TANTALUM AND NIOBIUM may be developed showing the percentage return as a function of operating level for the plant size selected.
where the maximum per cent return lies, differs from t h a t for maximum annual profit. Whether a plant should be expanded t o a point where maximum per cent return on the investment or the maximum annual profit is earned is a question which must be answered by management t o fit the particular product and situation. While it is recognized t h a t the problem has many facets, i t may be resolved generally around one focal point. First of all, no level of production should be considered which fails t o reach a prescribed minimum per cent return on the investment based upon the risk involved. If the per cent return is deemed t o be satisfactory a t the level of annual output which shows the maximum annual profit, then the expansion should be made t o the level of maximum annual profit, provided t h a t the per cent return at such an output exceeds the per cent return, commensurate with the risk, for any other possible investment which could be made. Otherwise the addition should be made t o the capacity shown for the maximum per cent returlq
The principles for evaluating profit remain the same for both an expansion or a new plant. Developing the components of profit, however, differs in a n expansion from that of a completely new plant. This difference centers principally in the result of using a greater proportion of multiple equipment units than would be employed in a new plant of the same total expanded size. Use of the mathematical approximations discussed will minimize the number of cost estimates required and yet provide adequate data for prediction purposes. Graphical portrayal of sales price, cost, and investment over the range of expansion contemplated will allow proper selection of optimum capacity t o take place on a maximum profitability basis. The range of profitable operation of the plant size selected may be indicated by a break-even chart.
Break-Even Point
literature Cited
Once the plant capacity has been selected, the effect upon costs and Profits by operation at less than full capacity Potential should be ascertained. Basically speaking, this type plot is called a break-even chart. Such a chart (Figure 6) is simply a plot of cost and sales for the specified plant size. The intersection of the sales and cost lines is the break-even point, above which production levels the plant will be profitable (4). Expressing the annual profit a t various levels between the break-even point and the maximum capacity as percentages of the investment, a curve
Summary
(1) Aries, R.
s.,
and Newton, R. D., “Chemical Engineering COST
Estimation” pp. 69-84, Chemonomics, New York, 1950. (2) Chfiton, H., them. E ~ ~57, . ,N ~ 4., 112-13 (1950). (3) Kistin, H. R., Cameron, C S., and Carter, A. P., Ibid., 60, No. 11, 191-5 (1953). (4) Newton, R. D., and Aries, R. S., Ibid., 58, No, 2 , 148-50 (1951). (5) Newton, R. D., and Aries, R. S., IND.ENG.CHEM.,43, 2304-6 (1951). (6) Williams, R. Jr., Chem. &g., 54, NO.12, 124-5 (1950). (7) Wessel, H. R., Ibid., 59, No. 7, 209-10 (1952). RECEIVED for review April 7, 1954. ACCEPTED September 9. 1954
c.
END OF PLANT ADAPTATION SYMPOSIUM
TANTALUM AND NIOBIUM Separation by Liquid-Liquid Extraction Hydrochloric Acid Extraction from Mixed Ketones JOSEPH R. WERNING’ U. S. Bureau o f
AND
KENNETH B. HlGBlE
Mines, Albany, Ore.
S
EPARATION of tantalum and niobium (columbium) has long presented a problem t o both the chemist and metallurgist. Attempts t o separate the two elements by chemical and physical means have, t o date, failed t o develop a substitute for the present commercial method of production, a process ( 3 ) which deviates only slightly from the Marignac process ( 4 ) described in 1866. Since t h a t date many separations have been proposed, but these have failed t o offer a satisfactory substitute for the Marignac process. During the past 2 years a t least three papers have appeared t h a t describe liquid-liquid separations of the two elements (2,6,6).Other studies have been made of the solvent extraction of the individual elements ( 1 ) . This paper describes still another liquid-liquid extraction process, which may merit industrial consideration. 1
Present address, Polychemicals Department, E. I. du Pant de Nemours
& Go., Inc., Wilmington, Del.
