Ind. Eng. Chem. Res. 1994,33, 854-859
854
MATERIALS AND INTERFACES Adsorption of Strong Acid on Polyaminated Highly Porous Chitosan: Equilibria Hiroyuki Yoshida,’ Noboru Kishimoto, and Takeshi Kataoka Department of Chemical Engineering, University of Osaka Prefecture, 1-1, Gakuen-Cho, Sakai 593, Japan
Adsorption of a strong acid on a new weakly basic ion exchanger, highly porous polyaminated chitosan (PEI-CH), which was fabricated by introducing poly(ethy1ene imine) (PEI) into highly porous chitosan spherical particles (CRCH), appeared feasible technically. The saturation capacity for adsorption of HC1 on PEI-CH was about 1.75 times larger than a commercial weakly basic resin DIAION WA30. HC1was adsorbed on them by a n acid/base neutralization reaction. Since DIAION WA30 has a single kind of fixed functional group, the experimental isotherm and titration curve were correlated by the Langmuir equation. As PEI-CH has four different fixed functional groups, the primary ammonium group of chitosan and primary, secondary, and tertiary ammonium groups of PEI, a theoretical equation for the equilibrium was derived by considering the adsorption on each functional group. It correlated the experimental titration curve (equilibrium isotherm) well. 1. Introduction
Weakly basic resins are commonlyused for removal and/ or recovery of acids from industrial aqueous streams and wastewaters. Adsorption of a strong acid on weakly basic resins involves ion exchange and is accompanied by reactions which were proposed by Helfferich (1965). He suggested that HC1 was adsorbed on a weakly basic resin by ion exchange accompanied by an acidlbase neutralization reaction. After his review,Adamset al. (1969),Warner and Kennedy (1970),Hubner and Kadlec (1978),Rao and Gupta (1982a,b), Helfferich and Hwang (19851, and Bhandari et al. (1992) have presented papers on intraparticle mass transfer for adsorption of strong acids on weakly basic resins. However, detailed experimental and theoretical studies for equilibrium isotherms may not have been reported. In the present work, we investigate the possibility of using a new weakly basic ion exchanger, highly porous polyaminated chitosan (hereafter called PEI-CH), for removal and/or recovery of strong acids from aqueous streams. PEI-CH has been developed by Kawamura et al. (1993) as an adsorbent of metal ions. PEI-CH was fabricated by introducing poly(ethy1eneimine) (hereafter called PEI) into the macropore of highly porous crosslinked chitosan (CRCH). Since PEI-CH is hard, the volume change caused by the adsorption of HC1 is much smaller than that in commercial weakly basic resins. Therefore, it is easier to use PEI-CH in a packed column than commercial weakly basic resins. We report the experimental and theoretical equilibrium isotherms and titration curves for adsorption of HC1 on PEI-CH and a commercial weakly basic resin DIAION WA30. DIAION WA3Q has only a single kind of fixed functional group (tertiary ammonium group). PEI-CH may have at least four different fixed groups, the primary ammonium group of chitosan and primary, secondary, and tertiary ammonium groups of PEL We consider the neutralization reaction of HCI with each functional group and develop
* Author to whom correspondenceconcerningthis paper should be addressed.
