Ind. Eng. Chem. Res. 1989,28, 1557-1562
1557
Happel, J.; Blank, H.; Hamill, T. D. Dehydrogenation of Butane and Butenes over Chrome-Alumina Catalyst. Znd. Eng. Chen. Fun-
6 = A H / ( c 'To) t = E/(Rfi) 6 = TITO
dam. 1966,5,289-294. Itoh, N. A Membrane Reactor using Palladium. AZChE J. 1987,33,
Subscripts C = reactant of dehydrogenation D = product of dehydrogenation H = hydrogen i = component i in the reaction side stream I = inert j = component j in the separation side stream 0 = oxygen p = permeation r = reaction side s = separation side W = water 0 = indicate T = To Superscript 0 = indicate value at inlet condition Registry No. Pd, 7440-05-3; HP,1333-74-0;1-butene, 106-989; butadiene, 106-99-0.
Literature Cited Antonson, C. R.; Gardner, R. J.; King, C. F.; KO, D. Y. Analysis of Gas Separation by Permeation in Hollow Fibers. Znd. Eng.Chem.
Process Des. Dev. 1977,16,463-469. Gryaznov, V. M. Hydrogen Permeable Palladium Membrane Catalyst. Platinum Metals Rev. 1986,30(2), 68-72. Gryaznov, V.M.; Smirnov, V. S.; Slinko, G. Heterogeneous Catalysis with Reagent Transfer through the Selectively Permeable Catalyst. Catalysis; Hightower, J. W., Eds.; American Elsevier: New York, 1973.
1576-1578. Itoh, N. Presented at The University of Cincinatti, Cincinnati OH,
45221,1988. Itoh, N.; Shindo, Y.; Haraya, K.; Obata K.; Yoshitome, H. Simulation of a Reac )r Accompanied by S, paration. Znt. Chem. Eng.
1985,25,138-142. Leder, H.; Butt, J. B. Surface Catalysis of Hydrogen-Oxygen Reaction on Platinum a t Low Temperature. AIChE J . 1966, 12,
718-728. Mohan, K.; Govind, R. Analysis of a Cocurrent Membrane Reactor.
AZChE J . 1986,32(12),2083-2086. Mohan, K.; Govind, R. Analysis of Equilibrium Shift in Isothermal Reactor with a Permselective Wall. AZChE J . 1988a, 34(9),
1493-1503. Mohan, K.; Govind, R. Effect of Temperature on Equilibrium Shift in Reactors with a Permselective Wall. Ind. Eng. Chem. 1988b,
27, 2604-2614. Shinji, 0.; Misonou, M.; Yoneda, Y. The Dehydrogenation of Cyclohexane by the Use of a Porous-glass Reactor. Bull. Chem. SOC.
Jpn. 1982,55,2760-2764. *To whom correspondence concerning this article should be addressed. Previously with National Chemical Laboratory for Industry, Tsukuba Science City, 305 Japan.
N.Itoh: R.Govind* Department of Chemical Engineering University of Cincinnati Cincinnati, Ohio 45221 Received for reuiew September 26, 1988 Revised manuscript received June 16,1989 Accepted July 6, 1989
Extraction of Nickel(I1) from Sulfate Solutions by Bis(2-ethylhexy1)phosphoric Acid Dissolved in Kerosene T h e extraction of Ni(I1) from 0.5 M aqueous sulfate medium by bis(2-ethylhexy1)phosphoricacid (HDEHP) dissolved in kerosene has been studied a t 25 "C as a function of the total extractant concentration, equilibrium p H value, and total metal concentration in the aqueous phase. T h e distribution data have been analyzed both graphically and numerically. T h e results have shown that the species extracted into the organic phase have the composition NiR2(HR)3and NiR2(HR)4. The stability constants of HS04-,NaS04-, and NiS04 in sulfate solutions have also been estimated from the extraction data.
