Nanofiltration flux models

For any other membrane (i.e., nanofiltration, reverse-osmosis, and so on), manipulation of the appropriate flux model should replace the right-hand side of Equation 9.9. The subscript ref denotes a chosen reference component. In Sections 9.5 and 9.6, component 2 is the reference component, and the following relative permeabilities have been assumed throughout ajj = 3, ot = 1, and Qt = 1.5. Similarly to previous chapters, these permeabilities can be arranged in a vector format such that = [3, 1, 1-5]. This is known as a... 

Concentration polarization can dominate the transmembrane flux in UF, and this can be described by boundary-layer models. Because the fluxes through nonporous barriers are lower than in UF, polarization effects are less important in reverse osmosis (RO), nanofiltration (NF), pervaporation (PV), electrodialysis (ED) or carrier-mediated separation. Interactions between substances in the feed and the membrane surface (adsorption, fouling) may also significantly influence the separation performance fouling is especially strong with aqueous feeds. 

Tu S.-C., Ravindran V, Badtiyha B.N., Pirbazari M. (1997), A membrane transport model for predicting permeate flux in nanofiltration processes, Proc. AWWA Membrane Technology Conference, New Orleans, Feb. 97, 487-498. 

Xu X., Spencer H.G. (1997), Transport of electrolytes through a weak acid nanofiltration membrane effects of flux and crossflow velocity interpreted using a fine-porous membrane model. 

The membrane permeability for toluene was determined from independent measurements of the pure toluene flux at different applied pressures. Docosane and TOABr membrane permeabilities were determined from the nanofiltration data assuming a concentration driving force and a solute flux experimentally determined at a low applied pressure of 4 bar, to avoid the influence of the exponential term in the solution-diffusion model and, the effect of concentration polarization. The model parameter values are summarized in Tab. 4.3. 

The use of film theory to describe solution mass transfer phenomena in pressure-driven membrane processes has a proven track record for aqueous systems. Under the flow conditions encountered in nanofiltration, the simplified film theory description of mass transfer has an accuracy close to solutions obtained by computational fluid dynamics (CFD) modeling (Zydney, 1997). The film theory, for component i, gives, for the total volumetric flux [see Peeva et al. (2004) for details] ... 

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