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

A. Idris, A.F. Ismail, M. Noorhayati, S.J. Shilton

Research output: Contribution to journalArticle

19 Citations (Scopus)

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.
LanguageEnglish
Pages45-54
Number of pages9
JournalJournal of Membrane Science
Volume213
Issue number1-2
DOIs
Publication statusPublished - 1 Mar 2003

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Osmosis
reverse osmosis
Molecular orientation
infrared reflection
Reverse osmosis
Dichroism
cellulose
dichroism
acetates
hollow
Cellulose
Shear deformation
shear
membranes
Infrared radiation
Membranes
fibers
Fibers
Extrusion
Convection

Keywords

  • shear rate
  • hollow fiber
  • membranes
  • reverse osmosis
  • fourier transform infrared spectroscopy

Cite this

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title = "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",
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.",
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T1 - 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

AU - Idris, A.

AU - Ismail, A.F.

AU - Noorhayati, M.

AU - Shilton, S.J.

PY - 2003/3/1

Y1 - 2003/3/1

N2 - 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.

AB - 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.

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