ENGINEERING. DESIGN. AND PROCESS DEVELOPMENT Table VII.
Equipment for Continuous Fixed-Bed Operation in High- and MediumPressure Catalytic Processes Vapor Phase Upflow
Type of Operation Reactor dimensions Length, f t . Inner diameter, in. Outer diameter, in. Reactor design d a t a hhterial
1
2
1.9 Croloy 7 mod)
Remarks
5.1 1.2
3.8
Working pressure, lb./sq. in. Temperature, C. Catalyst loading Volume, cu. In. Pellet size, in. Catalyst bed height, in. Heating (electrical) Temperature measurement Temperature control Pressure control
Liquid Phase Downflow
(AIS1 501
Croloy 7
2800
2800 500
Max. 6 . 1 Max. 0 . 2 X 0 . 2
Feet rate, cu. in./hr.
1-circuit furnace By coaxial thermowell 6 point on-off controller B y reducing valve in hydrogen supply Max. 3 0 . 5
Max. 30,5 Max. 0 . 2 X 0 . 2 29 3-circuit furnace B y coaxial therinowell 6 point on-off controller B y reducing valve in hydrogen supply Max. 120
Hydrogen supply, standard cu. ft.
Illax. 18
Max. 18
500
--
18
Capacity 1 and 2 kw.,resp. Outer diameter 0 . 4 3 in. Located between hydrogen storage bomb a n d unit B y plunger p u m p with adjustable sttoke
Acknowledgment
Literature cited
T h e authors wish t o express their sincere thanks t o the management of the Koninklijke/Shell-Laboratorium, Amsterdam, and the management of N.V. de Bataafsche Petroleum Maatschappij for permission t o publish the above information. They are equally indebted t o many colleagues for their helpful assistance i n the preparation of this paper and for their valuable criticism.
(1) Killeffer, D. H., "Genius of Industrial Research," p. 203, Reinhold, New York, 1948. (2) Marshall, J. A , , and Askins, J. W., IND.ENQ.CHEM.,45, 1603 (1953). (3) Trainer, R. P., Alexander, N. W., and Kunreuther, F., Ibid., 40, 175 (1948). RECEIVBD for review December 2, 1954.
ACCEPTED April 9, 1955.
Sodium Sulfite from Caustic Cell liquor Sodium Sulfite-Sodium Chloride-Water System KENNETH A. KOBE
AND
KATHERINE C. HELLWIG
U n k e r s i f y o f T e x a s , Austin, Tex.
I
N THE electrolysis of sodium chloride brine in diaphragm
electrolytic cells, the products are chlorine, hydrogen, and a solution of sodium chloride and hydroxide. A t times, the market situation has been t h a t the sodium hydroxide was a competitive product because of the caustic soda produced by causticization of soda ash. Even when the caustic soda was surplus, i t was necessary to concentrate the electrolytic solution, separate the
I
I For times of surplus caustic soda these phase relations show that
. . . conversion of cell liquor to sodium sulfite m a y be feasible as an alternate for carbonating to soda ash
. . .the mother liquor can be reused in the diaphragm cell
I 1116
sodium chloride, and produce for market a caustic soda of 50, 7 3 , or 1 0 0 ~ oconcentration. It would be desirable to have a process t h a t would avoid the evaporation of the caustic brine solution, b u t would permit i t to be used directly for the production of some chemical used in large amounts. Such a process directs attention t o t h e Hargreaves-Bird cell ( 1 0 )in which carbon dioxide unites with the alkali in the cathode chamber to form sodium carbonate. T h e recent announcement ( 1 6 ) t h a t the Dour Chemical Co. a t Freeport, Tex., will carbonate cell liquor t o produce sodium carbonate arouses new interest in this process. I n a similar manner, sulfur dioxide could be used t o form sodium sulfite. Thus, a three-component system, sodium chloride-sodium sulfite-water, would result. The necessity for separating the sodium chloride and sodium sulfite becomes apparent. T o determine the industrial feasibility of this separation, the phase relationships of the system must be known. Therefore, the phase properties of the system sodium chloridesodium sulfite-water a t O", 25", 40", 60°, 80", and 100" C. have been determined. The solubility of sodium chloride has been well established b y previous investigators. A summation of d a t a obtained b y Mulder in 1883, Andrae in 1884, and Berkeley in 1904 is presented
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 6
'
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT Table 1. Tyw., C. 0 25 40 60 80
100 a C
Solubility of Sodium Chloride in Water
Table II.
