Sorption of Th(IV) from aqueous solution to GMZ bentonite: effect of pH, ionic strength, fulvic acid and electrolyte ions

An approach for the efficient immobilization of 79Se using Fe-OOH modified GMZ bentonite

Because of high mobility, the immobilization of long-lived fission product 79Se (often existed as 79Se(IV) and 79Se(VI) anions) is a critical consideration in the repository of high-level radioactive waste. In this work, a Fe-OOH modified bentonite (Fe-OOH-bent) was synthesized as a potential filling material in the repository site for effective adsorption and present the migration of different species of 79Se. The adsorbent was characterized using FT-IR, XRD, XFS, zeta potential and BET to clarify its physical properties, compositions and structures. A good thermal and radiation stabilities of Fe-OOH-bent was confirmed by its stable uptake ratio for Se(IV) and Se(VI) compared to original samples. The batch experimental results show that Se(IV) and Se(VI) can be efficiently removed from aqueous by Fe-OOH-bent within 60 min with maximum adsorption capacities of 68.45 mg/g for Se(IV) and 40.47 mg/g for Se(VI) in the optimal conditions, indicating its high potential application in consideration of its simple synthesis process, low cost and high adsorption capacity in view of immobilization of 79Se. The surface species and variation of oxide state of Fe as well as Se(IV) and Se(VI) onto Fe-OOH-bent were investigated by XPS analysis. The values of relative area of Se(IV)–O and Se(VI)–O in XPS spectra followed the same tendency as their adsorption ratio with the variation of system pH, suggesting that the formation of complexes between selenium species and Fe-OOH-bent surface.

Removal of thorium (IV) ions from aqueous solution by a novel nanoporous ZnO: Isotherms, kinetic and thermodynamic studies

The adsorption of thorium (IV) from aqueous solutions onto a novel nanoporous ZnO particles prepared by microwave assisted combustion was studied using batch methods under different experimental conditions. The effect of contact time, solution pH, initial concentration and temperature on adsorption process was studied. The ability of this material to remove Th (IV) from aqueous solution was characterises by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption percent and distribution coefficient for nanoporous ZnO powders in optimum conditions were 97% ± 1.02; 8080 L kg(-1)for Th (IV), respectively. Based on the Langmuir model, the maximum adsorption capacity of nanoporous ZnO for Th (IV) was found to be 1500 g kg(-1). Thermodynamic parameters were determined and discussed. The results indicated that nanoporous ZnO was suitable as sorbent material for recovery and adsorption of Th (IV) ions from aqueous solutions. The radioactive Th (VI) in surface water, sea water and waste waters from technologies producing nuclear fuels, mining (uranium and thorium) and laboratories working with radioactive materials (uranium and thorium) can be removed with this nanoporous ZnO.

Plutonium(IV) sorption to montmorillonite in the presence of organic matter

The effect of altering the order of addition in a ternary system of plutonium(IV), organic matter (fulvic acid, humic acid and desferrioxamine B), and montmorillonite was investigated. A decrease in Pu(IV) sorption to montmorillonite in the presence of fulvic and humic acid relative to the binary Pu-montmorillonite system, is attributed to strong organic aqueous complex formation with aqueous Pu(IV). No dependence on the order of addition was observed. In contrast, in the system where Pu(IV) was equilibrated with desferrioxamine B (DFOB) prior to addition of montmorillonite, an increase in Pu(IV) sorption was observed relative to the binary system. When DFOB was equilibrated with montmorillonite prior to addition of Pu(IV), Pu(IV) sorption was equivalent to the binary system. X-ray diffraction and transmission electron microscopy revealed that DFOB accumulated in the interlayer of montmorillonite. The order of DFOB addition plays an important role in the observed sorption/desorption behavior of Pu. The irreversible nature of DFOB accumulation in the montmorillonite interlayer leads to an apparent dependence of Pu sorption on the order of addition in the ternary system. This work demonstrates that the order of addition will be relevant in ternary systems in which at least one component exhibits irreversible sorption behavior.