Water permeability in polymeric membranes, Part I

Experimental approaches to feed solution permeability in pressure-driven membrane separation processes

“…The experimental rig is similar to that thoroughly described in a previous work [4], where the cell-setting B is used. The types of RO membranes used were TFC-HR (thin film composite -high rejection) and TFC-ULP (thin film composite -ultra low pressure), which are manufactured by Koch Membranes Systems, Inc. (USA).…”

“…The value of P o can be taken as one pressure unit. For membranes with known microstructure, the expression for the pure water permeability, A wm , which is the upper limit for A w , has been described in previous works empirically (the SDPF model) [4] and analytically (the ASDPF model) [8]; however, for membranes with unknown microstructural specifications, other empirical forms can be suggested, such as:…”

“…The order for the polynomial function in Eq. (4) can be adjusted depending on the relationship observed for A wm versus P. The effect of the feed flow rate is neglected here, due to its low effect on A wm [4], while the temperature effect is assumed to be linear, as indicated by Eq. (5).…”

“…This approach assumes that A wm , as a function of P, proportionally shifts upwards or downwards depending on temperature increase or decrease, respectively. Actually, temperature dependence may be exponential or a power function [4]; however, Negative [11] Negative [11] a Value calculated from the MWCO by using an empirical relationship between molecular weight and diameter [12].…”

“…By this combination a new model, the SDPF model, is constructed [4], which is similar in principle to the solution diffusion imperfection (SDI) model [5][6][7]. According to the SDPF model, water flux across the membrane is jointly carried out by diffusion and pore flow mechanisms.…”