Table V.
Although less work was done with a Canadian pollucite ore sample (26% Cs), it responded as well to treatment, and processing costs should be about equal for Bikita ore.
Estimated Chemical Reagent Costs for Cesium Recovery from Pollucite Ore
Assumptions. Bikita pollucite ore (-25% cesium); roast flux of 2 parts of NaC1 and 1 part of Na2COa per part of ore; solvent extraction with carbonate stripping; over-all recovery of 96y0 Chemical
NaCl Na2CO3 Tartaric acid CO* HCI BAMBP
Consumption
Roasting Roasting Scrubbing Stripping Strimina Soli6le Toss to aqueous” Entrainment and spillageb
Consumption, Lb./Lb. Cs 8.7
4.4 0.023 0.24 0.015 0.006
Unit Cost, Cost: i/Lb. b/Lb. Cs
1.1 2.5
9.2 10.6
45 5 7.5 500
1. o 1.2 0.1 3.0
Organic 0,0038 gal. $10,75/gal. 4 . 1 phase Total 29.2 Loss of B A M B P to aqueous phase assumed to be 0.7 gram per liter of raflnate (measured losses in continuous run were considerably 1ouNer than thii ~
value. Solvent loss by entrainment and spillage assumed to be 0 . 0 ~ 5 7 ~ of raJinate uolume.
the run contained 163 grams of cesium and only 0.012 gram of rubidium per liter (Table IV). Total alkali metal impurities, based on cesium, amounted to 0.008%. Separations from silica, iron, and aluminum were also highly effective, the product solution containing negligible amounts of these and other contaminants. Evaporation of the carbonate strip solution to dryness gave a white crystalline product which was a mixture of cesium carbonate and cesium bicarbonate. Drying these solids for 1 hour at 430’ C. produced nearly all normal cesium carbonate-a convenient source of other cesium salts. OTHERPHENOLSA S EXTRACTS.Attempts to demonstrate the process with 1 M Santophen-1 in 50Y0 kerosine-50% Solvesso 100 diluent were not successful. T h e cesiumSantophen-1 complex has a limited solubility in this diluent. I t precipitated in the top extraction stages and in the scrub system, causing severe emulsions. Santophen-1 seems to be usable in trichloroethylene diluent, but this observation needs confirmation in continuous countercurrent tests. CHEMICAL REAGENT COSTS. Total chemical reagent costs for recovering cesium as cesium carbonate from Bikita pollucite ore of the grade studied (about 257, Cs) are estimated at about 29 cents per pound of cesium recovered (Table V). About 7001, of this cost is for roasting chemicals, and about 25% is for the loss of BAMBP, which was priced, for this study, a t $5 a pound. This high price would be appreciably reduced with large scale use of the process.
R ubidi u m Recovery Rubidium occurs in minerals as a replacement for other alkali metals and is n o t ’ a major constituent in any knoivn mineral. Alkarb (Table 111), which contains about 2054 rubidium and is readily solubla in bvater to the extent of 600 grams per liter, is a good source of rubidium. z41so. pollucite leach liquors might contain as much as 1 gram of rubidium per liter. Rubidium can be recovered from both of these sources by the Phenex process. A higher p H is required for efficient rubidium extraction than for cesium extraction. it’ith 1 M BAMBP in kerosine, coefficients for extraction of rubidium from Alkarb solutions are about 0.9 at p H 13.5 and 1.2 a t p H 14. More concentrated phenol solutions will> of course, give more efficient extraction. T h e coextraction of cesium and rubidium a t a p H of about 13.5: follo\ced by selective stripping of rubidium from the solvent to separate it from cesium, probably is the most attractive route for recovering cesium and rubidium from Alkarb. From pollucite liquors, it \could probably be best to raise the p H of the raffinate from the cesium extraction and to recover the rubidium in a second extraction cycle. Acknowledgment
T h e authors thank \V. B. Howerton and L. Ramos Salvador, Ivho assisted in the studies, and T. C. Rains and M. Ferguson of the O R S L Analytical Division for flame photometric analyses. literature Cited
(1) Berthold, C. E., . I . Metals 14, 355 (1962). (2) Can. Chem. Process. 45, 78 (October 1961). (3) Chem. Eng. .j-eres 41, 85 (Sept. 30, 1963). (4) Ibid., p. 34 (Dec. 23, 1963). (5) Chem. TleeX 89, 57 (Dec. 2. 1961). (6) Egan, B. Z., Zingaro, R. A , ? Benjamin, B. M., Oak Ridge National Laboratory. “Extraction of Alkali Metals by Substituted Phenols,” unpublished data. (7) Horner, D. E., Crouse, D. J.; Brown, K. B.; it’eaver, B.; .Vucl. Sci. E m . 17. 234 11963). (8) Parsons, H”. iV’., Vegina, ’J. A,. Simard, R., Smith. H. W., Can. M e t . Quart. 2, 1 (1963). (9) Perelman. F. M., Technical Documents Liaison Office, Unedited Rough Draft Translation NP-tr-783. (10) Plvushchev. V. E.. Shakhno. I. V.. Izuest. Vvsshtkh C’chebn. ‘ Zauedenit. Khim. t Khim. Tekhnol. 1958, No. 6,‘54-60; C. A . 53, 126000 (1959). (11) U. S. Dept. Interior, Bur. Mines Bull. 585, 177 (1960). RECEIVED for review September 25, 1964 ACCEPTED March 19. 1965 Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corp.
