Adsorbed amount of polymer

In the next run, a core pack was saturated with 8.6 cp (at 50° C) Ranger-zone crude oil and water flooded to residual oil saturation. Polymer flood was then initiated and about 1.2% of the original oil in place (OOIP) was recovered. The results are shown in Figure 4. The pressure profiles show behavior essentially similar to the previous run except that the pressure drop across the core increased to 100 psi within 4 PV of injection of polymer. The steady state values of pH and viscosity were 7.0 and 0.7 cp. respectively. The oil ganglia retained in larger pores resisting displacement probably reduced the amount of polymer adsorbed and reduced the number of pores that the polymer molecules needed to seal off in order to block the core. This could explain the more rapid plugging of the core. Effluent pH and viscosities remained much lower than influent values. 

The problems associated with the application of this (or any other) model have been discussed. Because of the form of the typical isotherm, which exhibits a broad plateau region, fitting of experimental results to the model requires that data be obtained over a very broad range of concentrations. This is often very difficult to accomplish in practice, especially when difference methods are used to determine the amount of polymer adsorbed. Evaluation of adsorption in real systems is further complicated by a lack of knowledge of the available solid surface area. The latter may be affected by particle size, shape and surface topography and by polymer bridging between particles. 

The amount of polymer adsorbed in gramsper gram Aerosil can be calculated from the mass balance, according... 

The amount of polymer adsorbed on each sample was measured by pressure filtration through a 0.1 m filter, followed by analysis of the filtrate for residual polymer by gel permeation chromatography with refractive index determination. Particle zeta potentials were measured by taking a small sample of the solids from the centrifuge and re-suspending them in the supernatant prior to analysis in a Malvern Instruments Zetasizer . The concentration of all other types of ions in the supernatant was analysed by ICP atomic emission spectroscopy. 

Obviously, the enthalpy gain can compensate for some unfavorable change in entropy. At a suitable value of adsorption energy, flexible macromolecules may reptate into narrow pores. Polystyrene of molar mass 173,000 g/mol and coil diameter 30 nm is reported to be capable of entering pores of silica gel with 10 nm average pore diameter8). This penetration will certainly be a slow process. It often has been observed that the amount of polymer adsorbed by porous adsorbents slowly increases over a protracted period of time. This may be due to similar effects. 

The adsorption from solution of polymers has been studied extensively. The amount of polymer adsorbed usually reaches a limiting value as the concentration of polymer in solution is increased, but this value is usually well in excess of that which would be expected for a monomolecular layer of polymer adsorbed flat on the solid surface. This suggests that the adsorbed polymer is anchored to the surface only at a few points, with the remainder of the polymer in the form of loops and ends moving more or less freely in the liquid phase179. 

Keeping the thickness of the adsorbed layer constant, the effect of varying the amount of polymer adsorbed was also examined. The volume fraction of the polymer in the adsorbed layer is varied from 0.10 to 0.30. The increase of this volume fraction again provides increased stability since it increases the magnitude of the repulsive steric forces. The calculated values shown in Table 3 exhibit the expected trend, although the variation is not as strong as that found with the thickness of the adsorbed layer. 

Water-soluble polymers coat hydrophobic solid surfaces with multilayers and thus render the solid hydrophilic (i.e., wetting). The number of adsorbed chains (or the amount of polymer adsorbed) per surface site (or unit weight of adsorbent) is related to the volume fraction of segments in each layer. As the length of the chains increases,... 

The usual way of representing polymer adsorption onto clay surfaces is to plot an isotherm showing the amount of polymer adsorbed in grams per gram of clay as a function of the equilibrium concentration of polymer in units of g cm 3. We have to be careful in comparing our results with standard isotherms because we are measuring the total amount of PEO inside the clay. This absorbed mass is not necessarily adsorbed onto the clay surfaces, but may be located in the interlayer solution. To reflect this difference, we have used the unusual nomenclature absorption isotherm rather than the usual adsorption isotherm in the presentation of the data. 

Bondor et al. (1972) assumed that the permeability reduction is caused by polymer adsorption, and the adsorption process is irreversible. They further assumed the maximum permeability reduction corresponds to the polymer adsorptive capacity on the rock, AdC. The permeability reduction factor is linearly interpolated based on the ratio of the amount of polymer adsorbed to the adsorptive capacity ... 

The amount of polymer adsorbed F (in mg or mol) per unit area of the particles. It is essential to know the surface area of the particles in the suspension. N itrogen adsorption on the powder surface may provide such information, by application of the Bmnauer-Emmett-Teller (BET) equation, provided that no change will occur in area when the particles are dispersed in the medium Eor many practical systems, a change in surface area may occur on dispersing the powder, in which case it would be necessary to use dye adsorption to measure the surface area (some assumptions must be made in this case). 

