Authors:C. Loos-Neskovic, B. Bartos, M. Hussonnois, and O. Constantinescu
Zinc and nickel hexacyanoferrates (II) present a high affinity for223Fr and no retention for223Ra in hydrochloric acid solutions with concentrations greater than 0.5N. Hydrated antimony pentoxide is the best sorbent for223Ra. Incorporated in a composite exchanger, it could be used for decontamination purposes.
The potential of hydrated titanium(IV) oxide as a granular inorganic sorbent for radiostrontium was studied by carrying out laboratory-scale column experiment. The feed to the column was a simulated waste solution of reprocessing plant origin. The breakthrough curve for removal of radiostrontium was determined. High decontamination factors were obtained for thousands of bed volumes. The column loading results were correlated with batch distribution data.
The determination of uranium in solutions and sorbents by measurement of absorption of soft gamma-rays is described. The use of 22 keV gamma-rays of109Cd enbled us to improve the sensitivity of the determination for nearly an order of magnitude when compared to the measurements using241Am source. The application to the continuous measurement of uranium concentration in pilot-plant streams and of concentration profiles of uranium sorbed on columns of ion exchangers is described.
Sorption and diffusion processes with134Cs and85Sr in natural bentonites have been investigated. The distribution coefficients (Kd) have been determined by a batch method. Various factors affecting theKd value as water-to-bentonite ratio, concentration of the competitive cations in the aqueous phase or bentonite-to-sand ratio
in the mixed sorbents have been evaluated. A comparison of the sorption and diffusion data has been made.
The purpose of this study was a preliminary evaluation of mineral-carbon sorbents preparation possibility by the method of
thermal decomposition of a mixture of aluminium oxide or hydroxide and acenaphthene and determination of their physicochemical
properties. The conditions of carbonization were established and the changes of physicochemical properties of obtained materials
as a function of organic substance content in the mineral-carbon mixture before the process of carbonization were tracked.
In these investigations the methods of thermal analysis, low-temperature nitrogen adsorption and benzene vapors adsorption
Authors:T. Todd, N. Mann, T. Tranter, F. Šebesta, J. John, and A. Motl
Ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) composite sorbents have been evaluated for the removal of cesium from Idaho National Engineering and Environmental Laboratory (INEEL) concentrated acidic tank waste. Batch contacts were performed to qualitatively evaluate the effects of increased nitric acid, sodium and potassium. An equilibrium isotherm was generated with simulated concentrated tank waste solutions and fit to the Langmuir equation. Additional batch contact experiments were performed to determine if mercury, plutonium and americium would sorb onto AMP-PAN. Dynamic sorption was evaluated in column tests employing 1.5 cm3 columns operating at 5, 10 and 20 bed volumes of flow per hour. Results indicate, as expected, that dynamic cesium sorption capacity is reduced as the flowrate is increased. Calculated dynamic capacities for cesium were 22.5, 19.8 and 19.6 mg Cs/g sorbent, for 5, 10 and 20 bed volume per hour flows, respectively. The thermal stability of loaded AMP-PAN was evaluated by performing thermogrovimetric analysis (TGA) on samples of AMP, PAN (polymer), and AMP-PAN. Results indicate that AMP-PAN is stable to 400 °C, with less than a 10% loss of weight, which is at least partially due to loss of water of hydration. The evaluation of AMP-PAN indicates that it will effectively remove cesium from concentrated acidic tank waste solutions.
Leach characteristics of 137Cs and 60Co radionuclides from spent mix bead ion exchange resins and both ordinary Portland cement and cement mixed with two kind
of natural sorbents (bentonite and clinoptilolite) have been studied using the International Atomic Energy's (IAEA) standard
leach method. The waste immobilization performance of low-level wastes in natural sorbent mixtures was determined. The solidification
matrix was a standard Portland cement mixed with 290-350 (kg/m3) spent mix bead exchange resins, with or without 1-10% of bentonite or/and clinoptilolite. The leaching rates from the cement-bentonite
matrix were measured after 300 days as 60Co: (1.20-9.72) . 10-5 cm/d and 137Cs: (1.00-9.22) . 10-4 cm/d. From the leaching data, the apparent diffusivity of cobalt and cesium in cement-bentonite or/and clinoptilolite matrix
with a waste load of 350 kg/m3 of spent mix bead exchange resin was calculated as 60Co: (1.0-5.9) . 10-6 cm2/d and 137Cs: (0.48-2.4) . 10-4 cm2/d. The compressive strength of these samples is determined according to the ASTM standards.
Authors:Elif Bursali, Melek Merdivan, and Muruvvet Yurdakoc
Olive cake as low-cost abundantly available sorbent has been characterized by N2 at 77 K adsorption, porosity analysis, elemental analysis and IR spectra and has been used for preconcentrating of uranium(VI)
and thorium(IV) ions prior to their determination spectrophotometrically. The optimum pH values for quantitative sorption
of U(VI) and Th(IV) are 4–7 and 3–7, respectively. The enrichment factor for the preconcentration of U(VI) and Th(IV) were
found to be 125 and 75 in the given order. The sorption capacity of olive cake is in the range of 2,260–15,000 μg g−1 for Th(IV) and in the range of 1,090–17,000 μg g−1 for U(VI) at pH 3–7. The sorbent exhibits good reusability and the uptake and stripping of the studied ions were fairly rapid.
The elution of U(VI) and Th(IV) was performed with 0.3–1 M HCl/1–2 M HNO3 and 0.3–0.8 M HCl/1 M HNO3, respectively. The precision of the method was 1.8 RSD% for U(VI) and 2.5 RSD% for Th(IV) in a concentration of 1.00 μg mL−1 for 10 replicate analysis. The influence of some electrolytes and cations as interferents was discussed. Separation of U(VI)
and Th(IV) from other metal ions in synthetic solution was achieved.
Authors:Abdelhakim Kadous, Mohamed Didi, and Didier Villemin
A new chelating polymeric sorbent has been developed using polystyrene resin grafted with ethylenediamino tris(methylenephosphonic)
acid. After characterisation by FTIR and elementary analysis, the new grafted resin has been investigated in liquid–solid
extraction of uranium(VI). The influence of analytical parameters including pH, amount of resin, metal ion concentration,
sample volume and ionic strength were investigated on the recovery of U(VI). Adsorption kinetic and isotherm studies were
also carried out to understand the nature of the sorption of uranium(VI) by the resin. The total sorption capacity was found
to be 41.76 mg/g under optimum conditions. The total desorption of the sorbed uranium ions was successfully performed with
0.1 M ammonium carbonate. Further, the effect of temperature was realized and the thermodynamic parameters were calculated.
The programmed heating of montmorillonite samples is accompanied by their dehydration and dehydroxilation, this being registered by means of Derivatograph. The form of the endothermal effects within the 80–250°C interval can be of simple or double character depending on the nature of exchange cations. Though this phenomenon has been known for a long time, no satisfactory explanation has been provided so far. The herewith paper contains the results of bound water researches at various forms (Na, Ca, Al, Fe) of montmorillonite by means of thermal analysis as well as other physico-chemical methods. It has been found that the form of dehydration endoeffects depends on the state of the active centers of the mineral. In certain conditions, by means of thermal analysis one can determine corresponding quantities of bound water that are in agreement with various kinds of active centers of the mineral sorbent.