results are obtained with ferric chloride. Preozonation is also of influence on the enhancement of the coagulation efficiency. Association of the ozoflotation process and bilayer filtration can solve the algae problems of waters presenting low turbidity and low organic content, and improve water quality.

Effect of frequency in A.C. high voltage on coalescence of water-in-oil emulsion stabilized with sorbitan monooleate type nonionic surfactant.

The liquid surfactant membrane has advantages superior to those of other types of liquid membranes, but its biggest bottleneck lies in the demulsification process for separating the stripping solution from the organic phase containing surfactant and carrier. This paper is concerned with the electrostatic coalescence of the W/O emulsion stabilized with surfactant in an a.c. high-voltage current applied between two insulated flat electrodes. Effects of the dispersed phase hold-up, the applied voltage and the frequency on the phase separation rate were studied.The separation rate was larger for lower initial hold-up of the dispersed phase. When the initial hold-up was less than 40%, the coagulation stage preceded the coalescence stage and the separation rate decreased. The separation rate increased approximately with the second order of the applied voltage. It also increased with frequency and tended to become constant at frequencies in the range of 1000 to 2000 Hz. The water content of the separated oil phase decreased with increase in frequency.

Structure formation during spinning of poly(p‐phenylenebenzobisthiazole) fiber

AbstractThe structure formed in the coagulation stage of the spinning process of poly(p‐phenylene benzobisthiazole) fiber is studied by electron microscopy. An oriented network of microfibrils with typical fibril diameters of about 80‐100Å is observed. We suggest that these microfibrils are the fundamental structural elements of the fiber. Thus, knowledge of the mechanism by which this initial structure is formed may allow for better control of final fiber properties. The relation of structure formation during coagulation to the phase diagram of a rigid polymer solution and to the kinetic mechanism of the phase transition is discussed.

Water-In-Crude Oil Emulsion Stability And Emulsion Destabilization By Chemical Demulsifiers

Abstract The measurement of static physico-chemical properties of oil-water interfaces provides a useful method of indicating where problem emulsion stability areas arise for water-in-crude oil emulsions and the effectiveness of chemical demulsifiers in resolving these problems. The paper includes a discussion of interfacial tension, interfacial shear viscosity and interfacial film compressibility, particularly as applied to complex crude oil systems, and deals with the modification of these properties on the addition of a chemical demulsifier. Introduction Stable water-in-crude oil emulsions occur at many stages during the production and processing of much of the world's oil. The breaking of these emulsions, frequently by the addition of a chemical demulsifier, is an essential step. Factors that affect the stability of such emulsions, and the role played by the demulsifier in destabilizing them, are of paramount importance. Little experimental information exists for complex crude oil systems. It has been suggested(1) that the structural mechanical properties of the natural crude oil emulsifiers in the interfacial layer surrounding the drop are important. This layer provides a resistance to coalescence in the final stage of emulsion breaking. The chemical demulsifier is thought to destabilize the emulsion by causing a disintegration of this layer at the interface. This work supports that viewpoint. Static physico-chemical properties of crude oil/water interfaces have been evaluated over a variety of conditions and correlations with emulsion stability, particularly those encountered during oil production and processes, have been sought. Thus, the relevance of oil/water interfacial tension to emulsion formation and stability has been investigated. The influence of interfacial shear viscosity (and viscoelasticity) on the coagulation stage of emulsion resolution has been examined. Also, the resistance of interfacial films to expansion/compression has been studied and the effect on coalescence elucidated. Finally, modification of these physico Mchemical interfacial properties on the addition of a chemical demulsifier has been investigated, with a view to determining the additive's ability to destabilize such emulsions. Interfacial Tension Oil/water interfacial tension changes were measured by the method outlined in reference (2). Previous work(3) has shown that interfacial tension lowering alone is not an emulsion stabilizing factor. Table 1 shows the influence of various dissolved salts on γ o/w of Ninian crude oil/ water interfaces. These systems have widely different emulsion stabilities at 25 °C, yet the interfacial tension values are hardly different. Mass Transport As well as adsorption of surfactants at the interface, mass transport of water-soluble crude oil components across the oil/water interface will also influence the measured γo/w lowering. Figure 1 shows the effect obtained by pre-equilibrating the crude oil/water phases. This results in a more rapid lowering of γ o/w with time, but with the same final value of interfacial tension being achieved. Where the illustrated effect of pre-equilibration is not observed, the anomalous behaviour can usually be attributed to bulk aqueous-phase pH drifts (in non-equilibrated systems) due to transport of acidic material (predominantly across the mid pH range). Any field-added chemical demulsifier in the crude oil will also cause anomalous effects.

Verification of Bhattacharya’s Equation for Slow Coagulation by Spectrophotometric Measurements in Copper Ferrocyanide and Zinc Ferrocyanide Sols

Abstract The copper ferrocyanide and zinc ferrocyanide sols have been prepared, and their precipitation values have been studied by using KCl, BaCl2 and AlCl3 and by employing the spectrophotometric method in the light of the equation: C=a+\fracm·1⁄tn+1⁄t It has been found that the values of a and m remain the same at all stages of coagulation, while the value of n depends to a great extent on the coagulation stage.