Separation of thallium-201 from Tl,Pb and Bi cyclotron target materials

Radiochemical methods of thallium-201 separation from proton-irradiated thallium, lead and bismuth targets have been developed. The procedures are based on the processes of coprecipitation, ion-exchange chromatography and high temperature gas chemistry. The purity of thallium samples complies with requirements of nuclear medicine for thallium-201 product.     

Separations involving sulphides : Separation of (a) bismuth,lead and cadmium from mercury,and (b) bismuth and mercury from indium

It has been shown that 2N sodium sulphide reagent can be successfully used in the seperation and estimation of: (a) bismuth, lead and cadmium from mercury, and (b) bismuth and mercury from indium     

Pb5.0(1)In8.4(1)Bi1.6(1)S20, a new quaternary lead indium bismuth sulfide

The title phase, first detected in the early 1980s but hitherto unpublished, has been resynthesized and structurally characterized. Unambiguous determination of the chemical composition was not possible by structure analysis alone, but required additional analytical methods. The complex structure shows a close similarity to the structures of two related compounds, one known by the formula Pb_1.6In₈Bi₄S₁₉ and the other being the ternary compound Pb₆In₁₀S₂₁. This is despite the fact that the three phases correspond to very different Pb:Bi ratios. A geometric mechanism is described by which the three structures can be transformed into each other, provided that the heavy atoms Pb and Bi are treated as equivalent.     

Separation of bismuth from lead, copper and other elements by means of anion exchange

The anion-exchange behaviour of bismuth and various other elements has been investigated in media consisting of methyl glycol and nitric acid. Through the determination of the distribution coefficients in such mixtures, a method for the anion-exchange separation of bismuth from many metal ions has been developed. A mixture of 90% methyl glycol and 10% 5M nitric acid is a suitable medium for this separation on the strongly-basic anion exchanger Dowex 1, X8. Only bismuth, thorium and lanthanum are strongly retained on the resin in these conditions. All other elements investigated, such as lead, copper, iron, etc., are either only weakly adsorbed or are not absorbed. By means of this ion-exchange procedure, a series of analyses of copper-base alloys for bismuth has been carried out. The results show that this method can be used successfully for the quantitative isolation of bismuth from such materials. The final determination of bismuth in the eluates is performed by complexometric titration.     

Selective separation of bismuth (212Bi) from A228Th source

Using alkyl radicals, the nuclides²¹⁶Po,²¹²Pb,²¹²Bi and²⁰⁸Tl can be transported from a²²⁸Th source to a detection position. The separation of the alkyl compounds was investigated either using thermal decomposition or a reaction with a gas which yields a non volatile compound. Whereas the thermal decomposition leads only to low enrichment factors,²¹²Bi was separated selectively by introducing chlorine into the gas phase system.     

Separation of NCA 88Zr from proton irradiated natY target: a novel approach using low cost bio-sorbent potato peel charcoal

Separation of no-carrier-added (NCA) ⁸⁸Zr from natural yttrium target irradiated with proton beam has been studied using nature-resourced material, potato peel, which is a commonly available domestic waste. Here, an attempt has been undertaken to exploit natural resource as separating agent. Good separation of NCA ⁸⁸Zr from bulk Yttrium target could be achieved at 0.01 M HCl concentration, when extraction was carried out using 20 mg potato peel charcoal—a natural bio-sorbent. ⁸⁸Zr was extracted in the solid phase leaving behind bulk Y in the aqueous phase.

     

Mössbauer study of (Bi,Pb)-2223 superconductors irradiated with 86Kr ions

⁵⁷Fe Mössbauer spectroscopy was used to study the effects of heavy ion irradiation on (Bi_0.93Pb_0.17)Sr_1.9Ca_2.05(Cu_1.02Fe_0.01)₃O_y superconductors. The Mössbauer spectra of the irradiated superconductor showed significant changes in the subspectra belonging to different Cu microenvironments into which Fe ions were substituted. The relative occurrence of Fe occupying the square pyramidal fivefold oxygen coordinated Cu sites decreased while Fe^{3 +} substituting the square planar fourfold oxygen coordinated Cu sites increased upon bombardment by 246 MeV ⁸⁶Kr⁸⁺ ions. This observation was interpreted on the basis of partial replacement of the apical oxygen atoms in the square pyramids surrounding one of the Cu sites. Such oxygen vacancies create additional square planar coordination sites for Cu. These results also support the covalent character of Cu-O bonds in the superconducting layer as well as the ionic character of bond of apical oxygen to Cu.     