(Solid phase = NaCl) Solubility, Grams NaC1/100 Grams 11zO This I.C.T. Seidell work (6) (12,1 5 )
35.5 36.1 36.4 37.2 38.1 39.3
35.7 35.9 36.3 37.0 38.0 39.2
Temp.,
c.
35.9Q(35.56) 36.0a 37.lC 37.3c 38.0C 39.60
-0.867 -0.76 -1.27 -1.37 -1.96 -2.23 -2.77
Zhdanov and Adamenkova. A. Seidell and Fisher. Kurnakov a n d Nikitina.
Solubility of Sodium Sulfite in Water Solubilitv. Grams NavSOa/100 Grams HzO Hartley Lewis Foerster and and This et a l . Barrett David work (2) (4) (8) Solid Phase = Tce
. . .. ... I . .
,..
*
, . .
...
-4.5b
...
...
=
9.44 Ice NazS0~.7HzO 11.70 ,.. li:48
+
... , . .
.. . . , . .
, . .
...
17.91
, . .
, . .
Solid Phase = NazSOs. 7Hz0
9 30
-1 -1
13.09 ,..
12:70
0 0
13.3
2 0 5 9 9 2
. . ,
14.4 ...
. .
10 6
18 19 23 24 25 26 28 29 29 33 37 21 31 33
0 0
85 2 006
30 09
2 6c jC
4c
32.95c 33.Sb 34.7; 35.9 33.00 33.82 34.5 35.6 37.00 37.5 40.00 41.0 42.5 46.0 47.0 47 5
56.0 52.5 55.6 57.5 58.1 59.8 AO
n
62.5 66.0 67.5
70.0 80.0 84.0 94.4 97.0 99.0 100.0 a c
18: i o
... ...
20:01 25:31
2 9 5b
...
14:82 17.61
23:io
16 5
Experimental techniques are designed to study phase relationships of sodium sulfite-sodium chloride-water system
June 1955
...
...
... ..
Solid Phase = Ice
by Seidell(19, 16). All sets of data agree well, and a comparison of results is given in Table I. Work on sodium sulfite has not been so extensive, as there are only three sets of data for its solubility in water. The first work was done in 1909 by Hartley and Barrett (4). They made their own anhydrous sodium sulfite a t 100" C. and performed all operations in a hydrogen atmosphere. They reported the transition temperature of the heptahydrate t o anhydrous salt t o be 21.6" C., and the solubility of the anhydrous salt to be almost constant with increasing temperature. Lewis and David ( 9 ) in 1924 determined the solubility of sodium sulfite in water b y extrapolating the isotherms in the system sodium sulfite-sodium sulfate-water, for their sulfite solutions always contained sulfate. They found a transition temperature of 31.5" C. Also in 1924, Foerster, Brosch, and Norberg-Schulz ( 2 ) reported the results of a n extensive study of sodium sulfite. They found a transition temperature of 33.4" C. and a definite increase in solubility with temperature. The data of all investigators are compared in Table I1 and Figure 1.
Sample Preparation. All chemicals used were of reagent grade which met ACS specifications. The sodium chloride and sodium sulfite obtained from J. T. Baker Chemical Co. assayed 99.8 and 100.1yo,respertively. Dissolved oxygen was removed from distilled water for sample preparation by boiling under reduced pressure at a temperature ranging from 60" t o 65' C. for 1 hour. The degassed water was stored under nitrogen atmosphere; however, as a precaution against oxygen intrusion during storage, an arbitrary maximum storage time of 5 hours was adopted. Borosilicate glass test tubes (25 X 250 mm.) were drawn so that the upper section contained either one or two short constrictions. The tubes with two constrictions were used for sam-
-3.45" -3.5Q
, . .
2.15 ... 4.21 6.24
...
