Depletion flocculation practical solubility science prof. Ballast flocculation for water treatment columbus et al 2006, charles d. Journal of colloid and interface science 75 2, 525541, 1980. Coagulation and flocculation process fundamentals 1 coagulation and flocculation. Review the documents for the research phase of the frame engineering design model. The microalgal cells began to coagulate when the ph decreased from ph 6. Flocculation is a process in chemistry wherein colloids are extracted from suspensions which then take the form of flake or floc. This knowledge will provide a basis for understanding the needs of the.
The aggregation of small particles into larger particles. In dispersed clay slurries, flocculation occurs after mechanical agitation ceases and the dispersed clay platelets spontaneously form flocs because of attractions between negative face charges and positive edge charges. The amount of chemical you use is an important consideration for a green engineer. Depletion flocculation in colloidal dispersions sciencedirect. Depletion flocculation in dispersions of stericallystabilised particles. Groundwater and surface water contain both dissolved and suspended particles. Stability against demixing, rheology and microstructure of emulsions that were. Now that you have completed this portion of the research phase, it is time to. In case of tapered flocculation, which is often a preferred option in efficient and energysaving flocculation process, g values can be set as follows. Freshwater microalgae harvested via flocculation induced by.
A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Ii flocculation and flocculation filtration dieter saal. Depletion flocculation practical solubility science. Flocculation definition of flocculation by medical dictionary. Theory of flocculation reprint with authorization by david l. The dispersed liquid is usually in the form of droplets and is referred to as the dispersed, discontinuous, or internal phase. Start studying coagulation, flocculation, sedimentation, and filtration. Emulsions an emulsion is a dispersed system consisting of at least two immiscible liquid phases. The binary mixtures used were either similar polymers of different molecular weights, or mixtures of chemically different polymers. Depletion flocculation and depletion stabilization of. At ph 4 bridging flocculation and droplet aggregates promoted emulsion instability. From dlvo theory we know that adding polymers to a particulate system can stabilize it. Depletion is an accrual accounting technique used to allocate the cost of extracting natural resources such as timber, minerals and oil from the earth.
Introduction to emulsion technology, emulsifiers and stability by. Serum separation and structure of depletion and bridging. Recent studies have demonstrated that microalga has been widely regarded as one of the most promising raw materials of biofuels. Flocculants, with their very high molecular weights long monomer chain and their charge content, fix the destabilized particles and aggregates along the polymer chain. The stability of a suspension depends on the number, size, and surface properties of the solid particles and on the dispersion medium. This improvement is achieved by bringing dispersed particles together, increasing the effective particle size of the solid phase. This can take place spontaneously or may be brought about by adding clarifying agents. Depletion flocculation, induced in dispersions of hydrophobic silica particles in nonpolar media by the presence of binary mixtures of nonadsorbing polymers, has been investigated both experimentally and theoretically. However, lack of an economical, efficient and convenient method to harvest microalgae is a bottleneck to boost their fullscale application. Ppt coagulation and flocculation linkedin slideshare. Freshwater microalgae harvested via flocculation induced. Flotation and flocculation underpin the key material supply chains for technologies that are central to minerals, fuel cells, ceramics, telecommunications, waste removalrecycling processes and many other.
For macroscopic bodies, the forces when summed over all the 1 molecules in the body vary as dii. Flocculation efficiencies for the three species of freshwater microalgal cells were studied in terms of ph variations figure 1. Flocculation definition of flocculation by medical. Introduction to emulsion technology, emulsifiers and stability. The binary mixtures used were either similar polymers having different molecular weights or mixtures of chemically different. Aggregation, coagulants, flocculants, destabilization, turbid matter, sedimentation, velocity gradient contents 1. The binary mixtures used were either similar polymers having different molecular weights or mixtures of chemically different polymers. Apr 25, 2019 depletion is an accrual accounting technique used to allocate the cost of extracting natural resources such as timber, minerals and oil from the earth.
Oct 23, 2017 flocculation is a process in chemistry wherein colloids are extracted from suspensions which then take the form of flake or floc. The polar, high molecular weight and hydrophobic compounds are best remove by coagulation and. Flocculation process where a solute comes out of solution in the form of flocs or flakes. Chapter 14 depletion of resource what depletion of resources is. 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. Another useful parameter in flocculation is gtc, where c represents for volume of flocs per unit volume of water. By combining expressions 11, 12 and 14 an expression for depletion gibbs. Flocculation is a process by which a chemical coagulant added to the water acts. Napper department of physical chemistry, the university of sydney, new south wales 2006, australia received december 10, 1979. Using dispersionflocculation phase diagrams to visualize.
Retention time for flocculation varies greatly but typically is longer than 15 minutes. 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. Fred magdoff environmentalists and scientists often refer to the two different ends of the environmental problem as sources and sinks. Depletion attraction this is a very interesting and in some sense somewhat mysterious interaction, sometimes useful, sometimes troublesome, that can occur in colloidal suspensions with more than one species suspended in the continuous phase, where one is substantially smaller than the other. To get a feel for the effect, play with the radius of the particles, the radius radius of gyration of the polymer, its concentration and mwt. Almost all physical, chemical, biological and other activities are responsible for environmental degradation. By combining the depletion interaction with the steric interaction, the overall interparticle pair potential is calculated. In flocculation and solids separation, this is a critical element in determining the.
