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Composite sorbents of inorganic ion-exchangers and polyacrylonitrile binding matrix

I. Methods of modification of properties of inorganic ion-exchangers for application in column packed beds

Journal of Radioanalytical and Nuclear Chemistry
Author: F. Šebesta

Abstract  

Methods of preparation of granules of inorganic ion exchangers as well as methods for improvement of granular strength of these materials are reviewed. The resulting ion exchangers are classified in three groups—intrinsic, supported and composite ion exchangers. Their properties are compared and possibilities of their technological application are evaluated. A new method of preparation of inorganic-organic composite sorbents of inorganic ion-exchangers and polyacrylonitrile binding matrix is described, advantages and disadvantages of such sorbents are discussed. Proposed fields of application include tratment of liquid radioactive and/or hazardous wastes, decontamination of natural water as well as analytical applications.

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Abstract  

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.

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Abstract  

The separation of Zn−Cd, Ag−Hg, Cd−Ag and Pb−Bi−Po by extraction chromatography in the system dithizone-carbon tetrachloride is reported. It is shown that it is possible to calculate optimum conditions for the separation of the metals from the extraction constants of the metal chelates and the stability constants of the metal complexes with masking agents.

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Abstract  

Procedure for direct separation of radionickel from boric acid concentrate was developed. Quantitative separation from 100 mL of real concentrate on the column filled with 3 mL of PAN-DMG composite material was achieved. PAN-DMG material (dimethylglyoxime in porous beads of polyacrylonitrile) was compared with Ni Resin and DMG-PAN material exhibited higher sorption capacity for nickel than Ni Resin.

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New type of sorbents based on polyethers and some hydrophobic anions

III. Coprecipitation of radium with polyethylene glycol — Metal(II) salts of heteropolyacids

Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Šebesta and M. Obdržálek

Abstract  

Coprecipitation of radium with precipitates composed of polyethylene glycol — metal(II) salts of heteropolyacids has been described. The calcium salt of phosphomolybdic acid, precipitated in the presence of polyethylene glycol (m. wt. 1000) has been chosen for the more detailed study of radium coprecipitation. The influence of acidity, amount of precipitate, concentration of calcium cations and of polyethylene glycol on radium coprecipitation has been determined. On the basis of the results obtained, suitable conditions for quantitative concentration of radium from aqueous solutions have been found. The described method of radium concentration can be used for determination of radium in aqueous samples.

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Abstract  

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.

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Abstract  

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.

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Extraction chromatography using chelating agents

III. N-Benzoyl-N-phenylhydroxylamine as a chelating agent

Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Šebesta and A. Lázníčková

Abstract  

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.

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Abstract  

Four composite materials with di-(2-ethylhexyl) phosphoric acid (HDEHP) as an extraction agent and PAN as a binding polymer were studied in this work. The intended use of these materials is in extraction chromatography. They were prepared by various methods and contained different amounts of HDEHP. The properties were compared by studying europium uptake from nitric acid solutions. Materials prepared by direct incorporation of extraction agent into PAN polymer during beads production and with up to 40% (w/w) of HDEHP are suitable for analytical separations. Materials with high capacity can be prepared by impregnation of ready-made PAN beads.

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Abstract  

Composite material PAN-DMG, containing chelating agent dimethylglyoxime (DMG) immobilized in porous matrix of binding polymer polyacrylonitrile (PAN), was used for nickel separation and concentration. Method for preparation of 59Ni source for low energy photon spectrometry was developed using homogeneous precipitation of nickel with DMG. The proposed method was tested with two types of real radioactive waste (boric acid concentrate from nuclear power plant (NPP) evaporator and spent ion exchanger from NPP).

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