Separation of Cadmium from Uranium, Cobalt, Nickel, Manganese, Zinc, Copper, Titanium, and Other Elements by Cation Exchange Chromatography F. W. E. STRELOW National Chemical Research laboratory, South African Council for Scientific and Industrial Research, Pretoria, South Africa
,A systematic study of the distribution curves of cations with AG 50W-X8 resin in hydrochloric acid showed that most cations are adsorbed strongly from O S N hydrochloric acid, while cadmium i s not. This fact was used to develop a cation exchange chromatographic procedure to separate cadmium from uranium, cobalt, nickel, manganese, zinc, copper, and titanium. Other cations that are completely separated include Mg+2, Ca+2, Sr+2, Fe+2, Fe+*, Alfal Zr0+2, Th+4, Y+a, La+a, and the rare earths, and Cs+. Stannic tin accompanies cadmium quantitatively and can be separated from the cations named above by a similar procedure.
Table
Exchange Type Cation Cation
I.
Published Cadmium Separations
Separation from Cu and Zn CU
Eluent 0.5N HCl for Cd Stability differences of thiosulfate complexes 0.25N ammonium citrate 0.5N oxalic acid for U, IN HCl for Cd Glycerol-NaOH mixtures for Bu, Pb, and Bi H2S04-KI or HNOs-KI mixtures for Zn, 0.01N HC1 for
Cation Cation
Zn
Cation
Cu, Pb, Bi
Anion
Zn
Anion
Zn and others
Anion
Mn, Co, Cu, Fe, AI, Ni, Cr, Ti (Zn Cd adsorbed from 0.12h HCl containing 10% w./v. NaCl)
U
Cd
A
amount of work has been done in recent years on the ion exchange separation of cadmium from various other elements. Table I shows the separations that have been published so far. While Kallmann’s (6) anion exchange method has successfully separated a considerable number of cations from cadmium, published methods on cation exchange have been applied to separate cadmium from only a small number of other cations, and are therefore of a limited application. A systematic study of distribution coefficients and elution curves in hydrochloric acid media involving 38 cations was made. AG 50W-X8, a sulfonated
+
CONSIDERABLE
polystyrene processed by the Bio-Rad Laboratories, Berkeley, Calif., from Dowex 50, was used as the resin. An investigation of the results suggested that the method of Yoshino and Kojima, who separated cadmium from copper and zinc using Amberlite IR-120 resin and 0.5N hydrochloric acid as eluent for cadmium, can be extended to a large number of other cations. Tin accompanies cadmium quantitatively and can be separated from the named cations by the same procedure. EXPERIMENTAL
The apparatus and methods used
0.6fN HC1 for Zn and others, 0.001N HC1 for Cd 2N NaOH containing 2% w . /v. NaCl for Zn
(6)
(6)
were similar to those outlined by Strelow (8). Distribution curves prepared previously were used to evaluate appro=mately the most favorable concentrations of hydrochloric acid used to separate cadmium from other cations. Single element elution curves were prepared for some concentrations in the favorable region for some of the indicative elements and for cadmium. These curves showed that 0.5N hydrochloric acid was the most effective eluent concentration, when a separation of cadmium from as many other cations as possible was contemplated. Subsequently, experimental composite elution curves for cation pairs were prepared using columns of AG 50W-X8
Cd
, I
I lil
CO
U
1 20:
330
LOO
1 503
-
1
- 4 1 600
120
u L.__ELUATE
200
. _ I .
300
ML
.
.
- 1 . it0
500
I
600
ELUATE
~
Figure 1.
Composite elution curve for cadmium-uranium Cadmium, 0.21 24 gram Uranium, 0.3649 gram
Figure 2.
Composite elution curve for cadmium-cobalt Cadmium, 0.21 24 gram Cobalt, 0.0944 gram
VOL. 32, NO. 3, MARCH 1960
363
\ I ::~ fl 08
-
I; SI O 6
-
I:
-
?I
E’ 51
$1
Cd
Cd
-
-
02
T I
L
I
-
100
1
/I
.
