Comparison of the removal of hydrophobic trace organic contaminants by forward osmosis and reverse osmosis

Ming Xie, Long D. Nghiem, William E. Price, Menachem Elimelech

Research output: Contribution to journalArticlepeer-review

207 Citations (Scopus)

Abstract

We compared the rejection behaviours of three hydrophobic trace organic contaminants, bisphenol A, triclosan and diclofenac, in forward osmosis (FO) and reverse osmosis (RO). Using erythritol, xylose and glucose as inert reference organic solutes and the membrane pore transport model, the mean effective pore size of a commercial cellulose-based FO membrane was estimated to be 0.74 nm. When NaCl was used as the draw solute, at the same water permeate flux of 5.4 L/m 2 h (or 1.5 μm/s), the adsorption of all three compounds to the membrane in the FO mode was consistently lower than that in the RO mode. Rejection of bisphenol A and diclofenac were higher in the FO mode compared to that in the RO mode. Because the molecular width of triclosan was larger than the estimated mean effective membrane pore size, triclosan was completely rejected by the membrane and negligent difference between the FO and RO modes could be observed. The difference in the separation behaviour of these hydrophobic trace organics in the FO (using NaCl the draw solute) and RO modes could be explained by the phenomenon of retarded forward diffusion of solutes. The reverse salt flux of NaCl hinders the pore diffusion and subsequent adsorption of the trace organic compounds within the membrane. The retarded forward diffusion effect was not observed when MgSO 4 and glucose were used as the draw solutes. The reverse flux of both MgSO 4 and glucose was negligible and thus both adsorption and rejection of BPA in the FO mode were identical to those in the RO mode.

Original languageEnglish
Pages (from-to)2683-2692
Number of pages10
JournalWater Research
Volume46
Issue number8
Early online date21 Feb 2012
DOIs
Publication statusPublished - 15 May 2012

Keywords

  • Bisphenol A
  • Diclofenac
  • Forward osmosis
  • Mean effective membrane pore size
  • Retarded forward diffusion
  • Reverse osmosis
  • Triclosan

ASJC Scopus subject areas

  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution
  • Ecological Modelling

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