Naslov
Partitioning and diffusion of differently sized hydrophilic and hydrophobic solutes in polyamide reverse osmosis membrane

Autori
Dražević, Emil ; Košutić, Krešimir

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
The 10th international conference on membrane and membrane processes

Mjesto i datum
Suzhou, Kina, 20.07.2014. - 25.07.2014

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
reverse osmosis; partitioning; diffusion; organics; polyamide

Sažetak
Reverse osmosis (RO) and nanofiltration (NF) membranes are widely used for removal of toxic organics (pesticides, pharmaceuticals, bisphenol A) from water. High energy of interaction between polyamide membranes and organics often limits their practical use in RO/NF processes. Often, a fairly good correlation may be found between estimated energy of interactions and rejections of organics by RO/NF membranes1. However, the energy of interactions and rejections of solutes are not intrinsic properties of the polymeric membranes, i.e., they do not give info on fundamentals of transport in the polymer matrix, such the diffusion coefficient or equilibrium concentration of organic solutes. A universal correlation has been found between intrinsic water permeability and equilibrium water content in RO membranes2. In addition, Ben – David et al.3 found that measured rejection of n – alcohols correlated well with the estimated equilibrium concentration of organics in selective layer of RO/NF polyamide membranes. In this sense, intrinsic permeability of organic solutes (permeability times thickness of the polyamide layer) could be entirely determined by equilibrium concentration and diffusion of organics in polyamide. Diffusion of organics in polyamide is size controlled ; it depends on solute size, cross –linking degree of polyamide and curvature of the selective paths4. Equilibrium partitioning depends on short range wan der Walls forces and hydrogen bonds which may become significant at a molecular scale and overwhelm steric effects5. This study uses relatively simple, attenuated total reflection Fouriertransform infrared (ATR- FTIR) spectroscopy based method, for measuring diffusion coefficients of differently sized hydrophobic (n – alcohols) and hydrophilic (ethers) organic solutes, in polyamide films6. The ATR – FTIR method measures intensity of a solute band over time and fits experimental data to a mathematical model derived from sorption kinetics and laws of ATR optics7. In order to accurately evaluate the diffusion coefficient, the thickness of the polyamide films was estimated by the use of atomic force microscopy (AFM), as explained elsewhere2, 8. Permeability of the solutes is estimated fitting the experimental data on rejection vs. volume flux to a well-known Spiegler – Kedem model. Partitioning of organics can be then estimated from measured permeability and diffusion coefficients, provided thickness of the swelled SWC4+ membrane is known. Partitioning and diffusion of differently sized organics (non –polar and polar) in polyamide are then critically discussed.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija, Interdisciplinarne tehničke znanosti

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