I n d . Eng. C h e m . Res 1990, 29, 857-861
Ki = dissociation constant, mol/L Kw = ionic product of water, mo12/L2 M = mass of hydrated resin, g n = (number of functional group types) - 1 N = number of exchangeable counterions p = skewness of binomial distribution function q A = solute concentration in resin phase, mmol/g of dry resin qo = resin ion-exchange capacity, mmol/g of dry resin Si,= selectivity coefficient for exchange of ion i with ion j Si,! = average selectivity coefficient for exchange of ion i with ion j S ’ = selectivity coefficient for exchange of monovalent cations with hydrogen ion S ” = selectivity coefficient for exchange of divalent cations with hydrogen ion V = solution volume, mL Wi,,j= heterogeneity parameter for exchange of ion i with ion J
XA= ionic fraction of cation A in solution Y A = ionic fraction of solute A in the resin Greek S y m b o l
dry resin density, g of dry resin/g of hydrated resin Registry No. L-Ala, 56-41-7; L-Val, 72-18-4; L-Isoleu, 73-32-5; L-Leu, 61-90-5; L-Phe, 63-91-2; L - G ~ u56-86-0; , L-LYS,56-87-1; Dowex 50W-X8, 11119-67-8.
ps =
Literature Cited Blackburn, S. Amino Acids and Amines. In Handbook of Chromatography; Zweig, G., Sherma, J., Eds.; CRC Press, Inc.: Boca Raton, FL, 1983. Carta, G.; Saunders, M. S.; DeCarli, J. P., 11; Vierow, J. B. Dynamics of Fixed Bed Separations of Amino Acids by Ion Exchange.
857
AIChE Symp. Ser. 1988,84, 54-61. Carta, G.; Saunders, M. S.; Mawengkang, F. Studies on the Diffusion of Amino Acids in Ion Exchange Resins, Presented at the Third International Conference on Fundamentals of Adsorption, Sonthofen, FRG; Engineering Foundation: New York, 1989. DeCarli, J. P., 11; Carta, G.; Byers, C. H. Displacement Separations by Continuous Annular Chromatography. Presented a t the AIChE Annual Meeting: Washington, DC, 1988. Helfferich, F. Ion Exchange; McGraw-Hill: New York, 1962; Chapter 5, pp 134-145. Meister, A. Biochemistry of the Amino Acids, 2nd ed.; Academic Press: New York, 1965; Vol. I, p 28. Myers, A. L.; Byington, S. Thermodynamics of Ion Exchange: Prediction of Multicomponent Equilibria from Binary Data. In Zon Exchange Science and Technology; Rodrigues, A. E., Ed.; NATO AS1 Series E., No. 107; Nijhoff Dordrecht, 1986; pp 119-145. Nozaki, Y.; Tanford, C. The Solubility of Amino Acids and Two Glycine Peptides in Aqueous Ethanol and Dioxane Solutions. J . Biol. Chem. 1971,246, 2211-2217. Pieroni, L. J.; Dranoff, J. S. Ion Exchange Equilibria in a Ternary System. AIChE J . 1963, 9, 42-45. Saunders, M. S.; Vierow, J. B.; Carta, G. Uptake of Phenylalanine and Tyrosine by a Strong Acid Cation Exchanger. AIChE J. 1989, 35, 53-68. Smith, N. D. Multicomponent Cation Exchange in Aqueous Systems. Ph.D. Dissertation, Illinois Institute of Technology, Chicago, 1960. Thien, M. P.; Hatton, T. A.; Wang, D. I. C. Separation and Concentration of Amino Acids using Liquid Emulsion Membranes. Biotechnol. Bioeng. 1988, 32, 604-615. Yu, Q.; Wang, N.-H. L. Multicomponent Interference Phenomena in Ion Exchange Columns. Sep. Purif. Methods 1986,15,127-158. Yu, Q.; Yang, J.; Wang, N.-H. L. Multicomponent Ion Exchange Chromatography for Separating Amino Acid Mixtures. React. Polym. 1987, 6, 33-44. Receiued for reuiew October 5, 1989 Accepted January 30, 1990
Selective Transport of Aldehydes across an Anion-Exchange Membrane via the Formation of Bisulfite Adducts Manabu Igawa,* Yasuko Fukushi, and Takashi Hayashita Faculty of Engineering, Kanagawa University, Rokkakubashi, Kanagawa-ku, Yokohama 221, J a p a n
Michael R. Hoffmann California Institute of Technology, W . M . Keck Laboratories 138-78, Pasadena, California 91125
