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Rejection of acetic acid and its improvement by combination with organic acids in dilute solutions using reverse osmosis
DESALINATION ELSEVIER
Desalination 104 (1996) 95-98
Rejection of acetic acid and its improvement by combination with organic acids in dilute solutions using reverse osmosis S. H a u s m a n n s , G. Laufenberg*, and B. Kunz Institut fiir Lebensmitteltechnologie der Universiti~t Bonn, ROmerstrasse 164, 53117 Bonn, Germany, Tel. +49-228-550458, Fax. +49-228-550429
Abstract
Detailed knowledge of the reciprocal interactions of different solute components in RO, their permeation capacity and their influence on the level of rejection is scarce. In order to examine whether and to what extent the rejection of a target substance is influenced by the addition of other substances during RO, the alteration of permeability of acetic acid through a polyamide membrane was investigated. Therefore, acetic acid was combined with 26 further acids. Keywords: Low pressure reverse osmosis; Multicomponent system; Organic acids; Selectivity; Intermolecular
interactions
1. Introduction Reverse osmosis can be used on a broader basis in the d o w n s t r e a m p r o c e s s i n g o f bioreactor constituents [1, 2]. Therefore, we need a pool of information which allows to determine the actual expected separating capacity by concentrating complex mixtures [3-5]. Thus, the rejection o f a target molecule can be influenced and a better separation of the solution will be reached,
Presented at the 7th International Symposium on Synthetic Membranes in Science and Industry, Tiabingen, Germany, August29- September 1, 1994.
• Corresponding . author.
What is decisive for the level of rejection of a particular c o m p o u n d through reverse o s m o s i s apart from the c o e f f i c i e n t o f diffusion is its solubility in the polymer of the membrane [6-8]. Driving forces for the solubility are hydrogen bonds as well as Deby- and dispersing interactions [9, 10]. These cannot only occur with the membrane [11] but also with other components of the solution [12-15]. The model of the transport of water clusters [16] for example is based on the formation of hydrate envelopes and on the interaction b e t w e e n w a t e r and the polymer. The effects that several organic substances can have on each other have not been examined so far. As a result the following question arises: In what way can interactions occurring b e t w e e n solved c o m p o n e n t s lead to an
0011-9164/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved. PII S001 1-9164 (96)0003 0-6
96
S. Hausmanns et al. /Desalination 104 (1996) 95-98
increase of the level of rejection of the target substance? Binary model solutions (solvent: water, 1 solute) were compared with ternary solutions containing a second organic acid with respect to the permeability of the solute flux. In all series of tests, the substance used for comparing was acetic acid. As you can conclude from Table 1, the s e c o n d component added was mono-, di-, ketonic- or hydroxycarboxylic acid. So conclusions can be drawn on the effects a functional group can produce. In order to generalize the results, the series were tried to be kept as homologous as possible,
Table 1 Low-molecular carboxylic acids under investigation
Monocarboxylic acids Formic Acetic Propionic Butyric
Valeric Isobutyric
Isovaleric Benzoic
Dicarboxylic acids
Hydroxycarboxylic acids
Oxalic Malonic
Glycolic Lactic
Succinic Glutaric Adipic Maleinuric Fumaric Phthalic
Mandelic Malic Tartaric Citric
Ketonic carboxylic acids Glyoxylic Pyruvic Oxoglutaric
Levulinic
a proportion of 1:1. This is to ensure that the substances to be c o m p a r e d have a concentration of 10 mmol/1 in all solutions. At a hydrostatic pressure of 10 bar, the feed flow was brought to a level of 2.5 1/min, the temperature rose from 18°C to about 22°C. By leading the permeate flow back into the feed solution, it was guaranteed that the concentration of the feed solution remains constant throughout the whole process. As the operating conditions remain the same during the tests, an alteration of the rejection of the acetic acid can only be rooted in the different characteristics of the solution added. After a steady state is reached, a sample of the permeate and retentate is taken ( C p and CR). So within 15 minutes five samples were taken. A component's rejection (R) is determined by the concentration of the permeate and the retentate. The following equation is used: R = 1 - Cp/CR * 100(%) For one component, five R-data were found Of which the median was determined. With
the help of the U-Test of Wilcoxon, Mann and Whitney [4], it was then checked if the median o f acetic acid in the binary solution was significantly better or worse than that of the respective component in a ternary solution (level of significance = 0.05).
