Koschmieder, E. L., J.Fluid Mech., 3 0 , 9 (1967). Krauss. W.. 6th FATIPEC Conar.. 332 (1962). Kresse,’ P., ‘Deut. Farben Z., 24,”52l (1970); see also Paint Technol., 35, 5 (1971). Lamm, T’. P., Of.Dig., 33,1408 (1961). LeBras, L. It., Bobalek, E. G., Von Fisher, W., Powell, A. S., ibid., 27, 607 (195.5).
Linde, H., Pfaff, S.,Zirkel, C., Z . Phys. Chem., 225, 72 (1964). Lock, A. B., J . Oil Colour Chem. Ass., 43,859 (1960). Logue, L. A., Paint Jfjr., 31, 5 (1961a). Logue, L. A,, ibid., 55 (1961b). Marwedel, G., Farbe Lack, 66,379 (1960). Rlarwedel, G., ibid., 74, 18 (1968). hlarwedel. G.. Jebsen-Marwedel., H.., Deut. Farben 2.. 24. 103
+
(1970a):
I
I
\ - - - - I
I
+
.
’
Marwedel, G., Jebsen-Marwedel, H. ibid., 157 (1970b). Marwedel, G., Jebsen-Marwedel, Farbe + Lack, 71, 91 (1965).
Nield, D. A., J . Fluid Xech., 19,341 (1964). Palm. E.. ibid.. 8. -18.1 - - (196Oi. Pattdn, T. C., “Paint Flow and Pigment Dispel:sion !” p 443, Riley, New York. York, N.Y.. N.Y., 1964. Pearson,’ J. K. A., J.’ J . FZuid‘Jlech., Fluid Jlech., 4, 489 (1958). Pearson, Ravleieh. Lord. Phil. Phzl. X a a . . 32 Ber. 6). 329 (1916). Schven, L. E.. Schven. E., Sternlinn. Sternling, %: V.. V., ‘.J. J . Flkyd Flu;d Jieih,, I f e i h , , 19, 324 (1964). Shur, E. G., Of.Dzg., 23, 867 (1951). Smith, K. X.,J . FluzdJIech., 24,401 (1966). Van Loo, AI., Of. Dig., 28, 1126 (1956). Wapler, D., Farbe Lack, 59,352 (1953). Whitehead, Jr., J. A., Amer. Sci., 59, 444 (1971). 1).
k.,
RECEIVED for review September 18, 1972 ACCEPTED November 21, 1972
Potassium Recovery from Bittern Solutions Fatma AI-Awadil and Abdulaziz K. Al-Mahdi*2 Chemistry Department, Kuwait University, Kuwait
Prior to potassium recovery, calcium was removed from seawater by increasing the concentration of brines, and magnesium by forming the magnesium ammonium phosphate complex. The Salutsky method was used. It depends upon the formation of a complex double salt of potassium sulfate and calcium sulfate which can be precipitated and separated from the bittern, after which the solid i s treated with fresh water and decomposed to the simple sulfates. This results in a K2S04 solution and a solid gypsum phase. The latter can be recycled, whereas potassium sulfate can be recovered from the former. Different conditions were tested, including types of gypsum, temperature, and the effect of NaCl on the recovery of potassium. Sulfuric acidtreated local gypsum used with multiple-batch treatments gave the highest recovery. Yields are tabulated and approximate economics discussed.
S e a w a t e r is the main source of supplying potable water to the 733,196 population of the State of Kurvait. Deep ground brackish water a t Xinagish and Sulaibiyah is the only other plentiful source of supply where the total dissolved solids do not exceed 3900 ppm. R a t e r demand is rising steadily by 200 million galjyr. Estimates show that the mater demand will rise to cover 250 million gal/yr when the population of the State reaches over a million. In a comprehensive survey of Kuwait’s water supply, Temperley (1965a) indicates the importance of the study of dissolved solids as by-products of the seawater distillation plant or the brackish water with higher total dissolved solids rrhich reaches to 10,000 ppm in some areas. Present address, Water Resources Development Centre, Shuwaikh, Kuwait. * Permanent address, Foundation of Scientific Research, Ministry of Higher Education & Scientific Research, Baghdad, Iraq. 70 Ind.
Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1 , 1973
The salinity of seawater and hence the chemical constitution differ from one area to another, the average total dissolved solids content being 36,000 ppm. The total dissolved solids content of the Arab Gulf ranges from 39,000 ppm in the open sea 30 miles from the coast to 42,000 ppni a t the Arabian coastline. Kuwait Bay seawater’s seasonal salinity varies bettveen 44,000 ppm in the cool season to 48,000 ppm at the end of the hot season (Temperley (1965b). The large number of known elements in seawater indicates that probably all of the earth’s naturally occurring elements exist in the sea. Knonm abundances of the different elements in seawater have been reported (Chem. Eng. LYews, 1967; Tallmadge e t al., 1964). K i t h the volume of the oceans being 1.37 billion km3, we can imagine what huge reservoirs and rich sources of various elements the oceans are. Nagnesium, bromine, sodium in various forms, and potassium have been recovered from seawater by various workers (Butt e t al., 1964; Salutsky et al., 1965; Thorp and Gilpiii,
~~
1949). Many of the products and processes applied to seawater or saline water have been reported by Tallmadge et al. (1964). From a n economical point of view, the recovery of sodium chloride, magnesia, and potash is the most promising potential for the future development of seawater chemical industries. I n this work, potassium recovery has been studied by taking into consideration local by-products (such as brine and bitterns) which are taksen as waste and sent back to the sea and the locally produced chemicals (such as gypsum) t h a t are needed in the process. Local Sources of Raw Materials. I n Kuwait in 1969 a n average production of some 16 million gallons per day (mgd) of distillate from the Shuwaikh and Shuaiba Distillation Plants was required. With a n average chloride ratio of 1.6 on the evaporator brine “chloride ratio,” each million gallons of distillate require 2.67 million gallons of feed water and discharge some 1.67 million gallons of brine. On this basis, some 26.72 million gallons of brine are available daily. Other estimations b:y the Board of Planning of Kuwait (1970) of the average disily need for distillate reached 27 mgd in 1970. This figure will rise to 113 mgd in 1980 and 300 mgd in 1990. Table I was compiled according to the average chloride ratio and the required feed water. Among other salts in these quantities of brine, the annual available amount of potassium as K f will be: Year
Available potassium, tons/yr
1969 1970 1980 1990
27192.5 46391.5 192866.0 512022.0
There would appear to be adequat’escope for the development of a chemical industry utilizing brine as a source of potassium and other metals and nonmetals of industrial importance. Bittern solutions are the last waste products of the local “Salt and Chlorine” plant after separation of the sodium chloride crystals. This plant depends on the brine water supplied from the Shuwaikh Distillation Plant. Some 7680 gal/ day of this bittern flows into the sea as waste. Bittern solutions, which contain large amounts of economically important minerals such as magnesium (56 g/L) and potassium (16 g/l.), have been used in this study. Gypsum is another ,waste product produced and collected from the gypsum separator. Some gypsum is formed as a suspension with the bittern solutions which can be separated by simple filtration. Experimental
Magnesium and Calcium Removal. Magnesium was separated from the filtered bittern solution by the ammonium phosphate method (Dunseth and Salutsky, 1964). This procedure involves the transference of 1 liter of the filtered bitterns solution to a large beaker. A stoichiometric amount of reagent grade o-phosphoric acid was added to react with the magnesium content of the bittern. Calcium was precipitated as calcium sulfate by increasing the concentration of bhe brine in the “Salt and Chlorine” plant and was separated there. Small amount,s of calcium sulfate still present in the bittern solution were filtered off before treatment with o-phosphoric acid and ammonia. The pH of the solution, measured after addition of the phosphoric acid, was 0.4.