The importance of adsorbed polymer conformation at interfaces was first recognized by Jenkel and Rumbach in 1951. A model of adsorbed polymer conformation was proposed based on the observation that amount of polymer adsorbed per unit area of the surface corresponds to a layer more than ten molecules thick. In that model, not all the segments of a polymer are in contact with the surface. As schematically shown in Figure 7.27, those segments that are in direct contact with the surface are termed trains, those between and extending into solution are termed loops, the free ends of the polymer extending into solution are termed tails. Sato and Ruch classified the possible conformations for most situations into the six types shown in Figure 7.28. 

It is clear from the above theories that for full characterization of polymer adsorption and configuration at the interface, one needs to measure the following values, i.e. the amount of polymer adsorbed per unit area of the surface, r(mol m ), the fraction of segments in direct contact with the surface (in trains), p, and the segment density distribution p(z). Measurement of F and p as a function of polymer concentration is fairly straightforward. The parameter F can be directly determined by equilibrating a known amount of disperse phase (particles or droplets) of known surface area with polymer solutions with various concentrations, starting... 

Adsorption isotherms The amount of polymer adsorbed on the particles was determined through the depletion method. PAM macromolecules were equilibrated for 24 hours with a ceria dispersion, then the particles and adsorbed polymer were removed through ultracentrifugation and the amount of polymer remaining in the supernatant was measured with a total organic carbon analyzer. This method requires 2 hours of... 

I hc reverse gas chromatography method implies control over equilibrium and elimination of a number of instrumental and methodical distortions (eg. the dependence of sorption on the amount of polymer adsorbent, the nature of motionless support for polymer, etc.) (Nesterov and Lipatov, 1976 Tager et al., 1978). The method is capable of determining x at small amounts of LMWL (v2 1). 

Several experimental methods can be applied to study adsorption and conformation of polymers at interfaces. The amount of polymer adsorbed, F, can be directly determined by equilibrating a known amount of the disperse phase (particles or droplets) with a polymer solution of known concentration, Cj. When the system reaches equilibrium (that may take hours or even days with high-molecular weight polymers), the disperse phase is separated (by filtration or centrifugation), and the equilibrium concentration of the polymer, C, is determined using a suitable analytical method. From Cj and C2 and the amount of disperse phase m and its surface area A (m /g, which may be obtained from a knowledge of the particle size distribution), F can be calculated, that is. 

One of the simplest experiments is to establish how much polymer is adsorbed onto the surface. This is known as the adsorbed amount and is determined from the adsorption isotherm (see Fig. 1). The adsorption isotherm relates the amount of polymer adsorbed at an interface to its equilibrium solution concentration. Determination of the adsorbed amount almost always involves measurement of the polymer concentration in solution before and after equilibration with a dispersion of known surface area. This usually requires separation of the dispersion particles from the supernatant by centrifugation. Separation of the bound and free polymer by dialysis can also be used but it is difficult to determine the amount of polymer that may be adsorbed onto the dialysis membrane. As these techniques require a knowledge of the amount of polymer removed from solution, they are known as depletion methods. 

An alternative method of analysis is to monitor the increase in the weight of the dried particles and equate the increase to the amount of polymer adsorbed on the particle surface. Since typical adsorbed amounts are of the order of a few mg/m the accuracy of these gravimetric methods can be questionable. 

Several experimental methods can be applied to study adsorption and conformation of polymers at interfaces. The amount of polymer adsorbed, T, can be directly determined by equilibrating a known amount of the disperse phase (particles or droplets) with a poly-... 

Consider the simple case of a dilute polymer solution in contact with a solid surface (2). Some of the chains are adsorbed on the surface. Such adsorbed chains have three main parts see Figure 12.20 (1). The polymer trains have all of their mers in contact with the substrate. The trains are separated by loops that are unbound and connect the trains, and the tails, which are nonadsorbed chain ends. An important parameter in calculations is the train or bound fraction,/ . The amount of polymer adsorbed on most such surfaces is of the order of one mg/m. ... 

The amount of polymer adsorbed, F, can be directly determined in a similar way as described for surfactants, except in this case one has to consider the relatively slow adsorption process, which may take several hours or even days to reach equilibrium. In addition, one needs very sensitive analytical methods to determine the polymer concentration in the early stages of adsorption (which can be in the ppm range). As mentioned before, the amount of adsorption F can be calculated from a... 

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