Bis(2-ethylhexy1)phosphoric acid (abbreviated as HDEHP or simply HR) has been extensively studied as an extractant reagent in hydrometallurgical processes for the separation and purification of a number of metals. It is able to extract first-row transition metals such as copper, cobalt, nickel, and zinc, as well as uranium and rare earths in familiar nuclear fuel reprocessing, in a wide range of operating conditions (Sekine and Hasegawa, 1977;Ritcey and Ashbrook, 1984;Huang and Juang, 1985, 1986a,b; Huang and Huang, 1987,1988). The extraction of nickel with HDEHP was investigated by many investigators. Madigan (1960)studied the separation of nickel between an aqueous sulfate solution and a solution of HDEHP in kerosene, and proposed that the NiR2 compounds were formed in the organic phase. Brisk and McManamey (1969) and Smelov and Chubukov (1973),working in both sulfate and nitrate media, found that a single dimeric acid molecule was formed in the extracted species under a vqiety of aliphatic and aromatic diluents. Grimm and KolGik (1974)and Komasawa et al.
(1981),using both aliphatic and aromatic diluents, explained the extraction of Ni2+ from nitrate medium by assuming the formation of NiR2(HR)4. Sat0 and Nakamura (1972)proposed the formation of NiR2(H20)2after spectroscopic studies on the solid compound obtained by loading of the metal in the organic phase. Komasawa et al. (1984)studied the effect of diluents on extraction from nitrate media and showed the existence of NiR2(HR)2 formed in alcohol diluents and NiR2(HR)4 formed in nonpolar or weak polar diluents. Fernlndez et al. (1985) worked in aqueous nitrate solutions and toluene diluents and proposed the formation of NiR2(HR)2 and NiRz species within the organic phase in the low pH range. Further experimental studies are necessary in order to clarify the uncertainties regarding species composition. In this work, the extraction of nickel by HDEHP is studied in detail to determine the composition of the extracted species of nickel in the organic phase consisting of HDEHP in kerosene. To get a complete understanding of the system, the extraction of nickel was studied first by slope
0888-5885189J 2628-1557$01.50/0 0 1989 American Chemical Society
1558 Ind. Eng. Chem. Res., Vol. 28, No. 10, 1989
analysis, which assumed no complexes to be formed in the aqueous phase. Then, by numerical analysis of the data, the values for the stability constants of the HSO,, NaS04-, and NiS04 complexes in the aqueous sulfate solutions can be obtained.
Experimental Section Reagents and Solutions. Bis(2-ethylhexy1)phosphoric acid used in this work was the product of Daihachi Chemical Ind. Co., Ltd., Osaka, Japan, with a purity of approximately 95%. It was precipitated as a copper complex from toluene and acetone solution and then dissolved in toluene and a 4 M sulfuric acid solution, following the procedure of McDowell et al. (1976). Kerosene (density = 0.7854 g/mL, boiling range = 200-250 "C), used as a diluent, was supplied by Chinese Petroleum Co., Taiwan, and washed twice with 1/5 volume of 98% H2S04to remove aromatics and then with distilled water until it was neutral (Sato, 1965). The other inorganic chemicals were of analytical reagent grade supplied by Hayashi Pure Chemical Ind., Ltd., Osaka, Japan. Metal solutions were always prepared by weighing the appropriate volumes of the stock solution and making up with diluent. Procedure. Twenty milliliters of the organic solution and an equal volume of aqueous solution were mixed in glass flasks with ground-glass stoppers and shaken by a mechanical shaker for at least 30 min at 25.0 f 0.2 "C until equilibrium was attained. A preliminary experiment had shown the reaction time needed to reach equilibrium to be less than 15 min. The organic solutions contained a 0.01-0.35 M monomeric form of HDEHP dissolved in kerosene. The aqueous-phase composition consisted of 0.5 M (Na+,H+,Ni2+)SOd2-. The total anion concentrations were kept constant. The concentrations of nickel ion in the initial aqueous solutions ranged from 1.0 x to 1.0 X low2M. The two phases were separated after they had been allowed to settle for 4 h in a thermostat at 25.0 f 0.2 "C. After phase separation, the equilibrium hydrogen ion concentration was measured with a pH meter. The concentration of nickel was measured with an IL-551 atomic absorption spectrophotometer (Instrumentation Laboratory Inc.) at a wavelength of 232.0 nm, coupled with background correction. Nickel in the organic phases was stripped with sulfuric acid, and the metal concentration in the acidic solutions was analyzed by AAS. The process was proved to be quantitative, and the mass balance for the metal was always fulfilled in the extraction-stripping procedure to within f 2 % . Results and Discussion Extraction Equilibrium of Nickel. The metal complex of HDEHP tends to form very large polymeric species in a fully loaded organic phase. These polymers are strongly depolymerized in the prescnce of free HDEHP molecules and ethylene glycol (Koldik and Grimm, 1976). Thus, it is necessary to assume that nickel is extracted as an m-merized complex into the slightly loaded organic phase. The extraction of Ni(I1) with HDEHP can be represented by the following general reaction:
-
mNi2++ {m(p+ q)/2)H2R2+ (NiR,(HR),),
+ mpH+
t___;
"-'35
40
50
45
PH Figure 1. Effect of pH on the extraction of nickel between 0.5 M (Na,H)S04and kerosene at 25 "C. (0) [ a ] = 5.0 X M, slope = 1.97; (0)[H,R,] = 1.0 X lo-* M, slope = 2.06. [Ni(I1)lt = 1.7 X 10-3 M.