Table 1. Estimated Products of Seawater in Kuwait Av
Year
daily distillate, mgd
Feed water required, mgd
Brine discharged, mgd
Bittern discharged, mgd
Potassium, tons/day
1969 1970 1972 1980 1990
16 27 52 113 300
42,72 72.39 138.84 301.81 801.00
26.72 45.39 86.84 188.71 501.00
1.71 2.90 5.55 12.07 32.04
74.5 127.1 242.1 528.4 1402.8
The neutralizing agent, 25y0 ammonium hydroxide solution, was then added until the solution’s pH reached 3.0, and the first fraction of the magnesium ammonium phosphate was filtered and separated. This descaling process was repeated a t different hydrogen ion exponents, the first a t pH 3.0, the second a t pH 5.0, the third a t pH 7.0, and the last a t pH 9.0 by successive additions of ammonia and filtration. The last filtrate of the treated bittern after the separation of magnesium as magnesium ammonium phosphate is the descaled bittern, later used for the recovery of potassium. Each liter of bittern descaled as above produces about 500 grams of magnesium ammonium phosphate. Potassium Recovery. Salutsky et al. (1965) studied several methods for the recovery of potassium. 111 this work the gypsum method was used in preference to other methods because of the availability of gypsum in large amounts as a local by-product in the “Salt and Chlorine” plant. The recovery of potassium was performed by precipitation with calcium sulfate as a complex compound. Calcium sulfate was used for this purpose under different conditions. Procedure. I n all experiments 200 ml of the descaled bittern solution were transferred to a three-necked 500-ml round-bottomed flask with the appropriate amounts of gypsum and sodium chloride as stated in each case. The fiask was fitted to a water condenser. The temperature was measured with a thermometer, and stirring was effected by a magnetic stirring bar. The flask was surrounded by a heating mantle and supported above a magnetic stirrer. Redistilled water (20 ml) was used to wash down the sides of the flask and to compensate for any volume loss. The flask and contents were digested for 2 hr a t different temperatures. Since digestion a t 80’ and 100°C gave similar results, digestion a t 80’C was used. At the end of the digestion period, the content of the flask was filtered hot. The solid was not washed but was dried overnight a t 84OC and weighed. The volumes of filtrates were measured and retained for potassium analysis by the tetraphenyl borate method (Vogel, 1968). To prevent precipitation of ammonium tetraphenyl borate, 1 ml of the sample was boiled n-ith sodium hydroxide solution. When all t’he ammonia (ammonium ion) was driven out as ammonium hydroxide, the solution was cooled and pH adjustment a t 3 was performed by the addition of hydrochloric acid. Precipitation was then completed, and the solid potassium tetraphenyl borate was washed as described by Vogel (I 968). Bittern solutions supplied by the “Salt and Chlorine” plant are not saturated with sodium chloride. The effect of S a C l concentrations on the recovery of potassium and the effect of different amounts of local gypsum concentrations were studied. Ind. Eng. Chem. Prod. Res. Develop., Vol. 1 2 , No. 1, 1973
71
Table II. Effect of Solid NaCl on Potassium Recovery with Reagent-Grade Gypsum NoCI, g
Solids recovered, g
0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 25.0 30.0 35.0 40.0 45.0 50.0
47.1 50.2 49.8 51.1 53.8 49.2 49.4 50.8 51.2 50.4 61.7 60.8 63.8 78.4 60.3
Filtrate Filtrate
Potorsium recovered
vol, ml
186 193 187 198 181 202 188 192 194 194 199 200 194 190 188
