F. Macášek

Influence of humic substances on sorption of cesium and strontium on montmorillonite

The effect of humic acid addition on the capacity of inorganic sorbents to sorb radioactive cesium and strontium was studied on montmorillonites in a calcium and potassium form. The Sips isotherm for humic acid sorption and multisite distribution model of ion sorption was found to suit well for the description of mobility of ions as a function of equilibrium humic acid concentration as a single variable at given pH and type of silicate. Complexation of the ions was of minor importance at the conditions investigated. Influence of humic acid on the specific radiocesium interception potential (SRIP) was also evaluated.

Membrane extraction in preconcentration of some uranium fission products

Theoretical comparison of the equilibria and kinetics of solvent extraction (SX) and emulsion liquid membrane extraction (MX) was performed using the distribution ratios at the outer inner boundaries of liquid membrane. Enhancement factors, pertraction factor (p) and mulitplication factor (N), were proposed to express efficiency of the MX technique. The extraction of cesium, strontium, cobalt(II), uranium(VI), cerium(III) and technetium(VII) was investigated from this point of view. The most perspective systems are those with chelating agents (e.g. di-2-ethylhexyl-phosporic acid and 8-hydroquinoline), especially at low concentrations (substioichiometric amounts), with which high enhancement factors can be achieved. The results with the ion-exchange systems (bis(1,2-dicarbollyl)-cobalt(III) and quaternary ammonium salts) may be interpreted as indicating some surface barriers which prevent the transport of ions. 20 references, 14 figures, 6 tables.

CESIUM, STRONTIUM, EUROPIUM(III) AND PLUTONIUM(IV) COMPLEXES WITH HUMIC ACID IN SOLUTION AND ON MONTMORILLONITE SURFACE

AbstractThe effect of Aldrich humic acid (HA) on the mobility of137Cs,85Sr,152Eu and239Pu radionuclides was studied in Ca-montmorillonite suspensions. Verified 2-sites-2-species (2s2s) models correspond to an intensive interaction of all elements with humificated surface, what is in a remarkable contrast with the weak complexation of cesium and even strontium in solutions — the neutral ligand interaction constants β (l/mol) are log β<−9.9 and 7.56±0.21 for Cs and Sr, respectively. The result for europium complexation in solution, log β=12.49±0.18 is in a good agreement with literature data. For plutonium(IV) not only a high proton competitive constant in solution was obtained, log β β=(−0.67±0.32)+3pH, but also a strong chemisorption, which at high concentrations of humic acid (above 0.05 g/l) indicates the formation of bridge humate complexes of plutonium on the humificated surface. Logarithms of heterogeneous interaction constants (

EMULSION MEMBRANE SYSTEMS FOR PRECONCENTRATION OF URANIUM

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Distribution and speciation of cesium, strontium, and europium in the aqueous two-phase system milk-pectin

24 l/g) of the elements with surface humic acid are 4.47±0.23, 4.39±0.08, and 6.40±0.33 for Cs, Sr, and Eu(III), respectively, and the logarithm of the proton competitive constant (

Radiolysis of carbon tetrachloride-nitrobenzene mixtures. Radiation yields of major liquid products

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