INDUSTRIAL AND ENGINEERING CHEMISTRY
JUNE, 1939
Table I11 presents the results with a beeswax emulsion in the cell. Favorable reductions in pull were observed. When 15 volts were used, the actual pull in pounds was the lowest observed in any experiment reported here. Beeswax was the most effective waxlike lubricant tried under the similar conditions reported previously (1). Unlike fatty acid which was also simultaneously deposited (Table 11), beeswax augmented efficiency because of its adhesive nature and typical waxy properties. Beeswax stably emulsified with soap is not particularly effective in reducing die pull. It is apparently not adsorbed readily. Electrodeposition of tallow from an emulsion containing 1.4 per cent tallow and 0.2 per cent potassium soap (pH 8.6 to 10) gave no enhanced effect under conditions identical to those in Table I. Here, as in the case of the soap solution containing appreciable quantities of free fatty acid, the waxlike nature of the copper soap was changed by the tallow. A rather heavy coating of tallow admixed with the greenish copper soap was readily observed, however. Emulsions of tallow in soap solutions have never shown any
727
advantage over soap solutions alone in this experimental device without the electrodeposition procedure. With 0.1 per cent sodium stearate (pH 9.9) no enhanced lubrication was observed and no visible deposition of green copper soap was noted a t room temperature when currents up to 30 volts were used. When the temperature of the solution was raised to 75” C. so that the sodium stearate “dissolved” and subsequently ionized, enhanced lubrication did result and copper stearate was formed in visible quantities. Regarding the time required to deposit an effective film from a soap solution such as is described in Table I, 0.1 second is sufficient. Thus commercial drawing speeds should offer no particular difficulty, if we take into consideration an electrodeposition “cell” of reasonable size. The original electrodeposited film is carried through three to four dies with a measurable lessening of die pull.
Literature Cited (1) Williams, R.C.,IND.ENQ.CHEM.,27, 64 (1935). (2) Williams, R.C., J.Phus. Chem., 36,3108 (1932). (3) Williams, R.C . , Wire & Wire Products, 12,754 (1937).
Reaction of Carbonic Acid with
the Zeolite in a Water Softener ROY E. KING
0. M. SMITH
Panhandle Power and Light Company, Borger, Texas
Oklahoma Agricultural and Mechanical College, Stillwater, Okla.
S
INCE the commercial introduction of the zeolite method or base exchange of water softening, it has usually been
considered that the only exchange reactions occurring were those involving the basic ions. Although Riedel (2) in 1909 described the reaction of dissolved carbon dioxide on zeolites, comparatively little consideration has been given to the basic properties of the hydrogen ion. I n this paper we show, as softening proceeds, that there is a gradual decrease in alkalinity with the formation of hydrogen zeolite, which subsequently exchanges its hydrogen ion with basic ions and thus forms free carbon dioxide and lowers the p H of the efluent water. Two stations of the Panhandle Power and Light Company are supplied by deep well water having an analysis similar to that shown in Table I. The only significant difference is STATION TABLEI. ANALYSISOF WELLWATERAT JOWETT P. p .
m.
Total solids a t 103” C. Total hardness as CaCO3 Total alkalinity
319 206 190
Silica FetOs and AlzOa Calcium Magnesium Sodium Bicarbonate Carbonate Chloride Sulfate Nitrate Carbon dioxide
24.8 1.2 73.0 6.0 26.2 232.0 0.018.0 33.0C 17.7 15.0
Grains/gal, 18.7 12.0 11.1 1.45 0.07 4.27 0.35 1.53 13.55 0.00 1.05 1.93 1.03 0.88
that the water a t Jowett Station, near Mobeetie, Texas, contains 15 p. p. m. of carbon dioxide, whereas the water used at Riverview Station, near Borger, Texas, contains 7 p. p. m. Because of the low sulfate-carbonate ratio the boiler feed water was treated a t Jowett Station with sulfuric acid prior to softening, and a t River view Station with acid following the softening. The total alkalinity of the water was reduced from 190 to 25 * 5 p. p. m. At Jowett Station it was observed that no matter how narrow the range of alkalinity in the influent to the softener, there was always a wide variation in the total alkalinity of the effluent.
