Fundamental understanding of nano-sized zeolite distribution in the formation of the mixed matrix single- and dual-layer asymmetric hollow fiber membranes

Lan Ying Jiang, Tai Shung Chung*, Chun Cao, Zhen Huang, Santi Kulprathipanja

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

129 Scopus citations


We have revealed, for the first time, the evolution of nano-particle distribution and the mechanisms of nano-particle movement during the formation of single-layer and dual- membranes. Both single-layer and dual-layer mixed matrix hollow fibers have been fabricated using nano-size zeolite beta. It is found that three factors play important roles in determining the nano-particle distribution in the resultant fibers. They are (1) shear within the spinneret, (2) die swell when exiting from the annulus spinneret and (3) elongation drawing in the air gap region. The shear stress induced within the spinneret determines the initial particle distribution. As a result, the particle distributions in both wet-spun single-layer and dual-layer hollow fibers follow the parabolic shape of dope's axial velocity profile in the spinneret. Die swell flattens and levels off the particle distribution, while elongation stretch redistributes the particles to the outer surface with the aid of (1) moving outer surface inward and (2) the outflow of solvents during the phase inversion process. The particle redistribution phenomenon is significantly magnified and enhanced during the co-extrusion of dual-layer hollow fiber membranes with an outer layer made of mixed matrix materials. The proposed causes and mechanisms for particle distribution have been verified by the EDX line scanning spectra of silicon and SEM pictures. Preliminary gas separation data indicate that the outer mixed matrix layer of the as-spun hollow fiber membrane has a defective skin for Knudsen diffusion. Further post-treatment is needed to eliminate defects for gas separation.

Original languageEnglish (US)
Pages (from-to)89-100
Number of pages12
JournalJournal of Membrane Science
Issue number1-2
StatePublished - Apr 15 2005
Externally publishedYes

Bibliographical note

Funding Information:
The authors would like to thank UOP and NUS for funding this research with the grant numbers R-279-000-140-592 and R-279-000-140-112, respectively. Ms. Jiang would like to express her appreciation to Universal Oil Products for partial financial support under the UOP grant number of R-279-000-140-592.


  • Dual-layer membrane
  • Mixed matrix hollow fibers
  • Mixed matrix membranes
  • Particle distribution
  • Shear and elongation effects

ASJC Scopus subject areas

  • Biochemistry
  • General Materials Science
  • Physical and Theoretical Chemistry
  • Filtration and Separation


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