Polyacrylamide parameter

Fig. 5. Effect of polymer dosage on different observed properties of flocculated slurry (40). Comparison of five parameters in a flocculation system (8%fluorite suspension + polyacrylamide Cyanamer P250). A, Rate of settling of floe boundary, in cm/s B, height of settled bed, cm C, height of consoHdated filter-cake, cm D, refiltration rate, arbitrary units and E, clarification, % optical transmission of 1 cm of supernatant Hquid after 3 min settling...

FIG. 23 Comparison of various one-parameter diffusion models. (Reproduced with permission from Ref. 448, Analysis of Diffusion and Structure in Polyacrylamide Gels by Nuclear Magnetic Resonance, M.S. Thesis, Florida State University, Copyright 1997, Brigita Penke.)... 

Electrostatic repulsion of the anionic carboxylate groups elongates the polymer chain of partially hydrolyzed polyacrylamides increasing the hydrodynamic volume and solution viscosity. The extensional viscosity is responsible for increased resistance to flow at rapid flow rates in high permeability zones (313). The screen factor is primarily a measure of the extensional (elonga-tional) viscosity (314). The solution properties of polyacrylamides have been studied as a function of NaCl concentra-tion and the parameters of the Mark-Houwink-Sakaruda equation calculated... 

The rate of permeation was found to depend on a number of parameters. In the separation of toluene from toluene/cyclohexane mixtures, with a polystyrene in polyacrylamide membrane, the rate increased with increasing temperature and toluene concentration, and decreasing polyacrylamide content [182], Selectivity, on the other hand, increased with decreasing temperature and increasing polyacrylamide content therefore selectivity is inversely related to permeation rate. Similar results were found in experiments on the separation of water from water/ethanol mixtures by hydrophilic-hydrophobic membranes [183],... 

The results from such experiments indicate that membrane ion current is very dependent on molecular packing with respect to the other membrane parameters of Table I. This factor must be considered in any new design for development of a sensing device to ensure that substantial molecular mobility may be incorporated Into stabilized membranes. Such a stabilized, e1ectrochemica 1 1y active membrane has been produced by lipid monolayer deposition onto hydrated polyacrylamide gel, demonstrating that device fabrication may be possIb1e. 

The power characteristic for viscoelastic fluids (Reher, 1969 Schiimmer, 1970) can also be described accurately by a relationship of the type Ne (Re ). Additional parameters to account for viscoelastic properties are needed only when the ratio of tangential to normal stresses is less than two (Reher, 1969). Power characteristics for the turbine stirrer in aerated non-Newtonian fluids (carboxymethylcellulose [CMC] and polyacrylamide [PAA] solutions) have been presented by Hocker and Langer (1962). 

Figure 5.39. Theoretical (a) and experimental (b) amount adsorbed as a function of the salt concentration for polyelectrolytes of varying charge density a, as Indicated. The theoretical figure was calculated for 0-6 and a surface charge density

Starting from these results, we extended the problem to much larger temperature ranges that include subzero temperatures. The largest temperature gradient used was 70°C (+30°C at the top of the apparatus and —40°C at the bottom). The anticonvection medium is a polyacrylamide gel polymerized in mixed solvent (50% final volume of ethylene glycol). The anticonvection effect is due to three factors the gel structure and both the density and viscosity of the hy-droorganic medium at subzero temperatures. These parameters will be discussed in Section IV. 

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