Application of porous glass in form of capillary tubes for low capacity ion exchange in hyperfiltration experiments is discussed. Efficiency of desalination by process of reverse osmosis is described. Stabilization of porous glass membrane by presence of aluminum chloride is analyzed

Ballou, E. V.

Leban, M. I.

Wydeven, T.

English

NASA Technical Reports Server

September 1972	 B72-10309 
NASA TECH BRIEF 
Ames Research Center
	 -4r 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Stabilization of Porous Glass Reverse-Osmosis Membranes 
Porous glass in the form of capillary tubes has been 
found to function as a low-capacity ion exchange 
membrane in hyperfiltration experiments. Thus, when 
dilute salt solutions (<0.2 molar) are kept in contact 
with the external walls of a closed-end porous glass 
capillary at 4 to 12 MN/M2 (40 to 120 atmospheres), 
the liquid which penetrates the porous glass has less 
salt than the solution supplied to the capillary. 
The efficiency of desalination by a reverse-osmosis 
system is defined as "percent rejection," that is, the 
percent reduction of the salt concentration in the 
solution fed to the system. Another parameter of 
interest is "flux," or the rate at which fluid flows 
through a unit area of membrane per unit pressure 
difference across the membrane. An annoying char-
acteristic of porous glass membranes is that the high 
initial rejection of salts (such as sodium chloride) 
rapidly declines and the flux increases. Since con-
siderable silica is leached from the porous membrane 
during hyperfiltration, it is probable that the mole-
cular structures responsible for salt rejection are de-
teriorated; leaching of silica presumably leads to 
increases in pore size and corresponding increases 
in flux. 
By treating porous glass membranes initially and 
then periodically with a 0.12 molar solution of alumi-
num chloride, deterioration of porous glass mem-
branes with respect to salt rejection is sharply cur-
tailed, and in some instances there even may be an 
improvement for a period of time. Moreover, if alumi-
num chloride is added to the solution fed to a hyper-
filtration cell, periodic pretreatment is not necessary; 
it appears that the porous glass membrane is stabilized 
by the presence of aluminum chloride.
An initial decrease of water flux through a mem-
brane may be observed after pretreatment with alumi-
num chloride, but the rate of decrease appears to 
level off after subsequent treatments. In experiments 
at 8.3 MN/M2
 (1200 psig), the loss of silica from 
membranes treated with aluminum chloride was 
about seven times less than from membranes which 
had not been treated; aluminum chloride appears to 
form an insoluble aluminosilicate on the surface of 
the porous glass. 
References: 
1. Ballou, E. V.; Leban, M. I.; and Wydeven, T.: Sta-
bilization of Porous Glass Hyperfiltration Mem-
branes by Aluminum Chloride Solution. Nature 
Physical Science, vol. 229, no. 4, p. 128, 1971. 
2. Ballou, E. V.; Wydeven, T.; and Leban, M. I.: 
Solute Rejection by Porous Glass Membranes. I. 
Hyperfiltration of Sodium Chloride and Urea Feed 
Solutions. Environmental Science & Technology, 
vol. 5, p. 1082, 1971. 
Notes: 
1. The porous glass is manufactured by leaching a 
solid phase; there remains a fine-pored structure 
with a narrow pore-size distribution (Corning 
Glass Works, Vycor No. 7930). 
2. No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94085 
Reference: B72-10809
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000308 2020-03-17T03:29:34+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: E. Vernon Ballou, Mark I. Leban, 
and Theodore Wydeven
Ames Research Center 
(ARC-10646)
. 
. 
. 
B72-10309	 Category 04


Stabilization of porous glass reverse-osmosis membranes

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