December 1954
The separation of tantalum a n niobium by i..e preferential extraction of tantalum from mixed aliphatic ketone solutions containing mixed anhydrous pentachlorides b y 12N hydrochloric acid is shown t o be feasible. The system methyl isobutyl ketone (3liBK)-diisobutyl ketone (DiBK)-l2N hydrochloric acid has been investigated and utilized in the preparation of relatively pure tantalum and niobium oxides. The presence of ferric chloride in the above system is shown to enhance, t o a certain degree, the possibilities of commercial application. A method for rapid separation of niobium from the residual iron in the ketone solution is presented. The work described in this paper utilizes tantalum and niobium fractions recovered from Geomines tin slags. The slags were obtained from the Compagnie Geologique e t Miniere des Ingenieurs e t Industriels Belges, South Africa, “Geomines.” These slags contain large quantities of iron and silicon. The silicon is removed easily by chlorination procedures, but the elimination of
INDUSTRIAL AND ENGINEERING CHEMISTRY
249 1
+
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT iron has not been successfully accomplished by this means. However, the iron may be removed by leaching with concentrated hydrochloric acid prior to the chloiination treatment. While this process is not too expensive, it is somewhat objectionable because of the handling time involved. For this reason, both chlorides containing iron and chlorides produced from material from which the iron had been leached wer? tested. When it became evident that iron niaterially improved the rate and efficiency of the tantalum-niobium separation, a niobium-iron separation was sought. The separation described in this paper was found to be efficient, and although it is based on a specific previous treatment it is believed that it can k~ erononiically applied for Iecovery of the valuable metals.
I
Q
-50 *
I
0
z
I
P
240’
W
I
30
’ I
P
~
None of the organics tested niateriall> affected the extraction of tantalum, while the extraction of niobium, in general. was reduced (Table I). Methyl isobutyl ketone, diisopropyl ketone, and n-butyl ethyl ketone exhibited the most pronounced influence. Because methyl isobutyl ketone 15 as ieadily available for industrial use, it was chosen for further investigation. The effect of the volumetric ratio (;\liBIC/DiBK) on the extraction of iron-free tantalum and niobium chlorides is show11 in Figure 1 for arbitrary tantalum aiid niobium concentrations of 53 aiid 26 grams per liter of diisobutyl ketone, respective1 ratio in the approximate range of 0.4 appears to offer optimum conditions for separation, although this ratio is not critical. Figure 2 shows similar data for tests employing crude tantalum and niobium chlorides a t arbitrary total metal concentrations of approximately 36 grams per liter each of tantalum and niobium and 62 grams per liter of iron in diisobutyl ketone. Optimum sepnration occurs a t a somewhat higher A!IiBR/DiBI< ratio than with the iron-free chlorides. The equilibrium distribution of tantalum and niobium from iron-free chlorides in the system 28.6y0 methyl isobutyl ketone, 71.4% diisobutyl ketone (MiBK/DiBK = 0.4), 12N hydrochloiic acid is shown in Figure 3 for an arbitrary weight ratio of niobium to tantalum equal to 0.91. The equilibrium relationship for tantalum and niobium from crude chlorides in the same system is shown in Figure 4. Weight ratios of niobium t o tantalum of 1.7 and 1.1 are shown. I n this range the effect of the original niobium to tantalum ratio is negligible.