2. Materials and methods 3. Results and discussion For the separation process an installation for reverse o s m o s i s ( S e m p a s M e m b r a n technik GmbH) was used, which disposes of a spiral w o u n d module. The c o m p o s i t e m e m b r a n e is c o m p o s e d of aromatic polyamide, the active membrane area is about 0.7 m 2 and 99% of rejection is reached for 0.026 mol/NaC1 at 14.4. bar. For all substances which were used, the rejection at a concentration of 10 mmol/1 was determined (binary solution). The ternary model solution was set at a concentration of 20 mmol/1 with the acetic acid and the respective second component being added in
The levels of rejection in each substance are listed in Fig. 1. As for the m o n o c a r b o x y l i c acids, the rejection increases with increasing molecular mass. As for the dicarboxylic acids, the rejection tends to decrease with increasing molecular mass. Apart from glycolic acid, hydroxycarboxylic acids are utterly retained. The situation with ketonic carboxylic acids is similar. The described tendencies are also found as for the influence of the above mentioned acids on the rejection of acetic acid in the
S. Hausmanns et al. /Desalination 104 (1996) 95-98
97
nq~noa h i 618>~ ×7
100
23m 8O
20. 25m** 21 9. S 2~. 12 19 ;6 4~24 ""10 11 14/15" ~ 8 13,
.22
3y "17
60 X
40
2 ~" M o n o c a r b o x y l i c
29 X1
0 0
acids
• Hydroxycarb. acids
!
1
;
!
50
100
150
2o0
Molecular Irmlm [glmol]
• Dicarboxylic acids
I
• Ketonic carboxylic acids
I
Fig. 1. Rejection in relation to molecular mass.
16
4
J 1
uUu U 3
4
6
7
8
9
10
ternary solution. It can be concluded that the r e j e c t i o n o f acetic acid is i m p r o v e d considerably through a combination of propionic, butyric, benzoic, phthalic, oxalic, and malonic acids (Fig. 2). As for the hydroxy- and ketonic carboxylic acids, only the combination with malic, g l y o x y l e or levuline acids lead to a deterioration of the rejection o f acetic acid. N o n e of the remaining acids o f these two groups revealed any influence on the rejection. As a consequence, it can be said that interactions take place in ternary solutions which have an effect on the rejection of acetic acid. Hence can be concluded from these results: - M o n o c a r b o x y l i c acids tend to cause an increase of the rejection of acetic acid with
11
12
15
16
20
23
26
Fig. 2. Significant alterations of the rej e c t i o n of acetic acid through a combination of other acids.
rising molecular mass whereas dicarboxylic acids tend to cause its decrease with rising molecular mass. Inspite o f their own positive rejection, hydroxycarboxylic acids show a neutral reaction; ketonic carboxylic acids reach neutral or in a deteriorating way. - Polar groups of the second component tend to have a negative effect on the rejection of acetic acid. - In contrast to the single compound, it can be observed in the combination that the more branched the added acid reveals to be, the more the rejection o f acetic acid decreases. - Aromatic carboxylic acids with no other functional groups have a positive effect on the level of rejection.
98
S. Hausmanns et al. /Desalination 104 (1996) 95-98 Relectlon [%]
60
16 * 10 • 9
50
•
24 •
14 .
19 *
40
15
18 * 17
25 • 22
•
4x 3~
8x
2
7
20 *.13 × 26 • 11 • 6×
21.
