Charged membrabe ultrafiltration of inorganic ions in single annd multi‐salt systems

Abstract

In a subsequent paper, the critical point condition will be discussed and the results of the first two papers illustrated with real systems, that is, the spinoidal and critical points of pure components and mixtures will be determined using typical equations of state. NOTATIONjugate coordinate of xj LITERATURE CITEDBeegle, B. L., M. Modell, and R. C. Reid, "Legendre Transforms andAn experimental study of the ultrafiltration of several ionic inorganic solutes, using a negatively-charged membrane, is detailed. Both single salt and multi-salt systems are investigated in a continuous flow, thin channel unit, with an average transmembrane pressure difference of 2.76 X lo5 N/m2 and a channel Reynolds number of 2800. The solute rejection is predictable to some extent in terms of Donnan ion exclusion theory, and the water flux is dictated by the combined effects of osmotic pressure and membrane-cation interaction.In the single salt experiments, the anion rejections can be related to the inlet (feed) concentration by power functions of the form: rejection = 1 -K Cia, in which 0 < a < 1.0. The power a is 0.4 for chloride salts, 0.25 for monovalent oxyanion salts, and 0.1 for divalent oxyanion salts, but a is independent of the cation present (Na+, Ca2+, or La3+). The constant K is generally a function of both the anion (except in the case of sod2-, HPOd2-, and Cr042-) and the cation, being determined by such factors as ion charge density and membrane-cation interaction. The membrane resistance to water flux is found to depend on cation charge and cation radius. For systems containing two or more salts, the presence of a divalent anion decreases the rejection of the monovalent anion. For multi-salt systems, a rejection of Ca2+ plus Mg2+ of 0.82 and a water flux of 12.9 X cm/s (27.2 gal/ft2-day) are achieved at a transmembrane pressure difference of 4.10 X lo5 N/m2 (4.1 atm), indicating that the process has considerable potential for industrial water softening. SCOPEUltrafiltration is a pressure-activated membrane process charged anisotropic membrane9 has been used primarily and is generally carried out at low pressures of about for the separation of modest molecular weight organic lo5 to lo6 N/m2. Ultrafiltration with conventional un-solutes, organic macromolecules, and colloids from

Retention of small charged impurities during ultrafiltration

“…This is in sharp contrast to the results presented for the retention of inorganic ions by Bhattacharyya et al (1974) and Jitsuhara and Kimura (1983). The key difference in these studies is that the ionic strength of the solution in our experiments is due primarily to the KCl, with relatively little contribution from the cibacron blue.…”

“…It is well established that small molecule retention by nanofiltration membranes is due to both steric and electrostatic interactions (Schaep et al, 1999), but this phenomenon has been studied much less extensively with larger pore size ultrafiltration membranes. Bhattacharyya et al (1974) and Jitsuhara and Kimura (1983) have demonstrated that highly charged ultrafiltration membranes can retain small inorganic ions due to electrostatic interactions, but the implications of these results for the clearance of charged impurities during ultrafiltration processes has not been appreciated.…”

Toxic metal ion separation by cellulose acetate/sulfonated poly(ether imide) blend membranes: Effect of polymer composition and additive

“…The resistance of the membrane, R m was evaluated from the slope of pure water flux (PWF) versus transmembrane pressure difference ( P) using the following equation [23]:…”

Bench-Scale and Pilot-Scale Treatment Technologies for the Removal of Total Dissolved Solids from Coal Mine Water: A Review

“…The most critical parameters affecting ion rejection in NF, according to the Donnan theory are: membrane charge capacity, influent ion concentrations, ion size, and influent ion's charge, but ion rejection rates also depend on pressure, crossflow velocity, pH, ion types, and concentrations. (Ahn et al 2007;Bhattach et al 1974;Hagg 1998;Vezzani and Bandini 2002). The main NF mechanisms are: electrostatic interactions between the membrane and the charged species, sieving or size effect, differences in diffusivity and solubility, and dielectric repulsion (Kosutic et al 2004).…”