Ferdinand Šebesta

Metal biosorption by PAN-immobilized fungal biomass in simulated wastewaters

Abstract The ability of microorganisms to remove metal ions from solution was investigated by using dead fungal biomass. The latter was immobilized by polyacrylonitrile, a known binding polymer for inorganic ion exchangers. This product was examined in batchwise experiments for the removal of toxic metals from aqueous mixtures containing copper, zinc and nickel (i.e. simulated wastewaters) in order to examine whether this separation technique may improve biomass performance as a metals sorbent. The metal removal capacities of the beads PAN-B/50% for zinc, copper and nickel were 16, 7 and 0.25 mg g−1, respectively, while the zinc, copper and nickel adsorption capacities of PAN-B/75% were 18, 7.9 and 0.25 mg g−1, respectively. The obtained results were compared with those using plain dispersed biomass. Certain column experiments were also performed. Promising results were obtained in the laboratory, as effective metal removals were observed.

Separation of Cesium and Strontium from Acidic Radioactive Waste Simulants Using a Microporous Tungstate/Polyacrylonitrile (PAN) Composite Adsorbent

Abstract The inorganic phase, Na0.2Mo0.03W0.97O3 · ZH2O (MoHTB), which has been previously shown to be selective for Cs+ and Sr2+ from acidic radwaste simulants (0.075 mmol · L−1, 1.0 M HNO3), has been granulated with polyacrylonitrile (PAN) to afford a composite adsorbent suitable for deployment in small scale, fixed‐bed columns. The uptake of Cs+ and Sr2+ by the MoHTB‐PAN composites from such an acidic radwaste simulant is optimal for granular material of mesh size <0.3 mm but satisfactory uptake rates are also observed with material of mesh size 0.3–0.63 mm. The fixed‐bed column adsorption of Cs+ and Sr2+ from acidic radwaste simulant affords breakthrough curves which are of a typical ‘S’ shape profile but desorption of adsorbed Sr2+ by Cs+ in the radwaste simulant occurs after the composite column achieves equilibrium with respect to Sr2+. A simplified model of the adsorption of Cs+ and Sr2+ by the MoHTB‐PAN composite fixed‐bed column has been applied to these initial results and has been shown to have utility in describing the performance of the fixed‐bed column setup at the equimolar concentrations of Cs+ and Sr2+ employed.

Composite absorbers of inorganic ion-exchangers and polyacrylonitril e binding matrix V. Influence of ionising radiation on the leachability of t37Cs from cemented composite NiFC-PAN absorber

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.

Composite absorbers consisting of inorganic ion-exchangers and polyacrylonitrile binding matrix

Both cementation and vitrification was shown by preliminary experiments to be applicable for treatment of the spent composite absorbers with polyacrylonitrile binding matrix for final disposal. Loadings of cement mix with composite absorbers up to 5–9% (w/w) were achieved Admixtures of natural clinoptilolite were found to improve compressive strength of the samples. The presence of PAN binding polymer was found not to disqualify the composite absorber tested from final treatment by vitrification.

Development of novel composite sorbents for the removal of actinides from environmental and analytical solutions

A novel approach to preparing granular sorbents for the separation of actinides has been developed, where the extractant is directly immobilized in an inert matrix. This allows substantially higher extractant loadings in the sorbent than for conventional extraction chromatography resins. This approach utilizes polyacrylonitrile (PAN) as the inert matrix material. The well-known actinide extractant octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) has been loaded into sorbent granules at extractant loadings from 20 to 33 wt.% CMPO. The porosity of the PAN matrix allows the active material to have rapid and complete access to the solution containing the impurities, resulting in improved kinetics and higher sorption capacities. Sorbents containing CMPO were prepared using PAN as a binding matrix, and tested against commercially available actinide extraction chromatography resins. Direct comparative batch contact tests performed with TRU-ResinÒ and CMPO-PAN using an INEEL tank waste simulant, resulting in distribution coefficient (Kd) values for Am approximately 2-90 times higher for CMPO-PAN than for TRU-ResinŇ. Batch distribution coefficient (Kd) values for Pu were approximately 60-150 times higher for CMPO-PAN than for the TRU-ResinŇ. Acid dependency curves were generated for Am and Pu with CMPO-PAN over a concentration range of 1 mM to 5M HNO3.

Separation of curium from americium using composite sorbents and complexing agent solutions

The EXAm and the AmSel liquid–liquid extraction processes have been used as bases for the development of chromatographic systems for separation of curium(III) from americium(III). The liquid organic phases were replaced by composite sorbents with PAN binding matrix and complexing agent in nitric acid solutions were employed as aqueous phases. The influence of complexing agent and nitric acid concentrations on weight distribution coefficients and separation factor and the kinetics of the actinide uptake were determined in batch experiments with trace amounts of 241Am and 244Cm. The efficiency of Cm(III) separation from Am(III) was evaluated in column experiment.

Sorption of Metal Oxoanions by Composite Biosorbents of Waste Material of Brown Seaweeds Ascophyllum nodosum and PAN

Two different composite sorbents of chemically modified dealginaded seaweed Ascophyllum nodosum (DS-2 and DS-3) were used for the selective removal of metal (W, Mo, and V) oxoanions. All experiments were carried out by dynamic column sorption. The effects of the pH, flow rate and the concentration of the accompanying anions in the feed solution were studied. Sorption of tungstate, molybdate and vanadate anions was successful. The composite sorbents exhibited high stability during more than 25 sorption cycles.

Rapid separation and determination of 107 Pd in radioactive waste produced during NPP A-1 decommissioning

Procedure for 107Pd determination in radioactive wastes coming from decommissioning of NPP A-1 is proposed and verified. 107Pd was separated and purified by Pd precipitation with dimethylglyoxime (DMG) and/or ferric hydroxide precipitation. 107Pd yield was determined gravimetrically by weighing the Pd(DMG)2 precipitate. 107Pd counting was performed using liquid scintillation counter (LSC-TDCR) and scintillation cocktail Hionic Fluor. In all analyzed samples the determined activities of 107Pd were lower than MDA. Nevertheless such analyses permit the decision concerning the storage of solidified wastes in the Mochovce regional repository.

The Dose Absorbed by an Ion‐Exchanger in a Column for the Separation of 137Cs

Abstract The case of an ion‐exchanger used for the separation of radiocesium from a liquid radioactive waste is analyzed. A simple method enabling the evaluation of the radiation‐dose imparted by 137Cs and its daughter 137mBa to the exchanger during the column operation is described. Using the technical data obtained during a full‐scale application of a composite inorganic‐organic ion‐exchanger NiFC‐PAN, the dose absorbed by the exchanger is calculated.

Correlation analysis of the contamination of freshwater sediments in the Labe (Elbe) river catchment with gamma-emitting radionuclides

Abstract One hundred and thirty-nine samples of sieved sediments of rivers and reservoirs in the Elbe (Labe) river catchment in Bohemia (Czech Republic) were analyzed by gamma-spectrometry for 134 Cs, 137 Cs, 226 Ra, 228 Ra and 228 Th. The results characterize contamination of the catchment with radiocesium mainly from the Chernobyl accident, with 226 Ra from uranium mining and milling, and natural background values for 226 Ra, 228 Ra and 228 Th. The data obtained were analyzed on the basis of their mutual correlations and correlations with parameters characterizing composition of the sediments: content of silica, carbonates, organic carbon, ferric oxide, phosphorus, sulphur, uranium, thorium, barium and magnesium.