1070-4272/03/7609-1479$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 9, 2003, pp. 1479!1482. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 9,
2003, pp. 1518!1521.
Original Russian Text Copyright + 2003 by Sagdullaev, Safonova, Khodzhaeva.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Effect of Contamination and Cleaning of a Microfiltration
Membrane in Filtration of an Aqueous Extract of Dog-Rose
B. T. Sagdullaev, E. V. Safonova, and M. A. Khodzhaeva
Yunusov Institute of Chemistry of Vegetable Compounds, Academy of Sciences of the Republic of Uzbekistan,
Received February 26, 2003
Abstract-The main factors responsible for decrease in the filtration flux (membrane throughput) in removal
of pectin substances from an aqueous extract from dog-rose fruits and reasons for membrane contamination
were studied. The method for membrane cleaning with distilled water and additional cleaning agents, aqueous
solutions of NaOH and HNO
, was optimized.
Microfiltration is one of baromembrane methods
for solution separation, which is used to remove
microparticles, bacteria, grease drops, yeast cells, and
colloids from suspensions. This method is based on
the sieve mechanism, i.e., the filtering membrane can
catch from solutions particles and large dissolved
molecules. This yields two products, retentate and
permeate. The retentate is a suspension that cannot
pass across the membrane, and, therefore, the retentate
concentration grows in the course of the filtration
process. The permeate is a solution that has passed
across the membrane and contains no large molecules
According to the IUPAC classification (1985),
microfiltration membranes have pores more than
50 nm in size .
Microfiltration is a promising and attractive meth-
od for concentration of macromolecules, desalination
(mainly for removal of low-molecular-weight com-
pounds from macromolecular solutions), fractionation
of macromolecules, and clarification, pasteurization,
and sterilization of juices, wines, beer, and dairy
products, and also in manufacture of biologically
active substances .
The main advantage of this method is its high
throughput. However, the throughput (filtration flux)
decreases in the course of filtration, which is mainly
due to membrane contamination and concentration
polarization . Commonly, the filtration flux de-
creases upon contamination, but occasionally the
membrane selectivity is also altered. These changes
are observed during the entire process and even may
make necessary membrane replacement .
The effect of factors responsible for membrane con-
tamination has been poorly studied. In principle, all
the components (with exception of the solvent) in-
volved in filtration can contaminate the membrane.
Physicochemical properties of individual components,
membrane, and the bulk of the flow being filtered
determine the nature and amount of contamination.
Not infrequently, substances dominating in the con-
tamination are present in trace amounts and their con-
centration has virtually no effect on the main compo-
nents involved in the separation process. For example,
the flux decreases in most of aqueous solutions
through deposition of particles or microorganisms
present in these solutions .
Certain difficulties are encountered in identifying
the component making the main contribution to con-
tamination and in determining the extent of this con-
Many researchers explain the fast decrease in the
permeate flux by the occurrence of concentration
polarization, which leads to formation of a gel layer
[10, 11]. The simultaneous decrease in the flux is at-
tributed to membrane contamination. However, the
contamination may occur very rapidly, since the time
necessary for adsorption of macromolecules on the
membrane surface may be as short as several seconds.
It should be noted that the factors responsible for the
decrease in the membrane throughput include slow
increase in the solution viscosity because of particle
retention (in solution concentration), concentration
polarization, and slow physicochemical changes in the
structure of the membrane or substances .
The cleaning of membrane is one of the most im-