IO+
'+I
10-2
[N[ , m o l / l Figure 2. Extraction of nickel between 0.5 M (Na,H)S04 and ke[HZR,] rosene at constant concentrations of HDEHP and 25 "C. (0) = 0.010 M; (0) = 0.025 M (A) = 0.05 M; (0) [ m ] = 0.10 M.
[m]
[a]
is the stoichiometric equilibrium constant for 0.5 M (Na,H)S04with kerosene as the diluent, and the bar indicates the species in the organic phase. The distribution ratio of nickel is defined as
D = [Ni(II)]/[Ni(II)]
(3)
Substituting eq 2 into 3, we obtain -
u=
m[(NiR,iHR),),I [Ni2+]
= mKmpq [Ni2+Im-l[ H2R2]m@+q)/2[ H+]-"P
(4)
A t constant concentrations of HDEHP and a low distribution ratio, [Ni2+]m-'[H2R2]m@+q)/2 will be approximately constant. Thus, a plot of log D versus pH will give a straight line with a slope of mp. The experimental results are shown in Figure 1. The straight lines have slopes of two, i.e., mp = 2. Thus, eq 4 can be simplified to [Ni(II)][H+I2= mKmpq [Ni2+]m[H2R2]m@+q)/2
(5)
(1)
where
A t constant concentrations of HDEHP, the degree of aggregation of the nickel-HDEHP complex in the organic phase, m, is obtained from the plot of log ([Ni(II)][H+I2) versus log [Ni2+].As shown in Figure 2, the straight lines have unit slopes. Therefore, the extracted species is mo-
Ind. Eng. Chem. Res., Vol. 28, No. 10, 1989 1559 Table I. Equilibrium Constants for the Different HDEHP Species in the 0.5 M (Na,H)SO,/HDEHP-KeroseneSystem (Huang and Juang, 1986a) reaction constant HR * R+ H+ pK, = 1.27 i 0.03 HR + HR log Kd = 3.54 0.02 - 2HR + H2Rz log Kz = 4.42 i 0.04
10-'2
/a-'
10-2
I00
I W 2 1 mol/( I
Figure 3. Effect of HDEHP concentrations on the extraction equilibrium of nickel between 0.5 M (Na,H)S04and kerosene at 25 OC. [Ni(I1)lt = 1.7 X slope = 2.70. ....
