Dynamic micellar enhanced ultrafiltration: Use of anionic (SDS)-nonionic(NPE) system to remove Cr3+ at low surfactant concentration

Mohamed Aoudia, Nora Allal, Ahcene Djennet, Leila Toumi

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85 Citations (Scopus)

Abstract

Ultrafiltration experiments were carried out with tangential cell system. The permeate flux and rejection characteristics of SDS and nonylphenol ethoxylated C9H19C6H4(CH2CH 2O)5CH2CH2OH (NPE) micellar solutions for a ceramic tubular membrane (zirconium oxide-Titanium oxide) were investigated. For both surfactants, micelle rejection increased with pressure and reached an asymptotic value at ΔP=250kPa beyond which micellar rejection remained unchanged (∼+99%). This was explained in terms of concentration polarization occurring in the vicinity of the membrane-solution interface. Time dependence of the permeate surfactant concentration was also investigated. During the first 2h of ultrafiltration, the surfactant concentration changed with time. Then a steady-state condition was reached and the permeate concentration remained invariant. This trend was attributed to a time-dependent gradual change of the state of packing of the micelles over the membrane surface. Cr3+ rejection by SDS-NPE mixed micelles yielded high Cr3+ rejection (+99.5%) at NPE molar fraction up to 0.2. Within this optimum composition and ΔP=250kPa, unexpectedly high rejection (33.50%) was measured below the critical micellar concentration (cmc). This was considered as due to a high surfactant concentration in the vicinity of the membrane surface where micelles are present, although the retentate surfactant concentration is below the cmc. Above the cmc, high Cr3+ rejections (+99%) were obtained. Interestingly, this rejection was found to be independent of the feed surfactant concentration within the range investigated in this study (3×cmc-30×cmc), suggesting that Cr3+ rejection is not a function of the surfactant concentration in the bulk retentate solution but a function of the surfactant concentration nearby the membrane surface. The presence of NaCl in the feed surfactant solution showed a drastic adverse effect on Cr3+ rejection by SDS-NPE micelles.

Original languageEnglish
Pages (from-to)181-192
Number of pages12
JournalJournal of Membrane Science
Volume217
Issue number1-2
DOIs
Publication statusPublished - Jun 1 2003

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Keywords

  • Concentration polarization
  • MEUF
  • Micelle rejection
  • Permeate flux

ASJC Scopus subject areas

  • Filtration and Separation
  • Polymers and Plastics

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