Electrodeposition of protactinium

J. Inorg.Nuc.LChem.. 1964.Vol.26, pp. 253 to 255. PergamonPressLtd. Printedin Northern

Ireland

ELECTRODEPOSITION OF PROTACTINIUM H. SHIMOJIMA and J. TAKAGI NAIG Nuclear Research Laboratory, Kawasaki, Japan

(Received 24 May 1963; in revised form 8 July 1963). A~tract--Electrodeposition of protactinium was investigated by using mainly ammonium formatesulphuric acid aqueous solution. Eighty per cent of protactinium was electrodeposited from 0"1 N ammonium formate--0.1 N sulphuric acid solution under a constant current density of 80 mA/cma at room temperature. From the result of 0t-spectrometry the deposited film of protactinium is considered to be thin and uniform enough to be used for or-counting and co-spectrometry. ELECTRODEPOSITEDfilms of the actinide elements are widely used for various purposes such as 0c-counting, 0c-spectrometry and nuclear reaction experiments. For ~-spectrometry thin, uniformly distributed films with countable activity are required. There is great difficulty in preparing such films o f the long-lived s-emitters but successful results ~1-5~ have been reported on the preparations of such films of most actinide elements using electrodeposition techniques. Protactinium electrodeposition has been reported by some authors 16,r) but high yield deposition has been a difficult problem. The authors attempted to electrodeposit protactinium on platinum plates with high yield and at the same time to prepare thin, uniformly distributed alpha sources o f protactinium --231. K o tS~ has reported the electrodeposition of the various actinide elements with g o o d yield using aqueous solutions o f a m m o n i u m formate and perchloric acid. The authors applied this a m m o n i u m formate-acid system to protactinium. Pa(V) is not stable for long periods o f time in ordinary aqueous solutions except in sulphuric or hydrofluoric acid solution, tS~ So, in the present work the authors adopted the amm o n i u m formate-sulphuric acid system, the o p t i m u m concentration of which was investigated. Some other electrolysis solutions were also investigated. EXPERIMENTAL The cell described by CA~,mRONand MORRISca' was used for the electrolysis with a slight improvement. The anode was made of coiled 0.5 mm diameter platinum wire which was rotated at a velocity of 100 rpm. A 0'2 mm thick platinum disk of 21 mm diameter ws used as the cathode, mPagO5 purchased from Amersham was digested with concentrated sulphuric acid for several hours and from ¢1~H. W. MILLERand R. J. BROtmS, Analyt, Chem. 24, 536 (1952). c~, C. R. WILSONand A. LANGER,Nucleonics 11 No. 8. 48 (1953). ca, V. B. DI~DOvand V. N. KOSYAKOV,Proceedings of the International Conference on the Peaceful Uses of Atomic Energy, Geneva 1955. 7, 369 (P/675). United Nations (1956). "' R. Ko, Nucleonics 14, No. 7, 74 (1956). ¢5, R. Ko, Nucleonics 15, No. 1, 72 (1957). ¢" C. FERRADINI,J. Chim. Phys. 50, 589 (1953). ~TjC. Fm~ADnCtand M. HAmSINSKVJ. Chim. Phys. 53, 722 (1956). ¢'~ W. H. Klmav, "The Radioebemistry of Protactinium" NAS-NS 3016. ¢'~ quoted from C. C. CASTO "Analytical Chemistry of the Manhattan Projects" NNES. Div 8-1,529, New York (1950). 253

254

H. SHIMOJIMA and J. TAKAGI

this solution the electrolysis solutions were prepared using commercially available reagents of reagent grade. Electrolysis was carried on with about 5 ml of the solution containing about 0-1/,g of protactinium under a constant current density of 80 mA/cm 2. A 6 V battery was used for the power supply, the current being controlled with resistance. After the electrolysis the solution was pipetted out and the cathode platinum plate was washed with water and acetic acid alternately. Then the plate was ignited to redness. The deposition yields were measured by counting alpha activity of both the plate and the feed solution. (An aliquot of the feed solution was evaporated to dryness on a platinum plate for counting.) RESULTS AND DISCUSSION

The deposition yields obtained are listed in Table 1. 0.1 N HaSO4-0" 1 N HCO~NH4 solution gave best result and the film was thin, uniform and adherent. It is believed TABLE 1.--ELECTRODEPOSITIONYIELD H,SO, 0-1 N 0.1 N 0.1 N 0"2 0"2 0.I 2 0.1

OF PROTACTINIUM

HCO,NH4

Other reagent

Time (hr)

Yield (%)

0'1 N 0.1 N 0.1 N 0.2 0"2 2 0.2 ~

---

4 6

71 4- 2 76 4- 2

--

8

8 0 4- 2

--

4

5 2 4- 2

HCIO~ 0"2 N -m NH~C1 4 N

4

,'--40 <5 ,~50 65 4- 2

4 4

4

that an insoluble hydroxide of protactinium is first deposited and after ignition converted to an adherent oxide film. It is an interesting fact that the anode platinum wire had considerable activity which was estimated to attain several per cent of activity in the feed solution after 4 hr.

f u

I 0

50

I00

Clmnnel number

FIG. l(a).--ce-spectrum of evaporated uxPa source.

Electrodeposition of protactinium

255

According to Ko's work rinsing the platinum plate with hot nitric acid and then with hot hydrochloric acid has a good effect on the deposition yield but in the present experiment polishing the platinum surface with fine powder proved to have a much greater effect. Several kinds of powders were used and best results were obtained with

5-00

200

--

49~] I y 1504

4.72MeV o

Channel number 50

I

~00

Flo. l(b).--:t-Spectrum of electrodeposited~8~Pasource. 600-800 mesh aluminum powder. Alumina powder may be used also. The polishing technique was very important and without it a uniformly distributed film was not obtained. Figure l(a) shows the ~-spectrum of a protactinium-231 source produced by evaporation o f a sulphuric acid solution and Fig. l(b) that of the source produced by the electrodeposition technique mentioned above. A p--n junction type silicon detector was used to measure the ~-spectra. The electrodeposited source showed remarkable improvement in resolution when compared to the evaporated source. Electrodeposition on stainless steel was also attempted but was not successful.