Cause of Variation in Alkalinity of Effluent investigationwas made to determine the extentand the cause of these variations. The usual methods of operating the water softener were followed. The total alkalinity of the influent and effluent during the softening period is shown in Figures 1 and 2. I n the beginning the total alkalinity of the effluent was much higher than that of the influent but gradually decreased as the softener became exhausted, until it was less than that of the influent. In following the idea that dissolved carbon dioxide in the water might be responsible for the observed changes, tests were made in which the quantity of free carbon dioxide was compared to the total alkalinity in the influent and effluent waters. Typical data from one of these tests are shown in Figure 1. The influent was untreated Jowett Station water with a free carbon dioxide content of 15 p. p. m. Similar
INDUSTRIAL AND ENGINEERING CHEMISTRY
128
data are shown in Figure 2 when using Riverview Station water which contains 7 p. p. m. of free carbon dioxide. During the initial portion of the run, free carbon dioxide was absent in both cases. From the point a t which free carbon dioxide began to appear until the end of the run, the carbon dioxide content increased gradually, and in the latter portion of the run it occurred in greater quantities than in the influent.
effluent
VOL. 31, NO. 6
This is evidence that the quantity of free carbon dioxide in the effluent is linked to the changes in alkalinity and that probably this carbon dioxide is the result of the reactions taking place in the zeolite bed. The assumption of the formation of hydrogen zeolite now seems quite logical. It is believed that the reaction which occurs between carbonic acid and sodium zeolite results in the formation of hydrogen zeolite and normal carbonate. When the quantity of free carbon dioxide in the influent is around 7 p. p. m., t h e increase in alkalinity which occurs in the early part of the softening run appears to be due to the formation of normal carbonate (Figure 2). However, if the free carbon dioxide content of the influent water is around 15 p. p. m. or higher, then normal carbonate does not appear in the effluent but instead the observed increase in total alkalinity appears to be due to the bicarbonate ion (Figure 1). The probable subsequent reaction of hydrogen zeolite also may explain the decrease in the total alkalinity of the effluent below that of the influent during the latter stages of softening, and the increase in the quantity of free carbon dioxide during this stage.
Zeolite Reactions
F I G U R E 1.
CHANGES I N CARBON DIOXIDE, TOTAL
ALKALINITY, AND pH O F SOFTEWED WATER AT
8.0
g7.0 6.0
0
+l
2
2
4
6
F I G U R E 2.
8
10
12
14
16
18
CHANGES I N CARBON DIOXIDE, NORMAL
20
H
As softening progresses, there is a decrease in the quantity of sodium zeolite remaining in the zeolite bed and a c o r r e sponding increase in the quantity of calcium, magnesium, and hydrogen zeolite. Finally, a limiting point is reached a t which the ability of the sodium zeolite to exchange completely with the hydrogen ion is exceeded. After this point is passed, there is an exchange reaction between the hydrogen zeolite and the calcium and magnesium ions entering the softener. This reaction would yield a hydrogen ion and either calcium or magnesium zeolite, and thus lower the total alkalinity and pH and form free carbon dioxide. Other workers (1) in this field observed the pH variation which occurs throughout the softening cycle and also suggested the possibility of hydrogen zeolite formation. The following experiments were made to check these assumptions. Carbon dioxide gas was passed through distilled water until the pH of the water was 6.8. The water was then allowed to percolate through a small quantity of greensand zeolite. The effluent had a pH of 9.0 and contained only carbonate alkalinity to the extent of 21 p. p. m. as sodium carbonate. Carbon dioxide gas was further passed through distilled water until the pH of the water was lowered to 4.9. When this water was allowed to percolate through the zeolite bed, the pH increased to 7.9 and only bicarbonate alkalinity appeared to the amount of 110 p. p. m. as sodium carbonate. Then when sufficient carbonated distilled water had been passed through the ~ e o l i t bed e so that no further change occurred, tap water of a pH of 7.5 and a total alkalinity of 190 p. p. m. was substituted for the carbonated water. The effluent water had a p H of 4.4 after it had been heated and aerated to drive off any carbon dioxide; the formation of hydrogen ions was thus indicated. This procedure also indicates that carbonic acid occurring in water is probably responsible for the observed changes which occur in the total alkalinity, pH, and dissolved carbon dioxide content of the effluent of a zeolite softener. Any hydrogen ion could form hydrogen zeolite by reaction with the sodium zeolite, but under normal operating conditions the formation of hydrogen zeolite is dependent only on the presence of carbonic acid in the influent. II
3
p: Ts
120
Literature Cited
(1) Behrman, A. S., and Gustafson,H., IND. ENQ.CHEM., 28, 1279-82 (1936). (2) Riedel, J. D., German Patent 224,934 (Nov. 23, 1909). PRIDBENTBD at the 95th Meeting of the American Chemical Society, Ddlas, Texae.
