Sorption of metal cations on suspended bentonite: effects of pH, ionic strength and complexing anions

Abstract

Sorption of metal cations on suspended bentonite: effects of pH, ionic strength and complexing anionsAbstract: Batch sorption experiments have been carried out to understand the interaction of different metal cations such as Am(III), Eu(III), Sr(II), and Cs(I) with bentonite clay at varying pH (1-9). The effects of other experimental parameters such as ionic strength (0.01-1 M (NaClO 4 )), clay to metal ion concentration ratio, and the presence of complexing anions such as oxalic acid (ox), carbonate (CO 3 2− ), ethylenediaminetetraacetic acid (EDTA), and humic acid (HA) on Eu(III) sorption have also been investigated. The sorption of Eu(III) has been found to be invariant with the change in ionic strength suggesting innersphere complexation on the bentonite surface. Near quantitative sorption of Eu(III) and Am(III) has been observed in the entire pH range and there is marginal influence of the presence of 1 × 10 −4 M of ox and CO 3 2− on the sorption profile. However, the presence of 1 × 10 −4 M EDTA suppresses the sorption of Eu(III) ion onto bentonite. Desorption studies of Eu(III) loaded onto bentonite using varying concentrations of HClO 4 (0.01-1.0 M) solutions re-veal that higher acidity favors the process. The sorption of Eu(III) on bentonite followed the Langmuir isotherm suggesting monolayer sorption process. The data fitting to D-R isotherm suggested that the Eu(III) sorption on bentonite follows ion exchange mechanism. The sorption capacity of bentonite clay was determined to be 3.8(±0.1) × 10 −4 moles/g using Langmuir and D-R isotherms.

Diglycolamic Acid-Functionalized MWCNT-Augmented Polymeric Beads for Efficient Separation of Trivalent Lanthanides and Actinides

“…Similar observations were observed by Gujar et al, who reported a decrease in the uptake of Am 3+ and Eu 3+ by the GO-PES beads beyond pH 4. Another study by Mohapatra et al also indicated the loss of Am 3+ at pH ≥ 5 due to adsorption on the glass surface. From these observations, the changes in the extraction profile with pH for both radionuclides were found to be quite similar.…”

Removal of americium from effluent generated during the purification of plutonium by anion exchange

“…Similarly co-precipitation with different metal hydroxides has also been reported from neutral or alkaline media [25]. Sorption of Am(III) on inorganic exchangers from near neutral media has also been reported [26,27]. However, only a few studies have described the separation of americium from highly acidic medium.…”