%
g
0.394 0.218 0.477 0.148 0.253 0.272 0.258 0.141 0.419 0.393 0,398 0.160 0.173 0.518 0.149
16,93 11.70 20.00 8.00 10.61 14.70 10.83 7.62 17.28 16.50 16.70 8.60 7.26 28.03 6.26
Table 111. Effect of Solid NaCl on Potassium Recovery with local Gypsum NaCl used, g
Solids recovered,
Filtrate
9
vol, ml
9
%
5 10 20 30 40 50
52.9 69.6 45.7 45.0 53.2 63.0
186 162 208 206 210 208
0.738 0.858 0.358 0.402 0,352 0.388
37.00 43.00 10.55 20.00 17.70 19.50
Potassium recovered
Table IV. Effect of Various Amounts of local Gypsum on Potossiurn Recovery Gypsum, 9
Filtrate vol, ml
Solids recovered, g
10 20 30 40 50
204 206 205 196 208
10.5 20.1 29 2 49 4 52 5
PotasSium recovered -~ g %
0 085 0.157 0 160 0 328 0 398
4 60 8.49 8.88 17.75 20.99
Effect of Solid NaCl on Potassium Recovery with 40 Grams of Gypsum. Salutsky and coworkers (1965) used saturated solut'ioiis of bitterns with SaC1. Because of the unsaturated bitterns supplied by the "Salt and Chlorine" plant in respect to XaC1, different' amounts of laboratory grade KaC1 were used in a number of experiments. Ot'her conditions of experiments were kept the same, namely, the use of 200 ml of bittern, 40 grams (laboratory reagent) of g y p sum, aiid a digestion period of 2 hr a t 80°C. The results obtained are shown in Table 11. This batch of descaled bitterns contained 11.9 g/ 1. of sodium aiid 140 g/l. of chloride. The recovery of potassium was attempted from untreated bittern solution with 40 grams of laboratory reagent gypsum arid 20 grams of sodium chloride. The potassium content of this batch was 16.2 g! l., and the magnesium content 260 g/l. The digestion period was 2 kr a t 80OC. The percentage of potassium recovered proved t o he in the same range as that recovered with treated bittern solution. Solids recovered from this experiment contain compounds other than potassium sulfate and calcium sulfate. These 72
Table V. Potassium Recovery from Descaled Bittern Solutions by Multiple-Batch Treatments
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1, 1973
Potassium recovered
vol, ml
g
%
202 206 211
0.238 0.359 0.115
12.8 22.5 9.5 44.8
include magnesium salts. Separation of potassium sulfate from other soluble salts that are likely existing is not a n easy task. Effect of Local Gypsum on Potassium Recovery. Experiments were repeated t o test t h e effect' of using t h e local gypsum instead of the imported brand (British Drug Houses Ltd., Poole, Dorset, U.K., laboratory reagent). The same batch of descaled bitterns containing 11.9 g/l. of potassium was used. Cases where the highest percent recovery of potassium with respect to NaC1 concentration were tried applying the same procedure. Locally produced gypsum collected from the gypsum separator was filtered, mashed with distilled water, and dried. The local gypsum crystals were larger than those imported and therefore provided less surface area for the precipitation of potassium sulfate. Xevertheless, the local gypsum gave a higher recovery of potassium, perhaps owing to the existence of potassium ions as shown in Table 111. Also, filtration with local gypsum is much easier and faster. Results are shown in Table IV for the same procedure with the descaled bitterns containing 9.25 g/l. of potassium and the same digestion period of 2 hr a t 80°C, but different amounts of local gypsum were used to test the effect of various amounts. Test for Potassium Recovery from Descaled Bittern Solutions by Multiple-Batch Treatments. .Ifter treatment with 40 grams of local gypsum, t'he