Solid Phase
Analytical Method. Sodium chloride in solution was determined by the mercurimetric method of Domask and Kobe (1). Sulfite ions in solution interfered with this method, so they were oxidized t o sulfate with hydrogen peroxide before titration. Sodium sulfite in solution was determined iodimetrically, as described by Hartley and Barrett (4). The complete analysis was performed under a nitrogen atmosphere. Crystals from each sample were examined through a microscope. crystalline sodium sulfite heptahydrate belongs to the prismatic class of the monoclinic system (4). Anhydrous sodium sulfite crystallizes in short hexagonal prisms terminated by pyramidal faces and a basal plane. As compared t o hydrated crystals, anhydrous crystals are small. Sodium chloride crystals are cubical and are rendered opaque with crossed nickels. I n studying the crystals, oil with a refractive index equal to t h a t of anhydrous sodium sulfite, 1.565 (S), was used. Thus, as the microscope stage was rotated, anhydrous sodium sulfite became extinct at 90" intervals, but the heptahydrate and sodium chloride were unaffected. Submergence of crystals under oil also made possible extensive study of each slide without danger of oxidation.
1,898 ... 3.88 ... ... 7.17
26:36 ... 30.7
... ... ...
34.9
29: 92
:
...
29 40
, . .
3i:io 34.00 ...
...
... ... ...
, . .
34:99 ..,
38:80 ... 44:OS ... ... 28.1 ... ... ... ... 39.1 Solid Phase = NazSOs.7I-IzO NazSOa 38.0 ... ... Solid Phase = NazSOa. 7Hz0 , . . 40.00 ... ... 40,50 ... , . . 42.6 ... Solid Phase = NazSOs
, . .
... ...
37.3
+
...
37.5 ...
... , . .
...
35.7
... 39.2 38.5 . . ...
...
37.3
36.6 28 104
... ...
...
... ...
...
35.8 ... ... 34.7
...
...
, , .
2s:i3 ,..
...
...
28.21 ...
32 9 2A:76 ... ...
31.7 31 7
...
. , .
...
...
26.3
...
... ...
35.7
...
34.6 ...
...
33.8 ... 32.8
...
31.8 ... ... , . .
30.9
...
31 3
. . ...
30.2 ...
27.3 27.1 27.7 ...
28:26 . . ... ... ...
. . . .
28.0
...
...
... ...
... ...
Cryohydric point. Metastable region. Incongruent melting point.
ples that ultimately would contain both salts. The first salt and water were added and the tube was sealed off a t the upper constriction. The salt was dissolved before the tube was placed in a n auxiliary bath a t a controlled temperature. I n order t o add the second salt, the tube was cut open below the top seal, the salt was added, and the solution was agitated b y injecting nitrogen. The tube was then sealed off a t the lower constriction and placed in the thermostated bath. The final length of the tube was about 125 mm. At 25' C., about 8" C. below the transition temperature of sodium sulfite heptahydrate to anhydrous salt, the rate of conversion of anhydrous salt to heptahydrate is extremely slow.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1117
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
TEMPERATURE, "C. Figure 1.