6 × 23 •
1 ×
x r
( x Monocarboxylic
/ * Hydroxycarb.
2
2,2
2,4
2,6
2,8
3
3,2
3,4
3,(;
3,s
pH-Value
- There is no general c o n n e c t i o n b e t w e e n the
[7]
m o l e c u l a r mass o f the acid added and the i n f l u e n c e on the rejection o f acetic acid. -
T h e r e is no d e c i s i v e i n f l u e n c e o f the p H value in the area b e t w e e n 2.0 and 3.6 as shown in Fig. 3.
[8]
Further tests with several c o m p o n e n t s are
[9]
supposed to corroborate these results. References [1] [2]
[3]
[4]
[5]
[6]
, Dicarboxylic
acids
= Ketonic carb. acids
t12
30
1,s
acids acids
H.F. Cuperus and H. Nijhuis, Applications of membrane technology to food processing, Trends Food Sci. & Techn. 4 (1983), 277-282. M.P. Tombs (Ed.), Biotechnologie in der LMIndustrie, Springer Verlag, Berlin, Heidelberg, New York, 1994. K. Kulozig, Einfltisse auf die Permeation von Wasser und gel0sten Stoffen sowie auf den Deckschichtabtrag bei der Umkehrosmose, Fortschrittberichte VDI DiJsseldorf, 3/120 (1986). Y. Fang, S. Sourirajan, and T. Matsuura, Reverse osmosis separation of binary organic mixtures using cellulose acetate butyrate and aromatic polyamide membranes, J. Appl. Polym. Sci. 44 (1992), 1959-1969. Y. Kiso et al., The effects of molecular width on permeation of organic solute through cellulose acetate reverse osmosis membranes, J. Membr. Sci. 74 (1992) 95-103. R. Rautenbach and W. Dahm, Membranverfahren zur Fraktionierung von Gemischen mit organischen Komponenten, Chem. Ing. Tech. 61 (1989) 535-537.
Fig. 3. The influence of the pH value in a ternary solution on the level of rejection of acetic acid.
Q.J. Zhou and S. Sourirajan, A transport model for reverse osmosis separation of binary organic mixtures, Chem. Eng. Comm. 104 (1991) 177-
208. H. Ohya, H. Jicai and Y. Negeshi, Studies on distribution and reverse osmosis properties of cellulose acetate derivatives for Membrane/Maku 18 (1993) 43-52.
alcohols,
J. Bansch, W. Holley, and D. Rehmann, Membran-
trennverfahren in der Lebensmittel-industrie: Membraneigenschaften, Verfahren, und Anwendungen, ZFL 6-8 Sonderdruck 1988, 5. [10] A.A. Alsaygh, P.A. Jennings, and M.S.H. Bader, Separation of organic solutes from water by low pressure reverse osmosis, J. Environm. Sci. Health A28/8 (1993) 1669-1687. [11] J.Y. Chen and W. Pusch, Solute membrane interactions in hyperfiltration, J. Appl. Polym. Sci. 33 (1987) 1809-1822. [12] J.M. Dickson, G. Whitacker, J. DeLeeuw, and J. Spencer, Dilute single and mixed solute systems in a spiral wound reverse osmosis module, Desalination 99 (1994) 1-18. [13] U. Kulozik and H.G. Kessler, Effect of salt ions and deposit formation on the permeation of organic molecules in complex media in reverse osmosis, J. Membr. Sci. 54 (1990) 339-354. [14] S. Thiel and D. Lloyd, Multicomponent effects in the pressure driven membrane separation of dilute solutions in nonelectrolytes, J. Membr. Sci. 42 (1989) 285-302. [15] F.J. Sapienza, Separation of ternary salt/acid aqueous solution using follow fiber reverse osmosis, J. Membr. Sci. 54 (1990) 175-189. [16] E. Staude (Ed.), Membranen und Membrantrennprozesse, VCH, Weinheim, New York, Basel, and Cambridge, 1992.
