of at least monovalent anions is influenced more by affinity of ion to solution than by affinity of ion to resin. It appears also from the foregoing experiments that unequally effective removal of cations and anions from a single solution by a mixed bed ion exchanger will usually occur. For example. using a mixture of NaR and RC1 to remove YII from the solution, Y + - + \vi11 be removed most effectively at a @ o f 5 X 1 0 - 2 a n d I - a t a p o f 1 . 4 X lW4.
8,OOC
7,000
6,000
5,000 REACTION 8
Summary
Lz
0 k
A REACTION 9
2 4,000 LL
1
> U 0
0
I
E
REACTION 10
3,000 A REACTION I I 2,ooc 0
I,OOC
,
REACTION 12
0 REACTION 13
In ion exchange s)stems. dilute and concentrated solutions behave differently. Single phase equilibrium relationships and the law of mass action appear applicable in relatively concentrated ion exchange svstems. I n dilute solutions. the abi1it)- of the resin to exchange specific ions at equilibrium is a function of ionic strength. maximum removal factor occurs at a specific ionic strength in every instance. Ionic strength can be adjusted to provide maximum removal of ions at least under equilibrium conditions. Acknowledgment
0
1
Figure 5.
2
3
The authors \\.ish to express their appreciation to associates at the Whirlpool Corp. for advice and interest in this work and to Louise Shultz and Donald Wood for technical assistance.
5
4
PP Removal factor vs. ionic strength for anions
activity coefficients, water transfer, and electrolyte uptake (7). Figures 4 and 5, plots of removal factor us. p ~ reveal , that in all the reactions which were investigated
+
+
A BR AR B, considered as either cation or anion exchange.
[(B)VLI(RF
-
1)
1. A maximum removal factor occurs in each instance. 2. Ionic strength is critical in determining maximum removal of an ion species. 3. .4t ionic strength greater than pmsx-i.e., p for the maximum removal factor-the law of mass action approximately obtains. The greater the ionic strength, the smaller the removal factor. 4. At ionic strengths less than pmaa, the smaller the ionic strength, the smaller the removal factor.
+ 2BR e AR? + 2B, R F l ' s / V ~ . for A + 3BR A R I + 3B, RF V S / V L . K / w 3; for A + BR2 Ft AR2 f B, R F E V S / V L . 3K/p; etc.
Also in solution so dilute that the initial concentration of reactant ion is small compared to the moles of resin (5), the removal factor (RF) at equilibrium is independent of the initial concentration of reactant ion except as it influences ionic strength, and ( 8 ) the concentration of reactant ion a t equilibrium is always inversely proportional to the moles of pure resin per liter of solution initially present. Deduction (5) is well illustrated by Reactions B and C, where the reactant ion concentration was maintained roughly constant and @ was varied. Both deductions resulted from the following treatment as illustrated by
From Figures 1, 2, and 3. in the very dilute region, K can be considered as a function of pn. l'alues for n, obtained from these figures, are higher than the exponents of p given in the RF relationships listed previously; hence, the decrease of RF with decreasing p in the very dilute region. Since, in the dilute region, a relationship K = kp" can be obtained (Figure l ) , ionic strength can predict removal factor for a particular ion exchange reaction at equilibrium. From Figure 5, pmar for optimum removal of I- occurred at 1.4 X even though four chemically different anion exchange resins were used. Perhaps this is an indication that removal
3 18
(mBR)
-
But m B A = Js' (Ao N Vs; R F >> 1 ; and B 1.1. Then R F V s / V L K,'p. Similarly it can be shown that 24)
for A
K/P2;
$
INDUSTRIAL AND ENGINEERING CHEMISTRY
E
Literature Cited
(11 Bauman, E. W., hrgersinger, W. J., Jr., J . Am. Chem. Soc. 78, 1130 (1956). (2) Duncan, J. F., A u s t ~ ~ l Ji .~ Chem. n 8, 1 (1955).
(3) Duncan, J. F., Proc. Roy. Soc. (London) A214, 344 11952). (4) Gluekauf, E., Zbid., A214, 207 (1952). (5) Harley, J. H., Hallden, N., Nucleonics 13, No. 1, 32 (1955). (6) Richman, D., Henry, T. C., J. Phys. Chem. 60, 237 (1956). (7) Shubert, J. S., J . Phys. G3 Colloid Chem. 5 2 , 340 (1948). (8) Shubert, J. C., Conn, E., Nucleonics 4, 2 (1948). RECEIVED for review February 4, 1957 ACCEPTED September 2, 1958
Correction Construction Digest 1958 In the "Construction Digest 1958"
[IND. ENG. CHEhf. 51, 6 5 A (January 1959)] subitems e and 1 under item KO. 197 should be deleted. These plants are actually properties of Canadian Liquid Air Co., Ltd.: and are given under item
No.198. Subitem j under irem No. 197 should read 40 million pounds of polyethylene and not 40 thousand tons.
