Flocculation effect

In low sohds muds, vinyl acetate—maleic anhydride copolymers were once used to extend or enhance the viscosity of bentonite suspensions (141). This function is largely performed by polyacrylamides. The vinyl acetate—maleic anhydride copolymers can also have a flocculating effect on drill sohds. Concentrations generally are quite low (0.14—0.57 kg/m (0.05—0.2 Ib/bbl)). 

The proper measure of flocculation effectiveness is the performance of subsequent solids separation units in terms of both effluent quality and operating requirements, such as filter backwash frequency. Effluent quality depends greatly on the reduction of residual primary size particles during flocculation, while operating requirements relate more to the floe volume applied to separation units. 

It should be noted that the flocculation effect produced by microdisperse forms of CP is applicable not only to protein solutions but also to solutions containing various organic ions. 

NOTE Many common polymeric dispersants typically produce a flocculating effect in a boiler when they are present at levels exceeding 100 to 120 ppm or so of active polymer. BWactives should not exceed 40 to 50ppm. 

Short HK, Vigneswaran S, Ngo HH et al (2005) Is semi-flocculation effective as pre-treatment to ultraflltration in wastewater treatment Water Res 39 147-153... 

Cationic starch in a paper mill furnish can have additional benefits beyond ash retention and strength. Properly added cationic starch can improve formation in a sheet. With an even distribution of fibers, the natural attraction of water for ionized anionic groups can be counteracted by the addition of cationic counter ions in the form of cationic starch. The flocculation effect that occurs produces much improved drainage on the paper machine. The result is increased speed on the machine yielding greater production rates and overall efficiency. To a paper mill, increased production means increased profitability. 

Mineral segregation in industry relies heavily on the selective adsorption of macromolecules onto the surfaces of those minerals that have particular industrial applications. This selectivity is governed mainly by the surface chemistry of the mineral and the type of polymer used as a flocculant. " Effectiveness of flocculation depends upon the charge, concentration and molecular weight of the polymer, and also the pH and salt concentration of the clay suspension. The bonding between the anionic flocculant polyacrylamide (PAM) and clay mineral surfaces has been effectively reviewed recently by Hocking et al and the reader is referred to this should they require an in-depth literature review. For more information on general colloidal chemistry of clay suspensions the reader is referred to the review of Luckham and Rossi." ... 

The particles in a sound field, however, behave in a peculiar manner which is not quite so simple. St. Clair points out that at a frequency of 5000 cycles, particles of 0.5 n or smaller (density = 1.5) have an amplitude and velocity the same as that of the surrounding gas, while particles of 10 p will scarcely vibrate at all. The intermediate sizes will pulsate out-of-phase with the pulsations of the gas stream. Thus particles 2 u will have an amplitude of 0.87 that of the gas and will be about 30 deg out-of-phase. It has been suggested by Brandt and Hiedemann that the flocculating effect is due to the increased number of collisions between the particles due to the kinetic energy imparted to them. However, as St. Clair points out, this cannot be the sole factor since flocculation is observed at a few hundred cycles for which the suspended particles remain stationary. 

They can also be used as flocculants for many substrates, such as cellulose fibers and in water treatment. The water-in-oil microlatices are destabilized and inverted by adding excess water, which releases the water-swollen polymer particle to the water phase. The efficiency of the usual polymers is however altered by rapid temperature changes, especially in winter, which favor the aggregation of the fine polymer particles, thus strongly decreasing their flocculation effect. The polyacrylamides prepared by... 

I. Activation of metallic ions in flocculation process Activation of flocculation by metallic ions is similar to that of mineral flotation using collectors discussed earlier. Metallic ions can activate minerals that do not normally have chemical reaction activity with the functional groups of flocculants, which enhance the flocculation effect. For example, for Cu " " -Si02- polymer system, the reaction can be illustrated as below ... 

In HEC-thickened formulations, low-shear-rate viscosities increase with decreasing latex particle size. This effect has been a major limitation in formulating small-particle latices. The phenomenon appears to arise from electro viscous, hydration, or flocculation effects, not a depletion layer mechanism. Associative thickeners achieve efficient viscosity in coating formulations via participation in synthesis and formulation surfactant micelles to form pseudo macromolecules and via an ion-dipole interaction between the cations of surface carboxylate groups on the latex and the ether linkages of the associative thickener. Generally, an excess of synthesis surfactant is found in the production of small-particle latices. The achievement of lower viscosities in small-particle ( 100 nm) latex coatings thickened with associative thickener appears to occur by extensive disruption of the polymer hydrophobe s participation in intermicellar networks. 

Macromolecular colloid solutions also play an important role in ensuring the stability of disperse systems (e.g. suspensions, emulsions). In the case of emulsions the polymer decreases the rate of separation by increasing viscosity on the one hand, and it has an enthalpy stabilizing effect by adsorption on the surface of the droplets on the other hand [3, 4, 7]. Depending on the concentration of the polymer, a protecting and flocculating effect can be observed during the interaction between suspensions and polymers. If the polymer concentration is low, the polymer adsorbed on the surface of the particles connects the particles into loose floccules. Thereby, the rate of... 

The effects that electrolytes exert on aqueous sterically stabilized dispersions are extremely complex and still poorly understood. The potency of an electrolyte in inducing flocculation is directly related to its ability to convert water into a poorer solvent for the stabilizing moieties. Napper (1970b) has shown that for poly(oxyethylene) stabilizing moieties the order of decreasing flocculation effectiveness for anions was S04 > Cr > NOj" > CNS > Br > I . This parallels the classical Hofmeis-ter series. The order of flocculation potency for the cations was found to be Rb = K+ = Na+ = Cs > NH/ = Sr + > = Ca + = Ba = Mg. This... 

The dependence of the optical density (A) of PSL on the concentration of various types of polyampholytes is presented in Fig. 26. The flocculating effectiveness of polyampholytes is arranged as follows PMAA-fo-PlM4VPCl >AA-VI >MAA-TMVEP >AA-DMVEP and is in good agreement with the sequence of their electrokinetic potential (Fig. 27). The kinetics of flocculation of PSL allow the evaluation of the magnitude of the retardation factor W which characterizes... 

Floe culant Flocculation effectivity (%) Number of floes theoretically calculated experimentally found Degree ofaggregation Flocculating concentration 10 molL i... 

Hence, the stated above results have shown that the molecular weight, macromolecular coil stmcture, characterized by its fractal dimension, and medium, in which flocculation occurs, are included in a factors number, influencing on adsorption of admixtures (flocculation) effectiveness by a pol mier flocculator PDMDAAC. The medium cans influence on flocculation process by two ways by a macromolecular coil fractal dimension change and viscosity variation. The latter factor can influence on diffusive processes intensity. The sole from the enumerated above factors, which will influence equally on fractal and compact objects properties, is a... 

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