a theoretical equation for the equilibrium isotherm and the titration curve. We show the way in which the equilibrium coefficients for adsorption of HC1 on each functional group are determined from the experimental titration curve. 2. Materials
We used PEI-CH (Fuji Spinning Co.) and DIAION WA30 (Mitubishi Kasei Co.) in this experimental study. Figure 1shows their unit molecular structures. DIAION WA30 is a commercial weakly basic ion exchanger. The network of WA30 is styrene-divinylbenzene, and its functional group is a tertiary amine. PEI-CH is a chitosan derivative which has been developed by Kawamura et al. (1993). Chitosan is produced from chitin, which is a natural biopolymer extracted from the shells of arthropods such as crabs, shrimps, lobsters, etc. Since the cross-linked chitosan (hereafter called CRCH) is a highly porous sphere (ep r 0.9), the concentration of the amino groups of c h i w in the adsorbent phase is lower than that in commercial weakly basic ion exchangers such as DIAION WA30 (see Table 1). In order to increase the concentration of the amino group in the adsorbent phase, poly(ethy1eneimine) (hereafter called PEI), with a molecular weight of 10 0o0, was introduced into the CRCH, and PEI-CH was developed (Kawamura et al., 1993). The ratio of primary, secondary, and tertiary amines of the PEI was 1:2:1 as shown in Figure 1 (Druzin et al., 1974). The experimental physical properties of CRCH, PEICH, and DIAION WA30 are listed in Table 1. The concentration of amino groups was determined by measuring the equilibrium isotherm for adsorption of HC1 as mentioned below. Since PEI was introduced into the pore of CRCH, the porosity of PEI-CH is smaller than that of CRCH. However it is still large (ep z 0.700). In spite of such large porosity, the amino group concentration of PEICH is about 1.75 times larger than that of WA30. The scanning electron micrographs of PEI-CH have been presented by Kawamura et al. (1993). They showed that the pore diameter was about 0.1 pm. The water content
0888-5885/94/2633-0854$Q4.50/0 0 1994 American Chemical Society
Ind. Eng. Chem. Res., Vol. 33, No. 4, 1994 855 CHzOH
result suggests that it is much easier to use PEI-CH in a packed column than the commercial weakly basic ion exchanger.
CH20H
I
I
3. Experimental Section Chitosan CHZOH
CH20H
k
k
NH
I
NH
EGDE-Residue
I
CH2CHCH2-PEI
I
OH PEI-CH
PEI -CH
-CH-
-CHz-CH-
P
CHzN (CHs )z
DIAION WA30
Figure 1. Unit molecular structures of chitosan, CRCH, PEI-CH; PEI;EDGE and DIAION WA30. Table 1. Experimental Physical Properties of CRCH, PEI-CH. and DIAION WA30 CRCH' PEI-CH WA30 concentration of amino groups 0.670 2.58 1.48 fixed in the adsorbent phase (kmol/ma of wet resin) water content 0.632 0.541 (kg of water/kg of wet resin) density 1360 1063 true (kgof dry resin/ ms of dry resin) apparent (kg of wet resin/ 1106 1026 ms of wet resin) porosity ~ 0 . 9 0.700 0.557 particle diameterb(m) 3.13 X lo-" 4.21 X lo-' free (in water) 3.32 X lo-' 4.96 X lo-' saturated by HCl (in 0.1 kmol/ms HC1 aqueous solution) VHdVfrd 1.19 1.64 0 Kawamura et al., 1993. b Mean value of one hundred particles. VHC~:volume of resin particle which was saturated by HC1 in 0.1 kmol/msHCl aqueoussolution. V h : volume of resin particle which was free in water.
and density of PEI-CH are larger than those of WA30. The particle of PEI-CH is spherical. The mean diameter of 100 particles is given in Table 1. The volume of the particles of PEI-CH which was saturated by HC1 in 0.1 kmol/m3 of HC1 solution was about 1.19 times larger than the resin volume which was free in water. But the volume of WA30 increased about 64% when it adsorbed HC1. This
