Polymer using sedimentation

To obtain a suitable concentrate, the flocculated particles must be separated from the suspension. The usual method is sedimentation of the floes combined with elutriation of the dispersed particles. Flotation of the flocculated particles is a possible method to achieve that separation. The effect of polymers used as flocculants on the flotation of a few minerals has received... 

Arlauskas RA, Burtner DR, Klein DH (1993) Calibration of a photosedimeter using sedimentation field-flow fractionation and gas chromatography. In Provder T (ed) Chromatography of polymers characterization by SEC and FFF. American Chemical Society, Washington, DC, pp 2-12... 

Stability in colloidal dispersions is defined as resistance to molecular or chemical disturbance, and the distance the system is removed from a reference condition may be used as a measure of stability. The stability can be analyzed from both energetic and kinetic standpoints. The kinetic approach uses the stability ratio, as a measure of the stability. W is defined as fhe ratio of the rate of flocculation in the absence of any energy barrier to that when there is an energy barrier due to adsorbed surfactant or polymer. These processes are referred to as rapid and slow flocculation with rate constants kj and kg, respectively, such that W = kjlk. The stability of colloidal suspensions can be evaluated using various techniques. In practice, two methods are mainly used sedimentation and rheology measurements. 

Imai (56) constructed a theory fear the intrinsic viscosity and sedimentation constant of ring polymers using the Fixman method shown in 2.3.2 for a model similar to the Hearst-Harris model which will be described in 4.2.2. This model reduces to the Rouse model in a limiting case. The excluded volume potential is included in the form of Eq. (2.26) and the same type of calculation as described in 2.3.2 was performed for a steady shear flow. Dynamic mechanical properties were not treated, although the extension to include this case is only a matter of tedious calculations. 

Ciassification Organo-sulfur polymer Uses Precipitant for removal of heavy metals from process wastewater, ground waters, and other polar soivs. stabilizer for detoxification and stabilization of heavy metals in contaminated solids, such as soils, sludges, ash and sediments... 

The investigation of hydrodynamic properties, sedimentation and translational and rotational friction of dilute solutions, of these polymers using modern theoretical concepts of behavior of macromolecules in solution made it possible to characterize the geometric properties of macromolecules, their size and equilibrium rigidity. 

A direct molecular weight method (216) employs the LALLS detector, but uses sedimentation velocity instead of GPC to separate the polymers. 

We begin with two experimental methods, sedimentation and electrophoresis, that measure the driven motion of polymer chains and colloidal particles. In each method, an external force is applied directly to particular molecules in solution, and particle motion is observed. The forces are buoyancy and the Coulomb force. Light pressure ( optical tweezers ) has also been used to move particles this method appears in Chapter 9. Chapter 2 presents phenomenology associated with sedimentation by polymers and sedimentation of particulates through polymer solutions. The sedimentation rate of polymers in homogeneous solution, and the sedimentation of particulate probes through polymer solutions, both depend on the polymer concentration and molecular weight and the size of the particulates. 

Quantitative studies of the hydrodynamic characteristics were conducted in [100-103] for the polymers and copolymers listed in Table 3.10, and only copolymers of 3 are soluble in tetrachloroethane [100], while alkylene aromatic polyethers are soluble in dichloroacetic and trifluoroacetic acids [101-103]. The use of acids with a high viscosity and density as solvents limits the possibilities of the sedimentation method. For this reason, for polydecamethylene-tere-phthaloyl di-p-hydroxybenzoate (P-IO-MTOC, polymer 1) and the totally aromatic polyether (PE) containing aromatic rings in the meta and para positions (polymer 2), the molecular weights of the fractions and samples were either determined with the Svedberg equation using sedimentation-diffusion data... 

Sedimentation experiments on semi-dilute solutions are appropriate and many experiments have been performed on neutral polymers like polystyrene and poly(a-methylsty-rene) in good solvents It has been found that the effective exponent Xj increases from 0.59 up to 0.8 as the concentration rises from 0.1 to 10%. Good solvents used in these experiments (benzene, bromobenzene and toluene) are far from athermal conditions (x — 0.45). Two monomers, belonging to a subchain of size and separated by n monomers, experience excluded volume effects when n > n, where iic oc (1 - 2x). As the concentration decreases, the number of monomer per subchain g, increases and excluded volume effects become more and more important. The effective exponent Xs, which is a combination of effective dynamic and static exponents tends monoti-cally to the asymptotic value 0.5 (g > He). Inversely, if the concentration increases, g decreases when g < He, the subchain exhibits purely Gaussian behaviour, and v = 0.5 which leads to oc and Sd °o This cross-over between excluded volume and Gaussian behaviour qualitatively explains the increase of Xj, if p increases. Detaib on the dependence of x, on the concentration can be found in Ref. 110. Whatever the exact value of the exponent, these experiments show that the frictional properties of semi-dilute solutions depend only on the concentration they are independent of the molecular weight of the polymer used 1. 

Typical examples of solid samples include large particulates, such as those found in ores smaller particulates, such as soils and sediments tablets, pellets, and capsules used in dispensing pharmaceutical products and animal feeds sheet materials, such as polymers and rolled metals and tissue samples from biological specimens. 

At first glance, the contents of Chap. 9 read like a catchall for unrelated topics. In it we examine the intrinsic viscosity of polymer solutions, the diffusion coefficient, the sedimentation coefficient, sedimentation equilibrium, and gel permeation chromatography. While all of these techniques can be related in one way or another to the molecular weight of the polymer, the more fundamental unifying principle which connects these topics is their common dependence on the spatial extension of the molecules. The radius of gyration is the parameter of interest in this context, and the intrinsic viscosity in particular can be interpreted to give a value for this important quantity. The experimental techniques discussed in Chap. 9 have been used extensively in the study of biopolymers. 

Protein molecules extracted from Escherichia coli ribosomes were examined by viscosity, sedimentation, and diffusion experiments for characterization with respect to molecular weight, hydration, and ellipticity. These dataf are examined in this and the following problem. Use Fig. 9.4a to estimate the axial ratio of the molecules, assuming a solvation of 0.26 g water (g protein)"V At 20°C, [r ] = 27.7 cm g" and P2 = 1.36 for aqueous solutions of this polymer. 

Salts of alkyl phosphates and types of other surfactants used as emulsifiers and dispersing agents in polymer dispersions are discussed with respect to the preparation of polymer dispersions for use in the manufactoring and finishing of textiles. Seven examples are presented to demonstrate the significance of surfactants on the properties, e.g., sedimentation, wetting behavior, hydrophilic characteristics, foaming behavior, metal adhesion, and viscosity, of polymer dispersions used in the textile industry [239]. 

The various physical methods in use at present involve measurements, respectively, of osmotic pressure, light scattering, sedimentation equilibrium, sedimentation velocity in conjunction with diffusion, or solution viscosity. All except the last mentioned are absolute methods. Each requires extrapolation to infinite dilution for rigorous fulfillment of the requirements of theory. These various physical methods depend basically on evaluation of the thermodynamic properties of the solution (i.e., the change in free energy due to the presence of polymer molecules) or of the kinetic behavior (i.e., frictional coefficient or viscosity increment), or of a combination of the two. Polymer solutions usually exhibit deviations from their limiting infinite dilution behavior at remarkably low concentrations. Hence one is obliged not only to conduct the experiments at low concentrations but also to extrapolate to infinite dilution from measurements made at the lowest experimentally feasible concentrations. 

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