filtrate was measured and tested for potassium. This filtrate was further treated with another 40 grams of local gypsum, measured, and tested for potassium. A third treatment with the same amount of gypsum was applied. Detailed result,s of these experiments are shown in Table V. X batch of descaled bitt'erns contained 9.28 g/1. of potassium. Potassium Recovery from Concentrated Seawater with Multiple-Batch Treatments. Descaled seawater used for these esperinients contained 6.3 g/L of potassium a f t e r reduction of t h e volume to a twentieth of its original volume. The procedure applied was t h a t used in the recovery of potassium from descaled bittern solutiolis by multiple-batch treatments. The results obtained are given in Table VI. Discussion of Results. The recovery of potassium as mentioned previously did not exceed 28%, except from the descaled bittern solutions by the multiple-batch treatments where it reached 44.8%. The results obtained are in good agreement with other ivorkers in various parts of the world who used brines and bitterns of different concentrations (Salutsky et al., 1965). For the sake of comparison, recovery of potassium by multiple-batch treatments has been performed from concentrated seawater, and it has shown the recovery of some 25,35y0 of the potassium content of the batch used. The effect of sodium chloride on the recovery of potassium was fully investigated, but it does not seem likely that the
Table VI. Potassium Recovery from Concentrated Seawater by iMultiple-Batch Treatments Concd seawater vol, ml
200 186 183
Table VIII. Effect of Temperature on Potassium Recovery
Filtrate vol, ml
g
%
194 186 188
45.7 51.0 48.7
0.115 0.093 0.077
9.16 8.40 7.79 25.35
K+ Na+ CaZ+ Mgz+
so42-
COa2c1-
Filtrate
Solids
OC
vol, ml
recovered, g
g
%
100 80
194 198 204
41.7 41.0 40.8
0.194 0.027 0.100
9.06 1.50 4.67
60
local gYFJsum batch, composition %
Bittern batch solution composition, g/I.
Major and minor seawater constituents in solids recovered, composition %
1.3 4: . 6 23.6 0.7 60.6 6 .0 I ,5
16.0 52.5 00.076 49.8 64.0 0.454 187.0
1.5 4 6 21 .o 0.5 64.0 .. . 4.0
presence of different amounts of NaCl affects the recovery of potassium. The curve relating the amounts of NaCl used and the percentage recover:y of potassium does not indicate much information and was not recorded. Points of interest found in this research were further investigated, such as effect of temperature, use of local gypsum (treated and untreated), and recovery of potassium with treated gypsum by the multiple-batch treatments. Analysis of reactants and products has not been regularly performed, but sample!j taken a t random have been analyzed. An example of percent composition of important constit’uents in a batch of local gypsum taken at random and a t different times from the “Salt m d Chlorine” plant is shown in Table VII. The composition of bittern solution varies from time to time, but the average composition of samples used is about the same as those figures shown in Table VII. The resultant precipitate taken a t random (by classical methods of analysis) shows that solids recovered would have the approximate composition shown in Table VI1 ; other elements present were not estimated. Effect of Temperature on Potassium Recovery. The same procedure was applied with 40 granis of local gypsum and descaled bitterns containing 10.7 g/l. potassium with the results in Table VI11 obtained a t different’ digestion temperatures. Perhaps this low recovery of potassium a t high temperatures (Le., 100’ and 80’C) is due t o t h e presence of calcium carbonate in t,he local gypsum, which was precipitated from the brine during evaporation in the “Salt and Chlorine” plant. Local gypsum used in this set of experiments was not ti:eated with sulfuric acid to convert the calcium carbonate into sulfate. dnalysis of the local gypsum indicated the presence of potassium ions, which are converted into sulfate upon treatment with sulfuric acid. The presence of minute amounts of potassium sulfate in the gypsum used might facilitate the formation of the double salt (or the complex) potassium sulfate-calcium sulfat,e. The results obtained, testing the effect of the gypsum treated wit,h sulfuric acid by use of 40 grams of gypsum and digesting a t 100°C, are shown in
Potassium recovered
Table IX. Effect of CaC03 Presence on Potassium Recovery Compared with Use of H2SO4-Treated Gypsum
Table VII. Rtrndom Samples Analysis of Reactants and Products
Ion
Temp,
Potassium recovered
Solids recovered, g
Filtrate
Solids
Expt
vol, ml
recovered, g
g
%
1
194 201 158
41 7 39.9 43.9
0 194 0.386 0.810
9.06 18.03 43 78
2 3
Potassium recovered
Table X. Effect of HsS04-TreatedGypsum on Potassium Recovery by Use of Multiple-Batch Treatments Treatment
Bittern vol, ml
Filtrate vol, ml
Solids recovered, g
1 2 3
200 171 166
174 169 166
54.9 41.8 42.9
Potassiumrecovered g %
35.98 16.17 7.14 59.29
0.ii
0.22 0.08 1.07
Table XI. Effect of Different Amounts of Treated local Gypsum on Potassium Recovery Treated gypsum, g
Filtrate vol, ml
Solids recovered, g
10 20 30 40 60
212 192 194 172 186
10.1 23.8 43.6 52.5 46.7
Potassium recovered
_._____
g
%
0.36 0.44 0.63
16.80 20.56 29.43 36.44 34,81
0.i8
0.75
Table IX. The gypsum used in experiments 1 aiid 2 contained different amounts of calcium Carbonate used without sulfuric acid treat’ment. In experiment 3 the gypsum batch was the same except that i t had been treated with sulfuric acid. The treatment with sulfuric acid involved shaking of stoichioniet~ricamounts of 0 . 1 S sulfuric acid with the batch of gypsum, drying in a n air oven a t around 100°C, and cooling and storing for future use. Obviously, the treatment of gypsum with sulfuric acid resulted in a high recovery a t the same digestion temperature. The sulfuric acid-treated gypsum was used to test the recovery of potassium by use of multiple-batch t’reatments. An even higher percent recovery was obtained. [-sing tiescaled bitterns coiitaining 10.7 g . 1. potassium gave the results shown in Table X. The same batch of descaled bit,terii aiid 40 grams of treated gypsum x e r e used in each case. I n all of the experiments in this work, 40 granis of gypsum, whether local or imported, were used. The effect of different aniounts of local gypsum treated n-ith sulfuric acid lias beeii tested. The results obtained with the tiescaled bitteriis colitaiiiing 1 0 . i g, 1. of potahsiu~i-I,n-it,ii 200 nil in each esperimeiit, are shown in Table XI. Economical Evaluation
veri appro\imate economical eraluatioii htudy of this research was made on the three niaiii procedures applied, the recovery of potassium sulfate by: Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1 , 1973
73
I liter bitlern starting malerial containing
Table XII. Results Obtained in Three Procedures Applied for Potassium Recovery Bittern or brine K content, s/l.
Procedure
Multiple-batch treatment recovery from seawater Recovery from bittern solutions Multiple-batch treatment recovery from bittern solutions
Dercaled bittern or brine K content, g/l.
