Flocculation coagulation, fast

The polymer radius has to be larger than 80% of the particle radius to avoid adsorption limitation under orthokinetic conditions. As a rule of thumb a particle diameter of about 1 pm marks the transition between perikinetic and orthokinetic coagulation (and flocculation). The effective size of a polymeric flocculant must clearly be very large to avoid adsorption limitation. However, if the polymer is sufficiently small, the Brownian diffusion rate may be fast enough to prevent adsorption limitation. For example, if the particle radius is 0.535 pm and the shear rate is 1800 s-, then tAp due to Brownian motion will be shorter than t 0 for r < 0.001, i.e., for a polymer with a... 

Paper and textile production retention, coagulation, flocculation, wet strength, dry strength improvement, dewatering, color fastness, dye fixation, antistatic agents, antimicrobial treatment... 

The experimental stability ratio is defined generally as the rate of fast flocculation divided by the rate of slow coagulation (see, e.g., Section 7.8 in R. J. Hunter, op. cit.1). Equation 6.70 is a mathematical interpretation of this definition in terms of experimentally accessible quantities related to floccule size. 

Plots of log W versus log C are shown in Figure 7.11. The condition log W = 0 (W = 1) is the onset of fast flocculation, and the electrolyte concentration at this point defines the critical coagulation concentration (ccc). Above the ccc, W will be less than 1 (due to the contribution of van der Waals attraction which accelerates the rate above the Smoluchowski value), whereas below the ccc, W will be greater than 1, and wiU increase in Hne with a decrease in electrolyte concentration. The data in Figure 7.11 also shows that the ccc decreases with an increase of valency. At low surface potentials, ccc oo 1/Z this referred to as the Schultze-Hardy mle. 

The stabihty of the latexes was determined by determining the critical coagulation concentration (ccc) using CaClj. Although the CCC was low (0.0175-0.05 mol dm ), it was higher than that for the latex prepared without surfactant The subsequent addition of INUTEC SPl resulted in a large increase in the CCC, as illustrated in Figure 17.2, which shows log W-log C curves (where W is the ratio between the fast flocculation rate constant to the slow flocculation rate constant, referred to as the stability ratio) at various additions of INUTEC SPl . 

The kinetic theory of fast irreversible coagulation was developed by von Smoluchowski. Later the theory was extended to the case of slow and reversible coagulation. In any case of coagulation (flocculation), the general set of kinetic equations reads... 

Note also that for imaginary particles, which experience neither long-range surface forces (JJi j = 0) nor hydrodynamic interactions (P = 1), Equation 5.325a yields a collision efficiency = 1 and Equation 5.321 reduces to the von Smoluchowski " expression for the rate constant of the fast irreversible coagulation. In this particular case. Equation 5.319 represents an infinite set of nonlinear differential equation. If all flocculation rate constants are the same and equal to Up the problem has a unique exact solution " ... 

However, settlers are also used for separation of floccules formed during coagulation in the process of clarification. The most convenient method is to arrange a fast mixer, flocculation and settling tanks into one unit with a horizontal through-flow of water (Fig. 3.51) [42, 43, 46]. 

Sorption stage. First, colloids coagulate and their agglomerates are adsorbed on the floccules of active sludge. This stage is very fast and takes only few minutes. 

Coagulation-flocculation ineffective, supernatant murky pH > 10/wrong dosage of alum or coagulant/pH < 4/increase in concentration of particles in feed/rpm of reels in flocculation basin too slow/feed temperature <12 °C/rpm of reels in flocculation basin too fast. 

Raba I contains a system of classic coagulation which consists of three chambers of fast mixers, twelve flocculation chambers, and two coagulation horizontal settling tanks of capacity 8000 m Then water is steered to 12 sand rapid filters of area 44 rtf each and total capacity 1200-1300 m /h. The last step of technological process is disinfection using gas chlorine. Treated water is pressed by pumping station to water tanks in Gorzkow, and then to water distribution subsystem. 

In the absence of a maximum in the variation of V (ji ), W is close to 1. Under these conditions, coagulation of the sol is fast. The flocculation rate is limited only by the... 

The intersection of the two linear parts of the diagram is the limit concentration beyond which the energy maximum of the energy baixier disappears. From a practical standpoint, the stability ratio W is the ratio of the fast flocculation rate of a sol in the presence of excess electrolyte to its flocdulation rate at a given electrolyte concentration. The ratio is determined by the ratio of the initial coagulation rates, as observed by spectrophotometry for example [28-31],... 

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