Before measuring the equilibrium isotherms, the ion exchange particles were packed in a column and were thoroughly washed with 1 kmol/m3 of HC1 aqueous solution. Thereafter the bed was washed with deionized distilled water. Then 1 kmol/m3of NaOH aqueous solution was flowed through the bed. After the effluent concentration of NaOH coincided with the influent concentration, the bed was washed with deionized distilled water thoroughly. The functional groups of the adsorbent phase became free by the above conditioning. PEI-CH particles were kept in deionized distilled water. Just before measuring the weight of the particles, the solution around the particles was removed using a centrifugal filter (Sanyou Rikagaku-Kiki Seisakusho) at 5000 rpm for 4 min. WA30 particles wefe dried at 343 K for 48 h and kept in a desiccator. We measured equilibrium isotherms for adsorption of HC1 by the batch method. The resin particles were contacted with the HC1 solution and gently mixed. The amount of HC1 adsorbed on the resin was measured after 2 , 4 , and 7 days. Since there was no difference between the results for 4 and 7 days, the resin particles and HC1 solution were contacted for 4 days. The pH of the solution for HC1was analyzed with a Horiba pH meter Model F-16. When the Concentration of HC1 in the liquid phase was higher than 5 mol/m3, HC1 was analyzed by neutralization titration. When it was lower than 5 mol/m3, HC1 was analyzed with the pH meter. The adsorbed-phase concentration of HC1 was calculated according to eq 1
where Co and C are the initial concentration and equilibrium concentration of HC1 in the liquid phase (kmol/ m3), respectively. q denotes the adsorbent-phase concentration of HC1 (kmol/m3of wet adsorbent). V and W are the volume of the solution and the wet adsorbent particles (m3), respectively. The titration curves for adsorption of HC1 on PEI-CH and DIAION WA30 were measured by the batch method. The experimental procedure was the same as that for the equilibrium isotherm. In order to get the equilibrium relations for a wide pH range, the initial concentrations of HC1 were changed widely. The adsorbent-phase concentration was calculated from eq 1. All experiments were carried out at 298 K. 4. Results and Discussion
4.1. Equilibrium Isotherm of HCl. Figure 2 shows the experimental equilibrium isotherms for adsorption of HC1 on PEI-CH and DIAION WA30. Both isotherms are very favorable. Since the equilibrium isotherms are independent of the initial concentration of HC1 (CO), HC1 may be adsorbed by the followingacid/base neutralization reaction. K
R-N
+ HC1+
R-NH+Cl-
(2)
Applying the mass action law to eq 2, the Langmuir
856 Ind. Eng. Chem. Res., Vol. 33, No. 4, 1994
r--l
2'o
WA30
+
4
6
HC1
+ WA3b.
+
HC1
298 K
v
0 ~ " ' ' " " " " " ' ' 0 0. 05 0. 10
0. 15
C (kmol/m3 1 Figure 2. Experimental equilibrium isotherms for adsorption of HCl on PEI-CH and DIAION WA30. (-1 eq 3, (to) CO= 0.1531 kmovm3, (0) c0= 0.1021 kmovm3, (0)c0= 0.05104 km0i/m3, ( 0 ) Co = 0.1091 kmol/m3, (m) Co = 0.05455 km0l/m3, ( 0 )Co = 0.02182 kmoUm3. Table 2. Experimental Langmuir Coefficients
K~ k m 0 1 ) 2.09 x 108 1.51 X 10'
PEI-CH WA30
0
2
8
PH Figure 4. Titration curve for adsorption of HCl on DIAION WA30. (- - -) eq 3,(0)The same data as in Figure 2.
8 (kmol/m9 2.58 1.48
2. 5 h
C
0. 15
.d
2 2.0
+ al
1.5
* n 0.10
0
6
\ 3
\ i
P
1.0
5 0.05
X
v
V
cr
0
0. 5 "
0 0. 05
0
0. 10
0
CIS Figure 3. Relation between C and C/q for PEI-CH and DIAION WA30. (-) eq 4,(0)CO= 0.1631kmol/m3, (0) Co= 0.1021 kmovm3, (0) CO5 0.05104 kmoUm3, (0)CO= 0.1091kmoUm3, (m) Co= 0.05455 kmol/m3, (0)CO= 0.02182 kmol/ms.
equation (eq 3) is derived.
KQC (3)
The solid lines in Figure 2 show the Langmuir isotherm. The data are correlated well by the Langmuir equation. The equilibrium constant K and saturation capacity Q are listed in Table 2. They were determined by the following equation to which eq 3 was transformed.
C = - z +1Q ( a ) c
(4)
Figure 3 shows the relation between C and C / q for PEICH and WA30. The data measured for three different CO are correlated well by the straight line without scattering. The values of Kand Q were determined from the intercept and slope of the straight lines, respectively. The saturation capacity for PEI-CH is about 1.75 times larger than that for WA30 (see Table 2). This result suggests that PEICH is more feasible as the adsorbent of acids than WA30. 4.2. Titration Curve. In order tp understand the adsorption mechanism of a strong acid for the new weakly basic chitosan ion exchanger PEI-CH and the commercial weakly basic ion exchanger DIAION WA30 more clearly, we measured the equilibrium relations for adsorption of HC1 over a wide range of pH. In Figures 4 and 5 , the equilibrium amount of HCl adsorbed is plotted versus the
2
'
I
*
?