INITIAL KINETIC STUDY OF UREA ADDUCTION WITH n-OCTANE, n-DECANE AND n-DODECANE L EPARATION
. E.
LA HT I
A ND F
processes are of vital importance to chemical
S technology and hence new methods attract great interest. O n e such recent method is adduction. Urea adducts are not formed by chemical reaction but should be considered as inclusion compounds (7, 3, 70, 73, 75). Inclusion compounds I present chemical ~ University, Lafayette, Ind.
254
~~
~ ~purdue
l&EC PROCESS DESIGN A N D DEVELOPMENT
. S. MANNING,
Carnegie Institute of Technology, Pittsburgh, Pa.
have been described as “combinations of complete organic molecules that are united spatially, leaving unaffected the bonding systems of the components” (7). Inclusion occurs when one compound, the “host,” because of its peculiar stereochemical properties or polarity, spatially encloses a second molecule, the “guest.” A wide background. of information on stoichiometry, data i ~ yields, ~Purity, ~ ~ ~ ~and ~thermodynamic ~ ~ i of~urea ~ adducts exists; however, very few kinetic data are available.
~
~
Solutions of kiiown concentrations of urea in ethanol and of n-octane, n-decane, or n-dodecane in ethanol were passed through a diverging tubular reactor. Adduct precipitation rates of urea with the n-alkane were computed from the steady-state temperature profiles as measured b y thermocouples. This preliminary work indicates that these reactions are exceedingly f a ~ t - 9 9 7 ~ complete in a fraction of a second-and that precipita#tionexhibited first-order growth rates. Nucleation and solution temperatures of solutions containing prepared concentrations of urea and n-alkane in ethanol and in 25y0 methanol-75yo propanol mixtures were also measured.
For urea-paraffin adducts. the mole ratio of urea to paraffin has been correlated by (6): m =: 0.653 n
+ 1.51
(1
Calorimetric determinations suggest that the exothermic heat of formation, AH, is linearly related to mole ratio, m (6) : -AH (kcal. 'mole adduct)
=
-6.5
+ 2.37m
(2)
h4cPldie and Frost (,?) found that formation curves of urea n-octane adducts from gaseous n-octane and solid urea were of the sigmoid type charac1.eristic of crystal groivth processes. No long induction periods Lvere noted and it appeared that the rate \vas not controlled by the formation of the surface lay-er of the crystal. Increasing temperature lengthened the induction periods, ~vhilethe rates in the linear portion of the formation curve decreased. Ho\vever. it appears from the heterogeneous system used that mass transfer might be controlling. 'The present rvork is an initial attempt to study these ureaparaffin adduct reactioris under conditions \\.here mass transfer effects are negligible. 'To this end, a common solvent is used for both the urea and the hydrocarbon solutions and these solutions are mixed an order of magnitude more rapidly than they can react. Roughton's thermal technique ( 7 7 ) is used to follo\v the extent of reaction. Equilibrium concentration data were obtained for all adducts investigated: urea adducts of n-octane. n-decane. and n-dodecane. Theory
Crystallization involves two distinct processes : nucleation and growth. I n pract.ice. nucleation and grolvth cannot be separated ; hoivever, a t 101s degrees of supersaturation, the crystal growth rate is apparently the largest factor. Berthoud and Valeton (8, 7-1) suggested that crystallization occurs by t\vo steps-viz.. a diffusion process, whereby solute molecules are transported from the bulk of the fluid phase to the solid surface. follo\ved by a first-order "reaction" Lvhen the solute molecules arrange themselves into the crystal lattice. Mathematically
Urea adduction involves the following equilibria : Urea (s) S urea (d)
(7)
Paraffin (1) S paraffin id)
18)
+ paraffin (d)