Desalination 104 (1996) 95-98
Rejection of acetic acid and its improvement by combination with organic acids in dilute solutions using reverse osmosis S. H a u s m a n n s , G. Laufenberg*, and B. Kunz Institut fiir Lebensmitteltechnologie der Universiti~t Bonn, ROmerstrasse 164, 53117 Bonn, Germany, Tel. +49-228-550458, Fax. +49-228-550429
Abstract
Detailed knowledge of the reciprocal interactions of different solute components in RO, their permeation capacity and their influence on the level of rejection is scarce. In order to examine whether and to what extent the rejection of a target substance is influenced by the addition of other substances during RO, the alteration of permeability of acetic acid through a polyamide membrane was investigated. Therefore, acetic acid was combined with 26 further acids. Keywords: Low pressure reverse osmosis; Multicomponent system; Organic acids; Selectivity; Intermolecular
interactions
1. Introduction Reverse osmosis can be used on a broader basis in the d o w n s t r e a m p r o c e s s i n g o f bioreactor constituents [1, 2]. Therefore, we need a pool of information which allows to determine the actual expected separating capacity by concentrating complex mixtures [3-5]. Thus, the rejection o f a target molecule can be influenced and a better separation of the solution will be reached,
Presented at the 7th International Symposium on Synthetic Membranes in Science and Industry, Tiabingen, Germany, August29- September 1, 1994.
• Corresponding . author.
What is decisive for the level of rejection of a particular c o m p o u n d through reverse o s m o s i s apart from the c o e f f i c i e n t o f diffusion is its solubility in the polymer of the membrane [6-8]. Driving forces for the solubility are hydrogen bonds as well as Deby- and dispersing interactions [9, 10]. These cannot only occur with the membrane [11] but also with other components of the solution [12-15]. The model of the transport of water clusters [16] for example is based on the formation of hydrate envelopes and on the interaction b e t w e e n w a t e r and the polymer. The effects that several organic substances can have on each other have not been examined so far. As a result the following question arises: In what way can interactions occurring b e t w e e n solved c o m p o n e n t s lead to an
0011-9164/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved. PII S001 1-9164 (96)0003 0-6
96
S. Hausmanns et al. /Desalination 104 (1996) 95-98
increase of the level of rejection of the target substance? Binary model solutions (solvent: water, 1 solute) were compared with ternary solutions containing a second organic acid with respect to the permeability of the solute flux. In all series of tests, the substance used for comparing was acetic acid. As you can conclude from Table 1, the s e c o n d component added was mono-, di-, ketonic- or hydroxycarboxylic acid. So conclusions can be drawn on the effects a functional group can produce. In order to generalize the results, the series were tried to be kept as homologous as possible,
Table 1 Low-molecular carboxylic acids under investigation
Monocarboxylic acids Formic Acetic Propionic Butyric
Valeric Isobutyric
Isovaleric Benzoic
Dicarboxylic acids
Hydroxycarboxylic acids
Oxalic Malonic
Glycolic Lactic
Succinic Glutaric Adipic Maleinuric Fumaric Phthalic
Mandelic Malic Tartaric Citric
Ketonic carboxylic acids Glyoxylic Pyruvic Oxoglutaric
Levulinic
a proportion of 1:1. This is to ensure that the substances to be c o m p a r e d have a concentration of 10 mmol/1 in all solutions. At a hydrostatic pressure of 10 bar, the feed flow was brought to a level of 2.5 1/min, the temperature rose from 18°C to about 22°C. By leading the permeate flow back into the feed solution, it was guaranteed that the concentration of the feed solution remains constant throughout the whole process. As the operating conditions remain the same during the tests, an alteration of the rejection of the acetic acid can only be rooted in the different characteristics of the solution added. After a steady state is reached, a sample of the permeate and retentate is taken ( C p and CR). So within 15 minutes five samples were taken. A component's rejection (R) is determined by the concentration of the permeate and the retentate. The following equation is used: R = 1 - Cp/CR * 100(%) For one component, five R-data were found Of which the median was determined. With
the help of the U-Test of Wilcoxon, Mann and Whitney [4], it was then checked if the median o f acetic acid in the binary solution was significantly better or worse than that of the respective component in a ternary solution (level of significance = 0.05).