4
6
8
PH Figure 5. Titration curve for adsorption of HCI on PEI-CH. eq 3, (-) eq 13,(0)The same data as in Figure 2.
-
(- -)
equilibrium value of pH of the solution using an open circle for WA30 and PEI-CH, respectively. The data for WA30 and PEI-CH shown in Figure 2 were also plotted using a closed circle in Figures 4 and 5, respectively. Although the data in Figures 4 and 5 were not obtained by the titration method but by the batch method for many different initial concentrations of HC1, these types of plots may be called titration curves and have been considered as an excellent means for studying ion exchange or adsorption characteristics (Kunin, 1958;Helfferich, 1962). The dashed lines show the Langmuir isotherms calculated from eq 3 using the Langmuir Coefficients listed in Table 2 which were determined using the data in Figure 2. In the case of WA30 (Figure 41, the dashed line is close to the data. This is because WA30 may have only one kind of functional group, a tertiary ammonium group, as shown in Figure 1. On the other hand, the data of PEI-CH deviate from the dashed line when the pH is larger than about 3 (Figure 5). This may be because PEI-CH has at least four different functional groups, the primary ammonium group of chitosan and primary, secondary, and tertiary ammonium groups of poly(ethy1ene imine). Since the Langmuir coefficients listed in Table 2 were determined mainly using the data with pH < 3.7, the data for pH > 3 may deviate from the dashed line in Figure 5 due to the above reason, 4.3. Equilibrium Theory for Adsorption of HCl on PEI-CH.When PEI-CH is used as an adsorbent of strong acid with relatively high concentration such as pH < 3, eq 3 may be enough to present the equilibrium isotherm. However, if PEI-CH is used for recovery of strong acid
from high pH solution such as pH > 3, eq 3 does not give an accurate isotherm. Further, when we consider the masstransfer mechanism, the accurate theoretical equilibrium isotherm may be necessary even in the low-pH region. The accurate theoretical treatment of the equilibrium isotherm becomes more important when PEI-CH is used for the recovery of a weak acid. We will show that the theoretical analysis for a titration curve is very important for the adsorption of glutamic acid on PEI-CH in our next paper. Assuming that HC1is adsorbed on each functional group of PEI-CH by an acid/base neutralization reaction, the reactions are expressed as follows: Kc
Rc-NH2 + HC1+ Rc-NHCCl-
+ HC1*
Rp3-NH+C1-
1
0. 5
0
1. 5
1. 0
2. 0
c h x io5 Plots of data for pH > 4.7 for adsorption of HC1 on PEI-
Figure 6. CH based on eq 14.
(5)
Kpa
Rp3-N
PEI-CH
1
PEI-CH
0
1
(6)
KPZ
Rp2-NH + HC1+ Rp2-NH;C1-
(7)
Kpi
Rpl-NH2 + HC1+ Rpl-NH;Cl-
(8)
where %NH2 denotes the primary ammonium group of chitosan, and RPI-NHz, Rpz-NH, and Rp3-N show the primary, secondary, and tertiary ammonium group of poly(ethy1ene imine) fixed in the adsorbent particle, respectively. Applying the mass-action law to eqs 5-8, the equilibrium relation for each functional group is given as follows:
qP3
KP~QP~C = 1 Kp3C
qp2
KP~QPzC = 1 Kp2C
+
4 = 4c + QP3 + Qp2 + QPl
K P ~ Q P ~ CKPZQPZC KpiQpiC (13) 1+Kp3C l + K p , C l + K p l C Muzzarelli (1977) presented that p(l/Kc) = 6.3 for the amino group of chitosan. Since the first inflection point of the titration curve in Figure 5 exists near pH = 6.3, we assume that the order of basic strength of the functional groups is Rc-NH2 > Rp3-N > Rp2-NH > RPI-NHP. The equilibrium coefficients K and Q in eqs 9-12 are determined in turn. We may assume that HC1 is adsorbed mainly on h-NH2, which shows the strongest basicity in +
+
4
io4
Figure 7. Plots of data for 3.5 < pH < 4.8 for adsorption of HCl on PEI-CH based on eq 16. Table 3. Experimental Coefficients of Eq 13 i
C P1 P2 P3 total PEI-CH 0.539 0.908 0.576 2.66 Qi (kmol/m8) 0.632 Ki (m3/kmol) 2.00 X 10s 2.89 X lo2 1.93 X 1@ 3.68 X 10' WA30 1.48 Q (kmoi/m3) Ki (m3/kmol) 1.51 X 10'
the four amino groups, around the first inflection point pH = 6.3. Under this assumption, only eq 5 occurs around pH = 6.3 and the isotherm is expressed by eq 9. Equation 9 is transformed to eq 14.
