Electrodialysis including filled cell electrodialysis (electrodeionization)

摘要

Electrodialysis ("ED") stacks are disclosed having components selected from the group: a) cation exchange ("CX") membranes and/or CX granules having in at least a surface a predominant amount of sulfonate exchange groups and a minor amount of weakly ionized exchange groups; b) anion exchange ("AX") membranes and/or AX granules having in at least a surface substantially only quaternary ammonium and/or phosphonium exchange groups which upon decomposition leave almost no amine or phosphine groups bound to the membranes or granules; c) AX and/or CX granules which are selective to monovalent ions at currents which are fractions of the limiting current of such granules; d) AX and/or CX membranes and granules, such membranes and granules selective to monovalent ions at currents which are fractions of the limiting current of such membranes and granules; e) ion exchange ("IX") granules in which the concentration of IX groups in the inner regions is a fraction (including zero) of the concentration in the outer regions; f) AX membranes and/or granules having in at least a surface AX groups having the formula <IMAGE> where the R's represent substituents other than hydroxyethyl having at least two carbon atoms, at least one of the R's represents the polymeric structure of such membranes or granules, or a connection thereto, where two or more R's may represent ring structures and A represents nitrogen or phosphorus. Also disclosed are processes for softening, de-nitrating, de-silicizing or demineralizing water or for removing ash from milk products.