CONDITIONS
To.53-iBK N b = Z 6 g , /Liter DiBK Vol DiBK .,o V o l IZNHCI
Nolbum,
1
i _
o O O 1
02
03
Volumetric
04
05M,Bi6 0 7
Ratio
-
Oh
Ok
IO
/D,aK
Effect of Ketone Ratio on Extraction of Figure 1. Tantalum and Niobium, Iron-Free Chlorides
Throughout this paper the twin “crude” chlorides refers to tantalum, niobium, and iron chlorides prepared from unleached Geomines tin slags. The composition of the chlorides varies slightly. The amount of iron present is approximately equal to or slightly less than the amount of tantalum plus niobium. The term “iron-free” chlorides refers t o chlorides obtained from Geoniines slags previously leached with hydrochloric acid. Iron is present in this product to the extent of about 0.1 %. Presence of Ferric Chloride Increases Efficiency of Tantalum Extraction
Tantalum has been found to be eltracted preferentially from aliphatic ketone solutions of tantalum and niobium pentachlorides by concentrated hydrochloric acid. There are two factoih limiting the system. .4s an operational necessity, appreciable inimiscibility must exist between the t n o phases, and the hydrochloric acid concentration must be high enough to keep the tantalum and niobium in solution. Diisobutyl ketone and approximately 1 2 5 hydrochloiic acid were found t o satisfy these conditions; the resulting system was sufficiently immiscible and stable to permit investigation and utilization. An attempt to evaluate the effect of other ketones on the distribution of tantalum and niobium in the above system was made. A solution containiiig a mixture of 16.6 grams of tantalum, 20.0 grams of niobium, and 45 grams of iron per liter was prepared by dissolving the iequired weight of mixed anhydrous chlorides in diisobutyl ketone. Aliquots (10 ml. each) of this solution were pipetted into glass separatory funnels and 2- and 4-ml. portions of various aliphatic ketones or related compounds were added. Each aliquot was extracted with 10 inl. of 12N hydrochloric acid. The layers were separated, evaporated to dryness, and ignited a t 1000” C. for 1 hour. The results of n-ray spectrographic analysis are shown in Table I.
2492
‘0
01
02
03
04
Volumetric
05
06
07
Ratio - MIBK/Q,BK
0.8
0.9
1.0
Figure 2. Effect of Ketone Ratio on Extraction of Tantalum and Niobium, Crude Chlorides
Table
I.
Extraction of Tantalum and Niobium in Diisobutyl Ketone plus Solvents Val. Added,
Compound Added None Acetonyl acetone n-Butyl ethyl ketone D i e t h y l ketone Diisopropyl ketone Methyl n-amyl ketone
hI1. 0 2 4 2
4
2 2
2
4
M e t h y l isobutyl ketone M e t h y l a-hexyl ketone SIethL-l nonyl ketone
Methyl isopropyl ketone Acetone
2 4 2
4 2 4 2 4 2 4
INDUSTRIAL AND ENGINEERING CHEMISTRY
Tantalum Extracted,
%
Niobium Extracted,
%
Separation Facto1
94.1 94.0 95.2 94.4
93.3 92.1 94.4 94.0 87.8 94.4
93.i 94.(i
92.6 95,1 91.4 94.2 93.1 97.0
97.2
vel. 46,No. 12
TANTALUM AND NIOBIUM The extraction of tantalum and niobium from a mixture of 28.6% methyl isobutyl ketone-71.4yo diisobutyl ketone by 12N hydrochloric acid is shown in Figure 5 to be a function of metal concentration in the original diisobutyl ketone for both crude and iron-free chlorides. The marked influence of ferric chloride on the extraction of tantalum is well illustrated in this figure. The separation of niobium and iron remaining in the organic phase after the extraction of tantalum was accomplished in the following manner: To the ketone solution an equal volume of hot dilute sulfuric acid was added. Sulfuric acid concentrations from 14 to 20% were used with success; concentrations below this range tended to emulsify the Pystem and render phase separation difficult or impossible, while higher concentrations failed to precipitate the niobium completely. The mixture was shaken vigorously for about 2 minutes and allowed to stand until the layers had separated. The aqueous phase, including a finely divided suspension of niobium, was drawn into a large beaker, digested slowly for about an hour, and filtered. The precipitate was washed twice with distilled water and twice with acetone t o produce a nio' iron. The filtrate bium product containing appioximately 0.1% was neutralized with 28% ammonium hydroxide to precipitate the iron. This iron product contained 1 to 2% niobium. The original ketone, thus freed from its metal content, way recovered by washing with 3 N hydrochloric acid until barium chloride failed to precipitate the insoluble barium sulfate from the washings. The ketone recovered in this manner was found t o effect essentially the same separation as fresh ketone.