300
200 ML
Figure 3.
LOO
I 500
J
I
100
600
Composite elution curve for cadmium-titanium
Figure 4.
Cation Cd + 2 and Zn + z KO, +z cu
c o +2 Xi + 2
Method of Determination Titration with EDTA using Eriochrome Black T as indicator Gravimetrically as UaOs after precipitation with parbonate-free ammonia Titration of iodine liberated from potassium iodide with thiosulfate using starch as indicator Gravimetrically as [CO(C+N)4 (I CXS)? Gravimetrically as dimethylglyoGme complex
Mn +2
Colorimetrically as permanganate after oxidation by periodate, or gravimetrically as RlnzPzO? Gravimetrically as oxinate, TiO(CSH~ON)2 Gravimetncallv as Be0 after precipitation with ammonia at pH 7.5 to 8.0
Ti + 2
Be + 2
Table 111.
Mg.
0.5,V hydrochloric acid acted as the eluent. Then 25-ml. amounts of the eluate were collected in 25-ml. graduates and the amounts of the cations were determined analytically. Composite elution curves for cadmium-uranium, -cobalt, -titanium, and -beryllium are given in Figures 1 to 4. The elution curves for cadmium-nickel, -manganese, and -copper were almost similar to that for cadmium-cobalt, so that the curve of the latter mill serve to illustrate them. Zinc appeared a little earlier in the eluate than these three, but later than the uranium. The analytical methods employed to determine the amounts of the cations are shown in Table 11. Analysis of Synthetic Samples. As a result of this work, a method of separation was elaborated and applied to synthetic solutions, prepared by measuring out and mixing amounts of the standardized solutions of the different cations. The cations were adsorbed on resin column of 22-cm. length and 1.15cm. diameter from a solution not more than 0.2iV in acid. Cadmium was eluted by passing 225 nil. of 0.5.V hydrochloric acid a t a flow
Results of Quantitative Separations of Synthetic Mixtures of Cations
123.1 12.3 246.2 123.1 12.3 246.2 123.1 12.3 246.2 246.2 12.3 123.1 246.2 12.3 123.1 123.1 123,l
364
Other Cation Taken, Mg. UOS +l 137.8 UOZ +z
uoz
+$
Zn f 2 Zn + 2
Zn +z c u +z c u +2 c u +z c o +Z
c o +2 c o +2 Ni +2 Ni +2
r\;i + 2
Mn + 2
Ti0 +z
ANALYTICAL CHEMISTRY
275.6 13.8 87.9 175.8 8.8 118.2 236.4 11.8 12.1 242.6 121.3 13.5 269.4 134.7 129.4 62.7
500
600
for cadmium-beryllium
Cadmium, 0.21 2 4 gram Beryllium, 0.0361 gram
(ill1 results given are means of triplicate determinations)
Cd Taken,
L 30
Composite elution curve
Cadmium, 0.21 2 4 gram Titanium, 0 . 0 6 2 2 gram
Table II. Analytical Method Used to Determine Different Cations
300
ML. ELUATE
ELUATE
resin, 100- to 200-mesh, 22-cm. length, and 1.15-cm. diameter; a flow rate of 2.0 to 2.5 ml. per minute was used and
200
Cd Found, Rlg.
Other Cation Found, Mg.