P 20
1
$ 1 ,
,
OO
4
,
,
, , I
8
12
Table 11. Results oP the Numerical Calculation for the Various Model Species, NiR.(IIR). model species (Pd log Kpq U,, a(log D) rejected' I (2,O) -8.58 max -8.35* 39.6 0.781 11 (2,1) -7.63 f 0.20' 19.3 0.545 111 (2,2) -6.68 f 0.12 6.26 0.310 0.523 0.090 IV (23) -5.73 f 0.03 V (24) -4.78 f 0.07 1.99 0.175 VI (2,5) -3.82 f 0.15 10.4 0.401 VI1 (2,6) -2.84 f 0.24 25.2 0.623 VI11 (2,7) -1.85 max -1.61 45.2 0.834 IX ( 2 8 -0.839 max -0.549 69.2 1.032 X (2,3), (2,O) 0.523 0.090 (2,O) XI ( 2 3 , (2J) 0.523 0.090 (2,l) XI1 ( 2 3 , (22) 0.523 0.090 (2,2) XI11 (2,3) -5.86 f 0.06 0.221 0.059 (24) -5.41 f 0.16 XIV (2,3) -5.78 f 0.03 0.256 0.063 (2.5) -5.01 f 0.19 -5.76 f 0.03 0.302 0.069 XV (2;3) (2,6) -4.57 f 0.23 XVI (2,3) -5.75 f 0.03 0.347 0.074 -4.16 max -3.95 (2,7) XVII (2,3) -5.75 0.03 0.387 0.078 -3.77 max -3.52 (2.8) XVIII'(2,4) -5.07 f 0.06 0.330 0.072 (22) -7.11 0.08 0.221 0.059 (2,2)
*
[~21-1/2. (i/mll"2
Figure 4. Effect of HDEHP concentrations on the extraction equilibrium of nickel between 0.5 M (Na,H)SO, and kerosene at 25 "C. [Ni(I1)lt = 1.7 X M, slope = 1.25, intercept = 3.26.
nomeric, Le., m = 1. And then, p = 2. Thus, eq 2 and 4 can be simplified to
'The species were rejected by the program because of the values of the equilibrium constants were set equal to zero. *The value after max corresponds to log [K + 3o(K)]. 'The error given corresponds to 3a(log K ) .
-
and D = K2q[a](2+q)/2[H+]-2 Rearranging eq 7, it follows that log (D) - 2pH = log (K2J + (2 + q)/2 log
[H,R,I
(7) (8)
First, it could be assumed that only species of the type NiR2(HR), - are formed. Thus, a plot of log (D[H+I2)versus log [H2R2]would give a straight line with an intercept equal to K29and a slope equal to (2 + q ) / 2 . In Figure 3, a straight line with a slope of 2.70 is obtained, i.e., q = 3.4. This implies that more than one species is formed. Next, considering two species to be formed in the organic phase, e.g., NiR2(HR)3and NiR2(HR)4,eq 3 could be expressed as
By the use of eq 6, eq 9 becomes D[H+I2 = K23[H2R2]5/2 + K24[H2R2]3
or
(10)
-
Now, a plot of D[H+I2/[H2R2l3 versus [H2R2]-1/2would give a straight line with a slope equal to K23 and an intercept equal to K24. In Figure 4, a straight line with a slope of 1.25 and a intercept of 3.26 are obtained; i.e., K23 = 1.25 x lo4 M-l12 and K24 = 3.26 X lo4 M-l. Reconfirmation of Extraction Equilibrium Formation by Computer Treatment. Numerical treatment of the data was performed by modifying the LETAGROPDISTR program (Liem, 1971) in order to apply it to the five-component system in this work. The aim of these calculations was to confirm the results obtained with the previous graphical analysis and to refine the values of the equilibrium constants. In this calculation, the computer searches for the best set of equilibrium constants that would minimize the error squares sum defined by where Dexpis the distribution ratio of nickel measured experimentally and Dcdcis the corresponding value calculated by the program obtained by solving the mass and Na+, using a balance equation for Ni2+,H2R2,Sod2-, given set of complexes and their equilibrium constants. The best model is the one that minimizes the error squares sum function and gives the lowest mean standard deviation u(log D),defined by u(log D)= (U/Np)'12 where Np is the degree of freedom.
