Znd. Eng. Chem. Res. 1990,29, 1889-1893 Postlethwaite, I.; Foo, Y. Robustness with Simultaneous Pole and Zero Movement Across the jw-axis. Automatica 1985, 21 (4), 433-443. Rosenbrock, H. H. Computer-Aided Control System Design; Academic Press: New York, 1976. Rotstein, H.; Desages, A.; Romagnoli, J. A.; Karim, N. Analysis and Control of Distillation Columns: A Quasi-Classical Approach. Proceedings of DYCORD86, IFAC, Bournemouth, England, 1986; pp 215-220. Ruiz, C. Estudio D i n h i c o de las Operaciones de Destilacibn. Magister in Chem. Eng., Thesis, Universidad Nac. del Sur, Bahia Blanca, Argentina, 1984. Ruiz, C. Desarrollo de una Politica de Control para Operaciones de Puesta en Marcha de Columnas de Destilacibn. Ph.D. Thesis, Universidad Nac. del Sur, Bahia Blanca, Argentina, 1986.
1889
Ruiz, C.; Cameron, I.; Gani, R. A Generalized Dynamic Model for Distillation Columns. Part 111: Study of Start up Operations. Comp. Chem. Eng. 1988,12 (l), 1-14. Shinskey, F. G. Distillation Control for Productivity and Energy Conservation; McGraw-Hill: New York, 1977; Chapters 2,8, and 10. Stewart, G. W. Error and Perturbation Bounds for SubsDaces Associated with Certain Eigenvalue Problems. SZAM R e i 1973,15 (4). 727-752. Tyreus, B.; Luyben, W. L. Controlling Heat Integrated Distillation Columns. Chem. Eng. Prog. 1976,59-66.
Receioed for review June 17, 1988 Revised manuscript received May 7, 1990 Accepted May 15, 1990
SEPARATIONS Selective Adsorption of Cationic Surfactants on Cross-Linked Poly(p -hydroxystyrene) Nariyoshi Kawabata,*Koichi Sumiyoshi, and Minoru Tanaka Department of Chemistry and Materials Technology, Faculty of Engineering and Design, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606, Japan
Cross-linked poly@-hydroxystyrene) (PHSresin) was found to be an excellent and selective adsorbent for cationic surfactants in aqueous solution. Its adsorption capacity was remarkably higher than those observed with cation-exchange resins and porous resins not possessing an ion-exchange functional group. In addition, ita adsorption capacity was not reduced by the presence of hydrochloric acid, sodium hydroxide, or sodium chloride and other inorganic salts. Elution of the adsorbed surfactants from PHS resin was easily accomplished by treatment with methanol, and the resin was effectively regenerated, in sharp contrast to adsorption on conventional cation-exchange resins. Cationic surfactants were concentrated into about 10 wt % solution in methanol. A significance for the acid-base interaction between the cationic surfactant and the phenolic hydroxyl group of PHS resin was suggested, and the action of an ion-exchange mechanism was excluded as a possibility.