Organic nonelectrolytes can be selectively transported through a n ion-exchange membrane if they are specifically converted to electrolytes in the membrane. Aldehydes react with bisulfite to form hydroxyalkanesulfonates (HASA), which are the conjugate bases of strong acids. Aldehydes are shown to be transported efficiently across an anion-exchange membrane via the coupled countertransport of HMSA ion with hydroxide ion and the relay of an aldehyde from one membrane-bound bisulfite ion to another. Permeation rates are in the order of formaldehyde > acetaldehyde > acetone; this relationship parallels the relative order of the stability constants for formation of the respective adducts with bisulfite ion. Aldehydes can be separated readily from other organic solutes by this method. The selective transport of organic solutes plays a very important role in biological membranes (Kotyk et al., 1988). However, in synthetic membranes, the controlled transport of organic solutes is very difficult to achieve. The selective transport system for aldehydes, which is described in this paper, may be useful as a commercial separation process. Similar systems can be developed to separate other organic solutes. There have been many reports on the selective and facilitated transport of electrolytes under a concentration
* To whom correspondence should be addressed.
gradient through polymer or liquid membranes. Macrocyclic compounds, such as monensin (Choy et al., 1974) and dibenzo-18-crown-6 (Reusch and Cussler, 1973), are very effective carriers for the selective transport of metal ions. Electrolytes can be separated from each other with various membranes by their ion sizes, ion valences, hydrophilicities, and chelate formation properties. On the other hand, only a few papers have been reported on the selective transport of organic nonelectrolytes. Nonelectrolytes have been separated by their sizes, hydrophobicities, and their degree of dissociation. The permselectivities of sugars were regulated by pH in polyvinyl-poly-
08S8-5885/90/2629-085~~02.50/0 0 1990 American Chemical Society
858 Ind. Eng. Chem. Res., Vol. 29, No. 5, 1990
I
I
Time(min)
t
I
Figure 1. h’eutralization dialysis cell and schematic ion transport: a, anion-exchange membrane; c, cation-exchange membrane; B, base solution compartment: D, desalination compartment; A, acid solution compartment
peptide membranes, and hydrophobic and small sugars were transported rapidly through the membrane (Chung et al., 1986). Hydrophobic solutes were partitioned effectively on a hydrophobic membrane surface and concentrated under a pressure gradient (Igawa et al., 1984, 1985). Amino acids were selectively transported across mosaic membranes (Hirahara et al., 1986) by adjustment of their degree of dissociation as a function of pH. In addition to these factors, the specific reaction of an organic nonelectrolyte with an electrolyte can be used to control the permeation rate across a membrane. Some examples of these reactions include the reaction of aldehydes with bisulfite ion (Boyce and Hoffmann, 1984) and the reaction of sugar with borate ion (Khym and Zill, 1951). Shinbo e t al. (1986) reported the selective transport of sugar through a liquid membrane containing borate ion as a carrier, while Koval and Spontarell (1988) reported on the facilitated transport of olefins through a cation-exchange membrane fixed with silver ion. Recently, we reported that formaldehyde was selectively transported across an anion-exchange membrane via the formation of an adduct with bisulfite ion (Igawa and Hoffmann, 1988). Aldehyde-bisulfite adducts are known to be important species as S(1V) reservoirs in cloud water droplets (Munger et al., 1986). The formation constant of hydroxymethanesulfonate (HMSA) form formaldehyde and bisulfite ion is (3.61 f 0.32) x lo6 over the pH range 3-6 (Deister et al., 1986). Aldehydes are transported efficiently by the coupled countertransport of HMSA ion with hydroxide ion across an anion-exchange membrane. In this paper we will report on the fundamental permeation properties, the permselectivity, and the permeation mechanism for the selective transport of aldehydes across an anion-exchange membrane.
