Effects of annealing on the microstructure and performance of cellulose acetate membranes for pressure-retarded osmosis processes

Jincai Su, Sui Zhang, Hangzheng Chen, Hongmin Chen, Y. C. Jean, Tai-Shung Chung*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

The effects of annealing on the microstructure and performance of cellulose acetate (CA) forward osmosis (FO) hollow fiber membranes have been studied. The mean pore radius decreases from 0.63nm to 0.39, 0.36, 0.30 and 0.30 upon annealing at 70, 80, 85 and 90°C, respectively. The density of free volume in the depth range of 0.31-1.33μm significantly decreases with depth with annealing at 80°C. Annealing causes the shrinkage of both the voids between nodule aggregates and the spaces between intra-molecular chain segments. At depths greater than 0.31μm, the amount of large cavities increases for all the membranes and its increase are greater for the membranes annealed at 85 and 90°C. The free volume radius and total free volume at a depth of 0.1μm increase with increasing annealing temperature. The amount of free volume at 0.1μm depth slightly decreases upon annealing at 70 and 80°C but increases upon annealing at higher temperatures. In the pressure-retarded osmosis (PRO) process, the CA membrane annealed at 80°C exhibits the highest water flux of 30.98Lm-2h-1 (LMH) with a salt leakage of 0.37gm-2h-1 (gMH) using 2.0M MgCl2 as the draw solution.

Original languageEnglish (US)
Pages (from-to)344-353
Number of pages10
JournalJournal of Membrane Science
Volume364
Issue number1-2
DOIs
StatePublished - Nov 15 2010

Keywords

  • Annealing
  • Cellulose acetate
  • Free volume
  • Pressure-retarded osmosis
  • Water flux

ASJC Scopus subject areas

  • Biochemistry
  • Materials Science(all)
  • Physical and Theoretical Chemistry
  • Filtration and Separation

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