2. Materials and methods 3. Results and discussion For the separation process an installation for reverse o s m o s i s ( S e m p a s M e m b r a n technik GmbH) was used, which disposes of a spiral w o u n d module. The c o m p o s i t e m e m b r a n e is c o m p o s e d of aromatic polyamide, the active membrane area is about 0.7 m 2 and 99% of rejection is reached for 0.026 mol/NaC1 at 14.4. bar. For all substances which were used, the rejection at a concentration of 10 mmol/1 was determined (binary solution). The ternary model solution was set at a concentration of 20 mmol/1 with the acetic acid and the respective second component being added in
The levels of rejection in each substance are listed in Fig. 1. As for the m o n o c a r b o x y l i c acids, the rejection increases with increasing molecular mass. As for the dicarboxylic acids, the rejection tends to decrease with increasing molecular mass. Apart from glycolic acid, hydroxycarboxylic acids are utterly retained. The situation with ketonic carboxylic acids is similar. The described tendencies are also found as for the influence of the above mentioned acids on the rejection of acetic acid in the
S. Hausmanns et al. /Desalination 104 (1996) 95-98
97
nq~noa h i 618>~ ×7
100
23m 8O
20. 25m** 21 9. S 2~. 12 19 ;6 4~24 ""10 11 14/15" ~ 8 13,
.22
3y "17
60 X
40
2 ~" M o n o c a r b o x y l i c
29 X1
0 0
acids
• Hydroxycarb. acids
!
1
;
!
50
100
150
2o0
Molecular Irmlm [glmol]
• Dicarboxylic acids
I
• Ketonic carboxylic acids
I
Fig. 1. Rejection in relation to molecular mass.
16
4
J 1
uUu U 3
4
6
7
8
9
10
ternary solution. It can be concluded that the r e j e c t i o n o f acetic acid is i m p r o v e d considerably through a combination of propionic, butyric, benzoic, phthalic, oxalic, and malonic acids (Fig. 2). As for the hydroxy- and ketonic carboxylic acids, only the combination with malic, g l y o x y l e or levuline acids lead to a deterioration of the rejection o f acetic acid. N o n e of the remaining acids o f these two groups revealed any influence on the rejection. As a consequence, it can be said that interactions take place in ternary solutions which have an effect on the rejection of acetic acid. Hence can be concluded from these results: - M o n o c a r b o x y l i c acids tend to cause an increase of the rejection of acetic acid with
11
12
15
16
20
23
26
Fig. 2. Significant alterations of the rej e c t i o n of acetic acid through a combination of other acids.
rising molecular mass whereas dicarboxylic acids tend to cause its decrease with rising molecular mass. Inspite o f their own positive rejection, hydroxycarboxylic acids show a neutral reaction; ketonic carboxylic acids reach neutral or in a deteriorating way. - Polar groups of the second component tend to have a negative effect on the rejection of acetic acid. - In contrast to the single compound, it can be observed in the combination that the more branched the added acid reveals to be, the more the rejection o f acetic acid decreases. - Aromatic carboxylic acids with no other functional groups have a positive effect on the level of rejection.
98
S. Hausmanns et al. /Desalination 104 (1996) 95-98 Relectlon [%]
60
16 * 10 • 9
50
•
24 •
14 .
19 *
40
15
18 * 17
25 • 22
•
4x 3~
8x
2
7
20 *.13 × 26 • 11 • 6×
21.
6 × 23 •
1 ×
x r
( x Monocarboxylic
/ * Hydroxycarb.