+
where C is the equilibrium concentration of HCl in the liquid phase [kmol/m31,qc, qp1, qp2, and qp3 denote the equilibrium amount of HC1 adsorbed on Rc-NH2, Rp1"2, Rpz-NH, and Rps-N, respectively (kmol/m3), and Qc, Qp1, Q P ~and , Qp3 show the saturation capacity for adsorption of HC1 on the functional group Rc-NH2, Rp1"2, Rp-NH, and Rps-N, respectively (kmol/m3). The total amount of HC1 adsorbed on the PEI-CH is given by eq 13.
---KcQcC l+KcC
3
2
c/(q-Q) x
+
C = Q c -c- -
1 Kc
Figure 6 shows the plots of the data for pH > 4.7 based on eq 14. The datd are correlated by a straight line when the pH is larger than about 5 (C is smaller than about 1 X kmol/m3). The straight line was determined using the least squares method using the data for pH > 5. The correlation coefficient for all data for pH > 5 was 0.996. When the pH is larger than 5, the data deviate from the straight line. This is caused by neglecting the reactions of eqs 6-8. KCand Qc were determined from the intercept and the slope of the straight line, respectively, and they are listed in Table 3. Next, it is assumed that HC1 is adsorbed on b N H 2 , which shows the strongest basicity, and Rps-N, which shows the second strongest basicity, simultaneously in the second pH region in the titration curve. Under the assumption, eqs 5 and 6 occur simultaneously and eq 15 is valid. Equation 16 is obtained from eqs 9 and 15. q=- KcQcC
l+KcC
+
KPSQPBC l+Kp3C
,-
858 Ind. Eng. Chem. Res., Vol. 33, No. 4,1994 0 -
h
0.2
6 h
\
.. 0. 1
0
8 X
z2
0
v
V
X
u 0
0
0
2
4
6
8
0
Figure 8. Plots of data for 2.11 C pH C 4.8 for adsorption of HCl on PEI-CH based on eq 18.
c
1
(16)
4 - 4c KP3
In eqs 15 and 16,Kc and Qc are known parameters (Table 3). Kp3 and Qp3 are unknown parameters. Therefore, qc in eq 16 can be calculated for any value of C using eq 9. Figure 7 shows the plot of the data for 3.5 < pH < 4.8 based on eq 16. The data are correlated by a straight line when the pH is larger than about 3.68 (C is smaller than about 1X 10-4 kmol/m3). The correlation coefficient was 0.894. The values of Kp3 and Qp3 were determined from the intercept and the slope of the straight line, respectively, and they are listed in Table 3. Similarly, assuming that eqs 5-7 occur simultaneously in the next pH region in the titration curve, eqs 17 and 18 are obtained. KcQcC '=-
+
K P ~ Q P ~ CK P ~ Q P ~ C (17) l+Kp3C 1+Kp2C +
In the above equations, Kp2 and Qp2 are unknown parameters. qc and qp3 are given by eqs 9 and 10, respectively. Since their equilibrium coefficients Kc, Qc, Kp3, and Qp3 are known parameters (see Table 3), qc and qp3 can be calculated for any value of C. Figure 8 shows the plot of the data for 2.11 < pH < 4.8 based on eq 18. The data are correlated by a straight line when the pH is larger than about 2.50 (C is smaller than about 3 X kmol/m3). The correlation coefficient was 0.957. The values of Kp2 and Qp2 were determined from the intercept and the slope of the straight line, respectively, and they are listed in Table 3. Finally, assuming that all reactions of eqs 5-8 occur simultaneously in the whole pH region of the titration curve, eq 19 is derived. C
-- 1
= Qpl 4 - (qc + qp3 + qp2) KPl
0. 2
I 0. 3
c/ { q - ( Q + q3+ 92) 1
C/{q-(qC+q3)}x io3
C = Qp3---
0. I
(19)
where Kp1 and Qp1 are unknown parameters. Figure 9 shows the plot of the data for 0.88 < pH < 4.8 based on eq 19. The data are correlated well by a straight line for pH > 0.88 (C is smaller than about 0.13 kmol/m3). The correlation coefficient was 0.988. The values of Kp1 and Qp1 were determined from the intercept and the slope of the straight line, respectively, and they are listed in Table 3. The correlation coefficients for the straight lines in Figures 6-9 were 0.996,0.894,0.957, and 0.988 as mentioned earlier. When the correlation coefficient is larger than about 0.9, the straight line determined using the least
Figure 9. Plots of data for 0.88 C pH < 4.8 for adsorption of HCl on PEI-CH based on eq 19.