Experimental Section Apparatus. The permeation experiment was carried out in a neutralization dialysis cell (Igawa et al., 1987). The cell is composed of two membranes, an anion-exchange membrane and a cation-exchange membrane, and three compartments divided by the two membranes, which were named as compartments A, B, and D, as shown in Figure 1. Formaldehyde transport is mediated by bisulfite ion and the permeation rate depends on the pH because the formation and dissociation rate of the sulfonate adduct are strong functions of pH (Smensen and Andersen, 1970). To maintain a constant pH, the neutralization dialysis technique was applied in this experiment. The ion-exchange membranes used in this study were commercial strong acid
Figure 2. Formaldehyde and S(IV) transport through an anionexchange membrane: 0, HCHO transport with S(1V); 0 , S(1V) transport; 0,HCHO transport without S(1V);- - -, concentration in compartment D; -. concentration in compartment B.
or strong base type ion-exchange membranes for electrodialysis, Selemion AMV and CMV (Asahi Glass Co., Ltd.). Each membrane area was 10 cm2,and the thickness of each compartment was 1 mm. The details of this cell were presented elsewhere (Igawa et al., 1987). An acidic solution, an alkaline solution,and a mixed solution of formaldehyde and sodium bisulfite were pumped from each reservoir into compartments A, B, and D, respectively. Unless otherwise stated, the solution in compartment B was 1.0 mM sodium hydroxide, the solution in compartment D was a mixed solution of 1 mM formaldehyde, 1 mM sodium bisulfite, and 0.1 mM hydrochloric acid, and the solution in compartment A was 1 mM hydrochloric acid. The volume of each solution was 100 mL, and the pumping rate was approximately 25 mL/min. An aliquot of the solution in each compartment was collected a t an interval, and the solute concentration was determined. The solute flux was calculated from the concentration change of the solute in compartment B. Analysis. The concentration of S(1V) was analyzed by the pararosaniline method as described by Dasgupta et al. (1980). Formaldehyde and acetaldehyde were determined by the modified MBTH (3-methyl-2-benzothiazolinone hydrazone) method (Sawicki et al., 1961; Igawa et al., 1989) as follows: 1 mL of 0.1 % 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate solution was added to a mixed solution of 1 mL of 0.1 M sodium hydroxide and 0.1 mL of the sample solution. After shaking and standing for 1 h, 1 mL of 0.1 M nitric acid was added to neutralize the solution, and then, 0.15 mL of 1% ferric chloride hexahydrate solution was added. After shaking and standing for 1 h, 2.7 mL of acetone was added, and the absorbance was measured a t 640 nm. This method gives total aldehyde concentration without interference from either bisulfite or sulfite ion. The absorbances of the colored solutions were measured by a Shimadzu UV-265 spectrophotometer. Methanol was determined by a Shimadzu GC-8A gas chromatograph equipped with a PEG 6000 column and a FID detector.