1
I
I
Figure 4. Equilibrium Distribution of Tantalum and Niobium between 12N Hydrochloric Acid and 28.6C7, Methyl Isobutyl Ketone in Diisobutyl Ketone, Crude Chlorides
Separation M a y Be Accomplished b y Single or Multiple Stage Extraction
The following are examples of separations that have been effected from initial solutions containing either crude chlorides or iron-free chlorides. Example 1. Extraction of Tantalum from Solutions of Crude Chlorides. SINGLESTAG=. A solution containing a mixture of 36 grams of tantalum, 36 grams of niobium, and 52 grams of iron per liter was prepared by dissolving the required weight of crude chlorides in diisobutyl ketone. Methyl isobutyl ketone (4 ml.) was added to a 10-ml. aliquot of the starting solution. The organic phase was extracted with 10 ml. of 12N hydrochloric acid by shaking in a separatory funnel for 55 minutes. One hour was allowed for the phases to separate, after which time they were drawn into separate porcelain dishes, evaporated t o dryness,
50
Metol Concentration in Di-lsobut I Ketone Extraction, $11.
40
before
Figure 5. Extractability of Tantalum and Niobium from 28.6% Methyl Isobutyl Ketone in Diisobutyl Ketone into 12N Hydrochloric Acid
r" 30 0. v) 3
0
: 20 E
OO
5 IO 15 20 25 Concentration in Orqonic Phose. 9/1.
30
Figure 3. Equilibrium Distribution of Tantalum and Niobium between 12N Hydrochloric Acid and 28.6% Methyl Isobutyl Ketone in Diisobutyl Ketone, Iron-Free Chlorides
December 1954
and ignited for 1 hour a t 1000" C. X-ray spectrographic analysis indicating the composition of the tantalum and niobium content of each phase are shown in Table 11. The tantalum in the acid layer was contaminated with approximately 0.1 yoiron, essentially all the iron remaining in the organic phase. MULTIPLESTAGE. Methyl isobutyl ketone (4 ml.) was added to a 10-ml. aliquot of the original solution described in Part A and extracted with 10 ml. of 12N hydrochloric acid by shaking in a separating funnel for 55 minutes. The acid phase was separated, washed twice with a mixture of 10 ml. of diisobutyl ketone and 4 ml. of methyl isobutyl ketone, and evaporated to dryness. The residue was ignited and the oxides were analyzed. The organic phase from the initial extraction was re-extracted twice TTith 10 ml. of 12N hydrochloric acid, evaporated, and
INDUSTRIAL AND ENGINEERING CHEMISTRY
2493
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT ignited, and the oxides xvere analyzed, as above. The composition of t,he tantalum and niobium content of each phase are s h o r n in Table 11. Example 2. Extraction of Tantalum from Solutions of IronFree Chlorides. A solution containing 21.0 grams of t a n h l u m and 17.5 grams of niobium per liter was prepared by dissolving the required weight of iron-free chlorides in diisobutj-1 ketone. Methyl isobutyl ketone (8 ml.) v a s added t o a 20-ml. aliquot of the start,ing solution, and the resulting organic solution T ~ extracted with 20 ml. of 1 2 5 hydrochloric acid. The samplcs vvere taken and prepared according t u the procedure outlined in Example 1. The analysis of resulting oxides is given in Table 11. Khile the tantalum extracted is of approximately the same purity as that obtained in the first extraction of Example 1, the orig'nal solution was somewhat richer in tantalum, and an appreciahly smaller percentage of the total tantalum was extracted. Example 3. Separation of Niobium and Tantalum from Iron. To test t8heindicated separation of tantalum and niobium from iron by the sulfuric acid digestion process, a solution \T-NS prepared by dissolving the crude chlorides in diisobutyl ketone which had previously been saturated with 