Determination of Radioactivity in Saline Waters S. GOLDIN, and RICHARD J. VELTEN Engineering Center, U. S. Department of Health, Education,
VINCENT J. SODD, ABRAHAM Robert A. Taft Sanitary
b A screening method for the determination of gross radioactivity in saline waters is based on the precipitation of many cations as sulfides from ammoniacal solution. Carrier lanthanum, iron(lll), cobalt(ll), zinc, and nickel are precipitated while the major sea water salts are left in solution. An alkaline earth fraction containing strontium, barium, and radium can b e recovered by precipitation of carbonates from the sulfide filtrate followed by precipitation of strontium carrier as nitrate. Cesium can b e recovered separately by precipitation with silicotungstic acid and conventional purification.
T
determination of radioactivity in waters of high salt content is of considerable imyortance. Radioactive wastes may reach such waters from naval or marine reactors, from stationary reactors on rivers or estuaries, or from the discharge of packaged materials. I n connection with all these activities, it is necessary to determine the present levels of activity as a part of preoperational surveys and to measure the quantity of radioactivitadded to sea water. Although radionuclide analysis is required for complete evaluation of contamination, a screening method for the determination of gross radioactivity would be of considerable value. The simplest and probably the most widespread method is evaporation (3, 6). Because of self-absorpt,ion losses from thr residual solids, evaporation techniqucs are limited to extremely small volumes, no more than 10 ml. of water of 3.5% solids content. When radioactivity levels are so small as to require the analysis of somewhat larger samples, carbonate precipitation has been used. I n ammonium-ammonium hydroxide si-stems, addition of sodium carbonate has precipitstpd some 75% of fission liroduct elements from 100to 250-ml. samplps ( 7 ) . Khen a still more sensitive determination was required, a method applicable to larger samples (1 liter or largcr) n-as sought. A comparison of the nature of the salt present in natural waters with the more common radioactive clements indicated that a chemical separation of many of the latter was feasible. The major cations in sea HE
and Welfare, Cincinnati, Ohio
water (4) are sodium, magnesium, calcium, and potassium; the major anions are chloride, sulfate, and bicarbonate. These ions amount to 99.77, of the solids content of sea water, with 0.23y0 of the remainder attributable to strontium, bromine, and fluorine. These same ions, incidentally, also make up the bulk of the solids content of surface and ground waters ( 5 ) . On the other hand, many of the more important radioelements are transition metals, rare earths, or polyvalent metals. Important among these are such fission products as cerium, yttrium, zirconium, niobium, and ruthenium, and such induced activities as cobalt, zinc, iron, nickel, and chromium. Conventional schemes of qualitative analysis indicated that most of the metallic elements should be recovered by precipitation as sulfides from ammoniacal solution. Those not precipitated would be the alkali, alkaline earth, and arsenic-antimony-tin groups. The most important radioelements which would not be recovered in such a precipitate would include cesium, strontium, barium, radium, and iodine. Accordingly, the method was extended to include ways of recovering these materials from the mother liquor remaining after precipitation of the sulfides.
Table I. Recovery of Tracers by Sulfide Precipitation
Per Cent Recovered ?;HIOH- NaOHthiothioKHaOHacetamide acetamide H2S 97 94 98 95 99
>99
...
...
... C06Q a
... >99 99 >99 >99
>99 >99 >99
93 >99
...
>99
Plus daughter activity in equilibrium.
hydroxide rather than ammonium hydroxide was used to make the solution basic before the thioacetamide precipitation. Although the tracer recoveries were excellent, the method was abandoned because of the mass of basic sulfide precipitate recovered, which would cause large self-absorption losses in beta counting. The results obtained from this procedure are also listed in Table I.