squares method has enough accuracy. Although the equilibrium coefficients were determined in turn from the plots of Figures 6-9, the accuracy of the calculation in the present study may be acceptable. The solid line in Figure 5 was calculated from eq 13 using the equilibrium coefficients listed in Table 3. The data are correlated reasonably well by the solid line for the whole pH region. The ratio of the primary, secondary, and tertiary amines of the PEI which was introduced into CRCH was 1:2:1 (Druzin et al., 1974). Table 3 shows that the ratio of Qpl:Qp2:Qp3 is 1:1.68:1.07. The value of Qp2 is about 30% smaller than the value expected from the molecular structure of the PEI. The concentration of the amino group of chitosan QCis 0.632 kmol/m3. It is close to 0.670 kmol/m3, which is the value of the original crosslinked chitosan particle CRCH (see Table 1). The total concentration of the four fixed amino groups of PEI-CH (Qc + QPI + Qp2 + Qp3) is close to the value determined from the data in Figure 2 for pH < 3.7 and eq 3 (see Tables 2 and 3). The equilibrium constant Kp3 for the tertiary ammonium group of PEI-CH is 3.68 X lo4 m3/kmol, and its order of magnitude is the same as that of the tertiary ammonium group of DIAION WA30 (1.51 X lo4m3/kmol) as shown in Table 3. The above procedure may be applied to determine the equilibrium coefficients not only for PEI-CH but also for any commercial ion exchange resins which have different fixed groups. 5. Conclusion
The adsorption of strong acid on the polyaminated highly porous chitosan (PEI-CH) appeared technically feasible. 1. The saturation capacity for adsorption of HCl on PEI-CH was 1.75 times larger than that for a commercial weakly basic ion exchanger DIAION WA30. 2. HC1was adsorbed on the weakly basic ion exchangers by an acid/base neutralization reaction. 3. The equilibrium isotherm for adsorption of HC1 on DIAION WA30, which has a single kind of fixed functional group (a tertiary ammonium group), was expressed by the normal Langmuir equation, eq 3, over the whole adsorption range. 4. The equilibrium isotherm for adsorption of HCl on PEI-CH, which has four different amino groups, could not be expressed by eq 3. HC1 was adsorbed on each functional group simultaneously, and the isotherm was given by eq 13. The equilibriumcoefficientsfor adsorption on each functional group were determined from the experimental titration curve in turn from high pH to low pH. The concentration of the amino group of chitosan in PEI-CH was close to that of the original chitosan particle CRCH. The ratio of the concentrations of the primary,
Ind. Eng. Chem. Res., Vol. 33, No. 4,1994 859 secondary, and tertiary amino groups in PEI-CHwas 1:1.67:1.07,which was a little different from the ratio 1:2:1 expected from the molecular structure of the PEI. The experimental titration curve was well correlated by eq 13.