Results and Discussion Facilitated Transport of Formaldehyde. Figure 2 shows the result of the permeation experiment in the cell. The solution pH of compartment D was adjusted to about pH 4 by the addition of hydrochloric acid. The adduct is most stable in the pH range 3-6 where HS03- is the dominant form of S(IV) (Deister et al., 19861, and the solution pH tends to remain constant a t about p H 4 in the neutralization dialysis cell (Igawa et al., 1987). Formaldehyde was transported across an anion-exchange membrane from compartment D to compartment B (JHCHO= 2.8 X mol cm-* min-’). Permeation of formaldehyde from com-
Ind. Eng. Chem. Res., Vol. 29, No. 5, 1990 859 partment D to compartment A across the cation-exchange membrane was not detected. Formaldehyde transport was facilitated by bisulfite ion because formaldehyde was not permeated to compartment B under the same experimental conditions other than the absence of bisulfite ion in compartment D as shown in this figure (square sign). Formaldehyde is retained on an anion exchanger, which adsorbs bisulfite ion, and eluted with base (Samuelson, 1953); the selective transport of formaldehyde through an anion-exchange membrane occurs on the same basis. Formaldehyde reacts with bisulfite ion to form hydroxymethanesulfonate (HMSA) according to the following stoichiometry: HCHO
+ HS03- = HOCHzS03-
Table I. T r a n s p o r t Rates of Aldehydes a n d Some Organic Solutes“ dissociation const of solute flux, mol hydroxyalkanesolute min-* sulfonic acid formaldehyde 2.8 x 10-8 1.2 x 10-7 acetaldehyde 2.4 X 2.5 X IO” acetone 9.2 x 10-9 4 x 10-3 methanol 4.1 x 10-9 a Compartment B, 1 mM NaOH; compartment D, 1 mM organic solute, 1 mM NaHS03, and 0.1 mM HCl; compartment A, 1 mM HC1. The dissociation constants of hydroxyalkanesulfonic acids are the data reported by DuVal et al. (1985).
(1)
HMSA is transported through the anion-exchange membrane on the basis of an ion-exchange reaction with the countertransport of hydroxide ion. There is a possibility that the dissociation reaction occurs in alkaline solution as follows after the permeation of HMSA through the anion-exchange membrane, HOCH,S03-
+ OH- = HCHO + SO3,- + H,O
(2)
where the dissociation constant is reported to be 8.6 X [OH-] s-l (Scarensen and Andersen, 1970). This is not the case, however, because the transport rate was not changed when the solution in compartment B contained only sodium chloride and chloride ion was countertransported instead of hydroxide ion. The permeation experiment was also carried out when the sodium hydroxide concentration in compartment B in the neutralization dialysis cell was changed to 0.01 M. The permeability of S(1V) increased by 2-fold because of the increased driving force (i.e., the increasing concentration gradient of hydroxide ion across the membrane), but the flux of formaldehyde showed little change (JHCHO = 3.0 x mol cm-, min-’). When the sodium hydroxide concentration in compartment B was high, the hydroxide concentration in the membrane was also high. HMSA was dissociated in the membrane and S(1V) was transported across the membrane in part without the associated transport of formaldehyde. The transport phenomena of Figure 2 occurred in the neutralization dialysis cell, and the pH change during the experiment was less than f0.2. The concentration of hydroxide ion permeated through the membrane was reduced in compartment D by the neutralization reaction with protons permeated through the cation-exchange membrane. When the experiment was carried out in a two compartment cell, that is, a cell with an anion-exchange membrane, compartment D, and compartment B, the solution pH in compartment D increased gradually from pH 4 to pH 6.5 during 90-min experiment. The formaldehyde flux decreased with the increase of pH in compartment D. After 90 min, the permeated amount of formaldehyde was reduced to 83% of that shown in Figure 2. The formaldehyde flux was reduced by the decrease of HMSA formation constant with the learning pH of the solution in compartment D and in the membrane. Selective Permeability of Some Organic Solutes. Acetaldehyde, acetone, and methanol were transported through the membrane under the same experimental conditions. These results are summarized in Table I, where the dissociation constants of bisulfite adducts are also given. Betterton et al. (1988) reported that the electronwithdrawing ability of the substituent group, R in RCHO is correlated to the adduct formation constant, and the constant increased linearly with Taft’s parameter. The
tompartmen1 B
I
.,
Figure 3. Concentration profile of formaldehyde and S(1V) in anion-exchange membranes: 0,-, HCHO; - - -,S(1V);compartment B, 1 mM NaOH; compartment D, 1 mM HCHO, 1 mM NaHS03, and 0.1 mM HC1; compartment A, 1 mM HC1.