1 2 4 hydroc,hloric acid. T o 100 ml. of this solution a n equal volunie of hot, 16% sulfuric acid was added. The system ivas shaken briefly arid the layers were allowed t o separate. The aqueous layer \\-as drawn int,o a beaker, digested slowly for one hour, arid filtered. The precipitate which collected on the filter paper ivas rashed with distilled water and then with acetone. T h e residue was airdried before it was ignited a t 1000" C. for 1 hour. The filt,rate was neutralized with 2870 ammonium hydroxide and filtered, and the residue vias air-dried and ignited. X-ray spectrographic of these samples showed the folloxing compositioii:
+
Tantalum Xiobiurn, Gram
Iron, Gram
Ta +Sh T a Xb T Fe
+
Precipitated by HzS04 0 750 0 0028 Precipitated hy ",OH 0 017 0 640 Tantalum and niobium recovered, % = 97.7
x
100
98.8
2 6
Process I s Especially Applicable to l o w Grade Ores Containing large Amounts of Iron
T h e separation of tantalum and niobium by the pit=feiential extraction of tantalum from aliphatic ketone solutions of the mixed anhydrous pentachluiides of tantalum and niobium has been shoFn t o be feasible. Concentrated hydrochloiic acid s o h tions have been used as the extracting medium. The use of mixed aliphatic ketones in some cases appreciably ietarde the extraction of niobium, and the presence of ferric chloiide as obtained from crude chlorides greatly increases the extraction of tantalum Tvithout materially increasing the amount of niobium
2494
T a b l e II. Tantalum,
R
P r e f e r e n t i a l Extraction of T a n t a l u m Siobium,
Gram
Ta
Nb
Nb - h x r m
Phase
Glam
Original llrid Organic
0 360 0.345 0 . 00e
0,360 0.064 0.246
Single Stage 50.0 84.3 2,4
50.0 Id . t i 97.6
.4cid Organic
0.331 0,002
0.001 0.187
Slultiple Stage 98.8 1.0
1.2 99,o
Original Acid Organic
0,426 0.128 0.287
0.356 0.022 0.337
Ta
~
loo
100
57.1 82.3 46.0
extracted. ;1 combination of tlirsr tn-o factors produces relatively pure tantalum and niobium products in a three or four stage, batchwise operat,ion. T h e final separation of iron froin niobium, accomplished by the digestion of the niobium x i t h dilute sulfuric acid, is effected with a relative degree of ease. T h e nature of the procePs is such that it should be ieadily adaptable t o conventional cont,inuous countercurrent cstimtiori procedures. A brief investigation of this possibilit,?. hns s!io~~--n promise. ST'hile this proreas is especially applicable t o low grade t a n talum arid niobium ores containing large quantities of iroir, it i p felt t o be by no mcam limited t o such orei. Acknowledgment
Special acknowledgment i i given t o 13. L. Gilbert,, hwd, Process Improvement Section, and 1%..L Johansen, head, MeEearch Section, for their continued advice and encouragc~ment throughout the period of this work. Recognition also should he given t o B. F. Speece and J. T. Grace, coworkers, for their collaborat,ion on the related problems encountered in thip invcst,igation. literature Cited
(1) Hicks, H. G., and Gilbert, 11. S.,A n d . C'hein.. 26, 1205 (1954). (2) Leddicotte, G . W., and Aloore, F. L., J . Am. Chem. Soc., 74, !til8 (1952). (3) Lee, J. A , , Chem. Eng., 55, KO.9, 110-12 (1945). (4) LIarignac, J., Ann. chi?n. piiys., 8, 5 (1866). ( 5 ) Stevenson, P. C., and Hicks, H. G., Ami. Chem., 2 5 , 1517 (1(35:3). (6) Kerning, J. R.. Higbie, K . E., arid associates, IXD. EXG.Ckmi,, 46,644 (1954). RECEIVED for reriew .Igril 21, 1831.
ACCEPTEDSeptember 2 0 . 1964. Presented before t h e Division of Pliysical and Inorganic Chemiatiy a t the 120th Meeting, A M I Z R S C ACiis1r1c.41. X SOCIETY, S e w York, S . Y .
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 12