Coulometric determination of lead(II) and lead(IV) in high-T c superconductors containing copper and bismuth

The behavior of Pb(II) and Pb(IV) was studied by voltammetry in supporting electrolytes containing 0.1 M NaOH or 0.1 M NaOH + 0.1 M Na₃Cit at a graphite and a mercury thin-film electrodes. The best conditions were found for the coulometric determination of Pb by the oxidation of Pb(0) to Pb(II) in the presence of 5- to 20-fold amounts of Bi(III) and Cu(II) within the range 0.2–2 mg Pb(II) with an error and a relative standard deviation of less than 0.5%. Along with the procedure proposed previously for the determination of Pb(II) and Pb(IV) present simultaneously using a platinum gauze electrode, this procedure was applied to the determination of Pb(II) and Pb(IV) in samples of high-T_c. Cu-Bi superconductors. For samples of high-T_c. Bi-Pb-A-Cu-0 superconductors (A = Ba or Sr-Ca) containing from 2 to 12% Pb(II), the relative standard deviation was less than 0.5%; for 0.6–7% Pb(IV), it was 1-0.2%.     

Oxygen exchange study in phase transformations of superconducting bismuth cuprates (Pb2212 and Pb2223)

The oxygen exchange between the condensed phase(s) and the gas phase was studied as a function of temperature for superconducting phases of the system (Bi,Pb)-Sr-Ca-Cu-O.An oxygen probe apparatus allowed confirmation that the variation in oxygen composition in the Pb2212 and Pb2223 superconducting phases is a reversible phenomenon on heating and cooling. It was demonstrated that the mass loss of both phases, for the 905 and 980°C isotherms, was due to the oxygen composition variation and to PbO loss (this latter phenomenon begin irreversible).     

Density-functional study of small neutral and cationic bismuth clusters Bi(n) and Bi(n) (+)(n=2-24)

Density-functional theory with scalar-relativistic pseudopotential and a generalized gradient correction is used to calculate the neutral and cationic Bi(n) clusters (2< or =n< or =24), with the aim to elucidate their structural evolution, relative stability, and magnetic property. The structures of neutral Bi clusters are found to be similar to that of other group-V elemental clusters, with the extensively studied sizes of n=4 and 8 having a tetrahedron and wedgelike structure, respectively. Generally, larger Bi clusters consist of a combination of several stable units of Bi(4), Bi(6), and Bi(8), and they have a tendency to form an amorphous structure with the increase of cluster sizes. The curves of second order energy difference exhibit strong odd-even alternations for both neutral and cationic Bi clusters, indicating that even-atom (odd-atom) sizes are relatively stable in neutral clusters (cationic clusters). The calculated magnetic moments are 1micro (B) for odd-atom clusters and zero for even-atom clusters. We propose that the difference in magnetism between experiment and theory can be greatly improved by considering the orbital contribution. The calculated fragmentation behavior agrees well with the experiment, and for each cationic cluster the dissociation into Bi(4) or Bi(7) (+) subclusters confirms the special stability of Bi(4) and Bi(7) (+). Moreover, the bond orders and the gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital show that small Bi clusters would prefer semiconductor characters to metallicity.     

Individual and simultaneous determination of lead, cadmium, and zinc by anodic stripping voltammetry at a bismuth bulk electrode

A bismuth bulk electrode (BiBE) has been investigated as an alternative electrode for the anodic stripping voltammetric (ASV) analysis of Pb(II), Cd(II), and Zn(II). The BiBE, which is fabricated in-house, shows results comparable to those of similar analyses at other Bi-based electrodes. Metal accumulation is achieved by holding the electrode potential at −1.4 V (vs. Ag/AgCl) for 180 s followed by a square wave voltammetric stripping scan from −1.4 to −0.35 V. Calibration plots are obtained for all three metals, individually and simultaneously, in the10-100 μg L⁻¹ range, with a detection limit of 93, 54, and 396 ng L⁻¹ for Pb(II), Cd(II), Zn(II), respectively. A slight reduction in slope is observed for Cd(II) and Pb(II) when the three metals are calibrated simultaneously vs. individually. Comparing the sensitivities of the metals when calibrated individually vs. in a mixture reveals that Zn(II) is not affected by stripping in a mixture. However, Pb(II) and Cd(II) have decreasing sensitivities in a mixture. The optimized method has been successfully used to test contaminated river water by standard addition. The results demonstrate the ability of the BiBE as an alternative electrode material in heavy metal analysis.     

