The isolation of minor uranium concentration from thorium matrix in HCl medium was investigated using liquid emulsion membrane
(LEM) containing TOPO as carrier, Span 80 as surfactant and sodium citrate as stripping agent. The factors affecting the stability
of the LEM were investigated. Different parameters affecting the permeation process were also studied. The results obtained
showed that, under certain conditions it is possible to isolate ca. 98% of U(VI) (120 ppm) in 1.0M HCl solution containing
Th (1000 ppm). The isolated U was found to be contaminated with less than 3% of Th.
It is found that from aqueous nitric acid media, Pd is highly extracted by chloroform solutions containing triphenylphosphine (Ph3P) and not extracted by triphenylphosphine oxide (Ph3PO) diluted with chloroform. The effect of diluent, nitric acid molarities, Ph3P concentration and temperature on palladium extraction by Ph3P was investigated. Slope analysis of the experimental results indicated that the main extracted species is in the form of Pd(NO3)2·2Ph3P.IR spectrum analysis of the extracted complex indicated the direct extraction of palladium as nitrate and bonding to phosphorus. Extraction of some fission product radionuclides from 2M HNO3 showed the selective extraction of palladium by Ph3P in chloroform.
Technetium(VII) was separated from interfering substances by extraction with 0.01M tetraphenylarsonium chloride in chloroform. To avoid back-extraction, enrichment at the hanging mercury drop electrode (HMDE) has been carried out directly in the organic phase after addition of 0.01M NaOH as an electrolyte and ethanol as a homogenized agent. By application of a deposition voltage of –1.6 V, as well as DPCSV, a distinct current signal at –0.26 V (vs. Ag/AgCl) was obtained. The detection limit was found to be 3·10–8 M Tc.
The extraction of Pd(II) by triphenylphosphine sulfide (Ph3PS) in benzene from nitric acid solutions has been investigated. The effect of different parameters on the extraction of palladium was studied. Based on the results, an equilibrium model is proposed. The stoichiometry of the extracted species was elucidated and found to be Pd(NO3)22Ph3PS. Possible interference with selected radionuclides that might exist in high level liquid waste was investigated and discussed.
Comparative studies between column and batch liquid emulsion membrane techniques based on HDEHP/HCl system were carried out to develop a system for isolation of234Th from natural uranium. For column investigations a spray column was constructed and used with two different modes. In the first mode the feed solution was circulated through the membrane while in the second mode the membrane phase was circulated through the feed solution. The results showed that, kinetically, the equilibrium for thorium separation using batch technique is faster than the continous column system. Quantitative permeation of thorium was achieved within one minute of mixing whereby the permeation of uranium reached equilibrium after 3 minutes with a permeation percentage less than 6%. A procedure was developed to separate234Th from natural uranium with high radiochemical purity of more than 98%.