(13)
1560 Ind. Eng. Chem. Res., Vol. 28, No. 10, 1989
log K23 = -5.86 f 0.06 and log K24= -5.41 f 0.16. @ 7 The experimental data for the above numerical calculation are given in Figures 1-3. The mass balance equation for H2R2inthe best model is given by __ [HzR2I, = W2R2I + j/zK2-1/2[HzRz]1/2 5/2KZ3[Ni2+] [m5/2[H+]-2 3KZ4[Ni2+] [H2R2]3[H+]-2(14)
+
Figure 5. Variation of U,, with the number of free monomeric HDEHP involved in the extracted species (Table 11, models I-IX). Table 111. Equilibrium Constants for Species NiR2(HR)3 a n d NiR2(HR), Calculated by Different Methods for Sulfate Solutions method of calculation conditional constants graphical numerical corrected for NiS04 complexation at zero ion strength" numerical corrected for NiS04 complexation at 0.5 M (Na,H)S04solutionsb numerical
log K73
Complexation of Nickel in Sulfate Solutions. In the sulfate medium, the equilibrium constants obtained are sort of "conditional" constants, since nickel is complexed by sulfate ions. Considering also the species eq 9 should be written as follows: K23[H,R,]5 / 2 [ H+]-2 + K24 [H+J -2 D = (15) 1+ @I[SO~~-] where the stability constant of NiS04 is defined by
[m
(16)
~ O PK7,
-5.90 -5.49 -5.86 f 0.06 -5.41 f 0.16 -4.70 f 0.06 -4.27 f 0.16 -5.06 f 0.01 -4.63 f 0.02
Olog & = 2.3, log & = 1.06, and log p3 = 1.99 obtained from Morel (1983). bThe optimal values of the stability constants from = 1.71 f 0.01, log & = 0.814 f 0.025, and calculation were log log p3 = 1.41 max 2.44.c 'The value after max corresponds to log [K + 3u(K)], and the error given corresponds to 3a(logK).
The equilibrium constants for the different HDEHP species between 0.5 M (Na,H)S04and the kerosene system used in the present work are given from Huang and Juang (1986a) and are shown in Table I. Table I1 summarizes the results obtained with some of the models tried. Figure 5 presents the plot of Uminversus q for models I-IX given in Table 11; the best q values are between 3 and 4. Then, two species formed in organic phase (models X-XVIII) were tried; the results showed the best one turns out to be the set of species (p,q) equal to (2,3) and (2,4). Furthermore, several more than two species calculations were carried out to investigate the possibility of finding other complexes that could improve the fit to the experimental data (summarized as models XIX and XX). From Table 11, the best fit for sulfate systems was obtained when the species were the same as those suggested by the graphical treatment, Le., NiR2(HR)3and NiR2(HR)4with
+
[SO:-] can be calculated from the mass balance expression for the sulfate concentration as given by [S042-]t= [S042-]+ [NiS04]+ P2[Na+l[S042-1+ P3[H+I[S042-1 (17) where p2 and p3 are the stability constants of NaS04- and HS04-, respectively, defined by [NaS04-] (18) p2 = [Na+][S042-] and
The values of log pl, log p2, and log p3 were taken to be 2.3, 1.06, and 1.99 at zero ionic strength (Morel, 1983). Table I11 summarizes the results of the graphical and computer calculations. However, in 0.5 M (Na+,H+,Ni2+)S042-systems, the ionic strength is not zero. Therefore, for minimizing error square sum calculations, the best log values of KB, K24, pl, p2,and P3 were obtained and shown in Table 111. The published values for the equilibrium constants are compiled in Table IV. Figure 6 represents the distribution diagram of Ni(I1) as a function of the total HDEHP concentration at various total concentrations of nickel and pH values. It is worth noting the increasing predominance of the NiR2(HR)4 species as the total concentration of HDEHP is increased.
Table IV. Equilibrium Constants for NiRJHR), Extracted by H D E H P Found i n t h e Literature Ion K,, aciueous phase temp, "C (2.2) (23 (24) diluent (2,O) 0.5 M (Na,H)S04 25 f 0.2 kerosene -5.06 f 0.01 -4.63 & 0.02 20 toluene -9.50 f 0.10 -7.00 f 0.03 1.0 M NaNO, 1.0 M (Na,HjN03 n-dodecane -4.34 0.5 M (Na,H)N03 25 f 0.2 n-heptane -4.35 no medium 25 f 0.2 n-heptane -4.10 0.5 M (Na,H)N03 25 f 0.2 toluene or benzene -5.82 no medium 25 f 0.2 toluene or benzene -5.70 xylene -5.70 (Na,H)N03 2-ethylhexyl alcohol -4.96 (Na,H)N03 -4.21 isodecanol (Na,H)N03 I = 0.05 M LiN03 22 f 1.0 n-octane -5.41 f 0.07 I = 0.05 M LiN03 22 f 1.0 carbon tetrachloride -6.24 f 0.03 I = 0.05 M LiN03 22 f 1.0 benzene -6.79 f 0.03 I = 0.05 M LiN03 22 f 1.0 chloroform -6.90 f 0.04 I = 0.10 M LiNO, 22 f 1.0 n-octane -5.44 f 0.06