Introduction Previous reports from this laboratory have demonstrated excellent and highly selective adsorption of phenol (Kawabata and Ohira, 1979) and carboxylic acids (Kawabata et al., 1981b) in aqueous solution on cross-linked poly(4vinylpyridine) (PVP resin). The resin showed excellent adsorption capacities for these acidic organic solutes. This phenomenon was explained in terms of an acid-base interaction between the acidic solutes and the pyridyl group of the resin and on the basis of hydrophobic interaction between the solutes and the resin surface (Kawabata et al., 1981a). In addition, since the pK, of pyridine is reported to be 5.17 at 25 "C (Brown and Mihm, 1955), pyridine is a much weaker base than primary, secondary, and tertiary aliphatic amines. Therefore, the adsorption of these acidic organic solutes on PVP resin did not proceed through an ion-exchange mechanism, and the presence of hydrochloric acid, sodium hydroxide, or sodium chloride and other inorganic salts did not reduce the adsorption capacity. As a result, PVP resin showed a highly preferential adsorption of acidic organic solutes over in-
* Corresponding author. 0888-5885/90/2629-1889$02.50/0
organic ions, in sharp contrast to the adsorption of these solutes on conventional anion-exchange resins, for which the capacity of adsorption was conspicuously reduced in the presence of inorganic salts (Kawabata and Ohira, 1979; Kawabata et al., 1981b). On the basis of these observations, basic resins can be classified into three categories (Kawabata, 1989): (A) strongly basic anion-exchange resins containing a quaternary ammonium group, which are effective ion exchangers over a wide pH range; (B) weakly basic anionexchange resins containing aliphatic amino groups, which are effective ion exchangers only at an acidic pH range; and (C) resins containing a pyridyl group, which do not exhibit ion-exchangefunction with inorganic ions and are selective adsorbents for acidic organic materials. According to this concept, acidic resins can be classified into three categories: (D)strongly acidic cation-exchange resins containing a sulfonic acid group, which are effective ion exchangers in a wide pH range; (E) weakly acidic cation-exchangeresins containing a carboxyl group, which are effective ion exchangers only at a basic pH range; and (F)resins containing a weakly acidic functional group, such as a phenolic hydroxyl group, which are expected to exhibit no ion-exchange function with inorganic ions and to behave 0 1990 American Chemical Society
1890 Ind. Eng. Chem. Res., Voi. 29, No. 9, 1990 Table I. Recipe for the Copolymerization of p -Acetoxystyrene with Divinylbenzene content of elemental p-acetyoxystyrene, mol % anal. of copolymer, % monomer resin mixture coDolvmer C H PHS-1 90 93 82.84 7.07 82 7.21 PHS-2 80 83.94 PHS-3 70 73 84.88 7.31 7.49 50 PHS-4 56 86.63 7.67 40 PHS-5 43 87.88 35 88.73 7.69 30 PHS-6 PHS-7 20 25 89.78 7.80 14 90.89 7.93 PHS-8 10
as selective adsorbents for basic organic materials in aqueous solution. In the present work, we have attempted to investigate the adsorption characteristics of the resins of class F and have studied the adsorption of cationic surfactants in aqueous solution on cross-linked poly(phydroxystyrene) (PHS resin). Cationic surfactants are used mainly as disinfectants and softening agents and are important organic pollutants of the aquatic erlvironment. Their biodegradability has been previously investigated from the environmental point of view (Gerike et al., 1978).
Experimental Section p-Acetoxystyrene (provided by Maruzen Petrochemical Co., Tokyo) was purified by distillation before polymerization. Commercially obtained styrene, divinylbenzene, and benzene were purified by distillation before polymerization. Commercial products of cationic surfactants and other chemicals and solvents were used without further purification. Nitrogen was purified by passing through a glass tube containing copper turnings, in a furnace a t 170 "C. Deionized water was wed throughout the experiments. PHS resin was prepared by hydrolysis of a copolymer of p-acetoxystyrene with divinylbenzene, according to a previously reported procedure (Packham, 1964), with minor modifications. Copolymerization of p-acetoxystyrene with divinylbenzene was performed at 80 "C for 3.5 h in 40 wt 5% benzene solution using 0.5 mol % 2,2'azobis(isobutyronitri1e) (AIBN) as the initiator, in a 2-L three-necked flask equipped with a reflux condenser, a mechanical stirrer, and a gas inlet under a nitrogen atmosphere. After the reaction, the copolymer was precipitated by pouring the contents of the flask into petroleum ether and was dried in vacuo to constant weight. The recipe for the copolymerization of p-acetoxystyrene with divinylbenzene and the mole fraction of p-acetoxystyrene in the resulting copolymer are given in Table I. The dried copolymer was ground by using an ishiusu (a Japanese