ketones and aldehydes with high formation constants reacted readily with bisulfite ion in the membrane and were diffused fast across an anion-exchange membrane. Concentration Profile in the Anion-Exchange Membrane. Concentration profiles in the anion-exchange membrane were measured to clarify the permeation mechanism. The anion-exchangemembrane in the cell was replaced by three anion-exchange membranes, and the membranes were fastened to each other by inserting a 1-mm-thick spacer in each compartment. In this experiment, the flux of formaldehyde across three anion-exchange membranes was 8.5 X mol cm-, min-’. The flux across a single-anion-exchange membrane was 2.8 X lo-@mol cm-2 min-’, which was about 3 times larger than that across a three-anion-exchange membrane. This result is reasonable, because the transport rate is inversely proportional to the membrane thickness. After the 90-min experiment, the anion-exchange membranes were removed from the cell and each membrane was immersed in a concentrated sodium chloride solution. The species in the membrane was exchanged by chloride ion, and the concentrations of formaldehyde and bisulfite ion in the sodium chloride solution were determined. The thickness and the water content of the anion-exchange membrane were reported to be 0.13 f 0.02 mm and 15.5 f 0.5’70,respectively, on a wet membrane basis (Itoi, 1981). The concentration of the species in the membrane can be expressed as the amount of the species divided by the solution volume in the membrane. The result is shown in Figure 3 where the curves of the concentration profile are straight lines and the concentration of bisulfite ion is about the same as that of formaldehyde. This result suggests that formaldehyde was transported in the membrane in the form of HMSA. The concentrations in the membrane were much higher than those in solution, and thus, formaldehyde reacted rapidly with bisulfite at the membrane surface to form HMSA. The formation rate of HMSA can be expressed as follows over the pH range in which HS03-
860 Ind. Eng. Chem. Res., Vol. 29, No. 5 , 1990
-
‘
-
-
3
-
’
m----o-* TJ..
0 .
I2 , 05
-Q
HMSA
;
I
0
0.
S(IV)
HCHO
1
0
-
OH-
I
I
e
50 Time (min)
100
Figure 4. Formaldehyde transport through anion-exchange membranes fixed with various anions: 0 , Cl--type membrane; 0 , SO:--type membrane; 0,HS0,--type membrane; - - -, concentration in compartment D; - , concentration in compartment B; compartment B, pure water; compartment D, 1 mM HCHO.