HYDROQEK SULFIDE. This method is essentially the same as the thioacetamide method. After the acidified solution was boiled, it was made basic m-ith ammonium hydroxide and the basic sulfides were precipitated by the addition of hydrogen sulfide gas. The precipitate EXPERIMENTAL was then treated in the same way Sulfide Methods. THIOACETAJIIDE. as in the thioacetamide method. These One liter of sea water, plus added lanresults, too, are listed in Table I. thanum, iron(III), cobalt(II), zinc, nickel, and cesium carriers (10 mg. Recovery of Alkaline Earth and each), and strontium carrier (44 mg.) Alkali Metal Activities. While exwas acidified, boiled, and made basic cellent for a screening of gross acwith ammonium hydroxide. Seventy tivity, the basic sulfide precipitate milliliters of 4% (w./v.) thioacetamide does not contain the alkali metal or were added to the basic solution and alkaline earth radionuclides. heated until the sulfide precipitate formed. The mixture was heated furTo determine the alkaline earth acther until the hydrogen sulfide odor tivity, the filtrate and washings from was no longer noticeable. It was often the sulfide precipitation were acidified necessary to dilute the mixture with diswith hydrochloric acid and boiled to tilled water to prevent crystallization of remove any residual hydrogen sulfide. the salts in solution. Sodium hydroxide was added to make After removal of the hydrogen sulfide, the solution strongly basic and the the sulfide precipitate was centrifuged, alkaline earths %ere precipitated with washed with water, dried, and counted. 50 ml. of 3N sodium carbonate. For evaluation the sulfide precipitate If a large amount of magnesium is was collected, dissolved in hydrochloricpresent, as in sea water, it can be nitric acid mixtures, and counted in removed by prior precipitation with solution by gamma scintillation using 8-quinolinol a t pH 7 ( I ) . Alternatively, a 20-channel spectrometer. The results the carbonate precipitate from the are listed in Table I. sodium hydroxide-sodium carbonate treatment may be dissolved in hydroIn a variation of this method, sodium VOL. 32, NO. 1, JANUARY 1960
* 25
chloric acid, made basic with excess ammonium hydroxide, and reprecipitated with sodium carbonate. The precipitate was collected, washed, and dried. Thirty milliliters of concentrated nitric acid were added and the mixture was digested warm for 10 to 15 minutes; then it was cooled in an ice bath to just below room temperature. The precipitated strontium nitrate was collected by centrifugation and Tvashed by treatment with 30 ml. of concentrated nitric acid as above. The strontium nitrate was dissolved in 1%-ater, and made basic with ammonium liydroxide, and the strontium was reprecipitated as carbonate by adding 10 nil. of 3N sodium carbonate. The carbonate precipitate was transferred to a suitable counting dish, dried, and betacounted for total alkaline earth activity. Cesium was precipitated from the first carbonate filtrate with silicotungstic acid. After concentration, the filtrate
was made 3N in hydrochloric acid, after which 0.125M silicotungstic acid, 2 ml. per 100 ml., was added. The precipitate was collected and purified in the standard manner (a), after which it was counted by gamma scintillation or in a beta-counter. By precipitation of basic sulfide, folloTved by carbonate and cesium precipitation steps, most isotopes of interest in sea water can be separated. If other elements are to be determined, separate portions must be taken for the analysis. The sulfide precipitate contains more than 95y0 of the activity due to rare earths (including yttrium), ruthenium, chromium, zinc, cobalt, and similar metals. The alkaline earth precipitate contains 90% of the strontium and presumably a similar amount of the barium-radium. The cesium
precipitate contains about 95% of the cesium. LITERATURE CITED
(1) Goldin, A. S., Velten, R.J., Frishkorn, G. W., ANAL.CHEIII.31, 1490 (1959). 1 2 ) Kahn. B.. Smith. D. K.. Straub.
Straub, (1958). N. IT., " PrenI
,
",
Water
Supply Paper 6 5 i (1952). (6) University of Washington Applied Fisheries Laboratory, AEC Doc. UWFL-42 ( h g . 15, 1955). ( 7 ) Zbid., UWFL-43 (Dee. 30, 1955). RECEIVED for review June 29, 1959. rlccepted October 16, 1959. Work supported in part by the -4tomic Energy Commission under Contract Yo. AT(495)-1288.
Cathodic Action of the Phenylenediamine Dihydrochlorides at the Dropping Mercury Electrode STEWART
R. COOPER
and OSCAR
F.
FOWLKES'
Howard University, Washington, D. C.
b The purpose of this investigation was to work out a method whereby the phenylenediamine dihydrochlorides could b e determined by reduction at a dropping mercury electrode. The ortho, meta, and para dihydrochlorides dissolved in tetramethylammonium bromide, with gelatin as a maximum suppressor, gave well defined waves in the 10-3M range. A plot of idvs. C gave a reasonably straight line. These compounds give waves that are easier to interpret than previous methods that have been proposed.
T
cathodic action of the phenylenediamine dihydrochlorides a t a dropping mercury electrode has been studied. The i d measurenents were made in the 10-3dI range and were read a t an E value of approximately -1.9 volts us. the saturated calomel electrode. A plot of i d 0s. C showed that it is possible to use such a graph in the estimation of these salts. Julian and Ruby (2) determined the oxidation-reduction potential of some substituted phenylenediamines polarographically using a platinum electrode. Bogdanov and Sukhobokova ( 1 ) determined p-phenylenediamine by titraHE
1 Present address, Riker Pharmaceutical Co., Northridge, Calif.
26
ANALYTICAL CHEMISTRY
€de
VS. S.C.E., VOLTS
Figure 1 . Current-voltage curves for o-phenylenediamine dihydrochloride in 0.1 M tetramethylammonium bromide and 0.01% gelatin 1 . 0.1M tetramethylammonium bromide o-Phenylenediamine dihydrochloride, X 10 - 3
2.
3. 4.
0.5 1.0 2.0
tion with ceric ion using a rotating platinum electrode. Lord and Rogers (3) analyzed the diamines by the anodic voltage scan method. Parker and Adams (4) determined the 0- and p-phenylenediamines by anodic oxidation using a rotating platinum electrode and the current scanning technique.
5.
4.0 6. 6.0
This investigation is concerned with the possibility of determining the three phenylenediamine dihydrochlorides through the use of a dropping mercury electrode acting as cathode. The limiting currents obtained appear to be more linear than those obtained by the voltage scan or current scan technique.
