Abstract water soluble polymer flocculants are important constituents of. Polymer thickeners can induce good dispersion, bridging, or depletion flocculation of latexes depending on the polymer structure and concentration. It can also be shown that there is a repulsive interaction between the two layers of dextran. Flocculation definition of flocculation by medical. Different time regimes in the development of the reduced scattering coefficient. Large, heavy particles settle out readily, but smaller and lighter particles settle very slowly or in some cases do not settle at all.
Synthetic flocculants are mostly made by free radical solution or. From a gibbs free energy perspective, at temperatures slightly above the ucep temperature, a singlephase liquid is marginally stable. The very same result can be derived using the kirkwoodbuff solution theory. A number of factors that affect selective fkjccu1ation of fines have been identified and the effect of e of parameters on p behavior has been explained with the help of a few case studies.
There follows, during the flocculation step,an increase in the size of the particlespresent in the water phase resulting in the formation of flocs. To our surprise, when depletion stabilization occurs, the suspension shows the stabilization at the cluster length scale, while maintaining fractal aggregates at the particle length scale. Ny 10027 abstract processing of fine particles in suspension is markedly affected by their state of dispersionaggregation. Therefore, we have developed phase diagrams to help visualize these interactions. This can take place spontaneously or may be brought about by adding clarifying agents. The critical volume fraction for depletion flocculation is found to decrease with increasing molar mass of free polymer. Chapter 14 depletion of resource what depletion of resources is. Subsequently, various authors 3,4 described the aggregation of red blood cells using hydrophilic polymers. Water supply system water supply system coagulation and flocculation.
Depletion flocculation could be confirmed by the fact that dilution of the sample with water to below the critical flocculation concentration yielded a well dispersed system. This practice covers a general procedure for the evaluation of a treatment to reduce dissolved, suspended, colloidal, and nonsettleable matter from water or wastewater by chemical coagulation floccula tion, followed by gravity settling. Figure 1, we can observe in the righthand tube, the coexistence of a. Flocculants, with their very high molecular weights long monomer chain and their charge content, fix the destabilized particles and aggregates along the polymer chain. Depletion flocculation in colloidal dispersions science. From my course ees 3030, water treatment systems, in the department of environmental engineering and earth sciences at clemson university. Coagulation, flocculation and clarification of drinking water. Flocculation definition, to form into flocculent masses. Many large scale industrial processes paper production, water treatment and dewatering processes require destabilization or flocculation of dispersed particulates. Co flocculation of yeast species, a new mechanism to govern population dynamics in microbial ecosystems.
This knowledge will provide a basis for understanding the needs of the. The various phases have a significant effect on coatings and applications properties. The interstitial free polymer concentration between two flat plates illustrated as a function of surface separation h. Pdf waste water treatment by coagulation and flocculation.
Walzdepletion flocculation induced by synergistic effects of. With no added electrolyte, depletion flocculation was observed at high values of 01. Pdf depletion flocculation in colloidal dispersions researchgate. Depletion flocculation practical solubility science. The effect of addition of free polymer to sterically stabilised dispersions, i. Flocculation and coalescence of oilinwarer emulsions volume 248 j. Business chemicals, plastics and rubber gas chromatography analysis nonionic surfactants chemical properties polymers. Depletion flocculation of aqueous, electrostericallystabilized latex. Controlling the dispersion or flocculation of colloidal. Runkana langmuir center for colloids and interfaces, columbiauniwrsity, new york. Identification of the instability phenomenon of an emulsion. Read depletion flocculation and thermodynamic incompatibility in whey protein stabilised ow emulsions, food hydrocolloids on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
However, there exist many problems in observing the flocculation and settling process of wholetailings, as. Nearly 90% of earths ozone is in the stratosphere and referred to as the ozone layer. An efficient lowcost method for harvesting microalgae is essential for largescale and lowcost production of microalgal biomass. The colloidal interactions of associative polymers and latexes in the presence of surfactant are complex. As a service to our customers we are providing this early version of. Hence, we should be aware and actions must be taken to ensure that ozone layer is not destroyed. Rapid dewatering and thickening of wholetailings with ultrafine particles is one of the most important processes for the wholetailings paste preparation. Microalgae are a promising new source of biomass for production of food, feed, fuel, or chemicals, but the cost and energy demand of largescale production is still too high. Flocculation could be nondestructively monitored by measuring the decrease in ultrasonic attenuation of the emulsions. Steric stabilisation and flocculation by polymers polymer journal. Depletion flocculation practical solubility science prof steven. Lekkerkerkerc a cavendish laboratory, madingley road, cambridge, cb30he, uk b department of physics and astronomy.
However, when the associative interactions are destroyed, depletion flocculation of the latex can result. Influence of added surfactant on particle flocculation in waterborne polymerparticle systems. Well, most of us are, and we have two models here to add to the difficulties. Pdf creaming and flocculation of oilinwater emulsions. This is a pdf file of an unedited manuscript that has been accepted for publication.