is the dominant form of S(1V) (Boyce and Hoffmann, 1984): d[HMSA]/dt = 0.43[S(IV)][HCHO] (M s-’)
(3)
Formaldehyde reacts with bisulfite ion very slowly to form HMSA, and the half-life of S(1V) is calculated to be about 40 min from eq 3 when the bisulfite concentration was equal to the formaldehyde concentration, 1 mM. In this experiment, formaldehyde was transported through the anion-exchange membrane as a sulfonate adduct, although the permeation experiments were carried out just after the preparation of the solution. It was ascertained that the flux of formaldehyde did not change when the reagentgrade HMSA was used instead of formaldehyde and sodium bisulfite. The adduct formation rate depends on the concentration ratio of bisulfite to formaldehyde because the HMSA formation is a second-order reaction. When one of the reagents is present in excess, the rate of formatior. is much faster (DuVal et al., 1985). Bisulfite ion is adsorbed rapidly at the surface of the anion-exchange membrane at first. Then, free formaldehyde in the solution reacts with bisulfite ion in the membrane to form HMSA, which is then transported across the membrane. Formaldehyde Transport Mediated by Fixed Ion on the Anion-Exchange Membrane. In Figure 2, the flux of formaldehyde was 2.8 x mol cm-2 min-’, the flux of S(IV) was 2.3 X lo-@mol cm-* min-’, and the former was a litter higher than the latter. If formaldehyde was transported by an ion-exchange process only, formaldehyde flux would not be higher than S(IV) flux. Thus, another transport process may be operative in this system. Figure 4 shows the formaldehyde transport mediated by fixed chloride, bisulfite, or sulfite ion on the anion-exchange membrane. These experiment were carried out in a twocompartment cell, where the source phase solution contained 1 mM formaldehyde and the receiving phase solution was pure water, and in a membrane, which was immersed in the concentrated sodium chloride, sodium sulfite, or sodium bisulfite solution and then rinsed thoroughly with water before the permeation experiment. The HCHO transport rate across the fixed chloride ion membrane was very small, and the formaldehyde permeation through the membrane was not detected. Formaldehyde transport across the fixed sulfite ion membrane or the fixed bisulfite ion membrane was detected. The transport rate across the fixed bisulfite ion membrane was higher than that across the fixed sulfite ion membrane as predicted by the HMSA formation constant (eq 1). The HMSA formation constant with bisulfite ion is larger than those for HCHO/HS03- or H C H O / H 2 0 6 0 P(Deister et al., 1986). The up-take rate through the fixed bisulfite ion membrane
Compartment E
Membrane ~ C o m p a r l m e n t3
Figure 5 . Formaldehyde permeation mechanism: scheme I, ionexchange diffusion process; scheme 11, carrier-relay diffusion process; F, formaldehyde; S, fixed S(IV); +, anion-exchange site.
is about the same as that accompanied by the countertransport of hydroxide ion as shown in Figure 1. The release rate from the fixed bisulfite membrane is, however, much smaller than that accompanied by the countertransport of hydroxide ion. In the diffusion process in the membrane or the release process from the membrane, the ion-exchange reaction contributes to the increased transport rate. Although the transport rate was small, formaldehyde can be transported through the membrane without the countertransport of hydroxide ion. Formaldehyde was partitioned to the fixed bisulfite membrane to form HMSA and diffused from bisulfite ion fixed on the exchange site to the other bisulfite ion fixed on the other exchange site under the concentration gradient of formaldehyde in the membrane. HMSA was dissociated at the reverse side surface of the membrane, and formaldehyde was released from the membrane. Thus, it is conceivable that formaldehyde can be transported in the form of formaldehyde interacting with bisulfite ions at the ionexchange sites. Transport Mechanism. The transport mechanism of formaldehyde across an anion-exchange membrane can be explained by two processes, the ion-exchange diffusion process (scheme I) and the carrier relay diffusion process (scheme 11) as shown in Figure 5 . In the ion-exchange diffusion process, bisulfite ion is adsorbed on the membrane via ion exchange with the anion (X) in the membrane: HSOB-
+ RX = X- + RHS03
(4)
