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|Title: ||Membrane characterisation: the need for a standard|
|Authors: ||Tarleton, E.S.|
Wakeman, Richard J.
|Issue Date: ||1992|
|Publisher: ||MCM / IBC|
|Citation: ||WAKEMAN, R.J. and TARLETON, E.S., 1992. Membrane characterisation: the need for a standard. Process Industry Journal, July, pp. 16-19.|
|Abstract: ||Biologists have been aware for at least 200 years that membranes in living creatures set up and
maintain concentration differences between different regions of an organism, without which life
could not occur. The search for synthetic membranes able to bring about useful separations in
industry was a conscious attempt to mimic nature; early successes were limited, and industrial
membrane technology has been a major development over the last 10 to 20 years. Now there are
at least a dozen widely differing processes that use membranes to bring about separations.
When the liquid to be treated contains colloidal particles or aggregated molecular structures larger
than about 0.01 μm in size, it is appropriate to think of it as a suspension rather than a solution.
Such large particles undergo relatively minor Brownian motion and sediment appreciably, if rather
slowly, under gravity. In order to separate them from the suspending liquid, which is usually a true
solution and may contain molecular solutes, it is appropriate to think of filtration as an alternative
to, for example, centrifugation.
Conventional filters made from compacted fibres or powders are available for removing
particulates smaller taken about 10 μm from liquid feeds. For this purpose, polymer technologists
have developed techniques to cast films using a combination of solvent and precipitants that
contain controllably small pores of fairly narrow size range. These ‘membrane microfilters' are
used extensively for the filtration of bacteria and colloidal particles and are coming up against
increasing competition from a rapidly growing range of ceramic microfilters.
Methods of characterising the membranes are diverse and no standard exists between different
manufacturers for the measurement of properties such as pore size and size distribution, pore
shape, asymmetry, permeability and wettability. These properties, together with measured
permeate flux decline and rejection data, are the ones that most affect the potential suitability of a
membrane to a particular industrial application.|
|Description: ||This article was published in the journal, Process Industry Journal.|
|Version: ||Accepted for publication|
|Appears in Collections:||Published Articles (Chemical Engineering)|
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