adduct (s) (9) where s? 1, and d refer to the solid. liquid, and dissolved phases. respectively. Redlich et ai. (70) and Terres and Siir (73) have measured equilibrium constants for adduct dissociation---Le., adduct (s) S u r e a (s) paraffin ( d ) . Terres and Sur (73) rcport that adduct formation proceeds a t a n increased rate if the urea and paraffin reactants are dissolved in a homogeneous solution. I n fact. they defined a special reaction constant for the homogeneous reaction brtbvcen dissolved urra and dissolved paraffin to form dissolved adduct. Hoivever. the concept of dissolved adduct molecules in a liquid solution is hard to accept, and if such a n ecluilibrillm step \sere to control. it should be possible to observe a large heat effect by merely mixing the reactants Lvithout forming a solid phase-i.e.. below equilibrium concentrations. Equation 6 may be modified to describe adduct formation without postulating that dissolved adduct molec~ilrs exist. Using a mass balance the concentration driving force term can be expressed in terms, of solid adduct formed instead of concentrations of reactant in solution. m Urea (d)
+
where the rate parameter. K,. describes the entire complicated adduct precipitation process and hence is a function of all experimental conditions under tvhich addiiction occurs. Integration of Equation 11 yields In (1 - C,4 ' C A f ) = K,It
ill)
Equipment and Procedure
Experimental equipment and procedure are described briefly? as further details are available elsexvhere ( I). and
dCc
- :=
dt
k,A (C, - C*)
(4)
T h e assumption of a first-order surface is questionable. M a n y inorganic salts crystallizing from aqueous solutions have shoxvn first-order rates but others have exhibited second-order reactions. I t is felt that k, varies from face to face on a crystal. but it is virtually impossible to measure this variation (8. page 1 17). Values of kd can also vary for different faces of the same crystal. as Berg's refractive index measurements shoiv ( 2 ) . I n practice, the interracial concentration is difficult to measure and hence is eliminated by considering a n over-all concentration driving force, (C - C*),
Solubility Measurements. Samples of desired concentrations were prepared by placing weighed quantities of urra, hydrocarbon. and ethanol in srnall ampoule bottles. which were then attached to the rotating shaft as shown in Figure 1 , A calibrated thermometer was placed in an alcohol-filled test tube, fitted rvith a stopper. which in turn \vas attached to thc shaft. hfising and niicleation in the samples \vert achieved by inclusion of a 4-inch Raschig ring and crushed glass particles in each bottle. Shaft rotation \vas begun and the adduct in the samples precipitated by adding cold ~ v a t e rto the bath. \Varm \Yarer \vas then alloived to flow through the bath so as to give a temperature rise of 10' C. per hoiir in the samples. T h e temperature a t which thr solid phaqc almo5t disappeared \ "C. 23.8 23 8 22 9 22 9 24 0 23 0 22 8 23 2 23 2 23 2 24 2 24 2 24.7 24.7 24.6 24.6 25.5 26.0 25.4 25.0
ethanol-hydrocarbon !systems to urea adduction runs, and because of the corrosive nature of acid-base systems, mixing chamber efficiencies were determined thereafter by mixing ethanol with the paraffins. An extensive search revealed that very few common solvents for urea and the normal paraffins exist. Absolute ethanol and a mixture of 25% methanol-757, propanol by volume worked satisfactorily for the C+2ln range. Figure 5 summarizes the solubility data for the urea-n-dodecane system. Similar curves ivere obtained for the urea-n-octane and urea-n-decane systems (4). Certain minimum concentrations of both guest and host are clearly required for adduct crystallization. Seeding of the urea-ethanol solution with some previously prepared adduct crystals caused adduct precipitation to occur a t slightly lower concentrations. T h e effect of various additives on