Nomenclature C = equilibrium concentration of HC1 in liquid phase, kmol/ m3 CO= initial concentration of HC1 in liquid phase, kmol/m3 K = equilibrium constant (eq 3), m3/kmol KC = equilibrium constant (eq 91, m3/kmol Kp1 = equilibrium constant (eq 121, ms/kmol Kp2 = equilibrium constant (eq 111, m3/kmol Kp3 = equilibrium constant (eq lo), mVkrnol Q = saturation capacity for adsorption of HCl, kmol/m3 QC= saturation capacityfor adsorptionof HCl on the primary ammonium group of chitosan fixed in PEI-CHI kmoVm3 Qpl = saturationcapacity for adsorptionof HC1on the primary ammonium group of PEI fixed in PEI-CH, kmol/m3 Qp2 = saturation capacity for adsorption of HCl on the secondaryammonium group of PEI fixed in PEI-CH, kmoY m3 Qp3 = saturation capacityfor adsorptionof HC1on the tertiary ammonium group of PEI fixed in PEI-CHI kmol/m3 q = equilibriumtotal adsorbent-phase concentration of HC1, km0i/m3 qc = equilibrium concentration of HC1 adsorbed on the primary ammonium group of chitosan fixed in PEI-CH, kmoVm3 qp1 = equilibrium concentration of HC1 adsorbed on the primary ammonium group of PEI fixed in PEI-CH, kmol/ m3 qp2 = equilibrium concentration of HC1 adsorbed on the secondaryammonium group of PEI fixed in PEI-CH, kmol/ m3 qp3 = equilibrium concentration of HCl adsorbed on the tertiary ammonium group of PEI fixed in PEI-CH, kmol/ m3 V = volume of solution, m3 W = volume of wet adsorbent particles, m3 Greek Symbols ep
= porosity of adsorbent particle
Rc-NH2 = primary ammonium group of chitosan fixed in PEI-CH Rpl-NHB = primary ammonium group of PEI fixed in PEICH Rp2-NH = secondary ammonium group of PEI fixed in PEICH Rps-N = tertiary ammonium group of PEI fixed in PEI-CH
Literature Cited Ad=, G.; Jones, P. M.; Millar, J. R. Kinetics of Acid Uptake by Weak-base Anion Exchangers. J. Chem. SOC.A 1969,A, 2543. Bhandari, V. M.; Juvekar, V. A,; Patwardhan, S. R. Sorption Studies on Ion Exchange Resins. 1. Sorption of Strong Acids on Weak Base Resins. Znd. Eng. Chem. Res. 1992,31,1060. Druzin, M. I.; Vakova, I. N.; Schenniloa, N. I.; Koroleva, L. I.; Kapapetyan, L. P.; Valkova, A. K.; Zaitaeva, I. V. Modification of Polyethylene Imine. J. Polym. Sci., Polym. Symp. 1974,47,369. Helfferich, F. Ion-Exchange Kinetics. V. Ion Exchange Accompanied by Reactions. J. Phys. Chem. 1965, 69, 1178. Helfferich,F.Capacity. InZon Exchange;McGraw-Hill: New York, 19621p 81. Helfferich, F. G.; Hwang, Y. L. Kinetics of Acid Uptake by Weak Base Anion Exchangers: Mechanism of Proton Transfer. AIChE Symp. Ser. 1985,81,(242),17. Hubner, P.; Kadlec, V. Kinetics Behavior of Weak Base Anion Exchangers. AIChE J. 1978,24,149. Kawamura, Y.; Miteuhashi, M.; Tanibe, H.; Yoehida, H. Adsorption of Metal Ions on Polyaminated Highly Porous Chitoean Chelating Resin. Znd. Eng. Chem. Res. 1993,32,386. Kunin, K. Anion Exchange Resin Characteristics. In Zon Ezchange Resins; John Wiley & Sons: New York, 1958,p 55. Muzzarelli, R. A. A. Chitin; Pergamon Press: Oxford, New York, 1977;p 184. Rao, M. G.;Gupta, A. K. Ion Exchange Procesees Accompanied by Ionic Reactions. Chem. Eng. J. 1982a,26,181. Rao, M. G.; Gupta, A. K. Kinetics of Ion Exchange in Weak Base Anion Exchange Resins. AZChE Symp. Ser. 1982b,78 (219),96. Warner, R. E.; Kennedy, A. M. Kinetics of Neutralization of Weak Electrolyte Ion-Exchange Resins. J. Macromol. Sci. 1970,A4, 1125.
Received for review August 18, 1993 Accepted December 21, 1993. 0 Abstract published in Advance ACS Abstracts, February 15,1994.