Addition of iOOml. H3PO4(9090 NH40H (25%)
Potosrium recovered from flitrate g
%
7.2
6.3
1.6
22.22
15 0
10.0
4.0
26.67
15 0
10.0
6.4
42.67
Lkroaling wilh ammmium phosphate
I
Addition o f gypaum (treated wilh H2SOd
A I
Filtration
Recycled 3 timer wilh fresh gypsum
Filtrate
Table XIII. Approximate Possible Production and Value of K2S04 Bittern discharged, Year
I./v
KzSO4 produced, tons/yr
1980 1990
200.45 X lo8 532.10 X lo8
2.859 X 1Oj 7.589 X lo5
Product value,
11.2622 X lo6 29.8947 X lo6
birr
Table XIV. Estimated Amounts of Product, By-Product, and Main Raw Materials Year
Estd production, tons
Estd consumption, tons
KxS04
NH40H
MgNH4POa
HaPo4
2.869 X 10 023 X 22.801 X 3 508 X 1Oj 105 106 106 1990 7 589 X 26.605 X 60.526 X 9.296 X 105 106 105 106 Present local commercial prices/ton Liquid ammonia (not less than 98YG) $36 Phosphoric acid (lOOYGacid) $120 $58 Potassium sulfate (52% K20) Magnesium ammonium phosphate $42 (calculated) 1980
Multiple-batch treatments from seawater Recovery from bitt'ern solutions Multiple-batch treatment's from bittern solutions Table XI1 summarizes the results obtained in each of these three cases (K content of descaled bittern, 10.7 g/L, was approximated to 10 g/l. for approximate evaluation purposes. From this table, it seems obvious t h a t the maximum recovery of potassium occurs in multiple-batch treatment recovery from bittern solutions; hence, the economical evaluation is based on the res1 ilts of this procedure. Figure 1 summarizes the procedure applied. From this figure and from the average daily distillate, the feed water required, and the brine discharge estimations referred to earlier, i t is possible to calculate the approximate possible production of potassium sulfate and a rough manufacturing value of the product (Table XIII). Most of the materials involved in t'his process are locally available, and some are, in fact, waste materials and are disposed of. The starting material (bittern solution) is thrown back to the sea, and t'he locally produced gypsum which proves t o be satisfactory is produced in large quantities and also thrown back to the sea. Sulfuric acid, though used in 74
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1, 1973
500 ml
Digestion with Hfl B filtration
I Filtrate
Residue
6 . 4 ~ polarsium .
Figure 1 . Schematic representation of procedure applied
small quantities, is also locally produced in large quantities. For the descaling with ammonium phosphate, use was made of orthophosphoric acid and ammonia. Though the laboratory reagent grade of these two reagents has been used in this work, the commercial grade could be successfully used in a pilot plant production. Estimations of the consumption of ammonia and phosphoric acid and the latter's high cost might make i t reasonable to think of a plant for the production of phosphoric acid. Ammonia is already produced on commercial scale locally. The sales of the by-product fertilizer magnesium ammonium phosphate would support the cost of such a plant. If we consider the present commercial high prices of the main raw materials (descaling agent) and take no account of the value of the distillate potable water, the product of this recovery (potassium sulfate) and the by-product fertilizer (magnesium ammonium phosphate) would be costly and would not compete with the prices of the conventional farm fertilizer. Table XIV indicates the estimated amounts of the product, by-product, and the main raw materials used in their production for the estimated 113 mgd (1980) and the 300 mgd (1990) distillates. A simple calculation with the prices in Table XIV shows that even large-scale production does not seem to make the process economical (Dunseth and Salutsky, 1964). The cost of phosphoric acid is the main reason for the high cost of the products. Perhaps local production of this main raw material would decrease the cost considerably. Improvement of the technique to recover a higher percentage of the potassium content of the bittern solution and recycling of the phosphate in the descaling process might help to make production more economical. Dunseth and Salutsky (1964) recommended the construction of a phosphoric acid plant for descaling of amounts of over 10 mgd of seawater. When hundreds of millions of gallons per day of seawater are being descaled in Kuwait,
obviously, a phosphoric acid plant would be of more use and is highly recommended. Acknowledgment
The authors express their appreciat,iont o Tom G. Temperley, Shuwaikh Distillation Plant, for fruitful discussions and use of personal 1iterat)ure; t o all who assisted in t’his work; and to the Kuwait Chemical Fertilizer Co. for providing commercial prices of raw material and products. literature Cited
Board of Planning, Preliminary Report,, State of Kuwait, May 1970.
Butt, J . B., Tallmadge, J. A,, Savage, H. R., Chem. Eng. Progr., 60 (ll),50-55 (1964).
