Standard Test Method for Molecular Weight Cutoff Evaluation of Flat Sheet Ultrafiltration Membranes (Withdrawn 2010)
This test method provides a convenient, rapid, reproducible method of comparing the intrinsic properties of ultrafiltration membranes. The use of nonfouling dextrans allows a direct comparison of membranes without interference from materials that may foul one membrane and not affect another. The degree of correlation between this test and actual performance on a commercial feed stream has not been completely established; however, a membrane can be exposed to the fouling solution in question and then the effect of that foulant determined by then running the test and comparing to the results on an appropriate unfouled membrane. It should be made clear that this test method does not substitute for the actual testing of a commercial or experimental membrane on a feed stream of interest. The low transmembrane pressures, lack of adsorption of the test permeants onto the membrane, and low recovery/pass are intended to eliminate interferences such as polarization and fouling that mask the properties of the membrane. It is likely that any system operated in a commercial fashion will experience fouling, adsorption, and polarization to some degree as well as a “compaction” phenomenon over the first several h of operation.
1.1 This test method covers the evaluation of the molecular weight cutoff of flat sheet ultrafiltration membranes with cutoffs between 4500 and 1000000 daltons. The nonadsorbing characteristics of the test penetrant utilized by this test method permit the test to be performed on a wide variety of membrane substrates, excluding those which strongly adsorb dextran, from highly hydrophilic to highly hydrophobic. This test method is not applicable for microfiltration membranes with pore sizes of 0.01 µm or larger, nor for reverse osmosis or dialysis membranes with less than 4500 molecular weight cutoff. (It is possible that this test method could be modified to expand the range from 100 to 2 000 000 daltons.) This test method is not applicable to membrane materials that strongly adsorb dextrans since these materials will potentially change the value of the measured molecular weight cutoff and hence will invalidate the test results.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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