classical hand-mill made of stone) and was sifted to 20-30 mesh. The sifted copolymer (100 g) was mixed with concentrated hydrochloric acid (500 mL), water (750 mL), and methanol (1750 mL). This mixture was allowed to react at room temperature for 60 h under occasional stirring with a mechanical stirrer. The hydrolyzed copolymer was filtered and extensively washed with water until the pH of the effluent became neutral, followed by drying in vacuo at room temperature to constant weight. The PHS resin was rinsed with 10 bed volumes of water by a batch method and was filtered before use for adsorption experiments. The content of p-vinylphenol in the PHS resin was evaluated based on that of p-acetoxystyrene in the copolymer of p-acetoxystyrene with vinylbenzene before the hydrolysis, which was determined by elemental analysis of the carbon content. Elemental analyses of the copolymer were performed a t the Elementary Analysis Center of Kyoto University. The results are given in Table I. The capacity of PHS resin for sodium hydroxide adsorption was determined by the continuous-flow column method, using aqueous 0.02 N sodium hydroxide solution. The characteristics of the PHS resin are given in Table 11. For comparison, four commercial resins provided by Rohm and Haas Co. Philadelphia, PA, were used. Amberlite IR-120B (IR-120B) was used as a strongly acidic cation-exchange resin that had a styrene-divinylbenzene matrix with a sulfonic acid group. Amberlite IRC-50 (IRC-50)was used as a weakly acidic cation-exchangeresin that had a styrene-divinylbenzene matrix with a carboxyl group. These cation-exchange resins were used in the hydrogen form. Amberlite XAD-2 and Amberlite XAD-4 (XAD-2 and XAD-4, respectively) were used as porous styrene-divinylbenzene resins not possessing an ion-exchange functional group. The surface areas of XAD-2 and XAD-4 were claimed by the supplier to be 300 and 784 m2/g, respectively. IR-12OB was preconditioned and transferred to the hydrogen form as follows: (1)placing it in a column 2.5 cm in diameter with a fitted glass filter; (2) washing with 10 bed volumes of methanol; (3) washing with 10 bed volumes of water; (4) slow contact with 10 bed volumes of 2 N hydrochloric acid; (5) washing with 10 bed volumes of water; (6) slow contact with 10 bed volumes of 2 N sodium hydroxide; (7) washing with 10 bed volumes of water; (8) repeating steps 4-7 several times; (9) slow contact with 20-30 bed volumes of 2 N hydrochloric acid; (10) extensive washing with water until the pH of the effluent became close to that of the influent. The ion-exchange capacity of the resin was 4.4 mequivldry g, which was determined by back titration with aqueous 0.1 N hydro-
Table 11. Characteristics of PHS Resins
resin PHS-1 PHS-2 PHS-3 PHS-4 PHS-5 PHS-6 PHS-7 PHS-8
p-vinylphenol content,* mol % 93 82 73 56 43 35 25 14
water content, wt%
44 32 25 33 41
29 47 52
av particle size, mm drv state wet state 0.28 0.38 0.30 0.40 0.23 0.33 0.33 0.40 0.25 0.38 0.30 0.38 0.33 0.35 0.30 0.38
capacity for NaOH adsorpn,O mequivldry g breakthrough total caDacitP capacitvd 1.23 1.45 0.77 0.87 0.51 0.70 0.34 0.49 0.38 0.31 0.17 0.31 0.16 0.25 0.12 0.16
nDetermined by a continuous-flow column method using 0.02 N solution of sodium hydroxide with a flow rate of 3 bed volumes/h. *Evaluated based on the content of p-acetoxystyrene before the hydrolysis of the copolymer of p-acetoxystyrene with divinylbenzene. Total amount of adsorbed sodium hydroxide until the effluent solution became alkaline, using phenolphthalein as the indicator. Total amount of adsorbed sodium hydroxide until the effluent concentration became close to the influent concentration.