source present work Fernhdez et al. (1985) Grimm and Kolaiik (1974) Komasawa et al. (1981) Komasawa et al. (1981) Komasawa et al. (1981) Komasawa et al. (1981) Komasawa et al. (1984) Komasawa et al. (1984) Komasawa et al. (1984) Smelov and Chubukov (1973) Smelov and Chubukov (1973) Smelov and Chubukov (1973) Smelov and Chubukov (1973) Smelov and Chubukov (1973)
Ind. Eng. Chem. Res., Vol. 28, No. 10, 1989 1561 in the aqueous phase. In this work, we adopted two approaches for considering the existences of NiS04, NaS04, and HSO, complexations. In the first approach, computer calculations on all sulfate system data were performed by introducing the values of the stability constants of the sulfates in the literature. In the second approach, the equilibrium constants of Ni-HDEHP complexes and sulfates were calculated a t the same time. New values of K23, K24, pl, &, and p3 were calculated and are given in Table 111. As can be seen in Table IV, the value of KZ4 obtained agree well with those obtained for the nitrate systems and aliphatic diluents. It is worth mentioning that some other models were tested and the best fit remained the same as that obtained by assuming the same species ( p , q ) equal to (2,3) and (2,4).
Acknowledgment This work was supported by a grant from the National Science Council of the Republic of China, under Grant NSC76-0402-Em-04, to which the authors wish to express their thanks.
Nomenclature D = distribution ratio, M/M K, = acid dissociation constant of monomeric HDEHP in the aqueous phase, M Kd = distribution constant of monomeric HDEHP between the organic and aqueous phases, M/M K , = dimerization constant of HDEHP in the diluent, M-' K, = equilibrium constant of nickel-HDEHP complexes m = degree of aggregation of the extracted species p = number of R groups except for the HR molecule involved in the extracted species q = number of free monomeric HDEHP involved in the extracted species Ni(I1) = metal species U = error squares sum [ It = total concentration of the species in the brackets, M Greek Letters Stability constants of sulfate complexes, M-l standard deviation
@ = u =
Figure 6. Nickel distribution diagrams as a function of the total HDEHP concentration at two different total concentrations of nickel and two different pH values. Lines 1, 2, 3 and 4 represent NiR2(HR),, NiR2(HR)4,Ni2+,and NiSO,, respectively. (a) [Ni(I1)lt = 1.7 X M, pH = 4.50; (b) [Ni(I1)lt = 5.0 X M, pH = 4.50; (c) M, pH = 3.50. [Ni(I1)lt = 1.7 X
Conclusions For the sulfate system, the nickel distribution data could be best explained by assuming the formations of two species: NiR2(HR)3and NiR2(HR)& Graphic and computer modeling of the data excluded the existence of the species NiR2(HR)2. It could also be established that the existence of these two species together gives the best fit for the distribution data, whereas the assumption that either of them exist? alone gives a considerably worse fit. Grimm and Kolafik (1974) and Komasawa et al. (1981) also reported the existence of NiR2(HR)4,as we identified, although the aqueous phase contained nitrate solutions. However, in the sulfate solutions, there existed NiR2(HR), at the same time, from the above graphical and numerical analyses. On the other hand, the numerical values of the "conditional" equilibrium constants determined for these two species depend on the composition of the aqueous phase. This is due to the possible complexation of nickel
Superscript
_ -- denotes the organic phase species or organic phase concentration Subscript min = minimum value Registry No. HDEHP, 298-07-7; Ni, 7440-02-0.