Comparison of solubility data for sodium sulfite-water system
Because all samples were prepared from the anhydrous salt, a special technique was used to prepare the sample. It was found t h a t the anhydrous salt formed whenever a large amount of solid phase crystallized, so the amount of solid phase was kept as small as possible. Two solutions, sodium sulfite in deoxygenated water and sodium chloride in deoxygenated water, were prepared for each sample Rhich would contain sodium chloride as the solid phase. Samples containing a small amount of sodium sulfite in solution were added to the corresponding sodium chloride samples, using a pipet flushed with nitrogen. Sufficient sodium chloride crystals were added to saturate the 25 ml. of splution, and the tube was sealed and allowed to come t o e uilibrium. As t h e amount of sulfite in the samples increase%, the invariant point was reached where sodium chloride forced sodium sulfite heptahydrate to crystallize out so t h a t both salts were present as solid phases. I n the regions where sodium sulfite heptahydrate was the stable phase, increasing amounts of sodium 1118
chloride crystals were added t o a saturated sodium sulfite solution and equilibrated until the heptahydrate crystallized out. At 40" C. and above, anhydrous sodium sulfite is the solid phase so t h e samples were prepared by one method. The desired amount of sodium sulfite was added to 25 ml. of deoxygenated water, the tube was sealed, and all sulfite was dissolved by heating the solution t o the temperature of the isotherm. The tube was opened, the desired amount of sodium chloride crystals was added, the tube was resealed, and the contents were allowed t o come t o equilibrium in the bath. Sealed samples which would have sodium sulfite as the solid phase were heated t o a sufficiently high temperature t o form sodium sulfite crystals before the tube was placed in the b a t h t o come t o equilibrium, otherwise crystal formation is very slow and supersaturation results. For the 0" C. isotherm the solution was cooled to form crystals of sodium sulfite heptahydrate before sodium chloride was added. The time required for equilibrium
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47,No. 6
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT was 9 days a: 0", 20 days at 25", 13 days a t 40°,9 days at 60", 8 days at 80 , and 6 d a j s at 100" C. T h e apparatus used was t h a t of Wendrow and Kobe ( 1 7 ) . Sampling Procedure. I n removing solution from t h e tubes for sulfite analysis, oxidation of t h e sulfite was prevented b y a special device. A 125-m1. Erlenmeyer flask was equipped with a magnetic stirring bar and a two-holed rubber stopper which contained two pieces of glass tubing with diameters of 6 and 10 mm., respectively. T h e 6-mm. tubing was closed with a short piece of rubber tubing and pinch clamp, while t h e 10-mm. tube was sealed with a small cork. Nitrogen was introduced into the flask through the 6-mm. tubing. a f t e r the system was thoroughly flushed, 80 ml. of standard iodine solution was added through t h e 10-mm. tubing from a buret. T h e tube was stoppered, and t h e flask and contents were tared and weighed. T h e top of t h e glass sampling tube was broken, and a portion of sample was drawn into a nitrogen flushed pipet through a small piece of filter paper attached t o the tip with cellulose tape (Scotch tape). The filter paper was then removed, and the sulfite sample was introduced into the flask through the 10-mm. tubing. I n all cases the tips of burets or pipets were projected below the bottom of the tube, and care was taken to prevent the tips from touching the walls of the tubing while the deliver) apparatus was withdrawn. T h e cork was again placed in the tube, and t h e flask was weighed-the difference in weight waB t h e amount of solution added. T h e excess iodine was titrated with sodium thiosulfate, while agitation was maintained with the magnetic stirrer. For the analysis of chloride in solution, portions of samples which contained small amounts of sodium chloride were withdrawn from the sampling tube by a pipet with filter paper attached to the tip and were delivered into tared and weighed 280ml stoppered Erlenmeyer flasks. T h e flasks were again weighed, a n d the samples were treated as previously described. Portions of samples which contained large amounts of sodium chloride were delivered into tared weighing bottles. T h e sample and bottle were weighed, and the solution was made up to 500 ml. in a calibrated volumetric flask. Portions of these samples were analyzed by t h e method described above.
Table 111.
Table IV.