Ind. Eng. Chem. Res., Vol. 29, No. 9, 1990 1891 Table 111. Capacity of
resin PHS-1 PHS-2 PHS-3 PHS-4 PHS-5 PHS-6 PHS-7 PHS-7 PHS-7 PHS-7 PHS-8 IR-12OB IRC-50 XAD-2 XAD-4
PHS Resin for Cationic S u r f a c t a n t Adsorptiona p-vinylphenol content: mol 70 93 82 73 56 43 35 25 25 25 25 14
cationic surfactant benzalkonium chloride benzalkonium chloride benzalkonium chloride benzalkonium chloride benzalkonium chloride benzalkonium chloride benzalkonium chloride dodecyltrimethylammonium chloride hexadecyltrimethylammonium bromide hexadecylpyridinium chloride benzalkonium chloride benzalkonium chloride benzalkonium chloride benzalkonium benzalkonium chloride
adsorption capacity, mg/dry g breakthrough total capacitv capacityd e 57 e 22 e 31 253 149 603 328 486 318 523 398 e 226 e 391 e 312 445 333 e 38 e 144 0 e e 66
Determined by the continuous-flow column method using an aqueous 2400-3500 mg/L solution of cationic surfactant a t room temperature with a flow rate of 3 bed volumes/h. *Evaluated based on the content of p-acetoxystyrene of the copolymer of p-acetoxystyrene with divinylbenzene before hydrolysis. Determined as the total amount of adsorbed surfactant until the effluent concentration reached 1 mg/L. dTotal amount of adsorbed surfactants until the effluent concentration became close to the influent concentration. Not determined.
chloric acid using phenolphthalein as the indicator after addition of 1 N sodium hydroxide solution. The percentage moisture of the resin was determined after drying in vacuo to constant weight. IRC-50 was preconditioned to the hydrogen ion form in a similar manner. XAD-2 and XAD-4 were preconditioned by washing with 10 bed volumes of methanol, followed by washing with 10 bed volumes of water. Column studies of the adsorption of cationic surfactant were conducted by using a glass column 1cm in diameter and 30 cm long, with a fitted glass filter connected with a 200-mL dropping funnel in a down-flow fashion, at room temperature. The preconditioned resin was placed in the column. The bed was carefully backwashed to eliminate entrained air and then tapped to ensure packing of the bed. The dropping funnel was used to contain the influent solution. Samples were taken manually and were checked for the concentration of cationic surfactant. The flow rate was 3 bed volumes/h throughout this work. The influent concentration of cationic surfactant was controlled to be in the range of 3000-3500 mg/L. Elution of the adsorbed surfactant from PHS resin was conducted by the continuous-flow column method, with a flow rate of 3 bed volumes/h in a down-flow fashion. Quantitative analysis of cationic surfactants in aqueous and organic solutions was performed with a Shimadzu UV-100-02 spectrophotometer. Concentrations of benzalkonium chloride and N-hexadecylpyridinium chloride were determined based upon the absorptivities at 210 and 214 nm, respectively, or with the aid of orange I1 (Few and Ottewill, 1956). Concentrations of hexadecylammonium bromide and dodecyltrimethylammonium chloride were determined with the aid of orange I1 (Few and Ottewill, 1956). The concentration of chloride anion was determined by titration with standard mercury(I1) nitrate solution (Domask and Kobe, 1952). Determination of the pH values of solutions was performed with a Horiba Model F-7AD pH meter.
Results and Discussion Capacity of PHS Resin for Cationic Surfactant Adsorption. The continuous-flow column study was performed to evaluate the capacity of PHS resin to adsorb cationic surfactants in aqueous solution. The adsorption capacity was determined in two different ways: (i) the breakthrough capacity, which was based on the total
I Influent Concentration & Y RI
E
t
i'i
2000
0'
t l
20
40
60
80
100
Effluent (bed vol) Figure 1. Adsorption of benzalkonium chloride (BKC) in an at room aqueous solution on PHS-5 resin (0)and on PHS-7 resin (0) temperature with a flow rate of 3 bed volumes/h and an influent concentration of 3060 mg/L.