Literature Cited Brisk, M. L.; McManamey, W. J. Liquid Extraction of Metals from Sulphate Solutions by Alkylphosphoric Acids. I. Equilibrium Distributions of Copper, Cobalt and Nickel with Di-(2-ethylhexy1)phosphoric Acid. J. Appl. Chem. 1969, 19(4), 103-108. Fernftndez, L. A.; Elizalde, M. P.; Castresana, J. M.; Aguilar, M.; Wingefors, S. Extraction of Ni(I1) by Di-(2-ethylhexyl)phosphoric Acid Dissolved in Toluene. Soluent Ertr. Ion Exch. 1985, 3(6), 807-823. Grimm, R.; Kolaiik, Z. Acidic Organophosphorus Extractants-XIX. Extraction of Cu(II), Co(II), Ni(II), Zn(I1) and Cd(I1) by Di(2ethylhexy1)phosphoric Acid. J . Inorg. Nucl. Chem. 1974, 36(1), 189-192. Huang, C. T.; Huang, T. C. The Equilibrium Reaction of the Extraction of Uranium(V1) with Db(2-ethylhexyl) Phosphoric Acid from Nitric Acid Solutions. Soluent Ertr. Ion Erch. 1987, 5(4), 611-631. Huang, T. C.; Huang, C. T. Kinetics of the Extraction of Uranium(VI) from Nitric Acid Solutions with Bis(2-ethylhexy1)phosphoric Acid. Ind. Eng. Chem. Res. 1988, 27(9), 1675-1680. Huang, T. C.; Juang, R. S. Solvent Extraction Chemistry of Zinc with DPEHPA. Hydrometall. Symp. 1985, 79-91.
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Huang, T. C.; Juang, R. S. Extraction Equilibrium of Zinc from Sulfate Media with Bis(2-ethylhexyl) Phosphoric Acid. Znd. Eng. Chem. Fundam. 1986a, 25(4), 752-757. Huang, T. C.; Juang, R. S. Kinetics and Mechanism of Zinc Extraction from Sulfate Medium with Di(2-ethylhexyl) Phosphoric Acid. J. Chem. Eng. Jpn. 1986b, 19(5), 379-386. KolaFik, Z.; Grimm, R. Acidic Organophosphorus ExtractantsXXIV. The Polymerization Behaviour of Cu(II), Cd(II), Zn(I1) and Co(I1) Complexes of Di(2-ethylhexy1)phosphoric Acid in Fully Loaded Organic Phases. J. Znorg. Nucl. Chem. 1976, 38(9), 1721-1727. Komasawa, I.; Otake, T.; Higaki, Y. Equilibrium Studies of the Extraction of Divalent Metals from Nitrate Media with Di-(2ethylhexyl) Phosphoric Acid. J. Znorg. Nucl. Chem. 1981,43(12), 3351-3356. Komasawa, I.; Otake, T.; Ogawa, Y. The Effect of Diluent in the Liquid-Liquid Extraction of Cobalt and Nickel Using Acidic Organophosphorus Compounds. J. Chem. Eng. Jpn. 1984, I7(4), 410-417. Liem, D. H. High-speed Computers as a Supplement to Graphical Methods. 12. Application of LETAGROP to Data for Liquidliquid Distribution Equilibria. Acta Chem. Scand. 1971,25(5), 1521-1534. Madigan, D. C. The Extraction of Certain Cations from Aqueous Solution with Di-(2-ethylhexyl)orthophosphate.Austr. J. Chem. 1960, 13, 58-66. McDowell, W. J.; Perdue, P. T.; Case, G. N. Purification of Di(2ethylhexy1)phosphoric Acid. J. Znorg. Nucl. Chem. 1976,38(11), 2127-2129.
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* Corresponding author. Ting-Chia Huang,* Teh-Hua Tsai Department of Chemical Engineering National Cheng Kung University Tainan, Taiwan 70101, R.O.C. Received for review December 13, 1988 Revised manuscript received J u n e 8, 1989 Accepted June 26, 1989
Complete Catalytic Oxidation of Diethyl Sulfide over a 1 % Pt/Al,O, Catalyst The complete oxidation of diethyl sulfide over a 1% Pt/A1203 catalyst was studied using a fixed bed catalytic reactor. The reaction was studied in dry air between 225 and 300 "C and 1.25 atm of total pressure. T h e concentration of diethyl sulfide was varied between 6 and 250 ppm (v/v). The reaction was found to be zeroth order in diethyl sulfide concentration over the range of conditions studied, suggesting that, a t even low concentrations, the reactant sulfide is strongly adsorbed by the active site. The zeroth-order rate constant was calculated to be 78.8 exp(-19117/RT) mol/(s.g of catalyst). Catalytic oxidation is widely used to purify streams of polluted air (e.g., industrial emissions, auto exhaust). When purifying air streams containing low concentrations (