Formaldehyde reacts rapidly with bisulfite ion on the membrane to form HMSA: RHSO, + HCHO = RHMSA (5) HMSA formed in the membrane is transported in the membrane and from the membrane to the solution with the coupled countertransport of hydroxide ion according to the following ion-exchange reactions: RHMSA + R’OH = ROH + R’HMSA (6) R’HMSA
+ OH- = R’OH + HMSA
(7)
In the case of the fixed bisulfite ion membrane, bisulfite ion plays the active role as the carrier of formaldehyde, although the ion is fixed on the membrane. Formaldehyde is relayed from one fixed bisulfite ion to the other fixed bisulfite ion under the concentration gradient of formaldehyde as follows: RHMSA = RHSO, + HCHO (8) R’HSO, + HCHO = R’HMSA (9) This process can be termed as the carrier relay mechanism,
Ind. Eng. Chem. Res., Vol. 29, No. 5 , 1990 861
which was proposed for the cation transport mediated by a macrocyclic compound under an electric field (Wipf et al., 1969). Because the interaction between bisulfite ion and formaldehyde is weaker than that between the anion-exchange site and bisulfite ion, formaldehyde can be transported under the concentration gradient of formaldehyde. This process is repeated in the membrane with the eventual release of formaldehyde from HMSA bound on the membrane to the solution: R’HMSA = R’HS03
+ HCHO
One additional mechanism that may explain the facilitated transport of formaldehyde across the anion-exchange membrane fixed with bisulfite was proposed originally by LeBlanc et al. (1980) to explain the enhanced transport of olefins across anion-exchange membranes fixed with silver ion. In this mechanism, Ag+ acts as the mobile carrier in the membrane. If bisulfite ion plays a similar role as the mobile carrier in our membranes, then the bisulfite ion concentration will be constant across the membrane and the concentration profile of bisulfite must be different from that of formaldehyde, which is transported according to its own concentration gradient. In the case of the coupled countertransport of HMSA with hydroxide ion, the concentration ratio of formaldehyde to bisulfite was found to be approximately constant in the membrane, as shown in Figure 3. Thus, the mechanism of LeBlanc et al. (1980) cannot be invoked to explain the facilitated transport of formaldehyde across the anionexchange membrane. We rely on a combination of the ion-exchange diffusion and the carrier-relay diffusion to explain the data shown in Figure 2. The carrier-relay diffusion process contributed approximately 36% of the total flux since the formaldehyde flux mediated by the fixed bisulfite ion was 1.0 x lo-* mol cm-* min-I, as shown in Figure 4.
Conclusion Since many aldehydes react selectively with bisulfite ion, it is possible to separate aldehydes from other nonelectrolytes by the method reported in this paper. Since other organic nonelectrolytes react reversibly with various ions (e.g., sugar with borate ion), it is also possible to permeate them selectively across ion-exchange membranes via their ion-molecule reactions. Similar transport mechanisms may be important in biological membranes. Registry No. Selemion AMV,42616-95-5; Selemion CMV, 42616-80-8; sodium bisulfite, 7631-90-5; formaldehyde, 50-00-0; acetaldehyde, 75-07-0; acetone, 67-64-1.
Literature Cited Betterton, E. A.; Erel, Y.; Hoffmann, M. R. Aldehyde-Bisulfite Adducts: Prediction of Some of Their Thermodynamic and Kinetic Properties. Enuiron. Sci. Technol. 1988, 22, 92-99. Boyce, S.; Hoffmann, M. R. Kinetics and Mechanism of the Formation of Hydroxymethanesulfonic Acid a t Low pH. J . Phys. Chem. 1984, 88,4740-4746. Choy, E. M.; Evans, D. F.; Cussler, E. L. A. Selective Membrane for Transporting Sodium Ion against Its Concentration Gradient. J .
Am. Chem. SOC.1974,96, 7085-7090. Chung, D.; Higuchi, S.; Maeda, M.; Inoue, S. pH-Induced Regulation of Permselectivity of Sugars by Polymer Membrane from Polyvinyl-Polypeptide Graft Copolymer. J . Am. Chem. SOC.1986, 108, 5823-5826.
Dasgupta, P. K.; Decesare, K.; Ullrey, J. C. Determination of Atmospheric Sulfur Dioxide without Tetrachloromercurate(I1) and the Mechanism of the Schiff Reaction. Anal. Chem. 1980, 52, 1912-1922.
Deister, U.; Neeb, R.; Helas, G.; Warneck, P. Temperature Dependence of the Equilibrium CH,(OH), + HSO; = CHz(OH)SO; + HzO in Aqueous Solution. J . Phys. Chem. 1986,90,3213-3217. DuVal, D. L.; Rogers, M.; Fritz, J. S. Determination of Aldehydes and Acetone by Ion Chromatography. Anal. Chem. 1985, 57, 1583-1586.