Chem. Eng. A’ewa, “Chemistry and the Oceans,” 12A (1967). Dunseth, M. G., Salutsky, &I. L., Ind. Eng. Chcm., 56 (6), 55-61 (1964). Salutsky, M. L., Di Luzio, F. C., Gillam, W. S., Leiserson, L., Research and Development Progress Report No. 137, U.S. Department, of the Interior, July 196,5. Tallmadge, J. A., Butt, J. B., Solomon, H. ,J., Znd. Eng. Chem., 56 17). 44-65 11964). Temperiky, T. G., Co&os. Sci., 5 , 581-89 (1965,). Temperley, T. G., Amar. Water R o r k s Ass., 57 (4), 416-22 (1965b). Thorp, H. W., Gilpin, W. C., International Chemical Engineering, summary of paper read a t the Chemical Engineering Group, S.C.I., 553-55 (1949). Vogel, .4.I., “A Textbook of Quantitative Inorganic Analysis,” 3rd ed., p 561, Wiley, New York, N.Y., 1968.
E ~ E C E I V E D for review July 8, 1971 ACCEPTED October 25, 1972
Perchlorate Degradation of Ethyl Oleate in Solid Propellants Alfred G. Smeeth* Chemistry Department, The City LTniversity, St. John Street, London, E.C.1, England
Glraham J. Spickernell The Explosives Research and Development Establishment, -1linistrg of Defence, Wallham Ahhey, Essex, England
John Warren Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, S.E.1, England
Plastic rocket propellant of the polyisobutene-ammonium perchlorate type undergoes a physical aging on long-term storage. Chemical, infrared, and chromatographic studies show that the oleate ester wetting agent used in propellant manufacture undergoes oxidation upon storage of the propellant. This oxidative degradation of the wetting agent i s correlated with the aging of the propellant. The addition of a few percent.of antioxidant inhibits the oxidation of the oleate function, and propellant formulated with wetting agent treated with antioxidant ages to a lesser extent than that formulated with untreated wetting agent.
w h e n plastic propellant is stored under hot or humid conditions, i t undergoes a n aging process result’ing in increases in strength and modulus: and a decrease in extensibility. A large proportion of this effect may be reversed by reworking t h e propellant’, but a pro’port’ionof the decrease in extensibility is irreversible. One possible cause of this permanent aging was investigated. The cc~mpositioncontained 10% of polyisobutene (mol wt, 40,000; viscosit,y, 500,000 P), 89% of finely divided ammonium perchlorate crystals, and 1% of a surfaceactire agent S101. This surfactant is a mixture of three surface-active substances: ethyl oleate, pentaerythritol dioleat’e,and sodium di-2-ethyl hexyl sulphosuccinate. Experimental
Preliminary Investigation of Aging Phenomenon. Irreversible aging might be caused by oxidat’iori of the surfactant. Each component of t’hesurfactant was stored separately with arid without ammonium perchlorate (specific surface area, S = 188 cm2/em3) for three days at 100OC. The organic material was then extracted with chloroform which was dis-
tilled off a t reduced pressure. Only the pentaerythritol dioleate and ethyl oleate showed alteration of physical properties, their colors darkening and viscosities great’ly increasing. This occurred both with t h e samples which had been in contact with ammonium perchlorate and air and with those stored in air alone. Stability Tests of Ethyl Oleate. Since ethyl oleate a n d pentaerythritol dioleate are similar in nature, only the oxidation of ethyl oleate was investigated. Four experiments were carried out t o establish whether oxidation was occurring and whether it was due t o air and/or ammonium perchlorate. I n two cases, 0.1 gram of ethyl oleate was intimately mixed with 4 grams of ammonium perchlorate (SO= 188 cm2/cni3) and stored for 68 hr a t 60°C: under nitrogen and under air. 111two other similar experiments, the ammonium perelllorate was replaced by 15 grams of glass ballotiiii (SO= 63 cm2/cm3)t o give a n inert surface the same in area as the ammonium perchlorate. The organic residues were then extracted with chloroform, and t h e iodine values determined (Kline, 1962). Table I lists the results, indicating Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1, 1973
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