~
Component
Concn., Grams/100 Grams Satd. S o h . NaCl NanSOa Temperature = 0' C. 0.00 11.7
Solid Phase NazS03.7Hz0
NazSOa. 7Hz0 NaCl NaCl
+
6.2 18.1
24.5 26.2 Temperature
NanS03 7Hn0 NaC1
+
NaCl
0.00 2.79 6.65 10.6 12.5 15.6 18.9 19.3 20.2 20.5 20.9 22.3 23.0 23.9 24.5 25.1 25.7 26.5
NazSOa
Temperature 0.00 5.00
NazSOa
9.83 15.5 23.2 24.0 25.2 26.7
+ NaCl
KaC1
Temperature KazSOa NanSOs XaCl
Industrial possibilities of sodium sulfite recovery and re-use of mother liquor are based on phase studies
Phase equilibrium d a t a for sodium sulfite-sodium chloridewater are given in Figure 2 and Table 111. For these isotherms t h e solubilities of the pure salts were taken from a smooth curve through t h e experimental results obtained. Solid phases consisted of sodium chloride and sodium sulfite heptahydrate at 0" and 26' C., and sodium chloride and anhydrous sodium sulfite a t 40°, 60°, 80°, and 100" C. Metastability was observed for the 28' and 40" C. isotherms, b u t none was observed for other temperatures. T h e invariant point for the 25" C. isotherm was determined from the intersection of the two equilibrium curves whose equations were found by the
Phase Equilibrium Data for System Sodium Sulfite-Sodium Chloride-Water
+ SaCl
Temperature 0.00
NazSOa Na280a NaCl
+ NaCI
a
10.3 20.5 26.1 26.8 27.6
2.83 0.00 = 25' C. 23.5 20.7 17.7 15.0 13.7 11.9 10.6 11.8 10.8 10.1 9.31 7.07 5.96 4.34 3.38 2.30 1.27 0.00 = 40' C. 26.3 20.5 15.8 10.4 5.86 4.51 2.39 0.00 = 60" C. 23.8 12.9 8.45 3.14 2.44 1.65 0.00 = 80a C. 21.9 11.9 4.56 2.45 1.25
0.00 Temperature = 100' C. 0.00 20.8
NazSOd NazSOa NaCl
0.00 10.3 15.8 25.2 26.6 26.1 27.1
7.85 3.87
+ NaCl
10.6 20.7 27.0 27.9 28.2
10.6 4.04 2.08 0.44 0.00
Concn., Grams/100 Grams HzO NaCl NazSOa 0.00
13.3 9.13 4.96
33.6 35.5
3.89 0.00
7.23 23.2
0.00 3.65 8.79 14.2 16.9 21.6 26.8 28.1 29.2 29.4 29.9 31.5 32.3 33.3 33.9 34.6 35.2 36.0
30.7 27.0 23.4 20.2 18.5 16.4 15 0 17.2 15.6 14.6& 13.3 10.0 8.39 6.05 4.68 3.25 1.74 0.00
6.71 13.2 20.9 32.6 33.6 34.8 36.5
0.00
35.6 27.6 21.2 14.0 8.26 6.31 3.30 0.00
0.00 13.4 20.8 35.1 35.6 36.1 37.2
31.2 16.8 11.2 4.38 3.39 2.28 0.00
0.00
28.0 15.4 6.08 3.43 1.74 0.00
0.00
26.3 13.4 5.37 2.93 0.61 0.00
13.2 27.3 36.5 37.2 38.1
13.5 27.6 38.0 38.9 39.3
Calculated intersecting point.
Separation of Sodium Sulfite and Sodium Chloride from Cell Liquor
Brine Composition Pounds Moles
~
(Basis, 100 lb. original cell liquor) After Reaction of SO, After Evaporation with N a O H a t 100' C. - a t 100' C. G./100 g. G./100g . Pounds HzO Pounds H20
After Cooling to 00 C. G./lOO g. Pounds HzO
After Addition of 13.61Lb. NaCl G./100 g. Hn0 Pounds
Vorce Cell; Liquor Temperature 60' C. (8) iTaC1 in soln. N a O H in soln. H20 NazSOa in soln. NazSOs crystallized o u t H20 crystallized o u t
15.79 8.61 75.60
... ...
0.270 0.215 4.20
... ...
...
...
15.79
:
77 50 6.75 6.81 , .
20.4
15.79
38.0
8.7
41.5 1.25 12.31
...
... ... ... ,..
...
...
...
3.0 ...
...
15.79 67:
is
3.24 10.32 10.32
23.5 ...
...
4.82 ...
...
29.4 , . .
77.5 2 32 11.24
...
38.0 ... ... 3.0
... ...
After Addition of 15.7Lb. NaCl Columbia-Hooker Cell; Liquor Temperature 90° C. ( 5 ) NaCl in soln. N a O H in soln. HzO NazSOs in soln. NazSOa crystallized o u t H z 0 crystallized out a
13.9 10.7 75.4
... ... ...
0.238 0.267 4.18
... ... ...
13.9
...
70.ga 6.53 10.32 , . .