Hirahara, K.; Takahashi, S.; Iwata, M.; Fujimoto, T.; Miyaki, Y. Artificial Membranes from Multiblock Copolymers. 5. Transport Behaviors of Organic and Inorganic Solutes through a ChargeMosaic Membrane. Ind. Eng. Chem. Prod. Res. Dev. 1986, 25, 305-313.
Igawa, M.; Hoffmann, M. R. Active Transport of Formaldehyde through an Anion-Exchange Membrane via the Formation of the Bisulfite Adduct. Chem. Lett. 1988, 597-600. Igawa, M.; Tachibana, T.; Yoshida, K.; Tanaka, M.; Seno, M. Enrichment of Organic Solutes with Hydrophobic Polymer Membrane. Chem. Lett. 1984, 1527-1528. Igawa, M.; Anzai, T.; Seno, M. Enrichment of Nonionic Surfactants with Fluorocarbon Polymer Membrane. Chem. Lett. 1985, 1703-1704.
Igawa, M.; Echizenya, K.; Hayashita, T.; Seno, M. Neutralization Dialysis for Deionization. Bull. Chem. Soc. Jpn. 1987, 60, 381-383.
Igawa, M.; Munger, J. M.; Hoffmann, M. R. Analysis of Aldehydes in Cloud- and Fogwater Samples by HPLC with a Postcolumn Reaction Detector. Enoiron. Sci. Technol. 1989, 23, 556-561. Itoi, S. Properties Evaluating Method of the Ion-exchange Membrane. Membrane 1981, 6, 185-196. Khym, J. X.; Zill, L. P. The Separation of Monosaccharides by Ion Exchange. J . Am. Chem. SOC. 1951, 73, 2399-2400. Kotyk, A.; JanBcek, K.; Koryta, J. Biophysical Chemistry of Membrane Functions; Wiley-Interscience: New York, 1988. Koval, C. A.; Spontarell, T. Condensed Phase Facilitated Transport of Olefins through an Ion Exchange Membrane. J . Am. Chem. SOC. 1988, 120, 293-295. LeBlanc, H. 0.;Ward, W. J.; Matson, S. L.; Kimura, S. G. Facilitated Transported in Ion-Exchange Membranes. J . Membr. Sci. 1980, 6, 339-343.
Munger, J. W.; Tiller, C.; Hoffmann, M. R. Identification of Hydroxymethanesulfonate in Fog Water. Science 1986,231,247-249. Reusch, C. F.; Cussler, E. L. Selective Membrane Transport. AIChE J . 1973, 29, 736-740. Samuelson, 0. Ion Exchanges in Analytical Chemistry; John Wiley & Sons, Inc.: New York, 1953; p 190. Sawicki, E.; Hauser, T. R.; Stanley, T. W.; Elbert, W. The 3Methyl-2-benzothiazolone Hydrazone Test. Anal. Chem. 1961,33, 93-97.
Shinbo, T.; Nishimura, K.; Yamaguchi, T.; Sugiura, M. Uphill Transport of Monosaccharides across an Organic Liquid MemChem. Commun. 1986, 349-351. brane. J . Chem. SOC., Smensen, P. E.; Andersen, V. S. The Formaldehyde-Hydrogen Sulphite System in Alkaline Aqueous Solution. Kinetics, Mechanisms, and Equilibria. Acta Chem. Scand. 1970,24,1301-1306. Wipf, H. K.; Pache, W.; Jordan, P.; Zahner, H.; Keller-Schierlein, W.; Simon, W. Mechanism of Alkali Cation Transport in Bulk Membranes Using Macrotetrolide Antibiotics. Biochem. Biophys. Res. Commun. 1969,36, 387-393.
Received f o r review June 21, 1989 Accepted January 19, 1990
