F. Šebesta

Composite ion exchanger with ammonium molybdophosphate and its properties

An organic binding polymer based on polyacrylonitrile (PAN) was used for the preparation of the composite exchanger containing ammonium molybdophosphate (AMP) as the active component. Due to the improvement of granulometric properties of powdered AMP with a binding polymer, an exchanger suitable for the application in column operations was prepared. Study of the properties of the exchanger AMP-PAN proved that kinetics of cesium sorption, capacity of the exchanger for cesium and desorption of cesium are not influenced by the binding polymer. The composite exchanger AMP-PAN described is therefore suitable for the selective separation and concentration of cesium and purification of radioactive wastes from137Cs.

Particulate forms of radium and barium in uranium mine waste waters and receiving river waters

Abstract A method of selective dissolution was used for analysis of particulate forms of radium and barium in a system consisting of uranium mine waste waters purified by coprecipitation with barium sulphate and of adjacent river waters. Four particulate forms of both the elements were distinguished: “loosely bound”, “acid soluble”, Ba(Ra)SO 4 and “in crystalline detritus”. It was found that the distribution of radium and barium between dissolved and particulate forms in waste waters depended on the time interval elapsing between the sampling and membrane filtration of the waters. No such dependence occurred in river water. The main particulate form of radium and barium in the system was Ba(Ra)SO 4 . River water upstream of the mine water discharge contained radium mainly in “acid soluble” form or “in crystalline detritus” and barium as BaSO 4 or “crystalline detritus”. In unpurified mine effluents, a large part of radium and barium was present as “crystalline detritus”. Abundance of the “loosely bound” form was very low in all the samples analyzed. The bond of radium in bottom sediments was approximately the same as that in the solids suspended in waste waters. Suitability and accuracy of the selective dissolution method for analysis of surface and waste waters has been demonstrated by the analysis of the results and by radiotracer experiments.

Method of selective dissolution for characterization of particulate forms of Radium and Barium in natural and waste waters

Abstract A new method is proposed for characterization of particulate forms of radium and barium in natural and waste waters. Particulate solids suspended in 1–3 l. of water are first concentrated by membrane filtration or by centrifugation to 20–50 ml of a concentrate which is then filtered through a small-size membrane filter. The solids retained by the filter are successively washed with three selective solvents releasing “loosely bound”, “acid soluble” and “barium sulfate” forms of radium and barium. Compositions and volumes of the selective solvents have been chosen using model experiments and partially checked by analysis of natural samples. Radium and barium “in crystalline detritus” remain on the filter and are determined after an acid digestion of the filter. The principal criteria and selectivity of the method are discussed.

A generator for preparation of carrier-free224Ra

The construction of a dynamic generator for the separation of carrier-free224Ra is described. The mother228Th was extracted on the top of the column with di-(2-ethylhexyl)phosphoric acid on hydrophobized Chromosorb W DMCS. The function of the generator was checked during 6 months by measuring the decontamination of224Ra from228Th. Simultaneously the yield of224Ra was determined as a function of the HCl concentration and of the means of milking. The best results were obtained with 0.01–0.1M HCl; the yield was about 75% of the theoretical value, and the224Ra contained less than 0.01% of228Th.

EXTRACTION CHROMATOGRAPHY USING CHELATING AGENTS

The extraction-chromatographic behaviour of zinc on a column with dithizone as chelating agent has been investigated in the absence and presence of oxalic acid as masking agent. From the results the extraction constant and the stability constants of zinc oxalate complexes have been determined. These values are in good agreement with the published data so that it seems possible to predict the extraction-chromatographic separation of various metals from known extraction and stability constants.

New type of sorbents based on polyethers and some hydrophobic anions

New type of sorbent, based on the complexing properties of polyethyleneglycols, with high selectivity for Ba and Sr is described. The dependences of Kd on the initial concentration of HNO3 for Ba, Sr, Eu, Ce, Cs and Na were studied. The capacity of two model sorbents for uptake of Cs and Sr is given. The properties of the sorbents are compared with those of the ammonium salts of heteropolyacids.

Synergistic extraction of radium using 2-thenoyltrifluoroacetone and tributyl phosphate or trioctylphosphine oxide

The extraction of radium into a mixture of 2-thenoyltrifluoroacetone (HTTA) and tributyl phosphate (TBP) or trioctylphosphine oxide (TOPO) in n-hexane or cyclohexane has been investigated with regard to the dependence on pH, and TBP and TOPO concentrations. It has been found that the formation of mixed complexes of the type Ra(TTA)2 (TBP)2 and Ra(TTA)2(TOPO)2 occurs and the overall extraction constants of both complexes were calculated. With the systems described, very high distribution ratios of radium have been attained; these may advantageously be used for the separation and concentration of traces of radium.

SCINTILLATION EMANOMETRIC DETERMINATION OF RADIUM-226 IN WATERS USING A NEW METHOD OF RADIUM PRECONCENTRATION

A modified method of scintillation emanometry for radium determination is described which uses a simple and effective preconcentration of dissolved radium by coprecipitation with a ternary complex of calcium phosphomolybdate and polyethylene glycol. After dissolution of the voluminous precipitate in an alkaline solution of ethylenediamine-tetraacetic acid and deemanation of radon by a simplified procedure, the activity of radon is measured in a scintillation cell. The accuracy and precision of the method are very good as shown by determination of radium-226 in standard solutions and in natural water samples distributed by IAEA in the frame of interlaboratory comparison program. Easy construction of a simple scintillation cell is described, yielding cells with reproducible parameters and sufficient sensitivity for radium analysis in natural waters.

SYNERGISTIC EXTRACTION OF RADIUM AND BARIUM USING 1-PHENYL-3-METHYL-4-BENZOYLPYRAZOL-5-ONE AND TRIOCTYLPHOSPHINE OXIDE

The extraction of radium and barium into a mixture of 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPy) and trioctylphosphine oxide (TOPO) in n-hexane or cyclohexane was investigated as a function of pH and TOPO concentration. It was found that the synergistic enhancement of the extraction is caused by the formation of mixed complexes of type M(Py)2 (TOPO)3 and the overall extraction constants of both complexes were calculated.

EXTRACTION CHROMATOGRAPHY USING CHELATING AGENTS III. N-BENZOYL-N-PHENYLHYDROXYLAMINE AS A CHELATING AGENT*

The extraction-chromatographic behaviour of copper, indium and thorium was investigated on a column with N-benzoyl-N-phenylhydroxylamine in chloroform. From the results the values of the extraction constanst of the metal chelates were calculated and found to be in good agreement with the published values. It is possible to calculate the optimum conditions for the separation of the different metals from known extraction constants. The separation of65Zn−64Cu;60Co−59Fe;60Co−64Cu−59Fe;238U−234Th(UX1) and232Th−233Pa in this system is reported. The described procedures were used for the preparation of carrier-free234Th(UX1) from uranyl nitrate and233Pa from irradiated thorium.