Analytic techniques flocculation

A major advantage of the simple model described in this paper lies in its potential applicability to the direct evaluation of experimental data. Unfortunately, it is clear from the form of the typical isotherms, especially those for high polymers (large n) that, even with a simple model, this presents considerable difficulty. The problems can be seen clearly by consideration of some typical polymer adsorption data. Experimental isotherms for the adsorption of commercial polymer flocculants on a kaolin clay are shown in Figure 4. These data were obtained, in the usual way, by determination of residual polymer concentrations after equilibration with the solid. In general, such methods are limited at both extremes of the concentration scale. Serious errors arise at low concentration due to loss in precision of the analytical technique and at high concentration because the amount adsorbed is determined by the difference between two large numbers. 

It was the proof of dispersion [4b], the conductivity jump based on it due to flocculation [17a] and the optimisation thereof [17b,d], that first forced us to develop the new non-equilibrium thermodynamics theory of heterogeneous systems [19,17c,37] that applies to carbon-black compounds and ICP blends. The presumed necessity to achieve good dispersions compelled us to polymerise ICPs of increasingly high purity and to develop, to this end, the analytical techniques that yielded contributions to the understanding of structural aspects (see Sections 3,7.1 and 3.6). 

To obtain reliable experimental data and to correctly interpret them, we used such physicochemical and analytical techniques as dilatometry, viscometiy, UV and IR spectroscopy, electroiuc paramagnetic resonance, Raman light scattering spectroscopy, electron microscopy, and gas-liquid chromatography. To analyze the properties of polymeric dispersions, the turbidity spectrum method was used, and the efficiency of flocculants was estimated gravimetrically and by the sedimentation speed of special water-suspended imitators (e.g. copper oxide). 

To analyze the aqueous phase for any of these substances, it must first be separated from the polymer particles. Both flocculation and membrane filtration techniques can be used for this purpose and they are described in more detail below. The detection of the substances listed above can then be performed with the usual array of analytical methods used for characterizing aqueous media. For the determination of emulsifiers, electrolytes and water-soluble monomers, ion chromatography (IC) and high-performance liquid chromatography (HPLC) are particularly suitable. The techniques of choice for characterizing oligomers are gel permeation chromatography (GPC) and capillary electrophoresis (CE). As these analytical techniques are not specific to colloidal chemistry, they will not be described further here and the reader should consult the literature for more information. 

Now the technique provides the basis for simulating concentrated suspensions at conditions extending from the diffusion-dominated equilibrium state to highly nonequilibrium states produced by shear or external forces. The results to date, e.g., for structure and viscosity, are promising but limited to a relatively small number of particles in two dimensions by the demands of the hydrodynamic calculation. Nonetheless, at least one simplified analytical approximation has emerged [44], As supercomputers increase in power and availability, many important problems—addressing non-Newtonian rheology, consolidation via sedimentation and filtration, phase transitions, and flocculation—should yield to the approach. 

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