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Isolation of the Mechanical Sieving Properties of Filters through Chemical Hindrance

IP.com Disclosure Number: IPCOM000114032D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Sherry, RW: AUTHOR [+2]

Abstract

A method is described for measuring the true mechanical sieving properties of membrane filter elements without the confounding effects of Zeta potential and the clogging effects of surfactants. The Zeta potential is neutralized by means of shifting the pH of the solvent instead of using a surfactant additive for the same purpose.

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Isolation of the Mechanical Sieving Properties of Filters through
Chemical Hindrance

      A method is described for measuring the true mechanical sieving
properties of membrane filter elements without the confounding
effects of Zeta potential and the clogging effects of surfactants.
The Zeta potential is neutralized by means of shifting the pH of the
solvent instead of using a surfactant additive for the same purpose.

      Polystyrene latex (PSL) spheres are the accepted industry
standard for simulation testing and calibration of liquid-borne and
aerosol particle counting devices.  In practice, an electrochemical
charge known as Zeta potential develops between the PSL spheres and
the filter.  Zeta potential causes particles that may be smaller than
the pore structure of the filter to be attracted and bound to the
filter as shown in the Figure.  Measurement of the size and quantity
of PSL spheres that pass through the filter under the influence of
Zeta potential does not yield a true indication of the mechanical
sieving properties of the filter under test.

      Surfactants have been used to dissipate or reverse Zeta
potential, but typical surfactants with high molecular weight alter
the flow characteristics of the filter and eventually will clog it,
invalidating the test.

      Semiconductor manufacturing grade deionized water is slightly
acidic (pH of 6.9 to 6.7.) A carboxalated PSL sphere in pure
deionized water is a negatively charged particle. ...