amount of adsorbed surfactant before the effluent concentration reached 1 mg/L; and (ii) the total adsorption capacity, which was based on the total amount of adsorbed surfactant until the effluent concentration became close to the influent concentration. In practical application of the resin for wastewater treatment, the breakthrough capacity would be more important than the total adsorption capacity, and emphasis was therefore focused on the former. For comparison, four commercial resins were also used in a similar manner. The results are given in Table 111. Under the experimental conditions used, the breakthrough capacity of PHS resin was remarkably higher than those of commercial cation-exchange resins (IR-12OBand IRC-50) and porous resins not possessing an ion-exchange functional group (XAD-2 and XAD-4). The capacity of PHS resin for cationic surfactant adsorption depended upon the content of p-vinylphenol in the resin. Maximum breakthrough capacity was obtained with PHS resin containing 25 mol % p-vinylphenol (PHS-7), and that of the total adsorption capacity was observed with resin containing 43 mol 7% p-vinylphenol (PHS-5). Sharp breakthrough curves were obtained in these cases, as shown in Figure 1. Essentially no leakage (less than 1 mg/L) occurred for the first 26 and 41 bed volumes of the illustrated runs, respectively. Table I1 shows that the capacity of PHS resin for sodium hydroxide adsorption increased uniformly with the content of p-vinylphenol in the resin. The total capacities of PHS-5 through PHS-8 for benzalkonium chloride ad-
1892 Ind. Eng. Chem. Res., Vol. 29, No. 9, 1990 Table IV. Capacity of PHS Resin for Cationic Surfactant Adsorption i n t h e Presence of Inorganic Saltsa concn, adsorption capacity,b resin salt mM mg/dry g PHS-7 none 398 2 460 PHS-7 NaCl 20 479 PHS-7 NaCl 20 486 PHS-7 KCI MgCI, 20 538 PHS-7 PHS-7 CaClz 20 548 33 IR-12OB none IR-12OB NaCl 20 66 144 IRC-50 none IRC-50 NaCl 20 90 I) XAD-2 none 20 83 XAD-2 NaCl 68 XAD-4 none 20 301 XAD-4 NaCl Determined by the continuous-flow column method using an aqueous 3000-3500 mg/L solution of BKC containing inorganic salts at room temperature, with a flow rate of 3 bed volumes/h. *The breakthrough capacity determined as the total amount of adsorbed surfactant until the effluent concentration reached 1 mg/L.
sorption, as given in Table 111, tended to increase with the content of p-vinylphenol in the resin. This result suggests a significance for acid-base interaction between the cationic surfactant and the phenolic hydroxyl group of PHS resin. However, the adsorption capacities of PHS-1 through PHS-4 indicated that incorporation of more than 50 mol 7'0 p-vinylphenol into PHS resin led to a marked decrease of adsorption capacity. When too large an amount of p-vinylphenol is incorporated into the resin, the phenolic hydroxyl group may aggregate by formation of a hydrogen bond, which would result in decreased efficiency of the intermolecular interaction between the cationic surfactant and the phenolic hydroxyl group of the resin. In the adsorption of sodium hydroxide, the intermolecular interaction between the alkali group and the phenolic hydroxyl group may be strong enough to destroy the aggregation, which would lead to a uniform increase of adsorption capacity with an increased content of p-vinylphenol in the resin. On the other hand, in the adsorption of cationic surfactant, the strength of the intermolecular interaction between the surfactant and the phenolic hydroxyl group may be insufficient to destroy the aggregation. As a result, incorporation of too much p-vinylphenol into the resin would decrease the capacity of PHS resin for cationic surfactant adsorption. PHS resin can be prepared by direct copolymerization of p-vinylphenol with divinylbenzene. In this case, however, the copolymerization did not proceed smoothly, probably because of the inhibitory effect of the phenolic hydroxyl group of p-vinylphenol. tert-Butylcatechol is well-known as an inhibitor for radical polymerization of vinyl compounds. Direct copolymerization of vinylphenol with divinylbenzene gave low yields of brittle resins that were not suitable for practical application to wastewater treatment, although execution of laboratory-scale adsorption experiments was not difficult. Effect of Inorganic Salts on the Adsorption Capacity. In practical use of adsorbents for wastewater treatment, it is difficult to avoid the presence of inorganic salts, which may reduce the capacity of PHS resin for cationic surfactant adsorption. The breakthrough capacities of PHS resin and commercial resins for benzalkonium chloride (BKC) adsorption, determined in the presence of several inorganic salts, are given in Table IV. The capacity of PHS resin to adsorb these inorganic salts was negligible. Except in the case of the weakly acidic cation-exchange
Table V. Capacity of PHS Resin for Cationic Surfactant Adsorption in t h e Presence of Acid a n d Alkaline Materials'
resin PHS-7 PHS-7 PHS-7 PHS-7 PHS-7 PHS-7 IRC-50 IRC-50 IRC-50 IRC-50 IRC-50 IRC-50 XAD-4 XAD-4 XAD-4 XAD-4 XAD-4 XAD-4
HC1, mmol/L 0.2 0.05
NaOH, mmol/L
0.06 5.0 23.2 0.2 0.02 0.005 5.0 23.2 0.2 0.02 0.005 4.2 23.2
pH Of the influent effluent soln soh 3.0 3.0 4.1 4.3 6.1 4.7 9.7 5.4 11.3 6.7 12.6 12.4 3.5 2.4 4.8 2.4 6.1 2.4 8.7 2.4 11.7 2.9 12.6 6.6 3.5 3.5 4.8 5.5 6.1 5.7 8.7 8.3 11.5 11.5 12.6 12.6
adsorption capacity,* mg/dry g 443 345 398 376 428 450 114
109 150 142 34 1 1900 106 103 91 104 173 263
a Determined by the continuous-flow column method using an aqueous 3000 mg/L solution of BKC containing acid or alkaline materials at room temperature, with a flow rate of 3 bed volumes/h. *Total amount of adsorbed BKC until the effluent concentration reached 1 mg/L.