123 2 f 0 2 124fO1 246 1 f 0 2 123 2 f 0 1 1 2 3 i O l 246 2 i 0 3 123 0 f 0 2 1 2 3 f 0 1 246 0 i 0 3 246 1 f 0 2 1 2 3 f 0 1 123 2 f 0 2 246 2 f 0 2 122fO1 123 0 f 0 1 123 1 f 0 2 123 1 f 0 1
137.7 f 0 . 1 275.6 f 0 . 2 13.8 i0 . i 88.0 f 0 . 1 175.7 f O..2 8.7 f0.1 118.2 f 0 . 1 236.3 f 0 . 2 11.8 0.1 12.0 it 0 . 1 242.1 f 0 . 3 121.4 f 0 . 2 13.5 f 0 . 1 269.5 f 0 . 2 134.6 i 0 . 1 129.3 f 0 . 2 62.8 f 0 . 1
*
rate of 2.0 to 2.5 ml. per minute through the column, and the other cations were eluted subsequently by 300 ml. of 2N hydrochloric acid a t the same flow rate. Higher acid concentrations were employed to elute cations such as calcium, strontium, barium, zirconium, and the rare earths. The amounts of the different cations n-ere determined by the procedures indicated above and the results of the determinations are given in Table 111.
DISCUSSION
The foregoing method provides a simple means for separating cadmium quantitatively from uranium, cobalt, nickel, manganese, zinc, copper, and titanium. Other cations that remain quantitatively on the column when cadmium is eluted with 225 ml. of 0.5N hydrochloric acid include magnesium, calcium, strontium, barium, ferrous and ferric iron, aluminum, thorium, yttrium, zirconium, lanthanum and the rare earths, and cesium. Ferrous iron and magnesium show elution curves that are similar to those for cobalt and nickel, while ferric iron, aluminum, calcium, strontium, barium, zirconium, thorium. yttrium, lanthanum, and the rare earths do not appear in the first 600 ml. of eluate when about 5 meq. are present. S o complete separation of cadmium from beryllium could be achieved by using a 22-cm. column, as is shown by Figure 4, but on a 35-cni. column the two peaks were situated far enough from each other to make a sfparation possible. Stannic tin, lithium, and sodium accompany cadmium quantitatively and can thus be separated from the cations named above by using the same procedure. Potassium, rubidium, and ammonium are eluted partly under the conditions described. Auric gold, platinic platinum, selenium, and quinquevalent vanadium and molybdenum are absorbed very slightly, if a t all, from 0.2N hydrochloric acid. They can be washed through the column
with 0.2N hydrochloric acid and thus be separated from cadmium. Trivalent bismuth interferes because it forms insoluble oxysalts at low concentrations of hydrochloric acid. Silver, mercurous mercury, lead, and thallous thallium interfere because they form insoluble chlorides. Tungsten interferes because it starts to precipitate as tungstic acid a t low concentrations of free acid. Nitrate and perchlorate do not interfere and sulfate can be tolerated up to a concentration of O.lN, provided no cat)ions are present to form insoluble sulfates. ACKNOWLEDGMENT
The author expresses gratitude to
W. E. Schilz of the University of Pretoria for his advice and interest in the work.
( 7 ) Kreshkow, A. P., Sayushkina, E. N., Issledovan. v Oblasti IonoobmennoX Khromatog., Akad. N a u k S.S.S.R., Otdel. K h i m . N a u k , T r u d y Soveshchaniya 1957,
LITERATURE CITED
191-8. (8) Strelow, F. W. E., ANAL.CHEX.31, 1201-4 (1959). (9) Vasil'ev, A., Toropova. V. F., Busy-
(1) Baggot, E. R., Willcocks, R. G. W., Analyst 80, 53 (1955). (2) Dizdar, Z., Rec. trav. inst. recherches structure matikre (Belgrade) 2, 85 (1953). (31 Gierst, L., Dubru, L., Bull. soc. chim. Belgea 63,379 (1954). (4) Hunter, J. A., Miller, C. C., Analyst 81,79 (1956). (5) Kallmann, S., Steele, C. G., Chu, N. Y., ANAL.CHEM.28,230-3 (1956). (6) Kraus, K. A., Nelson, F., Proceedings of International Conference on Peaceful Uses of Atomic Energy, Paper 837, Vol. 7 , p. 113, Session 9 B, United Nations, New York, 1956.
