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Transport of gases across membranes
Author(s)
Mokrani, Touhami
Date Issued
2000
Type
Thesis
Publisher
Peninsula Technikon
Abstract
Oxygen transport across biofilms and membranes may be a limiting factor in the
operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in
which fungi are immobilized within the wall of a porous polysulphone capillary
membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide)
were investigated in a bare membrane (without a biofilm being present). The work
provides a basis for further transport study in membranes where biomass is present.
The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet
membranes. The diaphragm-cell method employs two well-stirred compartments
separated by the desired membrane to be tested. The membrane is maintained
horizontally. -The gas (solute) concentration in the lower compartment is measured versus
time, while the concentration in the upper liquid-containing compartment is maintained at
a value near zero by a chemical reaction.
The resistances-in-series model can be used to explain the transfer rate in the system. The
two compartments are well stirred; this agitation reduces the resistances in the liquid
boundary layers. Therefore it can be assumed that in this work the resistance in the
membrane will be dominating.
The method was evaluated using oxygen as a test. The following factors were found to
influence mass transfer coefficient: i) the agitation in the two compartments; ii) the
concentration of the reactive solution and iii) the thickness of the membrane.
operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in
which fungi are immobilized within the wall of a porous polysulphone capillary
membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide)
were investigated in a bare membrane (without a biofilm being present). The work
provides a basis for further transport study in membranes where biomass is present.
The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet
membranes. The diaphragm-cell method employs two well-stirred compartments
separated by the desired membrane to be tested. The membrane is maintained
horizontally. -The gas (solute) concentration in the lower compartment is measured versus
time, while the concentration in the upper liquid-containing compartment is maintained at
a value near zero by a chemical reaction.
The resistances-in-series model can be used to explain the transfer rate in the system. The
two compartments are well stirred; this agitation reduces the resistances in the liquid
boundary layers. Therefore it can be assumed that in this work the resistance in the
membrane will be dominating.
The method was evaluated using oxygen as a test. The following factors were found to
influence mass transfer coefficient: i) the agitation in the two compartments; ii) the
concentration of the reactive solution and iii) the thickness of the membrane.
Additional information
Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000.
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