19.6
... ... 9.2 ... ...
13.9
...
36.6 1.10 15 73 ...
38.0 ..
...
3.0 ...
...
13.9
24.5
29.6
56:75
...
77.8 2.32 14.53 ...
2.75 14.10 14.10
...
4.85 ...
...
,..
38.0
...
... 3.0
..
...
6.9 lb. water evaporated a t 100' C.; 70.9 Ib. remain.
June 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
1119
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
GRAMS N~,S0~/100 GRAMS HO , Figure 2.
Sodium chloride-sodium sulfite-water system from 0' to 100'
method of least squares. Invariant compositions were determined experimentally for all other isotherms. Industrial Application. Several methods may be used to remove the sodium sulfite from caustic cell liquor after i t has been sulfited. The solution may be evaporated a t 100' C. to the invariant point to crystallize out sodium sulfite, cooled to 0" C. t o crystallize out sodium sulfite heptahydrate, or saturated with sodium chloride to give a solution of almost invariant composition. The effectiveness of these methods has been calculated for the liquor from a Vorce cell a t 60' C. ( 7 , 8) and a ColumbiaHooker cell a t 90" C. ( 5 ) . The results are given in Table I V on a basis of 100 pounds of original cell liquor. The reaction for sulfiting is 2NaOH SO2 -+ NalSOI HzO 80.0 64.0 = 126.0 18.0 pounds
+
+
+
+
Because this reaction is exothermic, the temperature of the liquor
1120
C.
from the Vorce cell would increase to approximately 100" C. A small amount of water would be evaporated from the liquor from the Columbia-Hooker cell so t h a t both sulfited liquors are assumed to be a t 100" C. All of the sodium chloride remains in solution, so the solubility of sodium sulfite can be determined from Figure 2. The water formed in the reaction must be added to t h a t in the original liquor. When the cell liquor is sulfited, part of the sodium sulfite crystallizes out in the anhydrous form, 50.3% from the Vorce cell liquor and 61.2% from the Columbia-Hooker cell liquor. Because the solution is saturated with sodium sulfite, evaporation of water will cause more sodium sulfite t o crystallize until the invariant composition a t 100" C. is reached, whereupon sodium chloride would also crystallize. A t this point 90.8% of the sodium sulfite has been recovered from the Vorce cell liquor and 93.5% from the Columbia-Hooker cell liquor.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 6
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
a
*
As a n alternative t o evaporation at 100” C., the solution may be cooled to 0 ” C. where sodium sulfite heptahydrate is the equilibrium phase. T h e anhydrous salt will be converted to the heptahydrate, with the removal of some water from t h e solution. B y using this method, 76.2y0 of t h e sodium sulfite can be recovered from the Vorce cell liquor and 83.7% from the ColumbiaHooker cell liquor. T o bring the composition of the sulfited liquor closer t o t h e invariant point, the solution can be saturated with sodium chloride at 100” C. by the addition of 13.6 pounds of sodium chloride t o t h e Vorce cell liquor and 15.7 pounds to the ColumbiaHooker cell liquor. This will cause the precipitation of sodium sulfite, so t h e recovery from Vorce cell liquor will be 83.0% and t h a t from Columbia-Hooker cell liquor will be 86.3%. Some sodium sulfite iemains in solution after each of these processes and it inust be removed or reduced considerably before the sodium chloride brine can be re-used in a n electrolytic cell. One possibility is t o oxidize the sulfite t o sulfate using aeration. T h e solution can then be cooled to 0 ” C. t o remove sodium sulfate decahydrate and leave a final solution containing 1.86 pounds of sodium sulfate and 36.4 pounds of sodium chloride per 100 pounds of water ( 1 3 ) . The raw brine from salt vi-ells or dissolvers must be processed t o remove calcium and magnesium ions before the brine can be used in the electrolytic cell. T h e reaction of sodium sulfite with calcium salts to form calcium sulfite is of interest. Lime slurry tould be added to the solution containing the residual sodium sulfite. For calcium sulfite in water, the solubility is 0.011 gram calcium sulfite per 1000 grams of solution at 100” C. ( 1 1 ) and a t 18” C. is 0.043 gram per liter of solution. T h u s the solution from the evaporation steps could be limed t o yield a
Potential for Steel
final solution containing only about 0.0005 pound calcium sulfite per 100 pounds of initial cell liquor. References
Domask, W. G., and Kobe, K. A., Anal. Chem., 24, 989-91 (1 952).