Flocculation and flocculation filtration dieter saal darmstadt, germany keywords. Flotation and flocculation from fundamentals to applications. Several products combine cf with halogen disinfection. Konikow eloise kendy keywords overabstraction groundwater managment groundwater development groundwater depletion introduction in the past halfcentury, ready access to pumped wells has ushered in a worldwide explosion of groundwater development for mu. The extent of asphaltene flocculation changes with fluid composition, temperature and pressure. In the context of heavy oil, asphaltenes are known to flocculate at the molecular level before precipitation and in the precipitated state.
Unesco eolss sample chapters common fundamentals and unit operations in thermal desalination systems vol. There follows, during the flocculation step,an increase in the size of the particlespresent in the water phase resulting in the formation of flocs. Pdf suppression of depletion flocculation in oilin. Flocculation can occur through these mechanismsdouble layer compression, specific ion adsorption, polymer bridging hunter, 1995 and depletion flocculation. 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. Pickering emulsions by combining cellulose nanofibrils and.
The colloidal interactions of associative polymers and latexes in the presence of surfactant are complex. This is because, in addition to good particle dispersion, both bridging and depletion flocculation can occur. Coagulationflocculation is used widely during water or wastewater treatment. The key is the attractive energy at short distances. Many plant operators remember when dosage control was based upon a visual evaluation of the flocculation basin and the clarifier.
In the flocculated system, there is no formation of. Nebraska new depletion plan for the platte river recovery. At ph 5 emulsions remain stable as a wpi sa bilayer was formed around the droplets. Coalescence involves the complete merging of two or more droplets and. Principles of flocculation, dispersion, selective flocculation 951 1 induced dipoles. Therefore, we have developed phase diagrams to help visualize these interactions. Depletion flocculation of nonaqueous dispersions containing. Suspended particles vary in source, charge, particle size, shape, and density. Coagulation, flocculation and clarification of drinking water terry l. The gain in translational entropy of the depletants, owing to the increased available volume, is much greater than the loss of entropy from flocculation. Three regimes of concentrationdependent depletion stabilization were established, including 1 creaming of nonflocculated droplets at low cnf concentration. Pdf depletion flocculation in colloidal dispersions. The depletion of the worlds natural resources is population the problem.
For precipitated asphaltenes, flocculation is also affected by the shear environment. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Henry krumb school of mines columbia university new york. These forces vary as where d is the intermolecular spacing. Flocculation of kaolinite clay using natural polymer. At all these dextran concentrations, the erythrocytes are coated with considerable amounts of dextran.
Depletion stabilization and depletion flocculation robert i. The various phases have a significant effect on coatings and applications properties. A condition in which clays, polymers or other small charged particles become attached and form a fragile structure, a floc. 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. One of the earliest reports of depletion forces that lead to particle coagulation is that of bondy, who observed the separation or creaming. Gel transition of depletion flocculated emulsions article in colloids and surfaces a physicochemical and engineering aspects 215. Emulsion instability induced by bridging or depletion flocculation is not. Depletion definition of depletion by the free dictionary. Depletion flocculation in colloidal dispersions article pdf available in advances in colloid and interface science 681. 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. Forbes introduction the efficiency of most solidliquid separation processes may be greatly improved by the application of synthetic polymeric flocculants. Coagulation control techniques have advanced slowly. Depletion stabilization and depletion flocculation. Coagulation flocculation free download as powerpoint presentation.
Through extensive jar testing an optimal time can be found. Frustratingly, if we add a little too much polymer, we can destabilize the system via a nonintuitive effect called depletion flocculation. Depletion flocculation practical solubility science prof steven. Various sizes of particles in raw water particle diameter mm type settling velocity 10 pebble 0. There is shortage of drinking water and water for irrigation. Many methods of harvesting microalgae, including mechanical, electrical, biological and chemical based, have been studied to. The flocculation process is also affected by ph, salts, alkalinity, turbidity, temperature and degree of mixing. Depletion forces and flocculation with surfactants, polymers and. Request pdf depletion forces and flocculation with surfactants, polymers and particles synergistic effects this paper provides an.
The depletion force is described as an entropic force because it is fundamentally a manifestation of the second law of thermodynamics, which states that a system tends to increase its entropy. Coagulation and flocculation play an important part in many liquidsolid separations and is widely used in wastewater treatment. The use or consumption of a resource, especially a natural resource. Coagulation, flocculation and clarification of drinking water. Coagulation flocculation chemistry physical sciences. Flotation and flocculation deals with cuttingedge research in the science and engineering of two of the worlds key separation processes. Coagulation vs flocculation in water treatment coagulation is an important step in water treatment which involves the addition of a coagulant to enhance the clotting of suspended particles in water. Elsevier depletion flocculation in colloidal dispersions paul jenkinsa, martin snowden b, alan wark research institute, university of south australia, warrendi road, the levels sa 5095, australia bschool of chemical and life sciences, university of greenwich, woolwich, london se18 6pf, uk abstract advances in colloid and advances in colloid and interface science interface 68 1996 5796.
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