Methanol Throughput (bed vol)
Figure 2. Elution of adsorbed BKC from PHS-7 resin and porous resins not possessing an ion-exchange functional group (XAD-2 and XAD-4), using methanol as the eluent, by the continuous-flow column method at room temperature with a flow rate of 3 bed volumes/h. (A), PHS-7; (B), XAD-2; (C), XAD-4.
resin IRC-50, the capacity did not decrease in the presence of these inorganic salts. The capacity for PHS resins to adsorb BKC increased in the presence of inorganic salts, which can be explained in terms of an effect of salting out by the salts. Effect of Acid and Alkaline Materials on the Adsorption Capacity. In practical use of adsorbents for wastewater treatment, it is also difficult to avoid the presence of acid and alkaline materials. The effects of hydrochloric acid and sodium hydroxide on the capacity of PHS resin for BKC adsorption were examined, and the results are summarized in Table V. The adsorption capacity of PHS resin, as well as those of commercial resins, did not decrease in the presence of hydrochloric acid but was increased in the presence of sodium hydroxide. Recovery of Cationic Surfactant from PHS Resin. Elution of surfactant from PHS resin was examined by a continuous-flow column method, using BKC as surfactant and methanol as the eluent. BKC adsorbed on PHS-7 was quantitatively recovered by using 3 bed volumes of methanol (Figure 2A), and the resin was effectively regenerated.
Ind. Eng. Chem. Res., Vol. 29, No. 9, 1990 1893
V
Organic Solvent Throughput (bed vol)
Figure 3. Elution of adsorbed BKC from cation-exchange resins by the continuous-flow column method a t room temperature with a flow rate of 3 bed volumes/h. (D) From IR-12OB using methanol as the eluent; (E) from IRC-50 using methanol as the eluent; (F) from IR-12OB using 2 N methanol hydrochloric acid as the eluent; (G) from IRC-50 using 2 N methanolic hydrochloric acid as the eluent.
For comparison, we also examined the recovery of BKC from commercial resins. BKC adsorbed on porous resins not possessing an ion-exchange functional group ( X A D - 2 and XAD-4) was quantitatively recovered by using 2-5 bed volumes of methanol (Figure 2, B and C). However, BKC adsorbed on strongly acidic cation-exchange resin (IR120B) in the hydrogen ion form was not eluted when methanol was used as the eluent (Figure 3D). Only 17% BKC adsorbed on weakly acidic cation-exchange resin (IRC-50) in the hydrogen ion form was eluted by using methanol as the eluent (Figure 3E). However, BKC was quantitatively recovered from these cation-exchangeresins when 2 N methanolic hydrochloric acid was used as the eluent (Figure 3, F and G). Interaction between Cationic Surfactant and PHS Resin. In the adsorption of BKC on commercial cationexchange resins (IR-120Band IRC-50) in the hydrogen ion form by the continuous-flowcolumn method, the chloride ion was quantitatively detected in the effluent solution, providing evidence for the action of an ion-exchange mechanism for this adsorption. @-SOaH
+
[RN(CH3)2CH2C6H5]+CI-
@SO,@-COOH
+
[RN(CH3)2CH2C6H5]+CI-
. )
[RN(CH3)2CH2C6HS]++ HCI
-
@-COO-[RN(CH3)2CH2C6H5]'
+
HCI
However, in the adsorption of BKC on PHS resin, chloride ion was not detected in the effluent solution and clearly excluded an ion-exchange mechanism for this adsorption.