Flocculation is a process in chemistry wherein colloids are extracted from suspensions which then take the form of flake or floc. Almost all physical, chemical, biological and other activities are responsible for environmental degradation. Scc sw chapter 1118 polymers in cosmetics depletion stabilization two particles in solution will be attracted to. Solution on ozone layer depletion september 16 was voted the world ozone day in the year 1994 by the united nations general assembly. This phase behavior is driven by entropically favourable molecular interactions between polymer in the coil conformation and solvent molecules.
Determination of depletion flocculation by various techniques. Numerical simulation of flocculation and settling behavior. Depletion flocculation modelled in prof steven abbotts practical solubility. Depletion flocculation of latex dispersion in ionic. Selective flocculation of fines columbia university.
Suspended particles cannot be removed completely by plain settling. A basic statisticalmechanical calculation of the force is presented and some di. Flocculation effluent treatment plant for the removal of microbial cells and suspended colloidal matter. Depletion flocculation scc sw chapter 1118 polymers in cosmetics 4. Depletion interactions in polymer solutions promote red blood cell adhesion to albumincoated surfaces. Depletioninduced flocculation of concentrated emulsions. It is shown that an attractive interaction arises from depletion of surfactant micelles and leads to a fluidsolid phase transition. Flocculation, in the field of chemistry, is a process in which colloids come out of suspension in the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. Surfactant and electrolyte effects on latex depletion. Read depletion flocculation of latex dispersion in ionic micellar systems, journal of colloid and interface science on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. In this paper, we give an overview of different approaches for achieving flocculation of.
On extending depletion flocculation phase behaviour models. Cell aggregation and flocculation flocculating agents are added in the fermentation media for dewatering. Creaming and flocculation of oilinwater emulsions containing sodium caseinate. This proves ozone depletion is a big issue that needs attention. Ozone absorbs a band of ultraviolet radiation called uvb. Physica elsevier physica a 222 1995 1024 depletion force in colloidal systems y. Depletion flocculation and depletion stabilization of erythrocytes.
Depletion stabilization and depletion flocculation sciencedirect. The procedure may be used to evaluate color, turbidity, and hardness reduction. Figure 3 shows the height of the sharp boundary between flocculated emulsion and the clear serum as a function of time for 20 % vv corn oil, 5 mgml soy protein and xanthan 0. Associative polymerlatex dispersion phase diagrams ii. Example problem for designing a flocculation basin.
Depletion flocculation gives rise to phase separation. Depletion flocculation was observed at higher free polymer concentrations. Engelhardt application development manager drinking water hach company photo by author the intent of this paper is to provide cursory information about coagulation, flocculation and clarification. These results show that depletion flocculation by gum arabic and modified starch can have an adverse effect on the stability of beverage emulsions.
Waste water treatment by coagulation and flocculation. Serum separation and structure of depletion and bridging. Depletion flocculation of beverage emulsions by gum arabic. Coagulation, flocculation and clarification of drinking water terry l. Because of this, the sedimentation step is usually preceded by a chemical process known as coagulation. Deepcone thickener, a kind of such process for the flocculation and settling of wholetailings, is particularly necessary to study. Henry krumb school of mines columbia university new york. A new way to treat the waste water 105 2sulfoethyl methacrylate is of limited commercial value owing to the hydrolytic instability of the ester linkage. Suppression of depletion flocculation in oilinwater emulsions. Depletion force in colloidal systems sciencedirect. An average of 3040 samples were prepared for each system to define the dispersion and flocculation. Depletion interactions in polymer solutions promote red.
As pva concentration increases, the microstructure evolves from bridging flocculation, steric stabilization, depletion flocculation to depletion stabilization. Depletion forces and flocculation with surfactants. Depletion flocculation and thermodynamic incompatibility. Another possible mechanism for particle aggregation is called depletion flocculation. There is shortage of drinking water and water for irrigation. Pdf suppression of depletion flocculation in oilin.
In the asakuraoosawa model for depletion forces, the change in free energy imposed by an excluded cosolute, is. A depletion force is an effective attractive force that arises between large colloidal particles that are suspended in a dilute solution of depletants, which are smaller solutes that are preferentially excluded from the vicinity of the large particles. Pdf all waters, especially surface waters, contain both dissolved and suspended particles. Depletion stabilization and depletion flocculation suppression of depletion flocculation in oilinwater emulsions.
This is because, in addition to good particle dispersion, both bridging and depletion flocculation can occur. But depletion flocculation is a very significant effect in realworld formulations, so its worth trying to understand what is going on so you can avoid the problem. An approximate theory of depletion stabilization and depletion flocculation i. Flocculation by depletion and bridging was induced by addition of the polysaccharide carboxymethylcellulose cmc to emulsions that were stabilised by lactoglobulin lg at ph 6. Somasundaran henry krumb school of mines columbia university new york. One of the earliest reports of depletion forces that lead to particle coagulation. Flocculation and coalescence of oilinwarer emulsions. Coflocculation of yeast species, a new mechanism to. Depletion stabilization scc sw chapter 1118 polymers in cosmetics 414. In the asakuraoosawa model for depletion forces, the change in freeenergy. Influence of added surfactant on particle flocculation in. For other industries and products such as foods, cosmetics, paints and pharmaceuticals, the goal often to promote stabilization and enhance shelf life and consumer appeal. Depletion forces and flocculation with surfactants, polymers and particles synergistic effects. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution.
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