Application of the de Job method in the evaluation of the stoichiometry of uranyl phosphate complexes sorbed on bentonite

Grabias, Ewelina; Gładysz–Płaska, Agnieszka; Lipke, Agnieszka; Pikus, S.; Majdan, Marek

doi:10.5155/eurjchem.7.1.42-48.1348

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“…This notwithstanding, the decrease in the log K d values for HDTMA-bentonite was not so sharp as that observed for the remaining bentonites. This was probably a consequence of the enhanced participation of U(VI) phosphate precipitation in the overall process of sorption, similarly to the result of our recent work [9] where have found the precipitation of (UO 2 ) 3 (PO 4 ) 2 Á4H 2 O in the interlamellar space of Na-bentonite. For all kinds of bentonite, with the exception of H-bentonite, the desorption isotherms differed from the sorption isotherms, which attested to the irreversibility of the entire sorption process.…”

Section: Resultssupporting

confidence: 75%

“…The evident perturbation of the Al-OHAl bending vibration upon the influence of the U(VI) phosphate complex results in the shift of the band from 918 to 913 cm -1 . This result is the confirmation of our earlier data [9] concerning U(VI) sorption on Na-bentonite in the presence of phosphates, when we have found evident interaction of UO 2 HPO 4 complex with bentonite aluminols :Al-OH. Additional proofs for the strong interaction of more strongly than P(V) ions (band at 1084 cm -1 ), which probably only form hydrogen bonds with Al-OH groups, which are more reactive than Si-OH groups.…”

Section: Ftir Spectra Of the Sorption Productssupporting

confidence: 81%

“…The mechanism of U(VI) sorption can be evaluated by different methods, among them the batch equilibrium method, thermal analysis and FTIR spectroscopy, which provide information on the role of the different surface groups of the mineral in the complexation of U(VI). We had partially explained the mechanism of U(VI) sorption in our earlier paper [9], in which de Job method had been used as a tool for the diagnosis of the stoichiometry of the surface complexes formed. In the present study, we investigated thermal degradation of sorption products to elucidate the mechanism of interaction between the surfactant and the bentonite matrix.…”

Section: Introductionmentioning

confidence: 99%

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A thermal, sorptive and spectral study of HDTMA-bentonite loaded with uranyl phosphate

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The influence of phosphate ions on the thermal stability of complexes obtained by adsorption of uranium(VI) on organobentonite was determined. Organoclay samples were prepared by the reaction of hexadecyltrimethylammonium bromide with bentonite. The isotherms of sorption/desorption of U(VI) from aqueous solutions containing phosphate ions onto different forms of bentonite were measured using the batch method. The highest amount of uranium was absorbed on HDTMAbentonite in the presence of phosphates. This may have been associated with the complexing of U(VI) ions by phosphate ions, which interacted with surfactant cations probably via electrostatic forces. A TG-DSC-MS study showed that the thermal decomposition of the surfactant sorbed on bentonite proceeded in two stages: at 200-400 and at 600-800°C. The first stage involved defragmentation and oxidation of surfactant cations present in the interior and on the surface of the mineral. The second stage involved oxidation of charcoal and simultaneous dehydroxylation of the sorbent. The oxidation of surfactant cations and the dehydroxylation of the mineral were suppressed in the presence of phosphates.