Novel quaternary lanthanum bismuth sulfides Pb(2)La(x)Bi(8-x)(S(14)), Sr(2)La(x)Bi(8-x)S(14), and Cs(2)La(x)Bi(10-x)S(16) with complex structures

The compounds Pb(2)La(x)Bi(8-x)S(14) (I), Sr(2)La(x)Bi(8-x)S(14) (II), and Cs(2)La(x)Bi(10-x)S(16) (III) were synthesized from the corresponding elements or binary sulfides at temperatures above 850 degrees C. Compounds I and II are isostructural, forming a new structure type, while the structure of III is related to the structure of the mineral kobellite. All compounds crystallize in the orthorhombic space group Pnma (No. 62) with a = 21.2592(4) A, b = 4.0418(1) A, c = 28.1718(3) A, Z = 4 for I, a = 21.190(1) A, b = 4.0417(2) A, c = 28.285(2) A, Z = 4 for II and a = 34.893(4) A, b = 4.0697(4) A, c = 21.508(2) A, Z = 4 for III. All compounds exhibit mixed site occupancy between Bi and La. Furthermore, I and II exhibit disorder between the divalent atom (Sr or Pb) and/or La and/or Bi. The structures of I and II consist of thin walls made of two metal-atom-thick NaCl-type blocks running in two opposite directions in the ac plane, forming rhombus-shaped tunnels. These tunnels are filled with Bi(2)Te(3)-type fragments. In the points where the walls intersect they form Gd(2)S(3)-type fragments. The structure of III consists of a complex three-dimensional framework with Cs-filled tunnels. All compounds are semiconductors with band gaps around 1.0 eV, and they melt around 740-860 degrees C.     

Wet-chemistry method for the separation of no-carrier-added 211At/211gPo from 209Bi target irradiated by alpha-beam in cyclotron

We present a fast and effective wet-chemistry method, used to obtain the pure alpha-emitter ²¹¹At/^211gPo (T _1/2 = 7.214 h/516 ms), produced by ²⁰⁹Bi(α,2n) reaction in NCA form. It is a selective radiochemical separation of the At radionuclides from the target and the impurities, characterized by a radionuclidic purity close to 100%, based on the dissolution and the dilution of the irradiated target in acidic medium, on the extraction with DIPE, followed by the back-extraction with NaOH. As a result, we obtain a yield greater than 90–97% in a range from 0.75M to 2.00M.     

Separation of (203)Pb by ion-exchange chromatography on chelex 100 after production of (203)Pb by the Pb(p, xn)(203)Bi--> EC.beta+ (203)Pb nuclear reaction

Bismuth radioisotopes, produced by 50-MeV proton bombardment of a lead target in a cyclotron, are separated from the lead target material by ion-exchange chromatography on a column containing 5.0 ml of Chelex 100. After a decay period of 24 hr, the (203)Pb formed in situ is eluted from the column and then separated from (200)Tl and (201)Tl on a second ion-exchange column containing 0.5 ml of Chelex 100. Separations are sharp and carrier-free (203)Pb is obtained.     

Separation of silver from waste waters by ion-exchange resins and concentration by microbial cells

Summary Waste waters of film processing plants are rich with silver. Part of the silver is regenerated electrochemically, but the rest (0.5 g) remains in waste waters and is sent to sewers. This is a bad politic from both the environmental (toxic waste waters) and the economical point of view (a waste of silver). In this work, the silver was isolated by ion-exchange resins and then concentrated by microorganisms. For exchange of silver, Ionenaustauscher I, II and IV were used. The batch method was used to obtain a static equilibrium. Silver elution from exchangers is based on silver transformation to a stable cation or anion complex. By varying the ligands, pH and eluent concentrations, optimum elution is found at 1 mol/l Na₂S₂O₃, 1 mol/l NH₃, 2 mol/l HNO₃ and 1 mol/l (NH₂)₂CO. The concentration of silver in the eluent is about 50 mg/l. The silver ion uptake from solutions after ion exchange by mixed bacterial culture isolated from photographic waste water drain and pure bacterial cultures Escherichia coli 3009 and Bacillus subtilis 3053. was studied. Experiments were carried out in submerse culture at pH 7 with different Ag⁺ concentrations (4, 8 and 40 mg/l) on a rotary shaker (100 rpm) at 37°C. At the lower Ag⁺ concentrations a good growth and simultaneous removal of Ag⁺ from the solutions was achieved. At Ag⁺ concentration of 40 mg/l growth and removal of Ag⁺ by mixed and pure culture differed significantly. Thus mixed bacterial culture grew well and at the same time removed efficiently Ag⁺ (approximately 90%) from medium. Pure bacterial cultures on the contrary were unable to grow at 40 mg/l Ag⁺, though their biomass showed to be an effective biosorbent for Ag⁺ (approximately 80% of Ag⁺ removal).