BKC adsorbed on PHS and XAD resins was quantitatively recovered by using methanol as the eluent (Figure 2). However, elution of BKC adsorbed on commercial cation-exchange resins was extremely difficult when methanol was used as the eluent (Figure 3, D and E ) .
These results also militate against an ion-exchange mechanism for the adsorption of cationic surfactant on PHS resin. The capacity of PHS resin for cationic surfactant adsorption was much higher than those of XAD resins and tended to increase with the content of the phenolic hydroxyl group in the resin. These observations suggest a significance for acid-base interaction between the cationic surfactant and the phenolic hydroxyl group of PHS resin. The possible importance of a hydrophobic interaction between the cationic surfactant and the resin surface is also conceivable. It is noteworthy that when a 3000 mg/L solution of BKC was passed through a glass column containing sodium salt of PHS-7 with a flow rate of 3 bed volumes/h, the resin adsorbed 161 mg/dry g of BKC before the breakthrough point, and the total adsorption capacity was 433 mg/dry g. In this case, the chloride ion was not detected in the effluent solution before the breakthrough point. BKC adsorbed on the sodium salt of PHS resin was quantitatively recovered when methanol was used as the eluent. An ion-exchange mechanism cannot, therefore, be postulated for this adsorption also. W
O
N
+
a + [RN(CH~)ZCH~C~H~I+CI@+O-[RN(CH3)C , H2C6HS]+
+ NaCl
Registry No. NaCl, 7647-14-5; KCl, 7447-40-7; MgC12, 778630-3; CaC12, 10043-52-4; HCl, 7647-01-0; NaOH, 1310-73-2; dodecyltrimethylammonium chloride, 112-00-5; hexadecyltrimethylammonium bromide, 57-09-0; hexadecylpyridinium chloride, 123-03-5.
Literature Cited Brown, H. C.; Mihm, X. R. The Base Strength of Pyridine, 2,6Lutidine and Monoalkylpyridine. J. Am. Chem. SOC. 1955,77, 1723-1726. Domask, W. G.; Kobe, K. A. Mercurimetric Determination of Chlorides and Water-soluble Chlorohydrins. Anal. Chem. 1952,24, 989-991. Few, A. V.; Ottewill, R. E. A Spectrophotometric Method for the Determination of Cationic Detergents. J. Colloid Sci. 1956,11, 34-38. Gerike, P.; Fischer, W. K.; Jasiak, W. Surfactant Quaternary Ammonium Salts in Aerobic Sewage Digestion. Water Res. 1978,12, 1117-1122. Kawabata, N. Removal by Selective Adsorption and Recovery of Acidic Organic Pollutants Using Cross-Linked Polyvinylpyridine. Environ. Sci. 1989,2,1-8. Kawabata, N.;Ohira, K. Vinylpyridine-Divinylbenzene Copolymer as a Polymeric Adsorbent for Removal and Recovery of Phenol from Aqueous Solution. Enuiron. Sci. Technol. 1979, 13, 1396-1402. Kawabata, N.; Higuchi, I.; Yoshida, J. Adsorption of Phenol and Carboxylic Acids on Cross-Linked Poly(4-vinylpyridine). Bull. Chem. SOC. Jpn. 1981a,54, 3253-3258. Kawabata, N.; Yoshida, J.; Tanigawa, Y. Separation of Carboxylic Acid from Aqueous Solution Using Cross-Linked Poly(4-vinylpyridine). Ind. Eng. Chem. Prod. Res. Dev. 1981b,20,386-390. Packham, D. I. Chelating Polymers Derived from Poly-4-hydroxystyrene. J. Chem. Soc. 1964,2617-2624. Received for review February 8, 1990 Revised manuscript received May 23, 1990 Accepted J u n e 8, 1990
