Sedimentation cumulative

Analyse granulometrique par sedimentation cumulative dans un liquide immobile - Methode de la balance de sedimentation... 

Geochemical Stage. The conversion of peat to bituminous coal is the result of the cumulative effects of temperature and pressure over a long time. The sediment covering the peat provides the pressure and insulation so that the earth s internal heat can be appUed to the conversion. The temperature increase is about 4 to 8°C for each 100 m of depth. The changes in plant matter are termed normal coalification. 

Size Recovery and Yield Centiifuges have been apphed to classify polydispersed fine particles. The size distribution of the paiticles is quantified by the cumulative weight fraction F less than a given particle size d for both the feed and the centrate streams. It is measured by a particle size counter which operates based on piinciples such as sedimentation or optical scatteiing. 

These instruments, sometimes referred to also as sediment accumulation devices, weight the sediment as it accumulates on a weigh-pan at the base of the sedimentation column. The methods are cumulative ones. With the development of sensitive electro balances, the cumulative sedimentation technique is generally easier to perform and more accurate than is the incremental technique. The powder may be dispersed initially in the bulk of the fluid or added instantaneously at the top. An advantage of this type of equipment is the absence of the conical base, needed in sediment extraction devices, upon the walls of which some sediment may adhere. The danger of particles sticking to the vertical walls is however still present... 

The toxicological or cumulative effect of illicit drugs on the ecosystems has not been studied yet. Moreover, their fate and transport in the environment is to a big extent still unknown. Due to their physical-chemical properties (octanol-water partition coefficient, solubility, etc.) some of them, such as cannabinoids, are likely to bioaccumulate in organisms or concentrate in sediments whereas the rest, much more polar compounds, will tend to stay in aqueous environmental matrices. However, continuous exposure of aquatic organisms to low aquatic concentrations of these substances, some of them still biologically active (e.g., cocaine (CO), morphine (MOR) and MDMA) may cause undesirable effects on the biota. 

Adsorption of nonionic and anionic polyacrylamides on kaolinite clay is studied together with various flocculation properties (settling rate, sediment volume, supernatant clarity and suspension viscosity) under controlled conditions of pH, ionic strength and agitation. Adsorption and flocculation data obtained simultaneously for selected systems were correlated to obtain information on the dependence of flocculation on the surface coverage. Interestingly, optimum polymer concentration and type vary depending upon the flocculation response that is monitored. This is discussed in terms of the different properties of the floes and the floe network that control different flocculation responses. Flocculation itself is examined as the cumulative result of many subprocesses that can depend differently on system properties. 

Another way in which these kinds of data are sometimes represented is as a cumulative curve in which the total number (or fraction) of particles nT>, having diameters less (sometimes more) than and including a particular d, are plotted versus dr Figure 1.18b shows the cumulative plot for the same data shown in Figure 1.18a as a histogram. The cumulative curve is equivalent to the integral of the frequency distribution up to the specified class mark. Cumulative distribution curves are used in Chapter 2 in connection with sedimentation. 

EXAMPLE 2.1 Analyzing Cumulative Sedimentation Data for Most Probable Settling Velocity. The following data show—as a function of time—the weight (as percentage of total) of suspended clay particles W, which has accumulated on a plate submerged 20 cm beneath the surface in a sedimentation experiment (Oden 1915). 

Criticize or defend the following proposition The data give the time required for particles to fall 20 cm, making it easy to convert time to sedimentation velocity for each point. Equation (11) may then be used to convert the velocity into the radius of an equivalent sphere. The resulting graph of W versus radius is a cumulative distribution function similar to that shown in Figure 1.18b. 

FIG. 2.5 Sedimentation of clay particles. Cumulative weight (as percentage) versus time for the data given in Example 2.1. The figure also shows the graphical construction explained in the example for obtaining the cutoff weight w associated with any time t. (Data from Oden, 1915.)... 

EXAMPLE 2.2 Use of the Sedimentation Equation for Particle Size Determination. A titanium dioxide pigment of density 4.12 g cm 3 is suspended in water at 33°C. At this temperature, the density and viscosity of water are 0.9947 g cm-3 and 7.523 10-3 P, respectively. A particle size analyzer (SediGraph, Micromeritics Instruments Corp., Norcross, GA 30093) plots the following data for cumulative weight percent versus equivalent spherical radius ... 

Solution These cumulative percentages are of the same form as in Figure 2.5 therefore, the particle size distribution peaks where the cumulative curve increases most steeply. This occurs at about 0.29 for this distribution. Equation (10) permits the sedimentation velocity for particles of this size to be calculated ... 

Imagine that system B is the water column of a lake and system A is the pore space of the lake sediments. In B, mixing is by turbulence and fairly intensive while in system A transport is by molecular diffusion. The above case corresponds to a situation in which at time t the concentration of a compound in the water suddenly rises to the value Cg. Then Eqs. 19-25 and 19-26 describe the cumulative and incremental mass flux of the compound into the infinitely deep sediment column. 

Lake % Organic Matter (core top) Cumulative Unsup. 2WPb (pCi/cm2) Modern Hg Cone, (ng/g) Preindustrial Hg Cone, (ng/g) SEF Sediment Accumulationa (g/m2 per year) Hg Flux Ratio (Modern/ Preindust.) Number of Cores... 

Figure 11. Primary flux of biogenic silica to the sediment surface a, cumulative flux b, flux and flux per period (milligrams/square meter).

Consider the ten year cumulative gas production prediction of the JOE model shown in Figure 7.46 (note the logarithmic scale of both axes). From the figure it is clear that hot water circulation alone will not be productive for a period after 0.02 years, due to the low thermal conductivity of the hydrates and sediments. However, depressurization does appear to be a favorable production mechanism, comparing favorably to hot water circulation with reduce bottom hole pressure, or partial hot water injection. 

Figure 2.11 Sedimentation of clay particles in an Oden balance experiment, showing the cumulative weight (%) versus time (a), cumulative weight of oversize material (%) versus time (b), and frequency by weight versus time (c). From Hiemenz [87]. Copyright 1986, Dekker.

Figure 7-4 Pb U log-transformed values histograms and cumulative probability curves for the Campania region 2389 stream sediments.

Isoelectric precipitation and acid precipitation are also used to separate antibodies. Isoelectric precipitation (also called euglobulin precipitation) uses the solubility properties of a protein near its isoelectric point.69 When a concentrated protein solution in a low ionic strength buffer is titrated to its isoelectric point, it precipitates very slowly. Table 4 shows a balance of a process for purification of murine monoclonal IgM antibodies.70 The success of precipitation can be followed by the cumulative IgM content in the centrifugate and the sediment. The procedure is very gentle, but very sensitive to environmental conditions. 

Figure 20-1 presents the data from Table 20-1 in both cumulative and frequency format. In order to smooth out experimental errors it is best to generate the frequency curve from the slope of the cumulative curve, to use wide-size intervals or a data-smootning computer program. The advantage of this method of presenting frequency data is that the area under the frequency curve equals 100 percent, hence, it is easy to visually compare similar data. A typical title for such a presentation would be Relative and cumulative mess distributions of quartz powder by pipet sedimentation. 

BS 3406, British Standard Method for determinig Particle Size Distribution is a comprehensive standard that includes methods for both incremental and cumulative methods of particle size deterination. Part 1, 1984, covers Recommendations for Gravitational Liquid Sedimentation Mehods for Powders and Suspensions. Part 5, 1985 covers... 

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