2
2,2
2,4
2,6
2,8
3
3,2
3,4
3,(;
3,s
pH-Value
- There is no general c o n n e c t i o n b e t w e e n the
[7]
m o l e c u l a r mass o f the acid added and the i n f l u e n c e on the rejection o f acetic acid. -
T h e r e is no d e c i s i v e i n f l u e n c e o f the p H value in the area b e t w e e n 2.0 and 3.6 as shown in Fig. 3.
[8]
Further tests with several c o m p o n e n t s are
[9]
supposed to corroborate these results. References [1] [2]
[3]
[4]
[5]
[6]
, Dicarboxylic
acids
= Ketonic carb. acids
t12
30
1,s
acids acids
H.F. Cuperus and H. Nijhuis, Applications of membrane technology to food processing, Trends Food Sci. & Techn. 4 (1983), 277-282. M.P. Tombs (Ed.), Biotechnologie in der LMIndustrie, Springer Verlag, Berlin, Heidelberg, New York, 1994. K. Kulozig, Einfltisse auf die Permeation von Wasser und gel0sten Stoffen sowie auf den Deckschichtabtrag bei der Umkehrosmose, Fortschrittberichte VDI DiJsseldorf, 3/120 (1986). Y. Fang, S. Sourirajan, and T. Matsuura, Reverse osmosis separation of binary organic mixtures using cellulose acetate butyrate and aromatic polyamide membranes, J. Appl. Polym. Sci. 44 (1992), 1959-1969. Y. Kiso et al., The effects of molecular width on permeation of organic solute through cellulose acetate reverse osmosis membranes, J. Membr. Sci. 74 (1992) 95-103. R. Rautenbach and W. Dahm, Membranverfahren zur Fraktionierung von Gemischen mit organischen Komponenten, Chem. Ing. Tech. 61 (1989) 535-537.
Fig. 3. The influence of the pH value in a ternary solution on the level of rejection of acetic acid.
Q.J. Zhou and S. Sourirajan, A transport model for reverse osmosis separation of binary organic mixtures, Chem. Eng. Comm. 104 (1991) 177-
208. H. Ohya, H. Jicai and Y. Negeshi, Studies on distribution and reverse osmosis properties of cellulose acetate derivatives for Membrane/Maku 18 (1993) 43-52.
alcohols,
J. Bansch, W. Holley, and D. Rehmann, Membran-
trennverfahren in der Lebensmittel-industrie: Membraneigenschaften, Verfahren, und Anwendungen, ZFL 6-8 Sonderdruck 1988, 5. [10] A.A. Alsaygh, P.A. Jennings, and M.S.H. Bader, Separation of organic solutes from water by low pressure reverse osmosis, J. Environm. Sci. Health A28/8 (1993) 1669-1687. [11] J.Y. Chen and W. Pusch, Solute membrane interactions in hyperfiltration, J. Appl. Polym. Sci. 33 (1987) 1809-1822. [12] J.M. Dickson, G. Whitacker, J. DeLeeuw, and J. Spencer, Dilute single and mixed solute systems in a spiral wound reverse osmosis module, Desalination 99 (1994) 1-18. [13] U. Kulozik and H.G. Kessler, Effect of salt ions and deposit formation on the permeation of organic molecules in complex media in reverse osmosis, J. Membr. Sci. 54 (1990) 339-354. [14] S. Thiel and D. Lloyd, Multicomponent effects in the pressure driven membrane separation of dilute solutions in nonelectrolytes, J. Membr. Sci. 42 (1989) 285-302. [15] F.J. Sapienza, Separation of ternary salt/acid aqueous solution using follow fiber reverse osmosis, J. Membr. Sci. 54 (1990) 175-189. [16] E. Staude (Ed.), Membranen und Membrantrennprozesse, VCH, Weinheim, New York, Basel, and Cambridge, 1992.