Electrokinetic molecular concentration

Abstract Investigations of alternate adsorption regularities of cationic polyelectrolytes a) copolymer of styrene and dimethylaminopropyl-maleimide (CSDAPM) and b) poly(diallyldimethylammonium chloride) (PDADMAC) and anionic surfactant - sodium dodecyl sulfate (SDS) on fused quartz surface were carried out by capillary electrokinetic method. The adsorption/desorption kinetics, structure and properties of adsorbed layers for both polyelectrolytes and also for the second adsorbed layer were studied in dependence on different conditions molecular weight of polyelectrolyte, surfactant and polyelectrolyte concentration, the solution flow rate through the capillary during the adsorption, adsorbed layer formation... 

In this paper we investigate the process of alternate adsorption of cationic polyelectrolyte and anionic surfactant, structure and properties of adsorbed layers depending on different factors (molecular weight of PE, concentration of polyelectrolyte and surfactant, adsorbed layer formation time, the flow rate of the solution) by measuring potential and streaming current using the capillary electrokinetic method. 

In order to insure the sufficient efficiency of electrokinetic removal of multiple heavy metals from porous media, it is essential to understand the main parameters affecting the transport and electrokinetic phenomena. Such parameters can be summarized as (a) the theoretical ionic mobility related to the ionic valance and molecular diffusion coefficient of species, (b) the delaying or retardation effect caused by the affinity of heavy metals in solid matrix, and (c) the chemical forms of metal contaminants initially existing in soils. In addition, some unexpected effects especially brought about in the electrokinetic remediation of mixed metal contaminants should be considered. The electrokinetic remediation for mixed metal contaminants generally shows lower removal efficiency than that for individual metal contaminants. High concentrations of multiple metal contaminants can be related to other parameters, for example, transference number, zeta potential, electroosmotic flow, and so on, which are factors that should be taken into consideration with regard to the removal mechanisms. 

Water-soluble polymers that adsorb due to hydrogen bonds on the quartz surface may be considered in the Gibbs sense as surfactants. As differentiated from ionic surfactants, capillary electrokinetics allows in this case investigation not of the adsorption state but the state of adsorbed polymer layers and its influence on surface charge of quartz capillaries. The experiments were performed with aqueous poly(ethylene oxide) (PEO) solutions of various concentration in a background KCl solution. As an example, the results obtained for PEO with molecular mass M = 6 x 10, M /Mn = 1.1 (Union Carbide) will be discussed. 

The generalized friction model which has been widely used in the interpretation of transport and electrokinetic processes in ion exchange membranes may be extended in due form to polyelectrolyte solutions. The significance of the different particle friction coefficients and how they may be evaluated in terms of molecular parameters is explained. The usefulness of the formulation will be substantiated by computing the electrical interaction parameters explicitely for some polyelectrolytes of different shape and charge however, no undue stress will be laid on the application to numerous models. Only limiting laws with respect to the salt-to-polymer concentration ratio are considered, namely the case of the most practical importance, when an excess of salt is present, is discussed. The case of salt-free-polyelectrolyte solutions which has been recently developed by the authors along the same lines [3, 4] is not treated in this paper. 

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