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The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs.

Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Measurement of rheologically induced molecular orientation using attenuated total reflection infrared dichroism in reverse osmosis hollow fiber cellulose acetate membranes and influence on separation performance

Idris, A. and Ismail, A.F. and Noorhayati, M. and Shilton, S.J. (2003) Measurement of rheologically induced molecular orientation using attenuated total reflection infrared dichroism in reverse osmosis hollow fiber cellulose acetate membranes and influence on separation performance. Journal of Membrane Science, 213 (1-2). pp. 45-54. ISSN 0376-7388

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Abstract

The objective of this study is to investigate the pure influence of shear and its capacity to increase the separation performance of cellulose acetate reverse osmosis hollow fiber membranes, produced using a dry/wet spinning process with forced convection in the dry gap. In order to achieve this, the experiments are designed to decouple the effect of extrusion shear from forced convection residence time by fixing the residence time at 0.615s. RO hollow fibers were spun at various dope extrusion shear rates ranging from 3.0 to 4.5ml/min corresponding to shear rates of around 13,479-20,219s-1, respectively, at the outer spinneret wall. Fourier transform attenuated total reflection (ATR) also known as internal reflection spectroscopy was used to probe the membrane active layer so as to examine if high shear rates may induce anisotropy at the molecular level in the active layer. The rejection rates of the membranes were evaluated using salt water. Results revealed that: (i) ATR can be used to determine qualitatively and quantitatively-the degree of molecular orientation in the sheared membranes; (ii) molecular orientation is enhanced as the dope extrusion rate increases; and (iii) there exist an optimum shear rate that can induce a certain degree of molecular orientation to yield membrane morphology with optimum separation performance.