I
I
I
EQUILIBRIUM CURVES SYSTEM : n-DODECANE -UREA IN E T H A N O L
24
c
\
r
Feed Flou Rates, Lb./Sec. Parajin C'rea
Initial Concentrations, Moles/Liter Parajin Urea
0.0132 0 0094 0 0169 0 0169 0 0094 0 0091 0 0114 0 0160 0 0171 0 0224 0 0110 0 0133 0.0134 0,0095 0.0195 0.0095 0.0173 0.0134 0.0211 0.0172
1.241 1 179 1 275 1 163 0 899 0 771 0 738 0 7x7 0 832 0 861 0 789 0 831 0.536 0.534 0.575 0.570 0.830 0.720 0.723 0,743
0.0176 0 0137 0 0214 0 0253 0 0137 0 0095 0 0129 0 0176 0 0176 0 0214 0 0126 0 0137 0.0137 0.0099 0.0199 0.0099 0.0146 0.0138 0.0215 0.0145
0.325 0 339 0 329 0 353 0 402 3 347 0 362 0 0 0 0 0
757
381 330 362 345 0.345 0.347 0.344 0.347 0.300 0 332
0,331 0.298
adduction rates were investigated qualitatively. Water should not be present in these solutions, as it decomposes the precipitate. Detergents catalyze the reaction, while dyes-e.g., bromocresol green-methyl red indicator-inhibit the reaction rate (4). Table I1 summarizes the operating data for all the kinetic runs, while the computed changes of adduct concentration with time are presented in Table 111. (Some points are omitted, for brevity.) Figure 6, which presents the variation of In (1 - CAiCA,) for the n-dodecane runs, is typical of all the runs. Runs 15 and 16 indicate that variation of flow velocity had no significant effect on the rate. Endothermic heats of mixing for ethanol and the normal paraffins were of the order of 100 cal per mole of mixture. Negligibly small, exothermic heat effects were observed M hen reactants of nearly equilibrium concentrations were mixed-
1
I
I
I
1
I
S Y S T E M : n-DODECANE-UREA IN SOLVENT
20-
8 c
3
Y
ya
16-
0 W
D
RUN
12C
#
ACC 0.3!
0.3! 3.0
3.0 3.6
8-
2.9,
3.I 0.6
UREA (wt. Ye) Figure 5. Typical equilibrium curves
,
0
.I
.2
.3
.4
.5
TIME (secl Figure 6. Variation of adduct concentration with time VOL. 4
NO. 3
JULY 1 9 6 5
257
Table 111.
Run NO. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
ACo, 70 1 75 2 4 3 6 4.1 2.0 0.95 1.95 1.8 2.5 1.6 0.3 0.5 0.35 0 35 3 0 3 0 3.6 2.9 3.1 0.6
CA,mole/ liter
t , sec.
0 0005 0 0006 0 0006
0 007 0 009 0 006 0.005 0.009 0.012 0.009 0.007 0.006 0.005 0.009 0.008
0.0005 0.0002 0.0004 0.0003 0.0004 0.0006 0.0004 0,0005 0.0004 0.0003 0 0003 0 0004 0 0003 0.0003 0.0004 0,0005 0.0003
Computed Results for Kinetic Runs Computed Adduct Concentrations at Computed Residence Time CA, mole/ C,, mole/ liter t , sec. liter t , sec. 0 094 0 0057 0 036 0 0087 0 0085 0 048 0 0112 0 126 0 0071 0 028 0 0087 0 076
0.008
0 011 0 006 0 011 0.007 0.008 0.005 0.007
0.0098 0.0040 0.0043 0,0049 0.0054 0.0095 0,0056 0,0037 0.0036 0.0016 0 0045 0 0070 0 0056 0.0052 0.0071 0.0108 0.0018
0.026 0.047 0.059 0.045 0.033 0.032 0.025 0,047 0.041 0.041 0 057 0 028 0 057 0,035 0.041 0.026 0,035
Le., no crystallization occurring. This evidence discredits the concept of adduct molecules existing in solution. Table 111 shows how fast the over-all crystallization is-the runs were completed in less than 1 second. These completion times are in strong contrast to the minutes and hours reported by previous investigators (5, 75) who worked with heterogeneous systems. Figure 6 shows that the adduct precipitation rate may be described qualitatively by Equation 11. T h e degree of supersaturation present a t the beginning of a run may be estimated, qualitatively a t least, by AC,. which is defined as the hydrocarbon concentration initially present minus the equilibrium value for the particular urea concentration present. T h e parameter, AC,, may be considered to be a n empirical measure of the over-all driving force for adduct crystallization. Values of ACo were obtained from plots illustrated by Figure 5. A qualitative comparison of the n-octane, n-decane, and n-dodecane runs suggested that the smaller the hydrocarbon, the faster the adduction rate. Nomenclature
