Liquid Adsorption on Membranes

One of the factors causing fouling in ultrafiltration membranes is the adsorption of solutes in the membrane pores. Since fouling, in general, has been discussed in the previous chapter, the discussion presented here will be restricted to the adsorption phenomenon. Clark et al. [37] studied the relationship between membrane fouling and protein adsorption on alumina ultrafiltration membranes. Equilibrium adsorption of bovine serum albumin (BSA) was measured by the standard static method at 7°C. Their study covered the concentration range between 1 and 10 g/1, pH values between 2 and 10 and NaCl 

Basic adsorption isotherms have been described in this chapter. For micro-porous membranes, the use of the DR equation to describe micropore filling has been shown to be quite adequate. Techniques for the determination of surface area and pore size distribution have ben presented. The use of potential functions for the determination of pore size distribution in microporous materials has been described. Although the potential function techniques give consistent and satisfactory results, caution must be exerted in using these techniques for the calculation of the pore size distribution, due to the uncertainty involved in the values of the parameters used in the calculation and the simplifying assumptions employed in the derivation of the model equations. 

Adsorption plays an important role in the separation of gaseous mixtures by microporous membranes and of liquids in ultra- and microfiltration. Adsorption can either enhance or reduce the selectivity coefficient, depending, in part, on the affinity of the individual gases. Adsorption can cause membrane fouling in ultra- and microfiltration. A thorough imderstanding of the interrelation between adsorption and separation in microporous membranes can provide information for improvement of membrane synthesis. 

Bhandarkar, A.B. Shelekhin, A.G. Dixon and Y.H. Ma, Adsorption, permeation and diffusion of gases in microporous membranes. I. Adsorption of gases on microporous glass membranes. /. Membr. Sci., 75 (1992) 221. 

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