gina, A. A., Uchenye Zapiski Kazan. Gosudarst. Univ. im. V . I . Ul'yanovaLenina 113, 91-102 (1953). (10) Yoshino, Y., Kojima, RI., Buriseki Kagaku 4,311-15 (1955). RECEIVED for review September 14, 1959. Accepted December 1, 1959. Abstracted from work done for a D.Sc. thesis a t the Department of Inorganic and Analytical Chemistry, University of Pretoria, Pretoris, South Africa. Published by permission of the South African Council for Scientific and Industrial Research.
Infrared Spectroscopy of Surface Coatings in Reflected Light HANS DANNENBERG, J. W. FORBES, and A. C. JONES Shell Development Co., Emeryville, Calif.
b Infrared spectroscopy has been applied to organic coatings on metal substrates by the use of a reflection method. A commercial spectrophotometer is employed with a special reflectance accessory. The infrared light beam passes through the coating, is reflected from the substrate, passes through the coating again, and finally enters the spectrophotometer. This method produces good spectra of clear surface coatings, 0.1 to 0.5 mil thick, on flat surfaces of specularly reflective metals such as tin-plated steel, cold-rolled steel, aluminum, and brass. The method appears to b e useful for qualitative and semiquantitative work. To make the reflection technique applicable to quantitative work, the influences of surface reflection and internal reflection must b e considered. These effects can be made negligible by placing an antireflective cover plate over the specimen.
T
ECHXIQUES of infrared spectroscopy have developed rapidly during the past few years, not only in the field of instrumentation, but also in the preparation of specimens and the scope of niaterials suitable for analysis with this tool. -4 major improvement has been the introduction of the pressed plate technique (5, 8 ) which can be applied to the analysis of insoluble resins and related materials ( 2 ) . Soluble substances and materials that are
available in the liquid state before being cured to the insoluble state have been examined on rock salt or potassium bromide plates (2, 5, 6). A supplementary infrared spectroscopic technique that is particularly suitable for the analysis of organic surface coatings has been developed by which an absorption spectrum of the coating deposited on a reflecting surface is obtained. Ordinarily, infrared absorption spectra of surface coatings are observed by the transmission of radiation by coatings deposited on polished sodium chloride plates. The new reflection technique is superior to the transmission method in many ways. Samples can be prepared more quickly, easily, and cheaply by procedures that surface-coating chemists are accustomed to use for the preparation of films for other physical tests. Such studies as rate of solvent loss, rate of eure, effects of catalysts on curing rates, and thermal stability of surface-coating materials may be followed under conditions more closely approaching those existing in actual applications. Possible extraneous effects such as the influence of the rock salt substrate on the crystallinity of the coating (4) are avoided. Surface coating materials that attack sodium chloride plates-e.g., water-based emulsions-and commercial coatings already mounted on metal substrates can be identified and examined. Although the basic equiprr,ent for the
application of the reflection technique has been available for several years, little has been published on its use. Recently, reflection techniques have been applied by Wolbert (9). THEORY
The reflection technique involves the use of a specular reflectance accessory in conjunction with an infrared spectrophotometer. Although specular reflectance accessories were designed and have been used for spectroscopic studies of the surface reflectance of materials, it is possible to obtain essentially absorption spectra of thin films of coating materials when they are mounted on reflective substrates. It is this latter technique with which the present work is concerned. The principle of the reflectance accessory is as follows. With the accessory in position in the light beam of the spectrophotometer, a planar mirror deflects the light beam to the sample from which it is reflected to a second planar mirror oriented so that it reflects the light beam back on its normal path to the spectrophotometer. For a sample consisting of a thin film of a surface coating material deposited on a reflecting surface, a n absorption spectrum of the film is obtained as the light passes through the film to the reflecting substrate and then back through the film a second time. VOL. 32, NO. 3, MARCH 1960
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