Boron transport in forward osmosis: Measurements, mechanisms, and comparison with reverse osmosis

Changwoo Kim, Sangyoup Lee, Ho Kyong Shon, Menachem Elimelech, Seungkwan Hong

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

The physical and chemical factors affecting boron solute flux behavior and membrane transport mechanisms in forward osmosis (FO) have been systematically investigated. Boron solute flux behavior in FO was further compared with that in reverse osmosis (RO) by employing identical plate-and-frame cells and membranes under the same filtration conditions. The influence of draw solution pH, draw solution type, and membrane orientation on boron solute flux was examined for FO, and the effects of water flux, cross-flow velocity, feed water boron concentration, and solution pH on boron solute flux were examined for both FO and RO. Results show that reverse salt diffusion, a unique feature of FO, is a key mechanism governing boron solute flux in FO. Boron solute flux through the FO membrane was inversely proportional to the degree of reverse salt diffusion by draw solution. The higher boron rejection observed in FO compared to RO is also attributed to reverse salt diffusion in FO. It is also shown that membrane orientation in FO plays an important role, affecting boron solute flux due to different degrees of internal concentration polarization. In both FO and RO, boron solute flux increased with increasing water flux. However, the influence of water flux on boron solute flux was less significant in FO than RO. Furthermore, boron solute flux decreased with increasing feed water pH due to the conversion of the neutral boric acid to borate anions. The findings provide new insight into the mechanisms and factors controlling boron solute transport in FO.

Original languageEnglish
Pages (from-to)42-48
Number of pages7
JournalJournal of Membrane Science
Volume419-420
DOIs
Publication statusPublished - 2012 Nov 15

Keywords

  • Boron solute flux
  • Forward osmosis (FO)
  • Internal concentration polarization (ICP)
  • Reverse osmosis (RO)
  • Reverse salt diffusion

ASJC Scopus subject areas

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

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