Influence of shear rate on the flux during ultrafiltration of colloidal substances

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Abstract

The shear rate at the surface of a membrane has a distinct influence on the membrane flux in systems containing colloidal substances. If the shear rate is decreased, flux decreases since the thickness of the boundary layer of retained solutes at the membrane surface then increases. When low molecular solutes are used, flux increases again when the shear rate is increased. However, if large solutes are used, polymeric and colloidal substances, for example, it sometimes happens that the flux cannot be increased to its original value again by increasing the shear rate: the flux decline is regarded as irreversible. Experiments, performed in a new type of turbulence-promoting module, which illustrate the influence of shear rate on flux when treating solutions containing colloidal substances, are presented in this paper. It is also shown that a flux decrease which can not be restored by increasing the shear rate, may be completely restored by a temporary interruption of the permeate flow.

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Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Chemical Engineering

Keywords

  • ULTRAFILTRATION, FOULING, PLANT EFFLUENT, WASTE WATER, TURBULENCE, PROMOTION
Original languageEnglish
Pages (from-to)93-99
JournalJournal of Membrane Science
Volume79
Issue number1
Publication statusPublished - 1993
Publication categoryResearch
Peer-reviewedYes