Foerster, F., Brosch, A., and Norberg-Schulz, C., 2. physik. Chem., 110, 443-55 (1924).
Handbook of Chemistry, N. A. Lange, editor, 6th ed., p. 871, Handbook Publishers, Sandusky, Ohio, 1946. Hartley, H., and Barrett, W. H., J. Chem. Soc., 95, 1178-85 (1909).
Heinemann, Gustave, Columbia-Southern Chemical Corp., Corpus Christi, Tex., personal communication, March 23, 1954.
International Critical Tables, IV, 235, 1928. Kirkpatrick, S. D., Chem. & Met. Eng., 35, 158-61 (1928). Kobe, K. A., “Inorganic Process Industries,” p. 133, Macmillan, h’ew York, 1948. Lewis, N. B., and David, A. C., J. Chem. Soc., 125, 1156-62 (1924).
Illantell, C. L., “Industrial Electrochemistry,” p. 420, McGrawHill Book Co., New York, 1950. Seidell, A., “Solubilities of Inorganic and Metal Organic Compounds,” 3rd ed., Vol. I, p. 327, Van Sostrand, New York, 1940. Ibid., pp. 1217-18. I b i d . , p. 1234. Ibid., pp. 1296-7.
Seidell, rl., and Linke, W. F., ”Solubilities of Inorganic and Metal Organic Compounds,” 3rd ed. suppl., pp. 450-3, Van Nostrand, Kew York, 1952. Thomoson. E. T.. Chem. Ena., 61, No. 6. 105 (1954). Wendrow, B., and Kobe, K: A., IND. ENG.CHEM.,44, 143947 (1952). RECEIVED for review- July 19, 1954.
Mill Waste Disposal
ACCEPTED January 3, 1955.
...
Electrolytic Treatment of Waste Sulfate Pickle liquor.Using Anion Exchange Membranes C. HORNER,
A. G. WINGER, G. W. BODAMER, AND R. KUNlN
Rohrn B Haas Co., Philadelphia, Pa.
PEST pickle liquor is produced by the process in which iron oxide scale is removed from semifinished steel by immersion in a dilute (15 t o 25%) sulfuric acid solution. The acid reacts with the oxide and some of the base metal t o form ferrous sulfate, and when the liquor is finally discarded it may contain from 12 t o 22% ferrous sulfate and from 0.5 to 10% unused free acid. It has been estimated t h a t nearly 1 billion gallons of spent liquor is produced annually. Since the latent values of the components of spent pickle liquor allow little margin for turning the waste into a profit, the problem has come to be treated almost exclusively as a problem of waste disposal. Years ago this presented little difficulty, for frequently the waste liquor could be disposed of b y discharging i t untreated into nearby rivers, lakes, or abandoned mines. More recently, however, in view of the growth of population, t h e establishment of suburban communities, and t h e enormous increase in the volume of liquor to b e disposed of, civic lune 1955
groups and legislative bodies have cooperated t o prohibit pollution of t h e rivers, lakes, and underground water tables in this way. It thus has become necessary to employ other means of disposal. Probably the least costly and most often employed disposal method is t h a t of neutralization with lime, followed by “lagooning” t h e resulting slurry. This method introduces the additional cost of neutralizing agent and its handling and involves t h e cost of lagooning areas. With the advent of Amberplex ( a trademark of the Rohm & Haas Co.) ion exchange membranes, however, another avenue is opened whereby the recovery of electrolytic iron and the regeneration of sulfuric acid may be effected, while at t h e same time t h e disposal problem is eliminated. Such a process would take on added significance in time of sulfuric acid shortages, as recently experienced. An ion exchange membrane is simply a n ion exchange resin in sheet form rather than in the conventional bead or granular
INDUSTRIAL AND ENGINEERING CHEMISTRY
1121