A
= total surface area of adduct crystals
solute concentration in liquid phase cc* = = equilibrium saturation concentration of solute ci = solute concentration in liquid phase a t crystal-solution interface
= concentration of solid adduct in slurry = concentration of crystals in slurry CAf = adduct concentration at completion of reaction
CA
c,
AGO = paraffin concentration in excess of equilibrium value, AH = heat of formation K = over-all mass transfer coefficient
0.0106 0.0041 0.0052 0.0059 0.0070 0.0124 0.0078 0.0080 0.0058 0 0048 0 0066 0 0072 0 0058 0.0061 0.0082 0.0108 0.0063
C A I mole/ liter 0 0087
0 0112 0 0087 0.0106 0.0046 0.0070 0,0061 0.0070 0.0124 0.0078 0.0090 0.0080 0.0059 0 0066 0 0072 0 0058 0.0061 0.0082 0.0108 0.0065
0.069 0.126 0.157 0.120 0.087 0.084 0.066 0.494 0.108 0.431 0 151 0 075 0 151 0.093 0.109 0,069 0.369
t, sec. 0 376 0 501 0 301 0.274 0.502 0,626 0.478 0.348 0.335 0.264 2.63 0.43 2.29 0 602 0 297 0 601 0,371 0.434 0.277 1.965
K,
= over-all rate parameter for adduct crystallization
kd k, rn n t
=
mass transfer coefficient due to diffusion
= rate constant for surface reaction = moles of urea per mole of paraffin in adduct crystal = number of carbon atoms in n-paraffin =
time
literature Cited
(1) Baron, M., Org. Chem. Bull. 29 (2), 1 ; (3), 1 (1957). (2) Berg, i V . F., Proc. Roy. Soc. A164, 79 (1938). (3) Kobe, K. A4., Domask, W. G., Petrol. Rejner 31 (3), 106; (S), 151 ; (7), 125 (1952). (4) Lahti, L. E., Ph.D. thesis, Carnegie Institute of Technology, Pittsburgh, Pa. (5) McAdie, H. G., Frost, G. B., Can. J . Chem. 36, 635 (1358). (6) McLaughlin, R. L., “Chemistry of Petroleum Hydrocarbons,” Vol. 1, pp. 241-74, Brooks, ed., Reinhold, New York, 1954. (7) Martinette, M., Sr., “Clathrate Inclusion Compounds,” Reinhold, New York, 1962. (8) Mullin, J. W., “Crystallization,” Butterworth, London, 1961. (9) Perry. J. H.. ed., “Chemical Engineer’s Handbook?” 3rd ed., McGraw-Hill, New York, 1950. (10) Redlich, O., Gable, C. M., Dunlop, A. K., Miller, R. I\-., J . A m . Chem. 5’06. 72, 4153 (1950). (11) Roughton, F. J . W., Z . Eltckrochem. 64, 1 (1960). (12) Swern, D., Division of Petroleum Chemistry, Symposium on Advances in Separations of Hydrocarbons and Related Compounds, 126th Meeting, ACS? New York, N. Y., September 1954. (13) Terres, V. E., Sur, S. N., BrmnstofChem. 38, 330 (1957). (14) Van Hook, A , “Crystallization. Theory and Practice,” Reinhold. New York. 1961. (15) Zimmerschied, W. J., Dinerstein, R. A . . Weitkamp, A . W., Marscher, R. F., Znd. Eng. Chem. 42, 1300 (1950).
yo RECEIVED for review December 7, 1964 ACCEPTED April 9, 1965
CHLORATE ETCHANT SYSTEMS FOR COPPER BA R R
Y MILLER AND T
. D.
N PROCESSES involving
S C H L A B A C H , Bell Telejhone Laboratories, Znc., Murray Hill, N . J .
chemical etching of a patterned film copper-e.g., printed circuitry and photoengravingcontinued interest exists in extending the capacity and increasing the control of dissolution rate of etchant baths. Such improved capabilities must be compatible with process requirements in areas of undercutting, recovery and regeneration of materials, and, in circuit board technology, contamina-
I of
258
l & E C PROCESS D E S I G N A N D D E V E L O P M E N T
tion and degradation of organic substrates. Improved control and capacity in systems found satisfactory for printed wiring applications are described. Black and Cutler ( 7 ) and Sharpe and Garn (5) reported the successful use of cupric chloride as a copper etchant via the reaction, in excess chloride, Cu(1I) C u o = 2Cu(I). T h e equilibrium constant is very favorable in sufficient chloride,
+
